nvc0: do upload-time fixups for interpolation parameters

Unfortunately flatshading is an all-or-nothing proposition on nvc0,
while GL 3.0 calls for the ability to selectively specify explicit
interpolation parameters on gl_Color/gl_SecondaryColor which would
override the flatshading setting. This allows us to fix up the
interpolation settings after shader generation based on rasterizer
settings.

While we're at it, we can add support for dynamically forcing all
(non-flat) shader inputs to be interpolated per-sample, which allows
st/mesa to not generate variants for these.

Fixes the remaining failing glsl-1.30/execution/interpolation piglits.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>

1 files changed, 29 insertions, 2 deletions

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gk110.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gk110.cpp
index 8f1542959c9..d712c9c300a 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gk110.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gk110.cpp
@@ -1437,6 +1437,30 @@ CodeEmitterGK110::emitInterpMode(const Instruction *i)
    code[1] |= (i->ipa & 0xc) << (19 - 2);
 }
 
+static void
+interpApply(const InterpEntry *entry, uint32_t *code,
+      bool force_persample_interp, bool flatshade)
+{
+   int ipa = entry->ipa;
+   int reg = entry->reg;
+   int loc = entry->loc;
+
+   if (flatshade &&
+       (ipa & NV50_IR_INTERP_MODE_MASK) == NV50_IR_INTERP_SC) {
+      ipa = NV50_IR_INTERP_FLAT;
+      reg = 0xff;
+   } else if (force_persample_interp &&
+              (ipa & NV50_IR_INTERP_SAMPLE_MASK) == NV50_IR_INTERP_DEFAULT &&
+              (ipa & NV50_IR_INTERP_MODE_MASK) != NV50_IR_INTERP_FLAT) {
+      ipa |= NV50_IR_INTERP_CENTROID;
+   }
+   code[loc + 1] &= ~(0xf << 19);
+   code[loc + 1] |= (ipa & 0x3) << 21;
+   code[loc + 1] |= (ipa & 0xc) << (19 - 2);
+   code[loc + 0] &= ~(0xff << 23);
+   code[loc + 0] |= reg << 23;
+}
+
 void
 CodeEmitterGK110::emitINTERP(const Instruction *i)
 {
@@ -1448,10 +1472,13 @@ CodeEmitterGK110::emitINTERP(const Instruction *i)
    if (i->saturate)
       code[1] |= 1 << 18;
 
-   if (i->op == OP_PINTERP)
+   if (i->op == OP_PINTERP) {
       srcId(i->src(1), 23);
-   else
+      addInterp(i->ipa, SDATA(i->src(1)).id, interpApply);
+   } else {
       code[0] |= 0xff << 23;
+      addInterp(i->ipa, 0xff, interpApply);
+   }
 
    srcId(i->src(0).getIndirect(0), 10);
    emitInterpMode(i);