[Mesa-dev] [PATCH 5/5] i965/fs: Emit a MOV instead of a SEL if the sources are the same.

[Matt Turner]

One program affected.

instructions in affected programs:     436 -> 428 (-1.83%)

Reviewed-by: Paul Berry <stereotype441 at gmail.com>
---
 src/mesa/drivers/dri/i965/brw_fs_sel_peephole.cpp | 42 +++++++++++++----------
 1 file changed, 23 insertions(+), 19 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_sel_peephole.cpp b/src/mesa/drivers/dri/i965/brw_fs_sel_peephole.cpp
index c875487..15027e0 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_sel_peephole.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_sel_peephole.cpp
@@ -164,26 +164,30 @@ fs_visitor::opt_peephole_sel()
             break;
          }
 
-         /* Only the last source register can be a constant, so if the MOV in
-          * the "then" clause uses a constant, we need to put it in a
-          * temporary.
-          */
-         fs_reg src0(then_mov[i]->src[0]);
-         if (src0.file == IMM) {
-            src0 = fs_reg(this, glsl_type::float_type);
-            src0.type = then_mov[i]->src[0].type;
-            mov_imm_inst[i] = MOV(src0, then_mov[i]->src[0]);
-         }
-
-         sel_inst[i] = SEL(then_mov[i]->dst, src0, else_mov[i]->src[0]);
-
-         if (brw->gen == 6 && if_inst->conditional_mod) {
-            /* For Sandybridge with IF with embedded comparison */
-            sel_inst[i]->predicate = BRW_PREDICATE_NORMAL;
+         if (!then_mov[i]->src[0].equals(else_mov[i]->src[0])) {
+            /* Only the last source register can be a constant, so if the MOV
+             * in the "then" clause uses a constant, we need to put it in a
+             * temporary.
+             */
+            fs_reg src0(then_mov[i]->src[0]);
+            if (src0.file == IMM) {
+               src0 = fs_reg(this, glsl_type::float_type);
+               src0.type = then_mov[i]->src[0].type;
+               mov_imm_inst[i] = MOV(src0, then_mov[i]->src[0]);
+            }
+
+            sel_inst[i] = SEL(then_mov[i]->dst, src0, else_mov[i]->src[0]);
+
+            if (brw->gen == 6 && if_inst->conditional_mod) {
+               /* For Sandybridge with IF with embedded comparison */
+               sel_inst[i]->predicate = BRW_PREDICATE_NORMAL;
+            } else {
+               /* Separate CMP and IF instructions */
+               sel_inst[i]->predicate = if_inst->predicate;
+               sel_inst[i]->predicate_inverse = if_inst->predicate_inverse;
+            }
          } else {
-            /* Separate CMP and IF instructions */
-            sel_inst[i]->predicate = if_inst->predicate;
-            sel_inst[i]->predicate_inverse = if_inst->predicate_inverse;
+            sel_inst[i] = MOV(then_mov[i]->dst, then_mov[i]->src[0]);
          }
       }
 
-- 
1.8.3.2