[Mesa-dev] [PATCH] r600g/llvm: don't export more colors than the number of CBs

[Marek Olšák]

See piglit/fbo-alphatest-nocolor.

Marek

On Sat, Aug 24, 2013 at 3:12 PM, Vadim Girlin <vadimgirlin at gmail.com> wrote:
> On 08/24/2013 02:31 PM, Marek Olšák wrote:
>>
>> Like Christoph said, COLOR0 (if available) must always be exported for
>> alpha test.
>
>
> Are there any piglit tests for that? I didn't see any regressions with this
> patch (at least on evergreen), possibly I messed up the testing somehow.
> Also I think old backend uses the same logic.
>
> Vadim
>
>
>>
>> Marek
>>
>> On Sat, Aug 24, 2013 at 3:30 AM, Vadim Girlin <vadimgirlin at gmail.com>
>> wrote:
>>>
>>> Currently llvm backend always exports at least one color in pixel
>>> shader even if no color buffers are enabled. With depth/stencil exports
>>> this can result in the following code:
>>>
>>> EXPORT             PIXEL 0     R0.xyzw  VPM
>>> EXPORT             PIXEL 61    R1.x___  VPM
>>> EXPORT_DONE        PIXEL 61    R0._x__  VPM  EOP
>>>
>>> AFAIU with zero color buffers no memory is reserved for colors in the
>>> export
>>> ring and all exports in this example actually write to the same location.
>>> The code above still works fine in this particular case, because correct
>>> values are written last, but reordering can break it (especially with SB
>>> which tends to reorder the exports).
>>>
>>> Signed-off-by: Vadim Girlin <vadimgirlin at gmail.com>
>>> ---
>>>
>>> This fixes regressions with LLVM+SB, so I consider it as a prerequisite
>>> for enabling SB by default. Also it fixes some issues with LLVM backend
>>> alone.
>>> Tested on evergreen only (I don't have other hw), needs testing on
>>> pre-evergreen GPUs.
>>>
>>>   src/gallium/drivers/r600/r600_llvm.c   | 2 +-
>>>   src/gallium/drivers/r600/r600_shader.c | 2 +-
>>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/src/gallium/drivers/r600/r600_llvm.c
>>> b/src/gallium/drivers/r600/r600_llvm.c
>>> index 03a68e4..d2f4aff 100644
>>> --- a/src/gallium/drivers/r600/r600_llvm.c
>>> +++ b/src/gallium/drivers/r600/r600_llvm.c
>>> @@ -333,8 +333,8 @@ static void llvm_emit_epilogue(struct
>>> lp_build_tgsi_context * bld_base)
>>>                  } else if (ctx->type == TGSI_PROCESSOR_FRAGMENT) {
>>>                          switch (ctx->r600_outputs[i].name) {
>>>                          case TGSI_SEMANTIC_COLOR:
>>> -                               has_color = true;
>>>                                  if ( color_count <
>>> ctx->color_buffer_count) {
>>> +                                       has_color = true;
>>>                                          LLVMValueRef args[3];
>>>                                          args[0] = output;
>>>                                          if (ctx->fs_color_all) {
>>> diff --git a/src/gallium/drivers/r600/r600_shader.c
>>> b/src/gallium/drivers/r600/r600_shader.c
>>> index fb766c4..85f8469 100644
>>> --- a/src/gallium/drivers/r600/r600_shader.c
>>> +++ b/src/gallium/drivers/r600/r600_shader.c
>>> @@ -1130,7 +1130,7 @@ static int r600_shader_from_tgsi(struct r600_screen
>>> *rscreen,
>>>                  radeon_llvm_ctx.face_gpr = ctx.face_gpr;
>>>                  radeon_llvm_ctx.r600_inputs = ctx.shader->input;
>>>                  radeon_llvm_ctx.r600_outputs = ctx.shader->output;
>>> -               radeon_llvm_ctx.color_buffer_count = MAX2(key.nr_cbufs ,
>>> 1);
>>> +               radeon_llvm_ctx.color_buffer_count = key.nr_cbufs;
>>>                  radeon_llvm_ctx.chip_class = ctx.bc->chip_class;
>>>                  radeon_llvm_ctx.fs_color_all = shader->fs_write_all &&
>>> (rscreen->chip_class >= EVERGREEN);
>>>                  radeon_llvm_ctx.stream_outputs = &so;
>>> --
>>> 1.8.3.1
>>>
>>> _______________________________________________
>>> mesa-dev mailing list
>>> mesa-dev at lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
>