[Mesa-dev] [PATCH] i965: vs optimization fix: Check val.negate in accumulator_contains()

Eric Anholt eric at anholt.net
Fri Jul 22 18:17:06 PDT 2011

On Fri, 22 Jul 2011 15:07:57 -0700, Paul Berry <stereotype441 at gmail.com> wrote:
> 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 flag.
> As a result, if the accumulator contained the negation of the desired
> value, we would generate an incorrect shader.
> Fixes piglit test vs-refract-vec4-vec4-float.
> Tested on Gen5 and Gen6.

Looks like val.abs doesn't currently need this treatement because we
never generate regs with it where they'd appear as the arg to MAD.

Reviewed-by: Eric Anholt <eric at anholt.net>
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