Make sure we don't return bits outside the mask in ComputeMaskedBits. PR12189.

llvm-svn: 152066

2 files changed, 24 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index b5811f2e8ae..b35e2074acb 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -691,8 +691,8 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
       if (P->hasConstantValue() == P)
         break;
 
-      KnownZero = APInt::getAllOnesValue(BitWidth);
-      KnownOne = APInt::getAllOnesValue(BitWidth);
+      KnownZero = Mask;
+      KnownOne = Mask;
       for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) {
         // Skip direct self references.
         if (P->getIncomingValue(i) == P) continue;
diff --git a/llvm/test/Transforms/InstSimplify/phi.ll b/llvm/test/Transforms/InstSimplify/phi.ll
new file mode 100644
index 00000000000..05cd40d9021
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/phi.ll
@@ -0,0 +1,22 @@
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+; PR12189
+define i1 @test1(i32 %x) {
+; CHECK: @test1
+  br i1 true, label %a, label %b
+
+a:
+  %aa = or i32 %x, 10
+  br label %c
+
+b:
+  %bb = or i32 %x, 10
+  br label %c
+
+c:
+  %cc = phi i32 [ %bb, %b ], [%aa, %a ]
+  %d = urem i32 %cc, 2
+  %e = icmp eq i32 %d, 0
+  ret i1 %e
+; CHECK: ret i1 %e
+}