[PATCH] D140811: [DAGCombiner][X86] `visitVECTOR_SHUFFLE()`: splats with a single non-undef element are not splats

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


================
Comment at: llvm/test/CodeGen/X86/horizontal-sum.ll:66
+; AVX2-SLOW-NEXT:    vinsertps {{.*#+}} xmm0 = xmm0[0,1,2],xmm1[0]
 ; AVX2-SLOW-NEXT:    retq
   %5 = shufflevector <4 x float> %0, <4 x float> poison, <2 x i32> <i32 0, i32 2>
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regression - we've gone from 3hops to 4hops + extra shuffles


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  https://reviews.llvm.org/D140811/new/

https://reviews.llvm.org/D140811