Fix icmp lowering
Summary:
During icmp lowering it can happen that a constant value can be larger than expected (see the code around the change).
APInt::getMinSignedBits() must be checked again as the shift before can change the constant sign to positive.
I'm not sure it is the best fix possible though.
Test Plan: Regression test included.
Reviewers: resistor, chandlerc, spatel, hfinkel
Reviewed By: hfinkel
Subscribers: hfinkel, llvm-commits
Differential Revision: http://reviews.llvm.org/D9147
llvm-svn: 237812
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 38e39e5..055406c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1730,7 +1730,8 @@
ShiftBits = C1.countTrailingZeros();
}
NewC = NewC.lshr(ShiftBits);
- if (ShiftBits && isLegalICmpImmediate(NewC.getSExtValue())) {
+ if (ShiftBits && NewC.getMinSignedBits() <= 64 &&
+ isLegalICmpImmediate(NewC.getSExtValue())) {
EVT ShiftTy = DCI.isBeforeLegalize() ?
getPointerTy() : getShiftAmountTy(N0.getValueType());
EVT CmpTy = N0.getValueType();