Fold shift by size larger than type size to undef
Make llvm undef values generate ISD::UNDEF nodes
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21261 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 634197c..613d098 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -755,19 +755,12 @@
case ISD::SHL:
case ISD::SRL:
- // If the shift amount is bigger than the size of the data, simplify.
- if (C2 >= MVT::getSizeInBits(N1.getValueType())) {
- if (TLI.getShiftAmountFlavor() == TargetLowering::Mask) {
- unsigned NewAmt =
- C2 & ((1 << MVT::getSizeInBits(N1.getValueType()))-1);
- return getNode(Opcode, VT, N1, getConstant(NewAmt,N2.getValueType()));
- } else if (TLI.getShiftAmountFlavor() == TargetLowering::Extend) {
- // Shifting all of the bits out?
- return getConstant(0, N1.getValueType());
- }
- }
- // FALL THROUGH.
case ISD::SRA:
+ // If the shift amount is bigger than the size of the data, then all the
+ // bits are shifted out. Simplify to loading constant zero.
+ if (C2 >= MVT::getSizeInBits(N1.getValueType())) {
+ return getNode(ISD::UNDEF, N1.getValueType());
+ }
if (C2 == 0) return N1;
break;