[Mesa-dev] [PATCH 05/12] i965/fs: Use offset a lot more places

[Matt Turner]

On Mon, Sep 22, 2014 at 1:40 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
> On Fri, Sep 19, 2014 at 5:34 PM, Matt Turner <mattst88 at gmail.com> wrote:
>> On Fri, Sep 19, 2014 at 1:10 PM, Jason Ekstrand <jason at jlekstrand.net>
>> > diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp
>> > b/src/mesa/drivers/dri/i965/brw_fs.cpp
>> > index af8c087..ea91705 100644
>> > --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
>> > +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
>> > @@ -310,8 +310,8 @@ fs_visitor::VARYING_PULL_CONSTANT_LOAD(const fs_reg
>> > &dst,
>> >           inst->mlen = 1 + dispatch_width / 8;
>> >     }
>> >
>> > -   vec4_result.reg_offset += (const_offset & 3) * scale;
>> > -   instructions.push_tail(MOV(dst, vec4_result));
>> > +   fs_reg result = offset(vec4_result, (const_offset & 3) * scale);
>> > +   instructions.push_tail(MOV(dst, result));
>>
>> Isn't this going to cause us to copy an fs_reg twice, rather than just
>> setting .reg_offset?
>>
>> I'd like to check the generated code.
>
> What's your concern there?  Just that we're useing more CPU?

Yeah, that we're now potentially copying an fs_reg twice when our
purpose is just to set a single integer.