nv50/ir: fix ConstantFolding with saturation

For mul(a, +-1) codegen can generate OP_MOV with a saturation flag
set which is ignored at emission. The same can happen with add(a, 0),
and others.

Adding an assert for detecting more of such issues.

Fixes wrongly rendered water in Hitman Absolution running under wine.
Also a few shaders in Mad Max and Alien Isolation produce such MOVs.

CC: <[email protected]>
Signed-off-by: Karol Herbst <[email protected]>
Reviewed-by: Tobias Klausmann <[email protected]>
[imirkin: generalize the fix for other cases]
Reviewed-by: Ilia Mirkin <[email protected]>

2 files changed, 9 insertions, 0 deletions

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_nvc0.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_nvc0.cpp
index 14c00bd1870..58594f02c7f 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_nvc0.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_nvc0.cpp
@@ -2006,6 +2006,7 @@ CodeEmitterNVC0::getSRegEncoding(const ValueRef& ref)
 void
 CodeEmitterNVC0::emitMOV(const Instruction *i)
 {
+   assert(!i->saturate);
    if (i->def(0).getFile() == FILE_PREDICATE) {
       if (i->src(0).getFile() == FILE_GPR) {
          code[0] = 0xfc01c003;
diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
index dac3e6f814c..cfc0dfc53cf 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
@@ -1509,6 +1509,14 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
    default:
       return;
    }
+
+   // This can get left behind some of the optimizations which simplify
+   // saturatable values.
+   if (newi->op == OP_MOV && newi->saturate) {
+      newi->saturate = 0;
+      newi->op = OP_SAT;
+   }
+
    if (newi->op != op)
       foldCount++;
 }