[Mesa-dev] [PATCH 2/5] i965: Add function to negate immediates.

[Jason Ekstrand]

On Fri, Jan 30, 2015 at 5:28 PM, Matt Turner <mattst88 at gmail.com> wrote:

> On Fri, Jan 30, 2015 at 4:02 PM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
> > On Fri, Jan 30, 2015 at 3:54 PM, Matt Turner <mattst88 at gmail.com> wrote:
> >> ---
> >>  src/mesa/drivers/dri/i965/brw_shader.cpp | 37
> >> ++++++++++++++++++++++++++++++++
> >>  src/mesa/drivers/dri/i965/brw_shader.h   |  1 +
> >>  2 files changed, 38 insertions(+)
> >>
> >> diff --git a/src/mesa/drivers/dri/i965/brw_shader.cpp
> >> b/src/mesa/drivers/dri/i965/brw_shader.cpp
> >> index c393bfc..ff2edf3 100644
> >> --- a/src/mesa/drivers/dri/i965/brw_shader.cpp
> >> +++ b/src/mesa/drivers/dri/i965/brw_shader.cpp
> >> @@ -620,6 +620,43 @@ brw_saturate_immediate(enum brw_reg_type type,
> struct
> >> brw_reg *reg)
> >>     return false;
> >>  }
> >>
> >> +bool
> >> +brw_negate_immediate(enum brw_reg_type type, struct brw_reg *reg)
> >> +{
> >> +   switch (type) {
> >> +   case BRW_REGISTER_TYPE_UD:
> >> +   case BRW_REGISTER_TYPE_D:
> >> +      reg->dw1.d = -reg->dw1.d;
> >> +      return true;
> >> +   case BRW_REGISTER_TYPE_UW:
> >> +      reg->dw1.d = -(uint16_t)reg->dw1.ud;
> >
> >
> > Do we really want to negate UW and UD sources?  If so, shouldn't we
> change
> > the register type to signed or something?  Maybe there's something I
> don't
> > know about the arch, but this seems fishy.
>
> I think it's okay. The source language lets you do it and the hardware
> lets you do it. I don't think D vs UD (or W vs UW) changes the
> operation the negation modifier performs (maybe except for the case of
> using it in conjunction with conditional mod).
>
> In any case, it doesn't catch anything in shader-db, so I don't mind
> just returning false for UD and UW.
>
> > Same comment applies on the next patch with abs().
>
> Surely an abs source modifier on an unsigned source is a no-op. Again,
> no changes in shader-db because of allowing it though, so I don't mind
> just returning false.
>

Right...


>
> > Other than that, everything in this series looks fine.
>
> Thanks. I'll slap your R-b on it.
>

Go ahead.
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