[PATCH] D96206: [X86] Fold bitcast(logic(bitcast(X), Y)) --> logic'(X, bitcast(Y)) for int-int bitcasts

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: llvm/test/CodeGen/X86/vec_saddo.ll:816
 ; SSE-NEXT:    pcmpgtd %xmm2, %xmm4
-; SSE-NEXT:    pshufd {{.*#+}} xmm5 = xmm4[0,0,2,2]
 ; SSE-NEXT:    pcmpeqd %xmm3, %xmm2
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pengfei wrote:
> RKSimon wrote:
> > pengfei wrote:
> > > I haven't figured the math here out yet, but the removal of this doesn't look correct to me.
> > > The previous math is `xmm4[0] & xmm2[1] | xmm4[1]`, but we are changing it to `xmm4[1] & xmm2[1] | xmm4[1]`.
> > I think this is SimplifyDemandedElts (called from one of the shuffles below) being able to remove the shuffle now that it can see everything as <4 x i32> - but I haven't confirmed that yet.
> Verified it locally by random number https://godbolt.org/z/61eTfr, the change here should be correct.
Nice! Thank you.


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  https://reviews.llvm.org/D96206/new/

https://reviews.llvm.org/D96206