sext(undef) = 0, because the top bits will all be the same.
zext(undef) = 0, because the top bits will be zero.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127649 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index bcb0ffe..c2711c8 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2483,7 +2483,8 @@
if (OpOpcode == ISD::SIGN_EXTEND || OpOpcode == ISD::ZERO_EXTEND)
return getNode(OpOpcode, DL, VT, Operand.getNode()->getOperand(0));
else if (OpOpcode == ISD::UNDEF)
- return getUNDEF(VT);
+ // sext(undef) = 0, because the top bits will all be the same.
+ return getConstant(0, VT);
break;
case ISD::ZERO_EXTEND:
assert(VT.isInteger() && Operand.getValueType().isInteger() &&
@@ -2498,6 +2499,9 @@
if (OpOpcode == ISD::ZERO_EXTEND) // (zext (zext x)) -> (zext x)
return getNode(ISD::ZERO_EXTEND, DL, VT,
Operand.getNode()->getOperand(0));
+ else if (OpOpcode == ISD::UNDEF)
+ // zext(undef) = 0, because the top bits will be zero.
+ return getConstant(0, VT);
break;
case ISD::ANY_EXTEND:
assert(VT.isInteger() && Operand.getValueType().isInteger() &&