[PATCH] D66680: [DAGCombiner][X86] Teach SimplifyVBinOp to fold VBinOp (concat X, undef/constant), (concat Y, undef/constant) -> concat (VBinOp X, Y), VecC

[Craig Topper via Phabricator via llvm-commits]

craig.topper marked an inline comment as done.
craig.topper added inline comments.


================
Comment at: llvm/test/CodeGen/X86/madd.ll:2761
-; AVX256-NEXT:    vextracti128 $1, %ymm0, %xmm1
-; AVX256-NEXT:    vpor %xmm1, %xmm0, %xmm0
-; AVX256-NEXT:    vpshufd {{.*#+}} xmm1 = xmm0[2,3,0,1]
----------------
We were just barely able to prove the bits were all 0 and therefore disjoint, but weren't able to remove the ADD/OR completely because the disjoint bits code gets to go one level deeper in computeKnownBits then SimplifyDemandedBits. This is because the disjoint check starts at a depth of 0 for the operands, but the SimplifyDemandedBits starts at a depth of 0 for the OR node itself.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D66680/new/

https://reviews.llvm.org/D66680