When emitting a MAC instruction in a vertex shader, brw_vs_emit()
calls accumulator_contains() to determine whether the accumulator
already contains the appropriate addend; if it does, then we can avoid
emitting an unnecessary MOV instruction.
However, accumulator_contains() wasn't checking the val.negate or
val.abs flags. As a result, if the desired value was the negation, or
the absolute value, of what was already in the accumulator, we would
generate an incorrect shader.
Fixes piglit test vs-refract-vec4-vec4-float.
Tested on Gen5 and Gen6.
Reviewed-by: Eric Anholt <eric@anholt.net>
(cherry picked from commit
d92463d5dc42aca09a54588c322fc60582cf9131)
if (val.address_mode != BRW_ADDRESS_DIRECT)
return GL_FALSE;
+ if (val.negate || val.abs)
+ return GL_FALSE;
+
switch (prev_insn->header.opcode) {
case BRW_OPCODE_MOV:
case BRW_OPCODE_MAC: