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i965: vs optimization fix: Check val.{negate,abs} in accumulator_contains()

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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>
This commit is contained in:
Paul Berry 2011-07-22 14:05:52 -07:00
parent 572f631895
commit d92463d5dc
1 changed files with 3 additions and 0 deletions
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src/mesa/drivers/dri/i965/brw_vs_emit.c
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@ -1821,6 +1821,9 @@ accumulator_contains(struct brw_vs_compile *c, struct brw_reg val)
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: