[Mesa-dev] [PATCH 2/6] nir/lower_alu_to_scalar: Return after lower_reduction

[Jason Ekstrand]

On Tue, Sep 22, 2015 at 7:50 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> On Tuesday, September 22, 2015 06:18:12 PM Jason Ekstrand wrote:
>> We don't use any of the code after the switch and, as far as I can tell, it
>> wouldn't work anyway.  The only reason this wasn't causing us problems is
>> that it's all dead and DCE cleans it up.
>
> Huh, really?  Right after that switch statement I see:
>
>    if (instr->dest.dest.ssa.num_components == 1)
>       return;

Right.

> and reductions should always produce a single component, so this change
> seems like it should do nothing.  It seems like a reasonable change
> regardless...but...

Sure.  I'll change the commit message.  That said, I think my
confusion is, itself, enough justification for the change.

>> ---
>>  src/glsl/nir/nir_lower_alu_to_scalar.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/glsl/nir/nir_lower_alu_to_scalar.c b/src/glsl/nir/nir_lower_alu_to_scalar.c
>> index 5ef5ec2..84d4943 100644
>> --- a/src/glsl/nir/nir_lower_alu_to_scalar.c
>> +++ b/src/glsl/nir/nir_lower_alu_to_scalar.c
>> @@ -86,7 +86,7 @@ lower_alu_instr_scalar(nir_alu_instr *instr, nir_builder *b)
>>     case name##3: \
>>     case name##4: \
>>        lower_reduction(instr, chan, merge, b); \
>> -      break;
>> +      return;
>>
>>     switch (instr->op) {
>>     case nir_op_vec4:
>>