[PATCH] D32293: InstructionSimplify: Simplify a shuffle with a undef mask to undef
Zvi Rackover via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 20 07:15:16 PDT 2017
zvi created this revision.
Following the discussion in pr32486, adding the simplification:
shuffle %x, %y, undef -> undef
Repository:
rL LLVM
https://reviews.llvm.org/D32293
Files:
lib/Analysis/InstructionSimplify.cpp
test/Transforms/InstSimplify/shufflevector.ll
Index: test/Transforms/InstSimplify/shufflevector.ll
===================================================================
--- test/Transforms/InstSimplify/shufflevector.ll
+++ test/Transforms/InstSimplify/shufflevector.ll
@@ -118,6 +118,14 @@
ret <4 x i32> %shuf
}
+define <4 x i32> @undef_mask_1(<4 x i32> %x, <4 x i32> %y) {
+; CHECK-LABEL: @undef_mask_1(
+; CHECK-NEXT: ret <4 x i32> undef
+;
+ %shuf = shufflevector <4 x i32> %x, <4 x i32> %y, <4 x i32> undef
+ ret <4 x i32> %shuf
+}
+
define <4 x i32> @identity_mask_0(<4 x i32> %x) {
; CHECK-LABEL: @identity_mask_0(
; CHECK-NEXT: ret <4 x i32> [[X:%.*]]
Index: lib/Analysis/InstructionSimplify.cpp
===================================================================
--- lib/Analysis/InstructionSimplify.cpp
+++ lib/Analysis/InstructionSimplify.cpp
@@ -4144,6 +4144,9 @@
auto *Op0Const = dyn_cast<Constant>(Op0);
auto *Op1Const = dyn_cast<Constant>(Op1);
+ if (isa<UndefValue>(Mask))
+ return UndefValue::get(RetTy);
+
// If all operands are constant, constant fold the shuffle.
if (Op0Const && Op1Const)
return ConstantFoldShuffleVectorInstruction(Op0Const, Op1Const, Mask);
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