[Mesa-dev] [PATCH] i965/vec4: use a temp register to compute offsets for pull loads

[Iago Toral]

Yes, I agree, thanks for bringing it up.

Iago

On Tue, 2018-02-20 at 16:38 +0200, Andres Gomez wrote:
> Iago, this looks like a good candidate to nominate for inclusion in
> the
> 17.3 stable queue.
> 
> What do you think?
> 
> On Wed, 2017-11-29 at 11:49 +0100, Iago Toral Quiroga wrote:
> > 64-bit pull loads are implemented by emitting 2 separate
> > 32-bit pull load messages, where the second message loads from
> > an offset at +16B.
> > 
> > That addition of 16B to the original offset should not alter the
> > original offset register used as source for the pull load
> > instruction
> > though, since the compiler might use that same offset register in
> > other
> > instructions (for example, for other pull loads in the shader code
> > that take that same offset as reference).
> > 
> > If the pull load is 32-bit then we only need to emit one message
> > and
> > we don't need to do offset calculations, but in that case the
> > optimizer
> > should be able to drop the redundant MOV.
> > 
> > Fixes the following test on Haswell:
> > KHR-GL45.gpu_shader_fp64.fp64.max_uniform_components
> > ---
> >  src/intel/compiler/brw_vec4_nir.cpp | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/intel/compiler/brw_vec4_nir.cpp
> > b/src/intel/compiler/brw_vec4_nir.cpp
> > index 0a1caa9fad..84f5b37a9d 100644
> > --- a/src/intel/compiler/brw_vec4_nir.cpp
> > +++ b/src/intel/compiler/brw_vec4_nir.cpp
> > @@ -888,7 +888,9 @@
> > vec4_visitor::nir_emit_intrinsic(nir_intrinsic_instr *instr)
> >        if (const_offset) {
> >           offset_reg = brw_imm_ud(const_offset->u32[0] & ~15);
> >        } else {
> > -         offset_reg = get_nir_src(instr->src[1], nir_type_uint32,
> > 1);
> > +         offset_reg = src_reg(this, glsl_type::uint_type);
> > +         emit(MOV(dst_reg(offset_reg),
> > +                  get_nir_src(instr->src[1], nir_type_uint32,
> > 1)));
> >        }
> >  
> >        src_reg packed_consts;