[Mesa-dev] [PATCH v2 4/7] nv50/ir: optimize shl(shr(a, c), c) to and(a, ~((1 << c) - 1))

[Karol Herbst]

From: Karol Herbst <git at karolherbst.de>

helps shaders in multiple games

total instructions in shared programs : 1910935 -> 1901781 (-0.48%)
total gprs used in shared programs    : 251728 -> 251728 (0.00%)
total local used in shared programs   : 5673 -> 5673 (0.00%)
total bytes used in shared programs   : 17521824 -> 17438576 (-0.48%)

                local        gpr       inst      bytes
    helped           0           0        1387        1387
      hurt           0           0           0           0

Signed-off-by: Karol Herbst <nouveau at karolherbst.de>
Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>
---
 src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
index eb43f6c..abee6a5 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
@@ -1202,6 +1202,14 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
             i->setSrc(1, bld.loadImm(NULL, imm0.reg.data.u32 + imm1.reg.data.u32));
          }
          break;
+      case OP_SHR:
+         if (si->src(1).getImmediate(imm1) && imm0.reg.data.u32 == imm1.reg.data.u32) {
+            bld.setPosition(i, false);
+            i->op = OP_AND;
+            i->setSrc(0, si->getSrc(0));
+            i->setSrc(1, bld.loadImm(NULL, ~((1 << imm0.reg.data.u32) - 1)));
+         }
+         break;
       case OP_MUL:
          int muls;
          if (isFloatType(si->dType))
-- 
2.7.0