[Mesa-dev] [PATCH] st/mesa: kill instruction if writemask=0 in eliminate_dead_code_advanced()

[Bryan Cain]

What does it do if there's no destination register?  In any case, I
don't think glsl_to_tgsi emits any ARLs of that form, so it shouldn't be
a problem.

Bryan

On 10/07/2011 01:06 PM, Marek Olšák wrote:
> I think ARL is allowed to have no destination register, right? In that
> case, there should be a special case not to eliminate ARLs.
>
> Marek
>
> On Fri, Oct 7, 2011 at 5:40 PM, Brian Paul <brian.e.paul at gmail.com> wrote:
>> From: Brian Paul <brianp at vmware.com>
>>
>> This fixes a bug where we'd wind up emitting an invalid instruction like
>> MOVE R[0]., R[1];  - note the empty/zero writemask.  If we don't write to
>> any dest register channels, cull the instruction.
>> ---
>>  src/mesa/state_tracker/st_glsl_to_tgsi.cpp |    8 +++++++-
>>  1 files changed, 7 insertions(+), 1 deletions(-)
>>
>> diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
>> index d8ef8a3..44b1149 100644
>> --- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
>> +++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
>> @@ -3776,8 +3776,14 @@ glsl_to_tgsi_visitor::eliminate_dead_code_advanced(void)
>>          iter.remove();
>>          delete inst;
>>          removed++;
>> -      } else
>> +      } else {
>>          inst->dst.writemask &= ~(inst->dead_mask);
>> +         if (inst->dst.writemask == 0) {
>> +            iter.remove();
>> +            delete inst;
>> +            removed++;
>> +         }
>> +      }
>>    }
>>
>>    ralloc_free(write_level);
>> --
>> 1.7.3.4
>>
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