On Sat, 23 Jul 2011 09:38:05 -0700, Paul Berry <stereotype...@gmail.com> wrote: > On 22 July 2011 18:17, Eric Anholt <e...@anholt.net> wrote: > > On Fri, 22 Jul 2011 15:07:57 -0700, Paul Berry <stereotype...@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. > > Oh, thanks for alerting me to the existence of val.abs. I believe > your analysis is correct, but if it's all the same to you I think I'd > rather switch to: > > if (val.negate || val.abs) > return GL_FALSE; > > Since the efficiency cost of checking val.abs is negligible, and it > takes less thinking to be certain that this is correct.
Sounds good.
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