[PATCH] D85765: [InstSimplify] Remove select ?, undef, X -> X and select ?, X, undef -> X transforms

[Nikita Popov via Phabricator via llvm-commits]

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

LGTM



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Comment at: clang/test/CodeGen/arm-mve-intrinsics/dup.c:246
+// CHECK-NEXT:    [[TMP2:%.*]] = select <8 x i1> [[TMP1]], <8 x half> [[DOTSPLAT]], <8 x half> undef
+// CHECK-NEXT:    ret <8 x half> [[TMP2]]
 //
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Does the lowering for these intrinsics need to be adjusted in some way? This looks a bit odd and is possibly not what was intended with this fold gone. @dmgreen 


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Comment at: llvm/lib/IR/ConstantFold.cpp:804
+  if (isa<UndefValue>(V1) && NotPoison(V2)) return V2;
+  if (isa<UndefValue>(V2) && NotPoison(V1)) return V1;
+
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craig.topper wrote:
> nikic wrote:
> > Why does this not use isGuaranteedNotToBeUndefOrPoison?
> I don't think IR library can depend on the Analysis library.
Oh, right, that makes sense. We'll probably want to extract this at some later point in time.


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  https://reviews.llvm.org/D85765/new/

https://reviews.llvm.org/D85765