[PATCH] D127253: [AMDGPU] Use v_mad_u64_u32 for IMAD32

Thu Jun 9 02:11:48 PDT 2022

foad added inline comments.

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Comment at: llvm/test/CodeGen/AMDGPU/mad_u64_u32.ll:46
+; GFX9-NEXT:    s_mov_b32 s0, 42
+; GFX9-NEXT:    v_mad_u64_u32 v[0:1], s[0:1], v0, v1, s[0:1]
+; GFX9-NEXT:    ; return to shader part epilog
----------------
rampitec wrote:
> foad wrote:
> > rampitec wrote:
> > > rampitec wrote:
> > > > foad wrote:
> > > > > As a follow up it would be nice if we could fold the "42" into the mad as an inline src2.
> > > > Sure. I will take a look why didn't it fold in a followup.
> > > This actually did not fold because of the IMPLICIT_DEF. This is technically not a constant, but a 64 bit partial undef:
> > > ```
> > >   %3:sreg_32 = S_MOV_B32 42
> > >   %5:sreg_32 = IMPLICIT_DEF
> > >   %4:sreg_64 = REG_SEQUENCE killed %3:sreg_32, %subreg.sub0, killed %5:sreg_32, %subreg.sub1
> > >   %7:vreg_64, %8:sreg_64 = V_MAD_U64_U32_e64 %0:vgpr_32, %1:vgpr_32, killed %4:sreg_64, 0, implicit $exec
> > > ```
> > Thanks! Can you add a test where the constant is too large to go inline, if there isn't one already? I guess this can be a literal on GFX10 but not on GFX9.
> I believe 42 cannot be inline? That's why I was using it in the first place.
Integers from -16 to 64 are inline.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D127253/new/

https://reviews.llvm.org/D127253