[Mesa-dev] [PATCH] svga: allow non-contiguous VS input declarations

[Brian Paul]

On 02/18/2016 11:36 AM, Charmaine Lee wrote:
>
>> From: Brian Paul <brianp at vmware.com>
>> Sent: Thursday, February 18, 2016 7:51 AM
>> To: mesa-dev at lists.freedesktop.org
>> Cc: Charmaine Lee
>> Subject: [PATCH] svga: allow non-contiguous VS input declarations
>>
>> This fixes a glDrawPixels regression since b63fe0552b5f.  The new
>> quad-drawing utility code uses 3 vertex attributes (xyz, rgba, st).
>> For glDrawPixels path we don't use the rgba attribute so there's a
>> gap in the TGSI VS input declarations (INPUT[0] = pos, INPUT[2] =
>> texcoord).  The TGSI->VGPU10 translations code did not handle this
>> correctly.  I missed this because my VM was configured for HWv11
>> while testing.
>>
>> Another way to fix this would be to change the tgsi_scan.c code so
>> that the tgsi_shader_info::num_inputs (and num_outputs) included
>> the unused inputs/outputs.  These counts would then actually be
>> "max input register index + 1" rather than "number of used inputs".
>> But that change could impact all drivers so put it off for now.
>>
>> No regressions found with piglit or typical GL apps.
>> ---
>> src/gallium/drivers/svga/svga_tgsi_vgpu10.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/gallium/drivers/svga/svga_tgsi_vgpu10.c b/src/gallium/drivers/svga/svga_tgsi_vgpu10.c
>> index 1223e44..384fb9e 100644
>> --- a/src/gallium/drivers/svga/svga_tgsi_vgpu10.c
>> +++ b/src/gallium/drivers/svga/svga_tgsi_vgpu10.c
>> @@ -2446,7 +2446,7 @@ emit_input_declarations(struct svga_shader_emitter_v10 *emit)
>>     else {
>>        assert(emit->unit == PIPE_SHADER_VERTEX);
>>>
>> -      for (i = 0; i < emit->info.num_inputs; i++) {
>> +      for (i = 0; i < emit->info.file_max[TGSI_FILE_INPUT] + 1; i++) {
>>           unsigned usage_mask = emit->info.input_usage_mask[i];
>>           unsigned index = i;
>
> num_inputs are referenced in other functions as well such as svga_get_generic_inputs_mask,
> don't we need to fix those as well?

svga_get_generic_inputs_mask() is only concerned with FS inputs so we're 
OK there.  IIRC, the GLSL linker (or maybe the GLSL->TGSI converter) 
allocates contiguous outputs/inputs between shader stages so there 
should be no gaps there.  I think it's just VS inputs where we can have 
gaps.

But now I'm looking at alloc_system_value_index() which uses 
info.num_inputs, potentially for the VS...

-Brian