mesa/program: Don't copy propagate from swizzles.

Do not propagate a copy if source and destination are identical.

Otherwise code like

MOV TEMP[0].xyzw, TEMP[0].wzyx
MOV TEMP[1].xyzw, TEMP[0].xyzw

is changed to

MOV TEMP[0].xyzw, TEMP[0].wzyx
MOV TEMP[1].xyzw, TEMP[0].wzyx

This fixes Piglit test shaders/glsl-copy-propagation-self-2 for drivers that
use Mesa IR.

NOTE: This is a candidate for the stable branches.
Signed-off-by: Fabian Bieler <fabianbieler@fastmail.fm>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp
index 0848462..363efe7 100644 (file)
--- a/src/mesa/program/ir_to_mesa.cpp
+++ b/src/mesa/program/ir_to_mesa.cpp
@@ -2768,6 +2768,8 @@ ir_to_mesa_visitor::copy_propagate(void)
       /* If this is a copy, add it to the ACP. */
       if (inst->op == OPCODE_MOV &&
          inst->dst.file == PROGRAM_TEMPORARY &&
+         !(inst->dst.file == inst->src[0].file &&
+           inst->dst.index == inst->src[0].index) &&
          !inst->dst.reladdr &&
          !inst->saturate &&
          !inst->src[0].reladdr &&