i915g: Emit better code for SEQ(x, 0) and SNE(x, 0)

total instructions in shared programs: 789000 -> 788481 (-0.07%)
instructions in affected programs: 16179 -> 15660 (-3.21%)
helped: 157
HURT: 0
helped stats (abs) min: 3 max: 12 x̄: 3.31 x̃: 3
helped stats (rel) min: 1.56% max: 14.29% x̄: 4.24% x̃: 2.56%
95% mean confidence interval for instructions value: -3.51 -3.10
95% mean confidence interval for instructions %-change: -4.70% -3.78%
Instructions are helped.

LOST:   0
GAINED: 3

v2: Drop setting src1 to zero.  Suggested by Emma.

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15210>

1 files changed, 54 insertions, 18 deletions

diff --git a/src/gallium/drivers/i915/i915_fpc_translate.c b/src/gallium/drivers/i915/i915_fpc_translate.c
index a17d73d8310..0acea54efe8 100644
--- a/src/gallium/drivers/i915/i915_fpc_translate.c
+++ b/src/gallium/drivers/i915/i915_fpc_translate.c
@@ -706,22 +706,40 @@ i915_translate_instruction(struct i915_fp_compile *p,
                       0);
       break;
 
-   case TGSI_OPCODE_SEQ:
+   case TGSI_OPCODE_SEQ: {
+      const uint32_t zero = swizzle(UREG(REG_TYPE_R, 0),
+                                    SRC_ZERO, SRC_ZERO, SRC_ZERO, SRC_ZERO);
+
       /* if we're both >= and <= then we're == */
       src0 = src_vector(p, &inst->Src[0], fs);
       src1 = src_vector(p, &inst->Src[1], fs);
       tmp = i915_get_utemp(p);
 
-      i915_emit_arith(p, A0_SGE, tmp, A0_DEST_CHANNEL_ALL, 0, src0, src1, 0);
-
-      i915_emit_arith(p, A0_SGE, get_result_vector(p, &inst->Dst[0]),
-                      get_result_flags(inst), 0, src1, src0, 0);
-
-      i915_emit_arith(p, A0_MUL, get_result_vector(p, &inst->Dst[0]),
-                      get_result_flags(inst), 0,
-                      get_result_vector(p, &inst->Dst[0]), tmp, 0);
+      if (src0 == zero || src1 == zero) {
+         if (src0 == zero)
+            src0 = src1;
+
+         /* x == 0 is equivalent to -abs(x) >= 0, but the latter requires only
+          * two instructions instead of three.
+          */
+         i915_emit_arith(p, A0_MAX, tmp, A0_DEST_CHANNEL_ALL, 0, src0,
+                         negate(src0, 1, 1, 1, 1), 0);
+         i915_emit_arith(p, A0_SGE, get_result_vector(p, &inst->Dst[0]),
+                         get_result_flags(inst), 0,
+                         negate(tmp, 1, 1, 1, 1), zero, 0);
+      } else {
+         i915_emit_arith(p, A0_SGE, tmp, A0_DEST_CHANNEL_ALL, 0, src0, src1, 0);
+
+         i915_emit_arith(p, A0_SGE, get_result_vector(p, &inst->Dst[0]),
+                         get_result_flags(inst), 0, src1, src0, 0);
+
+         i915_emit_arith(p, A0_MUL, get_result_vector(p, &inst->Dst[0]),
+                         get_result_flags(inst), 0,
+                         get_result_vector(p, &inst->Dst[0]), tmp, 0);
+      }
 
       break;
+   }
 
    case TGSI_OPCODE_SGE:
       emit_simple_arith(p, inst, A0_SGE, 2, fs);
@@ -741,21 +759,39 @@ i915_translate_instruction(struct i915_fp_compile *p,
       emit_simple_arith_swap2(p, inst, A0_SLT, 2, fs);
       break;
 
-   case TGSI_OPCODE_SNE:
+   case TGSI_OPCODE_SNE: {
+      const uint32_t zero = swizzle(UREG(REG_TYPE_R, 0),
+                                    SRC_ZERO, SRC_ZERO, SRC_ZERO, SRC_ZERO);
+
       /* if we're < or > then we're != */
       src0 = src_vector(p, &inst->Src[0], fs);
       src1 = src_vector(p, &inst->Src[1], fs);
       tmp = i915_get_utemp(p);
 
-      i915_emit_arith(p, A0_SLT, tmp, A0_DEST_CHANNEL_ALL, 0, src0, src1, 0);
-
-      i915_emit_arith(p, A0_SLT, get_result_vector(p, &inst->Dst[0]),
-                      get_result_flags(inst), 0, src1, src0, 0);
-
-      i915_emit_arith(p, A0_ADD, get_result_vector(p, &inst->Dst[0]),
-                      get_result_flags(inst), 0,
-                      get_result_vector(p, &inst->Dst[0]), tmp, 0);
+      if (src0 == zero || src1 == zero) {
+         if (src0 == zero)
+            src0 = src1;
+
+         /* x != 0 is equivalent to -abs(x) < 0, but the latter requires only
+          * two instructions instead of three.
+          */
+         i915_emit_arith(p, A0_MAX, tmp, A0_DEST_CHANNEL_ALL, 0, src0,
+                         negate(src0, 1, 1, 1, 1), 0);
+         i915_emit_arith(p, A0_SLT, get_result_vector(p, &inst->Dst[0]),
+                         get_result_flags(inst), 0,
+                         negate(tmp, 1, 1, 1, 1), zero, 0);
+      } else {
+         i915_emit_arith(p, A0_SLT, tmp, A0_DEST_CHANNEL_ALL, 0, src0, src1, 0);
+
+         i915_emit_arith(p, A0_SLT, get_result_vector(p, &inst->Dst[0]),
+                         get_result_flags(inst), 0, src1, src0, 0);
+
+         i915_emit_arith(p, A0_ADD, get_result_vector(p, &inst->Dst[0]),
+                         get_result_flags(inst), 0,
+                         get_result_vector(p, &inst->Dst[0]), tmp, 0);
+      }
       break;
+   }
 
    case TGSI_OPCODE_SSG:
       /* compute (src>0) - (src<0) */