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authorDuncan Sands <baldrick@free.fr>2012-10-02 15:03:49 +0000
committerDuncan Sands <baldrick@free.fr>2012-10-02 15:03:49 +0000
commit48da0be8b5821dddbb5233ad9cb198369031684b (patch)
treed07c95e8b95e64a915a84fcaabf2ec4c875b1a66 /lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
parent9e36496eb39656df8894a6a1cd56f3561f6672a4 (diff)
Fix PR13991: legalizing an overflowing multiplication operation is harder than
the add/sub case since in the case of multiplication you also have to check that the operation in the larger type did not overflow. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165017 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp')
-rw-r--r--lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp22
1 files changed, 15 insertions, 7 deletions
diff --git a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
index 1cccf1a057..a370faeb23 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -644,8 +644,9 @@ SDValue DAGTypeLegalizer::PromoteIntRes_XMULO(SDNode *N, unsigned ResNo) {
EVT SmallVT = LHS.getValueType();
// To determine if the result overflowed in a larger type, we extend the
- // input to the larger type, do the multiply, then check the high bits of
- // the result to see if the overflow happened.
+ // input to the larger type, do the multiply (checking if it overflows),
+ // then also check the high bits of the result to see if overflow happened
+ // there.
if (N->getOpcode() == ISD::SMULO) {
LHS = SExtPromotedInteger(LHS);
RHS = SExtPromotedInteger(RHS);
@@ -653,24 +654,31 @@ SDValue DAGTypeLegalizer::PromoteIntRes_XMULO(SDNode *N, unsigned ResNo) {
LHS = ZExtPromotedInteger(LHS);
RHS = ZExtPromotedInteger(RHS);
}
- SDValue Mul = DAG.getNode(ISD::MUL, DL, LHS.getValueType(), LHS, RHS);
+ SDVTList VTs = DAG.getVTList(LHS.getValueType(), N->getValueType(1));
+ SDValue Mul = DAG.getNode(N->getOpcode(), DL, VTs, LHS, RHS);
- // Overflow occurred iff the high part of the result does not
- // zero/sign-extend the low part.
+ // Overflow occurred if it occurred in the larger type, or if the high part
+ // of the result does not zero/sign-extend the low part. Check this second
+ // possibility first.
SDValue Overflow;
if (N->getOpcode() == ISD::UMULO) {
- // Unsigned overflow occurred iff the high part is non-zero.
+ // Unsigned overflow occurred if the high part is non-zero.
SDValue Hi = DAG.getNode(ISD::SRL, DL, Mul.getValueType(), Mul,
DAG.getIntPtrConstant(SmallVT.getSizeInBits()));
Overflow = DAG.getSetCC(DL, N->getValueType(1), Hi,
DAG.getConstant(0, Hi.getValueType()), ISD::SETNE);
} else {
- // Signed overflow occurred iff the high part does not sign extend the low.
+ // Signed overflow occurred if the high part does not sign extend the low.
SDValue SExt = DAG.getNode(ISD::SIGN_EXTEND_INREG, DL, Mul.getValueType(),
Mul, DAG.getValueType(SmallVT));
Overflow = DAG.getSetCC(DL, N->getValueType(1), SExt, Mul, ISD::SETNE);
}
+ // The only other way for overflow to occur is if the multiplication in the
+ // larger type itself overflowed.
+ Overflow = DAG.getNode(ISD::OR, DL, N->getValueType(1), Overflow,
+ SDValue(Mul.getNode(), 1));
+
// Use the calculated overflow everywhere.
ReplaceValueWith(SDValue(N, 1), Overflow);
return Mul;