[Mesa-dev] [PATCH 2/6] i965/fs: use the new helper function to create double immediates

[Kenneth Graunke]

On Monday, July 11, 2016 1:19:34 PM PDT Samuel Iglesias Gonsálvez wrote:
> 
> On 06/07/16 22:32, Kenneth Graunke wrote:
> > On Wednesday, July 6, 2016 12:09:58 PM PDT Samuel Iglesias Gonsálvez wrote:
> >> From: Iago Toral Quiroga <itoral at igalia.com>
> >>
> >> ---
> >>  src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 6 +++---
> >>  1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> >> index 268c847..d805d95 100644
> >> --- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> >> +++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> >> @@ -832,7 +832,7 @@ fs_visitor::nir_emit_alu(const fs_builder &bld, nir_alu_instr *instr)
> >>            * a register and compare with that.
> >>            */
> >>           fs_reg tmp = vgrf(glsl_type::double_type);
> >> -         bld.MOV(tmp, brw_imm_df(0.0));
> >> +         bld.MOV(tmp, setup_imm_df(0.0));
> > 
> > Does this need to be splatted out to a full SIMD-width?
> > Why not just do:
> > 
> >    fs_reg tmp = setup_imm_df(0.0);
> > 
> > and let the CMP compare against the stride 0 register?
> > 
> 
> I have just noticed this is not right.
> 
> CMP will use the 64-bit immediate as one of the sources of the CMP,
> which is not valid in gen8+. According to BDW+'s PRMs, an 64-bit
> immediate is only valid in source values for instructions with single
> source operands.
> 
> I am going to keep the original patch.
> 
> Sam

Ah, right, I missed that on Gen8+ setup_imm_df returns an actual
immediate, rather than a GRF register with the immediate loaded into it.

Feel free to ignore that suggestion.
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