diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 3947648e6a72..cfe71708fe04 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1965,6 +1965,7 @@ void SelectionDAG::ComputeMaskedBits(SDValue Op, APInt &KnownZero,
     APInt InMask = APInt::getLowBitsSet(BitWidth, VT.getSizeInBits());
     ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
     KnownZero |= (~InMask);
+    KnownOne  &= (~KnownZero);
     return;
   }
   case ISD::FGETSIGN:
diff --git a/llvm/test/CodeGen/X86/2012-07-16-fp2ui-i1.ll b/llvm/test/CodeGen/X86/2012-07-16-fp2ui-i1.ll
new file mode 100644
index 000000000000..17533a1e1649
--- /dev/null
+++ b/llvm/test/CodeGen/X86/2012-07-16-fp2ui-i1.ll
@@ -0,0 +1,12 @@
+; RUN: llc < %s -march=x86-64 -mcpu=corei7
+
+define void @autogen_SD3100() {
+BB:
+  %FC123 = fptoui float 0x40693F5D00000000 to i1
+  br i1 %FC123, label %V, label %W
+
+V:
+  ret void
+W:
+  ret void
+}