[PATCH] D32293: InstructionSimplify: Simplify a shuffle with a undef mask to undef

[Davide Italiano via Phabricator via llvm-commits]

davide requested changes to this revision.
davide added inline comments.
This revision now requires changes to proceed.


================
Comment at: lib/Analysis/InstructionSimplify.cpp:4147-4149
+  if (isa<UndefValue>(Mask))
+    return UndefValue::get(RetTy);
+
----------------
microopt: you can move this up to the beginning of the function.


================
Comment at: test/Transforms/InstSimplify/shufflevector.ll:113-119
 define <4 x i32> @undef_mask(<4 x i32> %x) {
 ; CHECK-LABEL: @undef_mask(
 ; CHECK-NEXT:    ret <4 x i32> undef
 ;
   %shuf = shufflevector <4 x i32> %x, <4 x i32> undef, <4 x i32> undef
   ret <4 x i32> %shuf
 }
----------------
We have a similar case here, maybe it makes sense to handle them together?


Repository:
  rL LLVM

https://reviews.llvm.org/D32293