[Mesa-dev] [PATCH] nv50/ir: optimise slct(t, f, set) to mov(set) or not(set)

[Karol Herbst]

From: Karol Herbst <karolherbst at gmail.com>

helps mainly Feral-ported games

changes in shader-db:
total instructions in shared programs : 3940749 -> 3935015 (-0.15%)
total gprs used in shared programs    : 481460 -> 481433 (-0.01%)
total local used in shared programs   : 27481 -> 27513 (0.12%)
total bytes used in shared programs   : 36115776 -> 36063344 (-0.15%)

                local        gpr       inst      bytes
    helped           6          31         854         854
      hurt          10           5           1           1
---
 .../drivers/nouveau/codegen/nv50_ir_peephole.cpp   | 26 ++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
index 48cf74950df..1e3dea95494 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
@@ -637,9 +637,31 @@ ConstantFolding::expr(Instruction *i,
       }
       break;
    case OP_SLCT:
-      if (a->data.u32 != b->data.u32)
+      // slct(a, a, b) -> a
+      if (a->data.u32 == b->data.u32) {
+         res.data.u32 = a->data.u32;
+      } else {
+         // slct_ne(true, false, bool) -> !bool
+         CmpInstruction *slct = i->asCmp();
+         Instruction *set = i->getSrc(2)->getInsn();
+         if (!set || set->op != OP_SET)
+            return;
+         if (isFloatType(set->dType))
+            return;
+         if ((slct->getCondition() == CC_NE && imm0.isInteger(-1) && imm1.isInteger(0)) ||
+             (slct->getCondition() == CC_EQ && imm0.isInteger(0) && imm1.isInteger(-1))) {
+            bld.setPosition(i, false);
+            bld.mkOp1(OP_MOV, i->dType, i->getDef(0), i->getSrc(2));
+            delete_Instruction(prog, i);
+         } else if (
+             (slct->getCondition() == CC_EQ && imm0.isInteger(-1) && imm1.isInteger(0)) ||
+             (slct->getCondition() == CC_NE && imm0.isInteger(0) && imm1.isInteger(-1))) {
+            bld.setPosition(i, false);
+            bld.mkOp1(OP_NOT, i->dType, i->getDef(0), i->getSrc(2));
+            delete_Instruction(prog, i);
+         }
          return;
-      res.data.u32 = a->data.u32;
+      }
       break;
    case OP_EXTBF: {
       int offset = b->data.u32 & 0xff;
-- 
2.14.3