summaryrefslogtreecommitdiff
path: root/src/glsl/linker.cpp
blob: 01526de56c6ed905a3c442152713abe49f40d457 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
/*
 * Copyright © 2010 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

/**
 * \file linker.cpp
 * GLSL linker implementation
 *
 * Given a set of shaders that are to be linked to generate a final program,
 * there are three distinct stages.
 *
 * In the first stage shaders are partitioned into groups based on the shader
 * type.  All shaders of a particular type (e.g., vertex shaders) are linked
 * together.
 *
 *   - Undefined references in each shader are resolve to definitions in
 *     another shader.
 *   - Types and qualifiers of uniforms, outputs, and global variables defined
 *     in multiple shaders with the same name are verified to be the same.
 *   - Initializers for uniforms and global variables defined
 *     in multiple shaders with the same name are verified to be the same.
 *
 * The result, in the terminology of the GLSL spec, is a set of shader
 * executables for each processing unit.
 *
 * After the first stage is complete, a series of semantic checks are performed
 * on each of the shader executables.
 *
 *   - Each shader executable must define a \c main function.
 *   - Each vertex shader executable must write to \c gl_Position.
 *   - Each fragment shader executable must write to either \c gl_FragData or
 *     \c gl_FragColor.
 *
 * In the final stage individual shader executables are linked to create a
 * complete exectuable.
 *
 *   - Types of uniforms defined in multiple shader stages with the same name
 *     are verified to be the same.
 *   - Initializers for uniforms defined in multiple shader stages with the
 *     same name are verified to be the same.
 *   - Types and qualifiers of outputs defined in one stage are verified to
 *     be the same as the types and qualifiers of inputs defined with the same
 *     name in a later stage.
 *
 * \author Ian Romanick <ian.d.romanick@intel.com>
 */

#include "main/core.h"
#include "glsl_symbol_table.h"
#include "glsl_parser_extras.h"
#include "ir.h"
#include "program.h"
#include "program/hash_table.h"
#include "linker.h"
#include "link_varyings.h"
#include "ir_optimization.h"
#include "ir_rvalue_visitor.h"
#include "ir_uniform.h"

#include "main/shaderobj.h"
#include "main/enums.h"


void linker_error(gl_shader_program *, const char *, ...);

namespace {

/**
 * Visitor that determines whether or not a variable is ever written.
 */
class find_assignment_visitor : public ir_hierarchical_visitor {
public:
   find_assignment_visitor(const char *name)
      : name(name), found(false)
   {
      /* empty */
   }

   virtual ir_visitor_status visit_enter(ir_assignment *ir)
   {
      ir_variable *const var = ir->lhs->variable_referenced();

      if (strcmp(name, var->name) == 0) {
	 found = true;
	 return visit_stop;
      }

      return visit_continue_with_parent;
   }

   virtual ir_visitor_status visit_enter(ir_call *ir)
   {
      foreach_two_lists(formal_node, &ir->callee->parameters,
                        actual_node, &ir->actual_parameters) {
	 ir_rvalue *param_rval = (ir_rvalue *) actual_node;
	 ir_variable *sig_param = (ir_variable *) formal_node;

	 if (sig_param->data.mode == ir_var_function_out ||
	     sig_param->data.mode == ir_var_function_inout) {
	    ir_variable *var = param_rval->variable_referenced();
	    if (var && strcmp(name, var->name) == 0) {
	       found = true;
	       return visit_stop;
	    }
	 }
      }

      if (ir->return_deref != NULL) {
	 ir_variable *const var = ir->return_deref->variable_referenced();

	 if (strcmp(name, var->name) == 0) {
	    found = true;
	    return visit_stop;
	 }
      }

      return visit_continue_with_parent;
   }

   bool variable_found()
   {
      return found;
   }

private:
   const char *name;       /**< Find writes to a variable with this name. */
   bool found;             /**< Was a write to the variable found? */
};


/**
 * Visitor that determines whether or not a variable is ever read.
 */
class find_deref_visitor : public ir_hierarchical_visitor {
public:
   find_deref_visitor(const char *name)
      : name(name), found(false)
   {
      /* empty */
   }

   virtual ir_visitor_status visit(ir_dereference_variable *ir)
   {
      if (strcmp(this->name, ir->var->name) == 0) {
	 this->found = true;
	 return visit_stop;
      }

      return visit_continue;
   }

   bool variable_found() const
   {
      return this->found;
   }

private:
   const char *name;       /**< Find writes to a variable with this name. */
   bool found;             /**< Was a write to the variable found? */
};


class geom_array_resize_visitor : public ir_hierarchical_visitor {
public:
   unsigned num_vertices;
   gl_shader_program *prog;

   geom_array_resize_visitor(unsigned num_vertices, gl_shader_program *prog)
   {
      this->num_vertices = num_vertices;
      this->prog = prog;
   }

   virtual ~geom_array_resize_visitor()
   {
      /* empty */
   }

   virtual ir_visitor_status visit(ir_variable *var)
   {
      if (!var->type->is_array() || var->data.mode != ir_var_shader_in)
         return visit_continue;

      unsigned size = var->type->length;

      /* Generate a link error if the shader has declared this array with an
       * incorrect size.
       */
      if (size && size != this->num_vertices) {
         linker_error(this->prog, "size of array %s declared as %u, "
                      "but number of input vertices is %u\n",
                      var->name, size, this->num_vertices);
         return visit_continue;
      }

      /* Generate a link error if the shader attempts to access an input
       * array using an index too large for its actual size assigned at link
       * time.
       */
      if (var->data.max_array_access >= this->num_vertices) {
         linker_error(this->prog, "geometry shader accesses element %i of "
                      "%s, but only %i input vertices\n",
                      var->data.max_array_access, var->name, this->num_vertices);
         return visit_continue;
      }

      var->type = glsl_type::get_array_instance(var->type->element_type(),
                                                this->num_vertices);
      var->data.max_array_access = this->num_vertices - 1;

      return visit_continue;
   }

   /* Dereferences of input variables need to be updated so that their type
    * matches the newly assigned type of the variable they are accessing. */
   virtual ir_visitor_status visit(ir_dereference_variable *ir)
   {
      ir->type = ir->var->type;
      return visit_continue;
   }

   /* Dereferences of 2D input arrays need to be updated so that their type
    * matches the newly assigned type of the array they are accessing. */
   virtual ir_visitor_status visit_leave(ir_dereference_array *ir)
   {
      const glsl_type *const vt = ir->array->type;
      if (vt->is_array())
         ir->type = vt->element_type();
      return visit_continue;
   }
};

/**
 * Visitor that determines the highest stream id to which a (geometry) shader
 * emits vertices. It also checks whether End{Stream}Primitive is ever called.
 */
class find_emit_vertex_visitor : public ir_hierarchical_visitor {
public:
   find_emit_vertex_visitor(int max_allowed)
      : max_stream_allowed(max_allowed),
        invalid_stream_id(0),
        invalid_stream_id_from_emit_vertex(false),
        end_primitive_found(false),
        uses_non_zero_stream(false)
   {
      /* empty */
   }

   virtual ir_visitor_status visit_leave(ir_emit_vertex *ir)
   {
      int stream_id = ir->stream_id();

      if (stream_id < 0) {
         invalid_stream_id = stream_id;
         invalid_stream_id_from_emit_vertex = true;
         return visit_stop;
      }

      if (stream_id > max_stream_allowed) {
         invalid_stream_id = stream_id;
         invalid_stream_id_from_emit_vertex = true;
         return visit_stop;
      }

      if (stream_id != 0)
         uses_non_zero_stream = true;

      return visit_continue;
   }

   virtual ir_visitor_status visit_leave(ir_end_primitive *ir)
   {
      end_primitive_found = true;

      int stream_id = ir->stream_id();

      if (stream_id < 0) {
         invalid_stream_id = stream_id;
         invalid_stream_id_from_emit_vertex = false;
         return visit_stop;
      }

      if (stream_id > max_stream_allowed) {
         invalid_stream_id = stream_id;
         invalid_stream_id_from_emit_vertex = false;
         return visit_stop;
      }

      if (stream_id != 0)
         uses_non_zero_stream = true;

      return visit_continue;
   }

   bool error()
   {
      return invalid_stream_id != 0;
   }

   const char *error_func()
   {
      return invalid_stream_id_from_emit_vertex ?
         "EmitStreamVertex" : "EndStreamPrimitive";
   }

   int error_stream()
   {
      return invalid_stream_id;
   }

   bool uses_streams()
   {
      return uses_non_zero_stream;
   }

   bool uses_end_primitive()
   {
      return end_primitive_found;
   }

private:
   int max_stream_allowed;
   int invalid_stream_id;
   bool invalid_stream_id_from_emit_vertex;
   bool end_primitive_found;
   bool uses_non_zero_stream;
};

} /* anonymous namespace */

void
linker_error(gl_shader_program *prog, const char *fmt, ...)
{
   va_list ap;

   ralloc_strcat(&prog->InfoLog, "error: ");
   va_start(ap, fmt);
   ralloc_vasprintf_append(&prog->InfoLog, fmt, ap);
   va_end(ap);

   prog->LinkStatus = false;
}


void
linker_warning(gl_shader_program *prog, const char *fmt, ...)
{
   va_list ap;

   ralloc_strcat(&prog->InfoLog, "warning: ");
   va_start(ap, fmt);
   ralloc_vasprintf_append(&prog->InfoLog, fmt, ap);
   va_end(ap);

}


/**
 * Given a string identifying a program resource, break it into a base name
 * and an optional array index in square brackets.
 *
 * If an array index is present, \c out_base_name_end is set to point to the
 * "[" that precedes the array index, and the array index itself is returned
 * as a long.
 *
 * If no array index is present (or if the array index is negative or
 * mal-formed), \c out_base_name_end, is set to point to the null terminator
 * at the end of the input string, and -1 is returned.
 *
 * Only the final array index is parsed; if the string contains other array
 * indices (or structure field accesses), they are left in the base name.
 *
 * No attempt is made to check that the base name is properly formed;
 * typically the caller will look up the base name in a hash table, so
 * ill-formed base names simply turn into hash table lookup failures.
 */
long
parse_program_resource_name(const GLchar *name,
                            const GLchar **out_base_name_end)
{
   /* Section 7.3.1 ("Program Interfaces") of the OpenGL 4.3 spec says:
    *
    *     "When an integer array element or block instance number is part of
    *     the name string, it will be specified in decimal form without a "+"
    *     or "-" sign or any extra leading zeroes. Additionally, the name
    *     string will not include white space anywhere in the string."
    */

   const size_t len = strlen(name);
   *out_base_name_end = name + len;

   if (len == 0 || name[len-1] != ']')
      return -1;

   /* Walk backwards over the string looking for a non-digit character.  This
    * had better be the opening bracket for an array index.
    *
    * Initially, i specifies the location of the ']'.  Since the string may
    * contain only the ']' charcater, walk backwards very carefully.
    */
   unsigned i;
   for (i = len - 1; (i > 0) && isdigit(name[i-1]); --i)
      /* empty */ ;

   if ((i == 0) || name[i-1] != '[')
      return -1;

   long array_index = strtol(&name[i], NULL, 10);
   if (array_index < 0)
      return -1;

   *out_base_name_end = name + (i - 1);
   return array_index;
}


void
link_invalidate_variable_locations(exec_list *ir)
{
   foreach_in_list(ir_instruction, node, ir) {
      ir_variable *const var = node->as_variable();

      if (var == NULL)
         continue;

      /* Only assign locations for variables that lack an explicit location.
       * Explicit locations are set for all built-in variables, generic vertex
       * shader inputs (via layout(location=...)), and generic fragment shader
       * outputs (also via layout(location=...)).
       */
      if (!var->data.explicit_location) {
         var->data.location = -1;
         var->data.location_frac = 0;
      }

      /* ir_variable::is_unmatched_generic_inout is used by the linker while
       * connecting outputs from one stage to inputs of the next stage.
       *
       * There are two implicit assumptions here.  First, we assume that any
       * built-in variable (i.e., non-generic in or out) will have
       * explicit_location set.  Second, we assume that any generic in or out
       * will not have explicit_location set.
       *
       * This second assumption will only be valid until
       * GL_ARB_separate_shader_objects is supported.  When that extension is
       * implemented, this function will need some modifications.
       */
      if (!var->data.explicit_location) {
         var->data.is_unmatched_generic_inout = 1;
      } else {
         var->data.is_unmatched_generic_inout = 0;
      }
   }
}


/**
 * Set UsesClipDistance and ClipDistanceArraySize based on the given shader.
 *
 * Also check for errors based on incorrect usage of gl_ClipVertex and
 * gl_ClipDistance.
 *
 * Return false if an error was reported.
 */
static void
analyze_clip_usage(struct gl_shader_program *prog,
                   struct gl_shader *shader, GLboolean *UsesClipDistance,
                   GLuint *ClipDistanceArraySize)
{
   *ClipDistanceArraySize = 0;

   if (!prog->IsES && prog->Version >= 130) {
      /* From section 7.1 (Vertex Shader Special Variables) of the
       * GLSL 1.30 spec:
       *
       *   "It is an error for a shader to statically write both
       *   gl_ClipVertex and gl_ClipDistance."
       *
       * This does not apply to GLSL ES shaders, since GLSL ES defines neither
       * gl_ClipVertex nor gl_ClipDistance.
       */
      find_assignment_visitor clip_vertex("gl_ClipVertex");
      find_assignment_visitor clip_distance("gl_ClipDistance");

      clip_vertex.run(shader->ir);
      clip_distance.run(shader->ir);
      if (clip_vertex.variable_found() && clip_distance.variable_found()) {
         linker_error(prog, "%s shader writes to both `gl_ClipVertex' "
                      "and `gl_ClipDistance'\n",
                      _mesa_shader_stage_to_string(shader->Stage));
         return;
      }
      *UsesClipDistance = clip_distance.variable_found();
      ir_variable *clip_distance_var =
         shader->symbols->get_variable("gl_ClipDistance");
      if (clip_distance_var)
         *ClipDistanceArraySize = clip_distance_var->type->length;
   } else {
      *UsesClipDistance = false;
   }
}


/**
 * Verify that a vertex shader executable meets all semantic requirements.
 *
 * Also sets prog->Vert.UsesClipDistance and prog->Vert.ClipDistanceArraySize
 * as a side effect.
 *
 * \param shader  Vertex shader executable to be verified
 */
void
validate_vertex_shader_executable(struct gl_shader_program *prog,
				  struct gl_shader *shader)
{
   if (shader == NULL)
      return;

   /* From the GLSL 1.10 spec, page 48:
    *
    *     "The variable gl_Position is available only in the vertex
    *      language and is intended for writing the homogeneous vertex
    *      position. All executions of a well-formed vertex shader
    *      executable must write a value into this variable. [...] The
    *      variable gl_Position is available only in the vertex
    *      language and is intended for writing the homogeneous vertex
    *      position. All executions of a well-formed vertex shader
    *      executable must write a value into this variable."
    *
    * while in GLSL 1.40 this text is changed to:
    *
    *     "The variable gl_Position is available only in the vertex
    *      language and is intended for writing the homogeneous vertex
    *      position. It can be written at any time during shader
    *      execution. It may also be read back by a vertex shader
    *      after being written. This value will be used by primitive
    *      assembly, clipping, culling, and other fixed functionality
    *      operations, if present, that operate on primitives after
    *      vertex processing has occurred. Its value is undefined if
    *      the vertex shader executable does not write gl_Position."
    *
    * All GLSL ES Versions are similar to GLSL 1.40--failing to write to
    * gl_Position is not an error.
    */
   if (prog->Version < (prog->IsES ? 300 : 140)) {
      find_assignment_visitor find("gl_Position");
      find.run(shader->ir);
      if (!find.variable_found()) {
        if (prog->IsES) {
          linker_warning(prog,
                         "vertex shader does not write to `gl_Position'."
                         "It's value is undefined. \n");
        } else {
          linker_error(prog,
                       "vertex shader does not write to `gl_Position'. \n");
        }
	 return;
      }
   }

   analyze_clip_usage(prog, shader, &prog->Vert.UsesClipDistance,
                      &prog->Vert.ClipDistanceArraySize);
}


/**
 * Verify that a fragment shader executable meets all semantic requirements
 *
 * \param shader  Fragment shader executable to be verified
 */
void
validate_fragment_shader_executable(struct gl_shader_program *prog,
				    struct gl_shader *shader)
{
   if (shader == NULL)
      return;

   find_assignment_visitor frag_color("gl_FragColor");
   find_assignment_visitor frag_data("gl_FragData");

   frag_color.run(shader->ir);
   frag_data.run(shader->ir);

   if (frag_color.variable_found() && frag_data.variable_found()) {
      linker_error(prog,  "fragment shader writes to both "
		   "`gl_FragColor' and `gl_FragData'\n");
   }
}

/**
 * Verify that a geometry shader executable meets all semantic requirements
 *
 * Also sets prog->Geom.VerticesIn, prog->Geom.UsesClipDistance, and
 * prog->Geom.ClipDistanceArraySize as a side effect.
 *
 * \param shader Geometry shader executable to be verified
 */
void
validate_geometry_shader_executable(struct gl_shader_program *prog,
				    struct gl_shader *shader)
{
   if (shader == NULL)
      return;

   unsigned num_vertices = vertices_per_prim(prog->Geom.InputType);
   prog->Geom.VerticesIn = num_vertices;

   analyze_clip_usage(prog, shader, &prog->Geom.UsesClipDistance,
                      &prog->Geom.ClipDistanceArraySize);
}

/**
 * Check if geometry shaders emit to non-zero streams and do corresponding
 * validations.
 */
static void
validate_geometry_shader_emissions(struct gl_context *ctx,
                                   struct gl_shader_program *prog)
{
   if (prog->_LinkedShaders[MESA_SHADER_GEOMETRY] != NULL) {
      find_emit_vertex_visitor emit_vertex(ctx->Const.MaxVertexStreams - 1);
      emit_vertex.run(prog->_LinkedShaders[MESA_SHADER_GEOMETRY]->ir);
      if (emit_vertex.error()) {
         linker_error(prog, "Invalid call %s(%d). Accepted values for the "
                      "stream parameter are in the range [0, %d].\n",
                      emit_vertex.error_func(),
                      emit_vertex.error_stream(),
                      ctx->Const.MaxVertexStreams - 1);
      }
      prog->Geom.UsesStreams = emit_vertex.uses_streams();
      prog->Geom.UsesEndPrimitive = emit_vertex.uses_end_primitive();

      /* From the ARB_gpu_shader5 spec:
       *
       *   "Multiple vertex streams are supported only if the output primitive
       *    type is declared to be "points".  A program will fail to link if it
       *    contains a geometry shader calling EmitStreamVertex() or
       *    EndStreamPrimitive() if its output primitive type is not "points".
       *
       * However, in the same spec:
       *
       *   "The function EmitVertex() is equivalent to calling EmitStreamVertex()
       *    with <stream> set to zero."
       *
       * And:
       *
       *   "The function EndPrimitive() is equivalent to calling
       *    EndStreamPrimitive() with <stream> set to zero."
       *
       * Since we can call EmitVertex() and EndPrimitive() when we output
       * primitives other than points, calling EmitStreamVertex(0) or
       * EmitEndPrimitive(0) should not produce errors. This it also what Nvidia
       * does. Currently we only set prog->Geom.UsesStreams to TRUE when
       * EmitStreamVertex() or EmitEndPrimitive() are called with a non-zero
       * stream.
       */
      if (prog->Geom.UsesStreams && prog->Geom.OutputType != GL_POINTS) {
         linker_error(prog, "EmitStreamVertex(n) and EndStreamPrimitive(n) "
                      "with n>0 requires point output\n");
      }
   }
}


/**
 * Perform validation of global variables used across multiple shaders
 */
void
cross_validate_globals(struct gl_shader_program *prog,
		       struct gl_shader **shader_list,
		       unsigned num_shaders,
		       bool uniforms_only)
{
   /* Examine all of the uniforms in all of the shaders and cross validate
    * them.
    */
   glsl_symbol_table variables;
   for (unsigned i = 0; i < num_shaders; i++) {
      if (shader_list[i] == NULL)
	 continue;

      foreach_in_list(ir_instruction, node, shader_list[i]->ir) {
	 ir_variable *const var = node->as_variable();

	 if (var == NULL)
	    continue;

	 if (uniforms_only && (var->data.mode != ir_var_uniform))
	    continue;

	 /* Don't cross validate temporaries that are at global scope.  These
	  * will eventually get pulled into the shaders 'main'.
	  */
	 if (var->data.mode == ir_var_temporary)
	    continue;

	 /* If a global with this name has already been seen, verify that the
	  * new instance has the same type.  In addition, if the globals have
	  * initializers, the values of the initializers must be the same.
	  */
	 ir_variable *const existing = variables.get_variable(var->name);
	 if (existing != NULL) {
	    if (var->type != existing->type) {
	       /* Consider the types to be "the same" if both types are arrays
		* of the same type and one of the arrays is implicitly sized.
		* In addition, set the type of the linked variable to the
		* explicitly sized array.
		*/
	       if (var->type->is_array()
		   && existing->type->is_array()
		   && (var->type->fields.array == existing->type->fields.array)
		   && ((var->type->length == 0)
		       || (existing->type->length == 0))) {
		  if (var->type->length != 0) {
                     if (var->type->length <= existing->data.max_array_access) {
                        linker_error(prog, "%s `%s' declared as type "
                                     "`%s' but outermost dimension has an index"
                                     " of `%i'\n",
                                     mode_string(var),
                                     var->name, var->type->name,
                                     existing->data.max_array_access);
                        return;
                     }
		     existing->type = var->type;
		  } else if (existing->type->length != 0
                             && existing->type->length <=
                                var->data.max_array_access) {
                     linker_error(prog, "%s `%s' declared as type "
                                  "`%s' but outermost dimension has an index"
                                  " of `%i'\n",
                                  mode_string(var),
                                  var->name, existing->type->name,
                                  var->data.max_array_access);
                     return;
                  }
               } else if (var->type->is_record()
		   && existing->type->is_record()
		   && existing->type->record_compare(var->type)) {
		  existing->type = var->type;
	       } else {
		  linker_error(prog, "%s `%s' declared as type "
			       "`%s' and type `%s'\n",
			       mode_string(var),
			       var->name, var->type->name,
			       existing->type->name);
		  return;
	       }
	    }

	    if (var->data.explicit_location) {
	       if (existing->data.explicit_location
		   && (var->data.location != existing->data.location)) {
		     linker_error(prog, "explicit locations for %s "
				  "`%s' have differing values\n",
				  mode_string(var), var->name);
		     return;
	       }

	       existing->data.location = var->data.location;
	       existing->data.explicit_location = true;
	    }

            /* From the GLSL 4.20 specification:
             * "A link error will result if two compilation units in a program
             *  specify different integer-constant bindings for the same
             *  opaque-uniform name.  However, it is not an error to specify a
             *  binding on some but not all declarations for the same name"
             */
            if (var->data.explicit_binding) {
               if (existing->data.explicit_binding &&
                   var->data.binding != existing->data.binding) {
                  linker_error(prog, "explicit bindings for %s "
                               "`%s' have differing values\n",
                               mode_string(var), var->name);
                  return;
               }

               existing->data.binding = var->data.binding;
               existing->data.explicit_binding = true;
            }

            if (var->type->contains_atomic() &&
                var->data.atomic.offset != existing->data.atomic.offset) {
               linker_error(prog, "offset specifications for %s "
                            "`%s' have differing values\n",
                            mode_string(var), var->name);
               return;
            }

	    /* Validate layout qualifiers for gl_FragDepth.
	     *
	     * From the AMD/ARB_conservative_depth specs:
	     *
	     *    "If gl_FragDepth is redeclared in any fragment shader in a
	     *    program, it must be redeclared in all fragment shaders in
	     *    that program that have static assignments to
	     *    gl_FragDepth. All redeclarations of gl_FragDepth in all
	     *    fragment shaders in a single program must have the same set
	     *    of qualifiers."
	     */
	    if (strcmp(var->name, "gl_FragDepth") == 0) {
	       bool layout_declared = var->data.depth_layout != ir_depth_layout_none;
	       bool layout_differs =
		  var->data.depth_layout != existing->data.depth_layout;

	       if (layout_declared && layout_differs) {
		  linker_error(prog,
			       "All redeclarations of gl_FragDepth in all "
			       "fragment shaders in a single program must have "
			       "the same set of qualifiers.\n");
	       }

	       if (var->data.used && layout_differs) {
		  linker_error(prog,
			       "If gl_FragDepth is redeclared with a layout "
			       "qualifier in any fragment shader, it must be "
			       "redeclared with the same layout qualifier in "
			       "all fragment shaders that have assignments to "
			       "gl_FragDepth\n");
	       }
	    }

	    /* Page 35 (page 41 of the PDF) of the GLSL 4.20 spec says:
	     *
	     *     "If a shared global has multiple initializers, the
	     *     initializers must all be constant expressions, and they
	     *     must all have the same value. Otherwise, a link error will
	     *     result. (A shared global having only one initializer does
	     *     not require that initializer to be a constant expression.)"
	     *
	     * Previous to 4.20 the GLSL spec simply said that initializers
	     * must have the same value.  In this case of non-constant
	     * initializers, this was impossible to determine.  As a result,
	     * no vendor actually implemented that behavior.  The 4.20
	     * behavior matches the implemented behavior of at least one other
	     * vendor, so we'll implement that for all GLSL versions.
	     */
	    if (var->constant_initializer != NULL) {
	       if (existing->constant_initializer != NULL) {
		  if (!var->constant_initializer->has_value(existing->constant_initializer)) {
		     linker_error(prog, "initializers for %s "
				  "`%s' have differing values\n",
				  mode_string(var), var->name);
		     return;
		  }
	       } else {
		  /* If the first-seen instance of a particular uniform did not
		   * have an initializer but a later instance does, copy the
		   * initializer to the version stored in the symbol table.
		   */
		  /* FINISHME: This is wrong.  The constant_value field should
		   * FINISHME: not be modified!  Imagine a case where a shader
		   * FINISHME: without an initializer is linked in two different
		   * FINISHME: programs with shaders that have differing
		   * FINISHME: initializers.  Linking with the first will
		   * FINISHME: modify the shader, and linking with the second
		   * FINISHME: will fail.
		   */
		  existing->constant_initializer =
		     var->constant_initializer->clone(ralloc_parent(existing),
						      NULL);
	       }
	    }

	    if (var->data.has_initializer) {
	       if (existing->data.has_initializer
		   && (var->constant_initializer == NULL
		       || existing->constant_initializer == NULL)) {
		  linker_error(prog,
			       "shared global variable `%s' has multiple "
			       "non-constant initializers.\n",
			       var->name);
		  return;
	       }

	       /* Some instance had an initializer, so keep track of that.  In
		* this location, all sorts of initializers (constant or
		* otherwise) will propagate the existence to the variable
		* stored in the symbol table.
		*/
	       existing->data.has_initializer = true;
	    }

	    if (existing->data.invariant != var->data.invariant) {
	       linker_error(prog, "declarations for %s `%s' have "
			    "mismatching invariant qualifiers\n",
			    mode_string(var), var->name);
	       return;
	    }
            if (existing->data.centroid != var->data.centroid) {
               linker_error(prog, "declarations for %s `%s' have "
			    "mismatching centroid qualifiers\n",
			    mode_string(var), var->name);
               return;
            }
            if (existing->data.sample != var->data.sample) {
               linker_error(prog, "declarations for %s `%s` have "
                            "mismatching sample qualifiers\n",
                            mode_string(var), var->name);
               return;
            }
	 } else
	    variables.add_variable(var);
      }
   }
}


/**
 * Perform validation of uniforms used across multiple shader stages
 */
void
cross_validate_uniforms(struct gl_shader_program *prog)
{
   cross_validate_globals(prog, prog->_LinkedShaders,
                          MESA_SHADER_STAGES, true);
}

/**
 * Accumulates the array of prog->UniformBlocks and checks that all
 * definitons of blocks agree on their contents.
 */
static bool
interstage_cross_validate_uniform_blocks(struct gl_shader_program *prog)
{
   unsigned max_num_uniform_blocks = 0;
   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
      if (prog->_LinkedShaders[i])
	 max_num_uniform_blocks += prog->_LinkedShaders[i]->NumUniformBlocks;
   }

   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
      struct gl_shader *sh = prog->_LinkedShaders[i];

      prog->UniformBlockStageIndex[i] = ralloc_array(prog, int,
						     max_num_uniform_blocks);
      for (unsigned int j = 0; j < max_num_uniform_blocks; j++)
	 prog->UniformBlockStageIndex[i][j] = -1;

      if (sh == NULL)
	 continue;

      for (unsigned int j = 0; j < sh->NumUniformBlocks; j++) {
	 int index = link_cross_validate_uniform_block(prog,
						       &prog->UniformBlocks,
						       &prog->NumUniformBlocks,
						       &sh->UniformBlocks[j]);

	 if (index == -1) {
	    linker_error(prog, "uniform block `%s' has mismatching definitions\n",
			 sh->UniformBlocks[j].Name);
	    return false;
	 }

	 prog->UniformBlockStageIndex[i][index] = j;
      }
   }

   return true;
}


/**
 * Populates a shaders symbol table with all global declarations
 */
static void
populate_symbol_table(gl_shader *sh)
{
   sh->symbols = new(sh) glsl_symbol_table;

   foreach_in_list(ir_instruction, inst, sh->ir) {
      ir_variable *var;
      ir_function *func;

      if ((func = inst->as_function()) != NULL) {
	 sh->symbols->add_function(func);
      } else if ((var = inst->as_variable()) != NULL) {
         if (var->data.mode != ir_var_temporary)
            sh->symbols->add_variable(var);
      }
   }
}


/**
 * Remap variables referenced in an instruction tree
 *
 * This is used when instruction trees are cloned from one shader and placed in
 * another.  These trees will contain references to \c ir_variable nodes that
 * do not exist in the target shader.  This function finds these \c ir_variable
 * references and replaces the references with matching variables in the target
 * shader.
 *
 * If there is no matching variable in the target shader, a clone of the
 * \c ir_variable is made and added to the target shader.  The new variable is
 * added to \b both the instruction stream and the symbol table.
 *
 * \param inst         IR tree that is to be processed.
 * \param symbols      Symbol table containing global scope symbols in the
 *                     linked shader.
 * \param instructions Instruction stream where new variable declarations
 *                     should be added.
 */
void
remap_variables(ir_instruction *inst, struct gl_shader *target,
		hash_table *temps)
{
   class remap_visitor : public ir_hierarchical_visitor {
   public:
	 remap_visitor(struct gl_shader *target,
		    hash_table *temps)
      {
	 this->target = target;
	 this->symbols = target->symbols;
	 this->instructions = target->ir;
	 this->temps = temps;
      }

      virtual ir_visitor_status visit(ir_dereference_variable *ir)
      {
	 if (ir->var->data.mode == ir_var_temporary) {
	    ir_variable *var = (ir_variable *) hash_table_find(temps, ir->var);

	    assert(var != NULL);
	    ir->var = var;
	    return visit_continue;
	 }

	 ir_variable *const existing =
	    this->symbols->get_variable(ir->var->name);
	 if (existing != NULL)
	    ir->var = existing;
	 else {
	    ir_variable *copy = ir->var->clone(this->target, NULL);

	    this->symbols->add_variable(copy);
	    this->instructions->push_head(copy);
	    ir->var = copy;
	 }

	 return visit_continue;
      }

   private:
      struct gl_shader *target;
      glsl_symbol_table *symbols;
      exec_list *instructions;
      hash_table *temps;
   };

   remap_visitor v(target, temps);

   inst->accept(&v);
}


/**
 * Move non-declarations from one instruction stream to another
 *
 * The intended usage pattern of this function is to pass the pointer to the
 * head sentinel of a list (i.e., a pointer to the list cast to an \c exec_node
 * pointer) for \c last and \c false for \c make_copies on the first
 * call.  Successive calls pass the return value of the previous call for
 * \c last and \c true for \c make_copies.
 *
 * \param instructions Source instruction stream
 * \param last         Instruction after which new instructions should be
 *                     inserted in the target instruction stream
 * \param make_copies  Flag selecting whether instructions in \c instructions
 *                     should be copied (via \c ir_instruction::clone) into the
 *                     target list or moved.
 *
 * \return
 * The new "last" instruction in the target instruction stream.  This pointer
 * is suitable for use as the \c last parameter of a later call to this
 * function.
 */
exec_node *
move_non_declarations(exec_list *instructions, exec_node *last,
		      bool make_copies, gl_shader *target)
{
   hash_table *temps = NULL;

   if (make_copies)
      temps = hash_table_ctor(0, hash_table_pointer_hash,
			      hash_table_pointer_compare);

   foreach_in_list_safe(ir_instruction, inst, instructions) {
      if (inst->as_function())
	 continue;

      ir_variable *var = inst->as_variable();
      if ((var != NULL) && (var->data.mode != ir_var_temporary))
	 continue;

      assert(inst->as_assignment()
             || inst->as_call()
             || inst->as_if() /* for initializers with the ?: operator */
	     || ((var != NULL) && (var->data.mode == ir_var_temporary)));

      if (make_copies) {
	 inst = inst->clone(target, NULL);

	 if (var != NULL)
	    hash_table_insert(temps, inst, var);
	 else
	    remap_variables(inst, target, temps);
      } else {
	 inst->remove();
      }

      last->insert_after(inst);
      last = inst;
   }

   if (make_copies)
      hash_table_dtor(temps);

   return last;
}

/**
 * Get the function signature for main from a shader
 */
ir_function_signature *
link_get_main_function_signature(gl_shader *sh)
{
   ir_function *const f = sh->symbols->get_function("main");
   if (f != NULL) {
      exec_list void_parameters;

      /* Look for the 'void main()' signature and ensure that it's defined.
       * This keeps the linker from accidentally pick a shader that just
       * contains a prototype for main.
       *
       * We don't have to check for multiple definitions of main (in multiple
       * shaders) because that would have already been caught above.
       */
      ir_function_signature *sig =
         f->matching_signature(NULL, &void_parameters, false);
      if ((sig != NULL) && sig->is_defined) {
	 return sig;
      }
   }

   return NULL;
}


/**
 * This class is only used in link_intrastage_shaders() below but declaring
 * it inside that function leads to compiler warnings with some versions of
 * gcc.
 */
class array_sizing_visitor : public ir_hierarchical_visitor {
public:
   array_sizing_visitor()
      : mem_ctx(ralloc_context(NULL)),
        unnamed_interfaces(hash_table_ctor(0, hash_table_pointer_hash,
                                           hash_table_pointer_compare))
   {
   }

   ~array_sizing_visitor()
   {
      hash_table_dtor(this->unnamed_interfaces);
      ralloc_free(this->mem_ctx);
   }

   virtual ir_visitor_status visit(ir_variable *var)
   {
      fixup_type(&var->type, var->data.max_array_access);
      if (var->type->is_interface()) {
         if (interface_contains_unsized_arrays(var->type)) {
            const glsl_type *new_type =
               resize_interface_members(var->type,
                                        var->get_max_ifc_array_access());
            var->type = new_type;
            var->change_interface_type(new_type);
         }
      } else if (var->type->is_array() &&
                 var->type->fields.array->is_interface()) {
         if (interface_contains_unsized_arrays(var->type->fields.array)) {
            const glsl_type *new_type =
               resize_interface_members(var->type->fields.array,
                                        var->get_max_ifc_array_access());
            var->change_interface_type(new_type);
            var->type =
               glsl_type::get_array_instance(new_type, var->type->length);
         }
      } else if (const glsl_type *ifc_type = var->get_interface_type()) {
         /* Store a pointer to the variable in the unnamed_interfaces
          * hashtable.
          */
         ir_variable **interface_vars = (ir_variable **)
            hash_table_find(this->unnamed_interfaces, ifc_type);
         if (interface_vars == NULL) {
            interface_vars = rzalloc_array(mem_ctx, ir_variable *,
                                           ifc_type->length);
            hash_table_insert(this->unnamed_interfaces, interface_vars,
                              ifc_type);
         }
         unsigned index = ifc_type->field_index(var->name);
         assert(index < ifc_type->length);
         assert(interface_vars[index] == NULL);
         interface_vars[index] = var;
      }
      return visit_continue;
   }

   /**
    * For each unnamed interface block that was discovered while running the
    * visitor, adjust the interface type to reflect the newly assigned array
    * sizes, and fix up the ir_variable nodes to point to the new interface
    * type.
    */
   void fixup_unnamed_interface_types()
   {
      hash_table_call_foreach(this->unnamed_interfaces,
                              fixup_unnamed_interface_type, NULL);
   }

private:
   /**
    * If the type pointed to by \c type represents an unsized array, replace
    * it with a sized array whose size is determined by max_array_access.
    */
   static void fixup_type(const glsl_type **type, unsigned max_array_access)
   {
      if ((*type)->is_unsized_array()) {
         *type = glsl_type::get_array_instance((*type)->fields.array,
                                               max_array_access + 1);
         assert(*type != NULL);
      }
   }

   /**
    * Determine whether the given interface type contains unsized arrays (if
    * it doesn't, array_sizing_visitor doesn't need to process it).
    */
   static bool interface_contains_unsized_arrays(const glsl_type *type)
   {
      for (unsigned i = 0; i < type->length; i++) {
         const glsl_type *elem_type = type->fields.structure[i].type;
         if (elem_type->is_unsized_array())
            return true;
      }
      return false;
   }

   /**
    * Create a new interface type based on the given type, with unsized arrays
    * replaced by sized arrays whose size is determined by
    * max_ifc_array_access.
    */
   static const glsl_type *
   resize_interface_members(const glsl_type *type,
                            const unsigned *max_ifc_array_access)
   {
      unsigned num_fields = type->length;
      glsl_struct_field *fields = new glsl_struct_field[num_fields];
      memcpy(fields, type->fields.structure,
             num_fields * sizeof(*fields));
      for (unsigned i = 0; i < num_fields; i++) {
         fixup_type(&fields[i].type, max_ifc_array_access[i]);
      }
      glsl_interface_packing packing =
         (glsl_interface_packing) type->interface_packing;
      const glsl_type *new_ifc_type =
         glsl_type::get_interface_instance(fields, num_fields,
                                           packing, type->name);
      delete [] fields;
      return new_ifc_type;
   }

   static void fixup_unnamed_interface_type(const void *key, void *data,
                                            void *)
   {
      const glsl_type *ifc_type = (const glsl_type *) key;
      ir_variable **interface_vars = (ir_variable **) data;
      unsigned num_fields = ifc_type->length;
      glsl_struct_field *fields = new glsl_struct_field[num_fields];
      memcpy(fields, ifc_type->fields.structure,
             num_fields * sizeof(*fields));
      bool interface_type_changed = false;
      for (unsigned i = 0; i < num_fields; i++) {
         if (interface_vars[i] != NULL &&
             fields[i].type != interface_vars[i]->type) {
            fields[i].type = interface_vars[i]->type;
            interface_type_changed = true;
         }
      }
      if (!interface_type_changed) {
         delete [] fields;
         return;
      }
      glsl_interface_packing packing =
         (glsl_interface_packing) ifc_type->interface_packing;
      const glsl_type *new_ifc_type =
         glsl_type::get_interface_instance(fields, num_fields, packing,
                                           ifc_type->name);
      delete [] fields;
      for (unsigned i = 0; i < num_fields; i++) {
         if (interface_vars[i] != NULL)
            interface_vars[i]->change_interface_type(new_ifc_type);
      }
   }

   /**
    * Memory context used to allocate the data in \c unnamed_interfaces.
    */
   void *mem_ctx;

   /**
    * Hash table from const glsl_type * to an array of ir_variable *'s
    * pointing to the ir_variables constituting each unnamed interface block.
    */
   hash_table *unnamed_interfaces;
};

/**
 * Performs the cross-validation of layout qualifiers specified in
 * redeclaration of gl_FragCoord for the attached fragment shaders,
 * and propagates them to the linked FS and linked shader program.
 */
static void
link_fs_input_layout_qualifiers(struct gl_shader_program *prog,
	                        struct gl_shader *linked_shader,
	                        struct gl_shader **shader_list,
	                        unsigned num_shaders)
{
   linked_shader->redeclares_gl_fragcoord = false;
   linked_shader->uses_gl_fragcoord = false;
   linked_shader->origin_upper_left = false;
   linked_shader->pixel_center_integer = false;

   if (linked_shader->Stage != MESA_SHADER_FRAGMENT ||
       (prog->Version < 150 && !prog->ARB_fragment_coord_conventions_enable))
      return;

   for (unsigned i = 0; i < num_shaders; i++) {
      struct gl_shader *shader = shader_list[i];
      /* From the GLSL 1.50 spec, page 39:
       *
       *   "If gl_FragCoord is redeclared in any fragment shader in a program,
       *    it must be redeclared in all the fragment shaders in that program
       *    that have a static use gl_FragCoord."
       */
      if ((linked_shader->redeclares_gl_fragcoord
           && !shader->redeclares_gl_fragcoord
           && shader->uses_gl_fragcoord)
          || (shader->redeclares_gl_fragcoord
              && !linked_shader->redeclares_gl_fragcoord
              && linked_shader->uses_gl_fragcoord)) {
             linker_error(prog, "fragment shader defined with conflicting "
                         "layout qualifiers for gl_FragCoord\n");
      }

      /* From the GLSL 1.50 spec, page 39:
       *
       *   "All redeclarations of gl_FragCoord in all fragment shaders in a
       *    single program must have the same set of qualifiers."
       */
      if (linked_shader->redeclares_gl_fragcoord && shader->redeclares_gl_fragcoord
          && (shader->origin_upper_left != linked_shader->origin_upper_left
          || shader->pixel_center_integer != linked_shader->pixel_center_integer)) {
         linker_error(prog, "fragment shader defined with conflicting "
                      "layout qualifiers for gl_FragCoord\n");
      }

      /* Update the linked shader state.  Note that uses_gl_fragcoord should
       * accumulate the results.  The other values should replace.  If there
       * are multiple redeclarations, all the fields except uses_gl_fragcoord
       * are already known to be the same.
       */
      if (shader->redeclares_gl_fragcoord || shader->uses_gl_fragcoord) {
         linked_shader->redeclares_gl_fragcoord =
            shader->redeclares_gl_fragcoord;
         linked_shader->uses_gl_fragcoord = linked_shader->uses_gl_fragcoord
            || shader->uses_gl_fragcoord;
         linked_shader->origin_upper_left = shader->origin_upper_left;
         linked_shader->pixel_center_integer = shader->pixel_center_integer;
      }
   }
}

/**
 * Performs the cross-validation of geometry shader max_vertices and
 * primitive type layout qualifiers for the attached geometry shaders,
 * and propagates them to the linked GS and linked shader program.
 */
static void
link_gs_inout_layout_qualifiers(struct gl_shader_program *prog,
				struct gl_shader *linked_shader,
				struct gl_shader **shader_list,
				unsigned num_shaders)
{
   linked_shader->Geom.VerticesOut = 0;
   linked_shader->Geom.Invocations = 0;
   linked_shader->Geom.InputType = PRIM_UNKNOWN;
   linked_shader->Geom.OutputType = PRIM_UNKNOWN;

   /* No in/out qualifiers defined for anything but GLSL 1.50+
    * geometry shaders so far.
    */
   if (linked_shader->Stage != MESA_SHADER_GEOMETRY || prog->Version < 150)
      return;

   /* From the GLSL 1.50 spec, page 46:
    *
    *     "All geometry shader output layout declarations in a program
    *      must declare the same layout and same value for
    *      max_vertices. There must be at least one geometry output
    *      layout declaration somewhere in a program, but not all
    *      geometry shaders (compilation units) are required to
    *      declare it."
    */

   for (unsigned i = 0; i < num_shaders; i++) {
      struct gl_shader *shader = shader_list[i];

      if (shader->Geom.InputType != PRIM_UNKNOWN) {
	 if (linked_shader->Geom.InputType != PRIM_UNKNOWN &&
	     linked_shader->Geom.InputType != shader->Geom.InputType) {
	    linker_error(prog, "geometry shader defined with conflicting "
			 "input types\n");
	    return;
	 }
	 linked_shader->Geom.InputType = shader->Geom.InputType;
      }

      if (shader->Geom.OutputType != PRIM_UNKNOWN) {
	 if (linked_shader->Geom.OutputType != PRIM_UNKNOWN &&
	     linked_shader->Geom.OutputType != shader->Geom.OutputType) {
	    linker_error(prog, "geometry shader defined with conflicting "
			 "output types\n");
	    return;
	 }
	 linked_shader->Geom.OutputType = shader->Geom.OutputType;
      }

      if (shader->Geom.VerticesOut != 0) {
	 if (linked_shader->Geom.VerticesOut != 0 &&
	     linked_shader->Geom.VerticesOut != shader->Geom.VerticesOut) {
	    linker_error(prog, "geometry shader defined with conflicting "
			 "output vertex count (%d and %d)\n",
			 linked_shader->Geom.VerticesOut,
			 shader->Geom.VerticesOut);
	    return;
	 }
	 linked_shader->Geom.VerticesOut = shader->Geom.VerticesOut;
      }

      if (shader->Geom.Invocations != 0) {
	 if (linked_shader->Geom.Invocations != 0 &&
	     linked_shader->Geom.Invocations != shader->Geom.Invocations) {
	    linker_error(prog, "geometry shader defined with conflicting "
			 "invocation count (%d and %d)\n",
			 linked_shader->Geom.Invocations,
			 shader->Geom.Invocations);
	    return;
	 }
	 linked_shader->Geom.Invocations = shader->Geom.Invocations;
      }
   }

   /* Just do the intrastage -> interstage propagation right now,
    * since we already know we're in the right type of shader program
    * for doing it.
    */
   if (linked_shader->Geom.InputType == PRIM_UNKNOWN) {
      linker_error(prog,
		   "geometry shader didn't declare primitive input type\n");
      return;
   }
   prog->Geom.InputType = linked_shader->Geom.InputType;

   if (linked_shader->Geom.OutputType == PRIM_UNKNOWN) {
      linker_error(prog,
		   "geometry shader didn't declare primitive output type\n");
      return;
   }
   prog->Geom.OutputType = linked_shader->Geom.OutputType;

   if (linked_shader->Geom.VerticesOut == 0) {
      linker_error(prog,
		   "geometry shader didn't declare max_vertices\n");
      return;
   }
   prog->Geom.VerticesOut = linked_shader->Geom.VerticesOut;

   if (linked_shader->Geom.Invocations == 0)
      linked_shader->Geom.Invocations = 1;

   prog->Geom.Invocations = linked_shader->Geom.Invocations;
}


/**
 * Perform cross-validation of compute shader local_size_{x,y,z} layout
 * qualifiers for the attached compute shaders, and propagate them to the
 * linked CS and linked shader program.
 */
static void
link_cs_input_layout_qualifiers(struct gl_shader_program *prog,
                                struct gl_shader *linked_shader,
                                struct gl_shader **shader_list,
                                unsigned num_shaders)
{
   for (int i = 0; i < 3; i++)
      linked_shader->Comp.LocalSize[i] = 0;

   /* This function is called for all shader stages, but it only has an effect
    * for compute shaders.
    */
   if (linked_shader->Stage != MESA_SHADER_COMPUTE)
      return;

   /* From the ARB_compute_shader spec, in the section describing local size
    * declarations:
    *
    *     If multiple compute shaders attached to a single program object
    *     declare local work-group size, the declarations must be identical;
    *     otherwise a link-time error results. Furthermore, if a program
    *     object contains any compute shaders, at least one must contain an
    *     input layout qualifier specifying the local work sizes of the
    *     program, or a link-time error will occur.
    */
   for (unsigned sh = 0; sh < num_shaders; sh++) {
      struct gl_shader *shader = shader_list[sh];

      if (shader->Comp.LocalSize[0] != 0) {
         if (linked_shader->Comp.LocalSize[0] != 0) {
            for (int i = 0; i < 3; i++) {
               if (linked_shader->Comp.LocalSize[i] !=
                   shader->Comp.LocalSize[i]) {
                  linker_error(prog, "compute shader defined with conflicting "
                               "local sizes\n");
                  return;
               }
            }
         }
         for (int i = 0; i < 3; i++)
            linked_shader->Comp.LocalSize[i] = shader->Comp.LocalSize[i];
      }
   }

   /* Just do the intrastage -> interstage propagation right now,
    * since we already know we're in the right type of shader program
    * for doing it.
    */
   if (linked_shader->Comp.LocalSize[0] == 0) {
      linker_error(prog, "compute shader didn't declare local size\n");
      return;
   }
   for (int i = 0; i < 3; i++)
      prog->Comp.LocalSize[i] = linked_shader->Comp.LocalSize[i];
}


/**
 * Combine a group of shaders for a single stage to generate a linked shader
 *
 * \note
 * If this function is supplied a single shader, it is cloned, and the new
 * shader is returned.
 */
static struct gl_shader *
link_intrastage_shaders(void *mem_ctx,
			struct gl_context *ctx,
			struct gl_shader_program *prog,
			struct gl_shader **shader_list,
			unsigned num_shaders)
{
   struct gl_uniform_block *uniform_blocks = NULL;

   /* Check that global variables defined in multiple shaders are consistent.
    */
   cross_validate_globals(prog, shader_list, num_shaders, false);
   if (!prog->LinkStatus)
      return NULL;

   /* Check that interface blocks defined in multiple shaders are consistent.
    */
   validate_intrastage_interface_blocks(prog, (const gl_shader **)shader_list,
                                        num_shaders);
   if (!prog->LinkStatus)
      return NULL;

   /* Link up uniform blocks defined within this stage. */
   const unsigned num_uniform_blocks =
      link_uniform_blocks(mem_ctx, prog, shader_list, num_shaders,
                          &uniform_blocks);
   if (!prog->LinkStatus)
      return NULL;

   /* Check that there is only a single definition of each function signature
    * across all shaders.
    */
   for (unsigned i = 0; i < (num_shaders - 1); i++) {
      foreach_in_list(ir_instruction, node, shader_list[i]->ir) {
	 ir_function *const f = node->as_function();

	 if (f == NULL)
	    continue;

	 for (unsigned j = i + 1; j < num_shaders; j++) {
	    ir_function *const other =
	       shader_list[j]->symbols->get_function(f->name);

	    /* If the other shader has no function (and therefore no function
	     * signatures) with the same name, skip to the next shader.
	     */
	    if (other == NULL)
	       continue;

	    foreach_in_list(ir_function_signature, sig, &f->signatures) {
	       if (!sig->is_defined || sig->is_builtin())
		  continue;

	       ir_function_signature *other_sig =
		  other->exact_matching_signature(NULL, &sig->parameters);

	       if ((other_sig != NULL) && other_sig->is_defined
		   && !other_sig->is_builtin()) {
		  linker_error(prog, "function `%s' is multiply defined\n",
			       f->name);
		  return NULL;
	       }
	    }
	 }
      }
   }

   /* Find the shader that defines main, and make a clone of it.
    *
    * Starting with the clone, search for undefined references.  If one is
    * found, find the shader that defines it.  Clone the reference and add
    * it to the shader.  Repeat until there are no undefined references or
    * until a reference cannot be resolved.
    */
   gl_shader *main = NULL;
   for (unsigned i = 0; i < num_shaders; i++) {
      if (link_get_main_function_signature(shader_list[i]) != NULL) {
	 main = shader_list[i];
	 break;
      }
   }

   if (main == NULL) {
      linker_error(prog, "%s shader lacks `main'\n",
		   _mesa_shader_stage_to_string(shader_list[0]->Stage));
      return NULL;
   }

   gl_shader *linked = ctx->Driver.NewShader(NULL, 0, main->Type);
   linked->ir = new(linked) exec_list;
   clone_ir_list(mem_ctx, linked->ir, main->ir);

   linked->UniformBlocks = uniform_blocks;
   linked->NumUniformBlocks = num_uniform_blocks;
   ralloc_steal(linked, linked->UniformBlocks);

   link_fs_input_layout_qualifiers(prog, linked, shader_list, num_shaders);
   link_gs_inout_layout_qualifiers(prog, linked, shader_list, num_shaders);
   link_cs_input_layout_qualifiers(prog, linked, shader_list, num_shaders);

   populate_symbol_table(linked);

   /* The pointer to the main function in the final linked shader (i.e., the
    * copy of the original shader that contained the main function).
    */
   ir_function_signature *const main_sig =
      link_get_main_function_signature(linked);

   /* Move any instructions other than variable declarations or function
    * declarations into main.
    */
   exec_node *insertion_point =
      move_non_declarations(linked->ir, (exec_node *) &main_sig->body, false,
			    linked);

   for (unsigned i = 0; i < num_shaders; i++) {
      if (shader_list[i] == main)
	 continue;

      insertion_point = move_non_declarations(shader_list[i]->ir,
					      insertion_point, true, linked);
   }

   /* Check if any shader needs built-in functions. */
   bool need_builtins = false;
   for (unsigned i = 0; i < num_shaders; i++) {
      if (shader_list[i]->uses_builtin_functions) {
         need_builtins = true;
         break;
      }
   }

   bool ok;
   if (need_builtins) {
      /* Make a temporary array one larger than shader_list, which will hold
       * the built-in function shader as well.
       */
      gl_shader **linking_shaders = (gl_shader **)
         calloc(num_shaders + 1, sizeof(gl_shader *));

      ok = linking_shaders != NULL;

      if (ok) {
         memcpy(linking_shaders, shader_list, num_shaders * sizeof(gl_shader *));
         linking_shaders[num_shaders] = _mesa_glsl_get_builtin_function_shader();

         ok = link_function_calls(prog, linked, linking_shaders, num_shaders + 1);

         free(linking_shaders);
      } else {
         _mesa_error_no_memory(__func__);
      }
   } else {
      ok = link_function_calls(prog, linked, shader_list, num_shaders);
   }


   if (!ok) {
      ctx->Driver.DeleteShader(ctx, linked);
      return NULL;
   }

   /* At this point linked should contain all of the linked IR, so
    * validate it to make sure nothing went wrong.
    */
   validate_ir_tree(linked->ir);

   /* Set the size of geometry shader input arrays */
   if (linked->Stage == MESA_SHADER_GEOMETRY) {
      unsigned num_vertices = vertices_per_prim(prog->Geom.InputType);
      geom_array_resize_visitor input_resize_visitor(num_vertices, prog);
      foreach_in_list(ir_instruction, ir, linked->ir) {
         ir->accept(&input_resize_visitor);
      }
   }

   if (ctx->Const.VertexID_is_zero_based)
      lower_vertex_id(linked);

   /* Make a pass over all variable declarations to ensure that arrays with
    * unspecified sizes have a size specified.  The size is inferred from the
    * max_array_access field.
    */
   array_sizing_visitor v;
   v.run(linked->ir);
   v.fixup_unnamed_interface_types();

   return linked;
}

/**
 * Update the sizes of linked shader uniform arrays to the maximum
 * array index used.
 *
 * From page 81 (page 95 of the PDF) of the OpenGL 2.1 spec:
 *
 *     If one or more elements of an array are active,
 *     GetActiveUniform will return the name of the array in name,
 *     subject to the restrictions listed above. The type of the array
 *     is returned in type. The size parameter contains the highest
 *     array element index used, plus one. The compiler or linker
 *     determines the highest index used.  There will be only one
 *     active uniform reported by the GL per uniform array.

 */
static void
update_array_sizes(struct gl_shader_program *prog)
{
   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
	 if (prog->_LinkedShaders[i] == NULL)
	    continue;

      foreach_in_list(ir_instruction, node, prog->_LinkedShaders[i]->ir) {
	 ir_variable *const var = node->as_variable();

	 if ((var == NULL) || (var->data.mode != ir_var_uniform) ||
	     !var->type->is_array())
	    continue;

	 /* GL_ARB_uniform_buffer_object says that std140 uniforms
	  * will not be eliminated.  Since we always do std140, just
	  * don't resize arrays in UBOs.
          *
          * Atomic counters are supposed to get deterministic
          * locations assigned based on the declaration ordering and
          * sizes, array compaction would mess that up.
	  */
	 if (var->is_in_uniform_block() || var->type->contains_atomic())
	    continue;

	 unsigned int size = var->data.max_array_access;
	 for (unsigned j = 0; j < MESA_SHADER_STAGES; j++) {
	       if (prog->_LinkedShaders[j] == NULL)
		  continue;

	    foreach_in_list(ir_instruction, node2, prog->_LinkedShaders[j]->ir) {
	       ir_variable *other_var = node2->as_variable();
	       if (!other_var)
		  continue;

	       if (strcmp(var->name, other_var->name) == 0 &&
		   other_var->data.max_array_access > size) {
		  size = other_var->data.max_array_access;
	       }
	    }
	 }

	 if (size + 1 != var->type->length) {
	    /* If this is a built-in uniform (i.e., it's backed by some
	     * fixed-function state), adjust the number of state slots to
	     * match the new array size.  The number of slots per array entry
	     * is not known.  It seems safe to assume that the total number of
	     * slots is an integer multiple of the number of array elements.
	     * Determine the number of slots per array element by dividing by
	     * the old (total) size.
	     */
            const unsigned num_slots = var->get_num_state_slots();
	    if (num_slots > 0) {
	       var->set_num_state_slots((size + 1)
                                        * (num_slots / var->type->length));
	    }

	    var->type = glsl_type::get_array_instance(var->type->fields.array,
						      size + 1);
	    /* FINISHME: We should update the types of array
	     * dereferences of this variable now.
	     */
	 }
      }
   }
}

/**
 * Find a contiguous set of available bits in a bitmask.
 *
 * \param used_mask     Bits representing used (1) and unused (0) locations
 * \param needed_count  Number of contiguous bits needed.
 *
 * \return
 * Base location of the available bits on success or -1 on failure.
 */
int
find_available_slots(unsigned used_mask, unsigned needed_count)
{
   unsigned needed_mask = (1 << needed_count) - 1;
   const int max_bit_to_test = (8 * sizeof(used_mask)) - needed_count;

   /* The comparison to 32 is redundant, but without it GCC emits "warning:
    * cannot optimize possibly infinite loops" for the loop below.
    */
   if ((needed_count == 0) || (max_bit_to_test < 0) || (max_bit_to_test > 32))
      return -1;

   for (int i = 0; i <= max_bit_to_test; i++) {
      if ((needed_mask & ~used_mask) == needed_mask)
	 return i;

      needed_mask <<= 1;
   }

   return -1;
}


/**
 * Assign locations for either VS inputs or FS outputs
 *
 * \param prog          Shader program whose variables need locations assigned
 * \param target_index  Selector for the program target to receive location
 *                      assignmnets.  Must be either \c MESA_SHADER_VERTEX or
 *                      \c MESA_SHADER_FRAGMENT.
 * \param max_index     Maximum number of generic locations.  This corresponds
 *                      to either the maximum number of draw buffers or the
 *                      maximum number of generic attributes.
 *
 * \return
 * If locations are successfully assigned, true is returned.  Otherwise an
 * error is emitted to the shader link log and false is returned.
 */
bool
assign_attribute_or_color_locations(gl_shader_program *prog,
				    unsigned target_index,
				    unsigned max_index)
{
   /* Mark invalid locations as being used.
    */
   unsigned used_locations = (max_index >= 32)
      ? ~0 : ~((1 << max_index) - 1);

   assert((target_index == MESA_SHADER_VERTEX)
	  || (target_index == MESA_SHADER_FRAGMENT));

   gl_shader *const sh = prog->_LinkedShaders[target_index];
   if (sh == NULL)
      return true;

   /* Operate in a total of four passes.
    *
    * 1. Invalidate the location assignments for all vertex shader inputs.
    *
    * 2. Assign locations for inputs that have user-defined (via
    *    glBindVertexAttribLocation) locations and outputs that have
    *    user-defined locations (via glBindFragDataLocation).
    *
    * 3. Sort the attributes without assigned locations by number of slots
    *    required in decreasing order.  Fragmentation caused by attribute
    *    locations assigned by the application may prevent large attributes
    *    from having enough contiguous space.
    *
    * 4. Assign locations to any inputs without assigned locations.
    */

   const int generic_base = (target_index == MESA_SHADER_VERTEX)
      ? (int) VERT_ATTRIB_GENERIC0 : (int) FRAG_RESULT_DATA0;

   const enum ir_variable_mode direction =
      (target_index == MESA_SHADER_VERTEX)
      ? ir_var_shader_in : ir_var_shader_out;


   /* Temporary storage for the set of attributes that need locations assigned.
    */
   struct temp_attr {
      unsigned slots;
      ir_variable *var;

      /* Used below in the call to qsort. */
      static int compare(const void *a, const void *b)
      {
	 const temp_attr *const l = (const temp_attr *) a;
	 const temp_attr *const r = (const temp_attr *) b;

	 /* Reversed because we want a descending order sort below. */
	 return r->slots - l->slots;
      }
   } to_assign[16];

   unsigned num_attr = 0;

   foreach_in_list(ir_instruction, node, sh->ir) {
      ir_variable *const var = node->as_variable();

      if ((var == NULL) || (var->data.mode != (unsigned) direction))
	 continue;

      if (var->data.explicit_location) {
	 if ((var->data.location >= (int)(max_index + generic_base))
	     || (var->data.location < 0)) {
	    linker_error(prog,
			 "invalid explicit location %d specified for `%s'\n",
			 (var->data.location < 0)
			 ? var->data.location
                         : var->data.location - generic_base,
			 var->name);
	    return false;
	 }
      } else if (target_index == MESA_SHADER_VERTEX) {
	 unsigned binding;

	 if (prog->AttributeBindings->get(binding, var->name)) {
	    assert(binding >= VERT_ATTRIB_GENERIC0);
	    var->data.location = binding;
            var->data.is_unmatched_generic_inout = 0;
	 }
      } else if (target_index == MESA_SHADER_FRAGMENT) {
	 unsigned binding;
	 unsigned index;

	 if (prog->FragDataBindings->get(binding, var->name)) {
	    assert(binding >= FRAG_RESULT_DATA0);
	    var->data.location = binding;
            var->data.is_unmatched_generic_inout = 0;

	    if (prog->FragDataIndexBindings->get(index, var->name)) {
	       var->data.index = index;
	    }
	 }
      }

      /* If the variable is not a built-in and has a location statically
       * assigned in the shader (presumably via a layout qualifier), make sure
       * that it doesn't collide with other assigned locations.  Otherwise,
       * add it to the list of variables that need linker-assigned locations.
       */
      const unsigned slots = var->type->count_attribute_slots();
      if (var->data.location != -1) {
	 if (var->data.location >= generic_base && var->data.index < 1) {
	    /* From page 61 of the OpenGL 4.0 spec:
	     *
	     *     "LinkProgram will fail if the attribute bindings assigned
	     *     by BindAttribLocation do not leave not enough space to
	     *     assign a location for an active matrix attribute or an
	     *     active attribute array, both of which require multiple
	     *     contiguous generic attributes."
	     *
	     * I think above text prohibits the aliasing of explicit and
	     * automatic assignments. But, aliasing is allowed in manual
	     * assignments of attribute locations. See below comments for
	     * the details.
	     *
	     * From OpenGL 4.0 spec, page 61:
	     *
	     *     "It is possible for an application to bind more than one
	     *     attribute name to the same location. This is referred to as
	     *     aliasing. This will only work if only one of the aliased
	     *     attributes is active in the executable program, or if no
	     *     path through the shader consumes more than one attribute of
	     *     a set of attributes aliased to the same location. A link
	     *     error can occur if the linker determines that every path
	     *     through the shader consumes multiple aliased attributes,
	     *     but implementations are not required to generate an error
	     *     in this case."
	     *
	     * From GLSL 4.30 spec, page 54:
	     *
	     *    "A program will fail to link if any two non-vertex shader
	     *     input variables are assigned to the same location. For
	     *     vertex shaders, multiple input variables may be assigned
	     *     to the same location using either layout qualifiers or via
	     *     the OpenGL API. However, such aliasing is intended only to
	     *     support vertex shaders where each execution path accesses
	     *     at most one input per each location. Implementations are
	     *     permitted, but not required, to generate link-time errors
	     *     if they detect that every path through the vertex shader
	     *     executable accesses multiple inputs assigned to any single
	     *     location. For all shader types, a program will fail to link
	     *     if explicit location assignments leave the linker unable
	     *     to find space for other variables without explicit
	     *     assignments."
	     *
	     * From OpenGL ES 3.0 spec, page 56:
	     *
	     *    "Binding more than one attribute name to the same location
	     *     is referred to as aliasing, and is not permitted in OpenGL
	     *     ES Shading Language 3.00 vertex shaders. LinkProgram will
	     *     fail when this condition exists. However, aliasing is
	     *     possible in OpenGL ES Shading Language 1.00 vertex shaders.
	     *     This will only work if only one of the aliased attributes
	     *     is active in the executable program, or if no path through
	     *     the shader consumes more than one attribute of a set of
	     *     attributes aliased to the same location. A link error can
	     *     occur if the linker determines that every path through the
	     *     shader consumes multiple aliased attributes, but implemen-
	     *     tations are not required to generate an error in this case."
	     *
	     * After looking at above references from OpenGL, OpenGL ES and
	     * GLSL specifications, we allow aliasing of vertex input variables
	     * in: OpenGL 2.0 (and above) and OpenGL ES 2.0.
	     *
	     * NOTE: This is not required by the spec but its worth mentioning
	     * here that we're not doing anything to make sure that no path
	     * through the vertex shader executable accesses multiple inputs
	     * assigned to any single location.
	     */

	    /* Mask representing the contiguous slots that will be used by
	     * this attribute.
	     */
	    const unsigned attr = var->data.location - generic_base;
	    const unsigned use_mask = (1 << slots) - 1;
            const char *const string = (target_index == MESA_SHADER_VERTEX)
               ? "vertex shader input" : "fragment shader output";

            /* Generate a link error if the requested locations for this
             * attribute exceed the maximum allowed attribute location.
             */
            if (attr + slots > max_index) {
               linker_error(prog,
                           "insufficient contiguous locations "
                           "available for %s `%s' %d %d %d\n", string,
                           var->name, used_locations, use_mask, attr);
               return false;
            }

	    /* Generate a link error if the set of bits requested for this
	     * attribute overlaps any previously allocated bits.
	     */
	    if ((~(use_mask << attr) & used_locations) != used_locations) {
               if (target_index == MESA_SHADER_FRAGMENT ||
                   (prog->IsES && prog->Version >= 300)) {
                  linker_error(prog,
                               "overlapping location is assigned "
                               "to %s `%s' %d %d %d\n", string,
                               var->name, used_locations, use_mask, attr);
                  return false;
               } else {
                  linker_warning(prog,
                                 "overlapping location is assigned "
                                 "to %s `%s' %d %d %d\n", string,
                                 var->name, used_locations, use_mask, attr);
               }
	    }

	    used_locations |= (use_mask << attr);
	 }

	 continue;
      }

      to_assign[num_attr].slots = slots;
      to_assign[num_attr].var = var;
      num_attr++;
   }

   /* If all of the attributes were assigned locations by the application (or
    * are built-in attributes with fixed locations), return early.  This should
    * be the common case.
    */
   if (num_attr == 0)
      return true;

   qsort(to_assign, num_attr, sizeof(to_assign[0]), temp_attr::compare);

   if (target_index == MESA_SHADER_VERTEX) {
      /* VERT_ATTRIB_GENERIC0 is a pseudo-alias for VERT_ATTRIB_POS.  It can
       * only be explicitly assigned by via glBindAttribLocation.  Mark it as
       * reserved to prevent it from being automatically allocated below.
       */
      find_deref_visitor find("gl_Vertex");
      find.run(sh->ir);
      if (find.variable_found())
	 used_locations |= (1 << 0);
   }

   for (unsigned i = 0; i < num_attr; i++) {
      /* Mask representing the contiguous slots that will be used by this
       * attribute.
       */
      const unsigned use_mask = (1 << to_assign[i].slots) - 1;

      int location = find_available_slots(used_locations, to_assign[i].slots);

      if (location < 0) {
	 const char *const string = (target_index == MESA_SHADER_VERTEX)
	    ? "vertex shader input" : "fragment shader output";

	 linker_error(prog,
		      "insufficient contiguous locations "
		      "available for %s `%s'\n",
		      string, to_assign[i].var->name);
	 return false;
      }

      to_assign[i].var->data.location = generic_base + location;
      to_assign[i].var->data.is_unmatched_generic_inout = 0;
      used_locations |= (use_mask << location);
   }

   return true;
}


/**
 * Demote shader inputs and outputs that are not used in other stages
 */
void
demote_shader_inputs_and_outputs(gl_shader *sh, enum ir_variable_mode mode)
{
   foreach_in_list(ir_instruction, node, sh->ir) {
      ir_variable *const var = node->as_variable();

      if ((var == NULL) || (var->data.mode != int(mode)))
	 continue;

      /* A shader 'in' or 'out' variable is only really an input or output if
       * its value is used by other shader stages.  This will cause the variable
       * to have a location assigned.
       */
      if (var->data.is_unmatched_generic_inout) {
         assert(var->data.mode != ir_var_temporary);
	 var->data.mode = ir_var_auto;
      }
   }
}


/**
 * Store the gl_FragDepth layout in the gl_shader_program struct.
 */
static void
store_fragdepth_layout(struct gl_shader_program *prog)
{
   if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] == NULL) {
      return;
   }

   struct exec_list *ir = prog->_LinkedShaders[MESA_SHADER_FRAGMENT]->ir;

   /* We don't look up the gl_FragDepth symbol directly because if
    * gl_FragDepth is not used in the shader, it's removed from the IR.
    * However, the symbol won't be removed from the symbol table.
    *
    * We're only interested in the cases where the variable is NOT removed
    * from the IR.
    */
   foreach_in_list(ir_instruction, node, ir) {
      ir_variable *const var = node->as_variable();

      if (var == NULL || var->data.mode != ir_var_shader_out) {
         continue;
      }

      if (strcmp(var->name, "gl_FragDepth") == 0) {
         switch (var->data.depth_layout) {
         case ir_depth_layout_none:
            prog->FragDepthLayout = FRAG_DEPTH_LAYOUT_NONE;
            return;
         case ir_depth_layout_any:
            prog->FragDepthLayout = FRAG_DEPTH_LAYOUT_ANY;
            return;
         case ir_depth_layout_greater:
            prog->FragDepthLayout = FRAG_DEPTH_LAYOUT_GREATER;
            return;
         case ir_depth_layout_less:
            prog->FragDepthLayout = FRAG_DEPTH_LAYOUT_LESS;
            return;
         case ir_depth_layout_unchanged:
            prog->FragDepthLayout = FRAG_DEPTH_LAYOUT_UNCHANGED;
            return;
         default:
            assert(0);
            return;
         }
      }
   }
}

/**
 * Validate the resources used by a program versus the implementation limits
 */
static void
check_resources(struct gl_context *ctx, struct gl_shader_program *prog)
{
   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
      struct gl_shader *sh = prog->_LinkedShaders[i];

      if (sh == NULL)
	 continue;

      if (sh->num_samplers > ctx->Const.Program[i].MaxTextureImageUnits) {
	 linker_error(prog, "Too many %s shader texture samplers\n",
		      _mesa_shader_stage_to_string(i));
      }

      if (sh->num_uniform_components >
          ctx->Const.Program[i].MaxUniformComponents) {
         if (ctx->Const.GLSLSkipStrictMaxUniformLimitCheck) {
            linker_warning(prog, "Too many %s shader default uniform block "
                           "components, but the driver will try to optimize "
                           "them out; this is non-portable out-of-spec "
			   "behavior\n",
                           _mesa_shader_stage_to_string(i));
         } else {
            linker_error(prog, "Too many %s shader default uniform block "
			 "components\n",
                         _mesa_shader_stage_to_string(i));
         }
      }

      if (sh->num_combined_uniform_components >
	  ctx->Const.Program[i].MaxCombinedUniformComponents) {
         if (ctx->Const.GLSLSkipStrictMaxUniformLimitCheck) {
            linker_warning(prog, "Too many %s shader uniform components, "
                           "but the driver will try to optimize them out; "
                           "this is non-portable out-of-spec behavior\n",
                           _mesa_shader_stage_to_string(i));
         } else {
            linker_error(prog, "Too many %s shader uniform components\n",
                         _mesa_shader_stage_to_string(i));
         }
      }
   }

   unsigned blocks[MESA_SHADER_STAGES] = {0};
   unsigned total_uniform_blocks = 0;

   for (unsigned i = 0; i < prog->NumUniformBlocks; i++) {
      for (unsigned j = 0; j < MESA_SHADER_STAGES; j++) {
	 if (prog->UniformBlockStageIndex[j][i] != -1) {
	    blocks[j]++;
	    total_uniform_blocks++;
	 }
      }

      if (total_uniform_blocks > ctx->Const.MaxCombinedUniformBlocks) {
	 linker_error(prog, "Too many combined uniform blocks (%d/%d)\n",
		      prog->NumUniformBlocks,
		      ctx->Const.MaxCombinedUniformBlocks);
      } else {
	 for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
            const unsigned max_uniform_blocks =
               ctx->Const.Program[i].MaxUniformBlocks;
	    if (blocks[i] > max_uniform_blocks) {
	       linker_error(prog, "Too many %s uniform blocks (%d/%d)\n",
			    _mesa_shader_stage_to_string(i),
			    blocks[i],
			    max_uniform_blocks);
	       break;
	    }
	 }
      }
   }
}

/**
 * Validate shader image resources.
 */
static void
check_image_resources(struct gl_context *ctx, struct gl_shader_program *prog)
{
   unsigned total_image_units = 0;
   unsigned fragment_outputs = 0;

   if (!ctx->Extensions.ARB_shader_image_load_store)
      return;

   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
      struct gl_shader *sh = prog->_LinkedShaders[i];

      if (sh) {
         if (sh->NumImages > ctx->Const.Program[i].MaxImageUniforms)
            linker_error(prog, "Too many %s shader image uniforms\n",
                         _mesa_shader_stage_to_string(i));

         total_image_units += sh->NumImages;

         if (i == MESA_SHADER_FRAGMENT) {
            foreach_in_list(ir_instruction, node, sh->ir) {
               ir_variable *var = node->as_variable();
               if (var && var->data.mode == ir_var_shader_out)
                  fragment_outputs += var->type->count_attribute_slots();
            }
         }
      }
   }

   if (total_image_units > ctx->Const.MaxCombinedImageUniforms)
      linker_error(prog, "Too many combined image uniforms\n");

   if (total_image_units + fragment_outputs >
       ctx->Const.MaxCombinedImageUnitsAndFragmentOutputs)
      linker_error(prog, "Too many combined image uniforms and fragment outputs\n");
}


/**
 * Initializes explicit location slots to INACTIVE_UNIFORM_EXPLICIT_LOCATION
 * for a variable, checks for overlaps between other uniforms using explicit
 * locations.
 */
static bool
reserve_explicit_locations(struct gl_shader_program *prog,
                           string_to_uint_map *map, ir_variable *var)
{
   unsigned slots = var->type->uniform_locations();
   unsigned max_loc = var->data.location + slots - 1;

   /* Resize remap table if locations do not fit in the current one. */
   if (max_loc + 1 > prog->NumUniformRemapTable) {
      prog->UniformRemapTable =
         reralloc(prog, prog->UniformRemapTable,
                  gl_uniform_storage *,
                  max_loc + 1);

      if (!prog->UniformRemapTable) {
         linker_error(prog, "Out of memory during linking.\n");
         return false;
      }

      /* Initialize allocated space. */
      for (unsigned i = prog->NumUniformRemapTable; i < max_loc + 1; i++)
         prog->UniformRemapTable[i] = NULL;

      prog->NumUniformRemapTable = max_loc + 1;
   }

   for (unsigned i = 0; i < slots; i++) {
      unsigned loc = var->data.location + i;

      /* Check if location is already used. */
      if (prog->UniformRemapTable[loc] == INACTIVE_UNIFORM_EXPLICIT_LOCATION) {

         /* Possibly same uniform from a different stage, this is ok. */
         unsigned hash_loc;
         if (map->get(hash_loc, var->name) && hash_loc == loc - i)
               continue;

         /* ARB_explicit_uniform_location specification states:
          *
          *     "No two default-block uniform variables in the program can have
          *     the same location, even if they are unused, otherwise a compiler
          *     or linker error will be generated."
          */
         linker_error(prog,
                      "location qualifier for uniform %s overlaps "
                      "previously used location\n",
                      var->name);
         return false;
      }

      /* Initialize location as inactive before optimization
       * rounds and location assignment.
       */
      prog->UniformRemapTable[loc] = INACTIVE_UNIFORM_EXPLICIT_LOCATION;
   }

   /* Note, base location used for arrays. */
   map->put(var->data.location, var->name);

   return true;
}

/**
 * Check and reserve all explicit uniform locations, called before
 * any optimizations happen to handle also inactive uniforms and
 * inactive array elements that may get trimmed away.
 */
static void
check_explicit_uniform_locations(struct gl_context *ctx,
                                 struct gl_shader_program *prog)
{
   if (!ctx->Extensions.ARB_explicit_uniform_location)
      return;

   /* This map is used to detect if overlapping explicit locations
    * occur with the same uniform (from different stage) or a different one.
    */
   string_to_uint_map *uniform_map = new string_to_uint_map;

   if (!uniform_map) {
      linker_error(prog, "Out of memory during linking.\n");
      return;
   }

   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
      struct gl_shader *sh = prog->_LinkedShaders[i];

      if (!sh)
         continue;

      foreach_in_list(ir_instruction, node, sh->ir) {
         ir_variable *var = node->as_variable();
         if ((var && var->data.mode == ir_var_uniform) &&
             var->data.explicit_location) {
            if (!reserve_explicit_locations(prog, uniform_map, var)) {
               delete uniform_map;
               return;
            }
         }
      }
   }

   delete uniform_map;
}

void
link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
{
   tfeedback_decl *tfeedback_decls = NULL;
   unsigned num_tfeedback_decls = prog->TransformFeedback.NumVarying;

   void *mem_ctx = ralloc_context(NULL); // temporary linker context

   prog->LinkStatus = true; /* All error paths will set this to false */
   prog->Validated = false;
   prog->_Used = false;

   prog->ARB_fragment_coord_conventions_enable = false;

   /* Separate the shaders into groups based on their type.
    */
   struct gl_shader **shader_list[MESA_SHADER_STAGES];
   unsigned num_shaders[MESA_SHADER_STAGES];

   for (int i = 0; i < MESA_SHADER_STAGES; i++) {
      shader_list[i] = (struct gl_shader **)
         calloc(prog->NumShaders, sizeof(struct gl_shader *));
      num_shaders[i] = 0;
   }

   unsigned min_version = UINT_MAX;
   unsigned max_version = 0;
   const bool is_es_prog =
      (prog->NumShaders > 0 && prog->Shaders[0]->IsES) ? true : false;
   for (unsigned i = 0; i < prog->NumShaders; i++) {
      min_version = MIN2(min_version, prog->Shaders[i]->Version);
      max_version = MAX2(max_version, prog->Shaders[i]->Version);

      if (prog->Shaders[i]->IsES != is_es_prog) {
	 linker_error(prog, "all shaders must use same shading "
		      "language version\n");
	 goto done;
      }

      prog->ARB_fragment_coord_conventions_enable |=
         prog->Shaders[i]->ARB_fragment_coord_conventions_enable;

      gl_shader_stage shader_type = prog->Shaders[i]->Stage;
      shader_list[shader_type][num_shaders[shader_type]] = prog->Shaders[i];
      num_shaders[shader_type]++;
   }

   /* In desktop GLSL, different shader versions may be linked together.  In
    * GLSL ES, all shader versions must be the same.
    */
   if (is_es_prog && min_version != max_version) {
      linker_error(prog, "all shaders must use same shading "
		   "language version\n");
      goto done;
   }

   prog->Version = max_version;
   prog->IsES = is_es_prog;

   /* Geometry shaders have to be linked with vertex shaders.
    */
   if (num_shaders[MESA_SHADER_GEOMETRY] > 0 &&
       num_shaders[MESA_SHADER_VERTEX] == 0 &&
       !prog->SeparateShader) {
      linker_error(prog, "Geometry shader must be linked with "
		   "vertex shader\n");
      goto done;
   }

   /* Compute shaders have additional restrictions. */
   if (num_shaders[MESA_SHADER_COMPUTE] > 0 &&
       num_shaders[MESA_SHADER_COMPUTE] != prog->NumShaders) {
      linker_error(prog, "Compute shaders may not be linked with any other "
                   "type of shader\n");
   }

   for (unsigned int i = 0; i < MESA_SHADER_STAGES; i++) {
      if (prog->_LinkedShaders[i] != NULL)
	 ctx->Driver.DeleteShader(ctx, prog->_LinkedShaders[i]);

      prog->_LinkedShaders[i] = NULL;
   }

   /* Link all shaders for a particular stage and validate the result.
    */
   for (int stage = 0; stage < MESA_SHADER_STAGES; stage++) {
      if (num_shaders[stage] > 0) {
         gl_shader *const sh =
            link_intrastage_shaders(mem_ctx, ctx, prog, shader_list[stage],
                                    num_shaders[stage]);

         if (!prog->LinkStatus)
            goto done;

         switch (stage) {
         case MESA_SHADER_VERTEX:
            validate_vertex_shader_executable(prog, sh);
            break;
         case MESA_SHADER_GEOMETRY:
            validate_geometry_shader_executable(prog, sh);
            break;
         case MESA_SHADER_FRAGMENT:
            validate_fragment_shader_executable(prog, sh);
            break;
         }
         if (!prog->LinkStatus)
            goto done;

         _mesa_reference_shader(ctx, &prog->_LinkedShaders[stage], sh);
      }
   }

   if (num_shaders[MESA_SHADER_GEOMETRY] > 0)
      prog->LastClipDistanceArraySize = prog->Geom.ClipDistanceArraySize;
   else if (num_shaders[MESA_SHADER_VERTEX] > 0)
      prog->LastClipDistanceArraySize = prog->Vert.ClipDistanceArraySize;
   else
      prog->LastClipDistanceArraySize = 0; /* Not used */

   /* Here begins the inter-stage linking phase.  Some initial validation is
    * performed, then locations are assigned for uniforms, attributes, and
    * varyings.
    */
   cross_validate_uniforms(prog);
   if (!prog->LinkStatus)
      goto done;

   unsigned prev;

   for (prev = 0; prev <= MESA_SHADER_FRAGMENT; prev++) {
      if (prog->_LinkedShaders[prev] != NULL)
         break;
   }

   check_explicit_uniform_locations(ctx, prog);
   if (!prog->LinkStatus)
      goto done;

   /* Validate the inputs of each stage with the output of the preceding
    * stage.
    */
   for (unsigned i = prev + 1; i <= MESA_SHADER_FRAGMENT; i++) {
      if (prog->_LinkedShaders[i] == NULL)
         continue;

      validate_interstage_inout_blocks(prog, prog->_LinkedShaders[prev],
                                       prog->_LinkedShaders[i]);
      if (!prog->LinkStatus)
         goto done;

      cross_validate_outputs_to_inputs(prog,
                                       prog->_LinkedShaders[prev],
                                       prog->_LinkedShaders[i]);
      if (!prog->LinkStatus)
         goto done;

      prev = i;
   }

   /* Cross-validate uniform blocks between shader stages */
   validate_interstage_uniform_blocks(prog, prog->_LinkedShaders,
                                      MESA_SHADER_STAGES);
   if (!prog->LinkStatus)
      goto done;

   for (unsigned int i = 0; i < MESA_SHADER_STAGES; i++) {
      if (prog->_LinkedShaders[i] != NULL)
         lower_named_interface_blocks(mem_ctx, prog->_LinkedShaders[i]);
   }

   /* Implement the GLSL 1.30+ rule for discard vs infinite loops Do
    * it before optimization because we want most of the checks to get
    * dropped thanks to constant propagation.
    *
    * This rule also applies to GLSL ES 3.00.
    */
   if (max_version >= (is_es_prog ? 300 : 130)) {
      struct gl_shader *sh = prog->_LinkedShaders[MESA_SHADER_FRAGMENT];
      if (sh) {
	 lower_discard_flow(sh->ir);
      }
   }

   if (!interstage_cross_validate_uniform_blocks(prog))
      goto done;

   /* Do common optimization before assigning storage for attributes,
    * uniforms, and varyings.  Later optimization could possibly make
    * some of that unused.
    */
   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
      if (prog->_LinkedShaders[i] == NULL)
	 continue;

      detect_recursion_linked(prog, prog->_LinkedShaders[i]->ir);
      if (!prog->LinkStatus)
	 goto done;

      if (ctx->Const.ShaderCompilerOptions[i].LowerClipDistance) {
         lower_clip_distance(prog->_LinkedShaders[i]);
      }

      while (do_common_optimization(prog->_LinkedShaders[i]->ir, true, false,
                                    &ctx->Const.ShaderCompilerOptions[i],
                                    ctx->Const.NativeIntegers))
	 ;

      lower_const_arrays_to_uniforms(prog->_LinkedShaders[i]->ir);
   }

   /* Check and validate stream emissions in geometry shaders */
   validate_geometry_shader_emissions(ctx, prog);

   /* Mark all generic shader inputs and outputs as unpaired. */
   for (unsigned i = MESA_SHADER_VERTEX; i <= MESA_SHADER_FRAGMENT; i++) {
      if (prog->_LinkedShaders[i] != NULL) {
         link_invalidate_variable_locations(prog->_LinkedShaders[i]->ir);
      }
   }

   /* FINISHME: The value of the max_attribute_index parameter is
    * FINISHME: implementation dependent based on the value of
    * FINISHME: GL_MAX_VERTEX_ATTRIBS.  GL_MAX_VERTEX_ATTRIBS must be
    * FINISHME: at least 16, so hardcode 16 for now.
    */
   if (!assign_attribute_or_color_locations(prog, MESA_SHADER_VERTEX, 16)) {
      goto done;
   }

   if (!assign_attribute_or_color_locations(prog, MESA_SHADER_FRAGMENT, MAX2(ctx->Const.MaxDrawBuffers, ctx->Const.MaxDualSourceDrawBuffers))) {
      goto done;
   }

   unsigned first;
   for (first = 0; first <= MESA_SHADER_FRAGMENT; first++) {
      if (prog->_LinkedShaders[first] != NULL)
	 break;
   }

   if (num_tfeedback_decls != 0) {
      /* From GL_EXT_transform_feedback:
       *   A program will fail to link if:
       *
       *   * the <count> specified by TransformFeedbackVaryingsEXT is
       *     non-zero, but the program object has no vertex or geometry
       *     shader;
       */
      if (first == MESA_SHADER_FRAGMENT) {
         linker_error(prog, "Transform feedback varyings specified, but "
                      "no vertex or geometry shader is present.\n");
         goto done;
      }

      tfeedback_decls = ralloc_array(mem_ctx, tfeedback_decl,
                                     prog->TransformFeedback.NumVarying);
      if (!parse_tfeedback_decls(ctx, prog, mem_ctx, num_tfeedback_decls,
                                 prog->TransformFeedback.VaryingNames,
                                 tfeedback_decls))
         goto done;
   }

   /* Linking the stages in the opposite order (from fragment to vertex)
    * ensures that inter-shader outputs written to in an earlier stage are
    * eliminated if they are (transitively) not used in a later stage.
    */
   int last, next;
   for (last = MESA_SHADER_FRAGMENT; last >= 0; last--) {
      if (prog->_LinkedShaders[last] != NULL)
         break;
   }

   if (last >= 0 && last < MESA_SHADER_FRAGMENT) {
      gl_shader *const sh = prog->_LinkedShaders[last];

      if (first == MESA_SHADER_GEOMETRY) {
         /* There was no vertex shader, but we still have to assign varying
          * locations for use by geometry shader inputs in SSO.
          *
          * If the shader is not separable (i.e., prog->SeparateShader is
          * false), linking will have already failed when first is
          * MESA_SHADER_GEOMETRY.
          */
         if (!assign_varying_locations(ctx, mem_ctx, prog,
                                       NULL, sh,
                                       num_tfeedback_decls, tfeedback_decls,
                                       prog->Geom.VerticesIn))
            goto done;
      }

      if (num_tfeedback_decls != 0 || prog->SeparateShader) {
         /* There was no fragment shader, but we still have to assign varying
          * locations for use by transform feedback.
          */
         if (!assign_varying_locations(ctx, mem_ctx, prog,
                                       sh, NULL,
                                       num_tfeedback_decls, tfeedback_decls,
                                       0))
            goto done;
      }

      do_dead_builtin_varyings(ctx, sh, NULL,
                               num_tfeedback_decls, tfeedback_decls);

      if (!prog->SeparateShader)
         demote_shader_inputs_and_outputs(sh, ir_var_shader_out);

      /* Eliminate code that is now dead due to unused outputs being demoted.
       */
      while (do_dead_code(sh->ir, false))
         ;
   }
   else if (first == MESA_SHADER_FRAGMENT) {
      /* If the program only contains a fragment shader...
       */
      gl_shader *const sh = prog->_LinkedShaders[first];

      do_dead_builtin_varyings(ctx, NULL, sh,
                               num_tfeedback_decls, tfeedback_decls);

      if (prog->SeparateShader) {
         if (!assign_varying_locations(ctx, mem_ctx, prog,
                                       NULL /* producer */,
                                       sh /* consumer */,
                                       0 /* num_tfeedback_decls */,
                                       NULL /* tfeedback_decls */,
                                       0 /* gs_input_vertices */))
            goto done;
      } else
         demote_shader_inputs_and_outputs(sh, ir_var_shader_in);

      while (do_dead_code(sh->ir, false))
         ;
   }

   next = last;
   for (int i = next - 1; i >= 0; i--) {
      if (prog->_LinkedShaders[i] == NULL)
         continue;

      gl_shader *const sh_i = prog->_LinkedShaders[i];
      gl_shader *const sh_next = prog->_LinkedShaders[next];
      unsigned gs_input_vertices =
         next == MESA_SHADER_GEOMETRY ? prog->Geom.VerticesIn : 0;

      if (!assign_varying_locations(ctx, mem_ctx, prog, sh_i, sh_next,
                next == MESA_SHADER_FRAGMENT ? num_tfeedback_decls : 0,
                tfeedback_decls, gs_input_vertices))
         goto done;

      do_dead_builtin_varyings(ctx, sh_i, sh_next,
                next == MESA_SHADER_FRAGMENT ? num_tfeedback_decls : 0,
                tfeedback_decls);

      demote_shader_inputs_and_outputs(sh_i, ir_var_shader_out);
      demote_shader_inputs_and_outputs(sh_next, ir_var_shader_in);

      /* Eliminate code that is now dead due to unused outputs being demoted.
       */
      while (do_dead_code(sh_i->ir, false))
         ;
      while (do_dead_code(sh_next->ir, false))
         ;

      /* This must be done after all dead varyings are eliminated. */
      if (!check_against_output_limit(ctx, prog, sh_i))
         goto done;
      if (!check_against_input_limit(ctx, prog, sh_next))
         goto done;

      next = i;
   }

   if (!store_tfeedback_info(ctx, prog, num_tfeedback_decls, tfeedback_decls))
      goto done;

   update_array_sizes(prog);
   link_assign_uniform_locations(prog, ctx->Const.UniformBooleanTrue);
   link_assign_atomic_counter_resources(ctx, prog);
   store_fragdepth_layout(prog);

   check_resources(ctx, prog);
   check_image_resources(ctx, prog);
   link_check_atomic_counter_resources(ctx, prog);

   if (!prog->LinkStatus)
      goto done;

   /* OpenGL ES requires that a vertex shader and a fragment shader both be
    * present in a linked program. GL_ARB_ES2_compatibility doesn't say
    * anything about shader linking when one of the shaders (vertex or
    * fragment shader) is absent. So, the extension shouldn't change the
    * behavior specified in GLSL specification.
    */
   if (!prog->SeparateShader && ctx->API == API_OPENGLES2) {
      if (prog->_LinkedShaders[MESA_SHADER_VERTEX] == NULL) {
	 linker_error(prog, "program lacks a vertex shader\n");
      } else if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] == NULL) {
	 linker_error(prog, "program lacks a fragment shader\n");
      }
   }

   /* FINISHME: Assign fragment shader output locations. */

done:
   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
      free(shader_list[i]);
      if (prog->_LinkedShaders[i] == NULL)
	 continue;

      /* Do a final validation step to make sure that the IR wasn't
       * invalidated by any modifications performed after intrastage linking.
       */
      validate_ir_tree(prog->_LinkedShaders[i]->ir);

      /* Retain any live IR, but trash the rest. */
      reparent_ir(prog->_LinkedShaders[i]->ir, prog->_LinkedShaders[i]->ir);

      /* The symbol table in the linked shaders may contain references to
       * variables that were removed (e.g., unused uniforms).  Since it may
       * contain junk, there is no possible valid use.  Delete it and set the
       * pointer to NULL.
       */
      delete prog->_LinkedShaders[i]->symbols;
      prog->_LinkedShaders[i]->symbols = NULL;
   }

   ralloc_free(mem_ctx);
}