[InstCombine] Fix Incorrect fold of ashr+xor -> lshr w/ vectors

Fixes https://bugs.llvm.org/show_bug.cgi?id=43665
llvm · Mar 26, 2020 · 7a89a5d · 7a89a5d
1 parent fe025a3
commit 7a89a5d
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Showing 2 changed files with 7 additions and 3 deletions.
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -3069,8 +3069,12 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
     // ~(C >>s Y) --> ~C >>u Y (when inverting the replicated sign bits)
     Constant *C;
     if (match(NotVal, m_AShr(m_Constant(C), m_Value(Y))) &&
-        match(C, m_Negative()))
-      return BinaryOperator::CreateLShr(ConstantExpr::getNot(C), Y);
+        match(C, m_Negative())) {
+      Constant *NewC = ConstantExpr::getNot(C);
+      if (C->getType()->isVectorTy())
+        NewC = getSafeVectorConstantForBinop(Instruction::LShr, NewC, false);
+      return BinaryOperator::CreateLShr(NewC, Y);
+    }
 
     // ~(C >>u Y) --> ~C >>s Y (when inverting the replicated sign bits)
     if (match(NotVal, m_LShr(m_Constant(C), m_Value(Y))) &&

diff --git a/llvm/test/Transforms/InstCombine/vector-xor.ll b/llvm/test/Transforms/InstCombine/vector-xor.ll
@@ -140,7 +140,7 @@ define <4 x i32> @test_v4i32_not_ashr_negative_const(<4 x i32> %a0) {
 
 define <4 x i32> @test_v4i32_not_ashr_negative_const_undef(<4 x i32> %a0) {
 ; CHECK-LABEL: @test_v4i32_not_ashr_negative_const_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = lshr <4 x i32> <i32 2, i32 4, i32 undef, i32 8>, [[A0:%.*]]
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr <4 x i32> <i32 2, i32 4, i32 0, i32 8>, [[A0:%.*]]
 ; CHECK-NEXT:    ret <4 x i32> [[TMP1]]
 ;
   %1 = ashr <4 x i32> <i32 -3, i32 -5, i32 undef, i32 -9>, %a0