[PATCH v2] nv50/ir: optimize shl(a, 0) to a

[Karol Herbst <karolherbst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

helps two alien isolation shaders

shader-db:
total instructions in shared programs : 4251497 -> 4251494 (-0.00%)
total gprs used in shared programs    : 513962 -> 513962 (0.00%)
total local used in shared programs   : 29797 -> 29797 (0.00%)
total bytes used in shared programs   : 38960264 -> 38960232 (-0.00%)

                local        gpr       inst      bytes
    helped           0           0           2           2
      hurt           0           0           0           0

v2: handle potential mods on src0

Signed-off-by: Karol Herbst <karolherbst@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
---
 src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
index 015def0391..82da0d3e48 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
@@ -1284,6 +1284,13 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
 
    case OP_SHL:
    {
+      if (s == 1 && imm0.isInteger(0)) {
+         i->op = i->src(0).mod.getOp();
+         if (i->op != OP_CVT)
+            i->src(0).mod = 0;
+         i->setSrc(1, NULL);
+         break;
+      }
       if (s != 1 || i->src(0).mod != Modifier(0))
          break;
       // try to concatenate shifts
-- 
2.12.2

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