[PATCH] D61806: [DAGCombiner] try to move bitcast after extract_subvector

Sun May 12 06:29:36 PDT 2019

RKSimon accepted this revision.
RKSimon added a comment.
This revision is now accepted and ready to land.

LGTM - cheers.

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Comment at: llvm/test/CodeGen/X86/sad.ll:1452
 ; AVX2-NEXT:    vmovd %xmm0, %eax
 ; AVX2-NEXT:    vzeroupper
 ; AVX2-NEXT:    retq
----------------
spatel wrote:
> RKSimon wrote:
> > weird - if this is all xmm code now why hasn't the vzeroupper gone?
> There seem to be several potential missed opportunities to squash this, but we have the following heading into isel:
>           t142: v4i32 = scalar_to_vector Constant:i32<1>
>         t143: v8i32 = insert_subvector undef:v8i32, t142, Constant:i64<0>
>       t141: v8i32 = X86ISD::VZEXT_MOVL t143
>     t178: v4i32 = extract_subvector t141, Constant:i64<0>
> 
Thanks for checking - that should be easy enough to fix.

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https://reviews.llvm.org/D61806