[Mesa-dev] [PATCH 1/9] glsl: don't lower fragdata array if the output data types don't match

[Matt Turner]

On Tue, Feb 24, 2015 at 10:02 AM, Eduardo Lima Mitev <elima at igalia.com> wrote:
> From: Samuel Iglesias Gonsalvez <siglesias at igalia.com>
>
> Commit 7e414b58640aee6e243d337e72cea290c354f632 broke the gl_FragData array
> into separate gl_FragData[i] variables, so drivers can eliminate useless
> writes to gl_FragData improving their performance.
>
> The problem occurs when GLSL IR code is linked in the following case:
>
> * The FS output variable base data type does not match gl_FragData one (float
>   vector)
> * The FS output variable is replaced by gl_out_FragDataX because of commit
>   7e414b58640aee6 with X from 0 to GL_MAX_DRAW_BUFFERS.
>
> Then the FS output variable base data type is lost in the resulting GLSL IR,
> making that the driver does a wrong assignment to gl_out_FragData components
> because of unmatching data types.
>
> This patch reverts the fragdata array lowering when the output var base data type
> doesn't match gl_out_FragData, i.e., when output variable base data type is
> not a float or a float vector.
>
> This patch fixes 250 dEQP tests (tested in an Intel Haswell machine)
>
> dEQP-GLES3.functional.fragment_out.random.* (22 failed tests)
> dEQP-GLES3.functional.fragment_out.array.uint.* (120 failed tests)
> dEQP-GLES3.functional.fragment_out.array.int.* (108 failed tests)

All of these pass for me on Haswell with today's master branch --
finally a case of NIR's screwing up the types helping something :)

I've confirmed that this generates the same code with non-NIR and NIR
after this patch.

Reviewed-by: Matt Turner <mattst88 at gmail.com>

>
> Signed-off-by: Samuel Iglesias Gonsalvez <siglesias at igalia.com>
> ---
>  src/glsl/opt_dead_builtin_varyings.cpp | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/src/glsl/opt_dead_builtin_varyings.cpp b/src/glsl/opt_dead_builtin_varyings.cpp
> index 50c8aa7..4919c8b 100644
> --- a/src/glsl/opt_dead_builtin_varyings.cpp
> +++ b/src/glsl/opt_dead_builtin_varyings.cpp
> @@ -99,6 +99,16 @@ public:
>           }
>           else {
>              this->fragdata_usage |= 1 << index->get_uint_component(0);
> +            /* Don't lowered fragdata array if the output variable

typo: lower