From d10a9fb25a2f96850e375f3974d749803a1c3d84 Mon Sep 17 00:00:00 2001 From: Juergen Ributzka Date: Sat, 26 Apr 2014 02:58:04 +0000 Subject: [DAG] During DAG legalization keep opaque constants even after expanding. The included test case would return the incorrect results, because the expansion of an shift with a constant shift amount of 0 would generate undefined behavior. This is because ExpandShiftByConstant assumes that all shifts by constants with a value of 0 have already been optimized away. This doesn't happen for opaque constants and usually this isn't a problem, because opaque constants won't take this code path - they are not supposed to. In the case that the opaque constant has to be expanded by the legalizer, the legalizer would drop the opaque flag. In this case we hit the limitations of ExpandShiftByConstant and create incorrect code. This commit fixes the legalizer by not dropping the opaque flag when expanding opaque constants and adding an assertion to ExpandShiftByConstant to catch this not supported case in the future. This fixes git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207304 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'lib/CodeGen/SelectionDAG') diff --git a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp index f5e583b328..e622ca2b60 100644 --- a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp +++ b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp @@ -1272,6 +1272,7 @@ std::pair DAGTypeLegalizer::ExpandAtomic(SDNode *Node) { /// and the shift amount is a constant 'Amt'. Expand the operation. void DAGTypeLegalizer::ExpandShiftByConstant(SDNode *N, unsigned Amt, SDValue &Lo, SDValue &Hi) { + assert(Amt && "Expected zero shifts to be already optimized away."); SDLoc DL(N); // Expand the incoming operand to be shifted, so that we have its parts SDValue InL, InH; @@ -1714,9 +1715,13 @@ void DAGTypeLegalizer::ExpandIntRes_Constant(SDNode *N, SDValue &Lo, SDValue &Hi) { EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0)); unsigned NBitWidth = NVT.getSizeInBits(); - const APInt &Cst = cast(N)->getAPIntValue(); - Lo = DAG.getConstant(Cst.trunc(NBitWidth), NVT); - Hi = DAG.getConstant(Cst.lshr(NBitWidth).trunc(NBitWidth), NVT); + auto Constant = cast(N); + const APInt &Cst = Constant->getAPIntValue(); + bool IsTarget = Constant->isTargetOpcode(); + bool IsOpaque = Constant->isOpaque(); + Lo = DAG.getConstant(Cst.trunc(NBitWidth), NVT, IsTarget, IsOpaque); + Hi = DAG.getConstant(Cst.lshr(NBitWidth).trunc(NBitWidth), NVT, IsTarget, + IsOpaque); } void DAGTypeLegalizer::ExpandIntRes_CTLZ(SDNode *N, -- cgit v1.2.3