[Mesa-dev] [PATCH] compiler: add SYSTEM_VALUE_VARYING_COORD

[Rob Clark]

On Mon, Aug 20, 2018 at 6:54 PM Bas Nieuwenhuizen
<bas at basnieuwenhuizen.nl> wrote:
>
> On Tue, Aug 21, 2018 at 12:38 AM, Marek Olšák <maraeo at gmail.com> wrote:
> > On Fri, Aug 10, 2018 at 9:26 AM Rob Clark <robdclark at gmail.com> wrote:
> >>
> >> Used internally in freedreno/ir3 for the vec2 value that hw passes to
> >> shader to use as coordinate for bary.f (varying fetch) instruction.
> >> This is not the same as SYSTEM_VALUE_FRAG_COORD.
> >>
> >> Signed-off-by: Rob Clark <robdclark at gmail.com>
> >> ---
> >> Up until now, we'd been hard-coding the location of this value (ie. to
> >> r0.xy), mostly because originally in the early a3xx days I didn't know
> >> which bits could configure this value (blob was always using r0.xy so
> >> in cmdstream traces it always showed up as 0's).
> >>
> >> But starting with a6xx, the address register aliases r0.x, which kinda
> >> throws a monkey-wrench in the existing scheme of hard-coding.  The good
> >> news is that I know the bits to configure this value for a3xx-a6xx.
> >>
> >> So I'm shifting over to handling this like a sysval.
> >>
> >>  src/compiler/shader_enums.c                | 1 +
> >>  src/compiler/shader_enums.h                | 6 ++++++
> >>  src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 1 +
> >>  3 files changed, 8 insertions(+)
> >>
> >> diff --git a/src/compiler/shader_enums.c b/src/compiler/shader_enums.c
> >> index a874083a0b7..0210b503d3f 100644
> >> --- a/src/compiler/shader_enums.c
> >> +++ b/src/compiler/shader_enums.c
> >> @@ -244,6 +244,7 @@ gl_system_value_name(gl_system_value sysval)
> >>       ENUM(SYSTEM_VALUE_DEVICE_INDEX),
> >>       ENUM(SYSTEM_VALUE_VIEW_INDEX),
> >>       ENUM(SYSTEM_VALUE_VERTEX_CNT),
> >> +     ENUM(SYSTEM_VALUE_VARYING_COORD),
> >>     };
> >>     STATIC_ASSERT(ARRAY_SIZE(names) == SYSTEM_VALUE_MAX);
> >>     return NAME(sysval);
> >> diff --git a/src/compiler/shader_enums.h b/src/compiler/shader_enums.h
> >> index f8e22925f35..5c36f55283c 100644
> >> --- a/src/compiler/shader_enums.h
> >> +++ b/src/compiler/shader_enums.h
> >> @@ -601,6 +601,12 @@ typedef enum
> >>      */
> >>     SYSTEM_VALUE_VERTEX_CNT,
> >>
> >> +   /**
> >> +    * Driver internal varying-coord, used for varying-fetch instructions.
> >> +    * Not externally visible.
> >> +    */
> >
> > Can you improve the documentation, so that mere mortals understand
> > what it means? Does it correspond to something in AMD hw?
>
> I'd expect this to correspond to stuff like PERSP_CENTER on AMD?
>
> Which begs the question, does this need distinguishing on
> center/centroid/per-sample?

so, adreno, being gles hw, has just "smooth" and "flat" varyings..

that said, I've been kinda thinking of this as an opaque driver
specific sysval without paying too much attention to what the value
actually is other than "the thing you pass to bary.f to get non-flat
varyings"..  I confess to not having looked into how this works on
other hw..

BR,
-R


>
> - Bas
> >
> > Marek
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