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author | Daniel Dunbar <daniel@zuster.org> | 2010-06-23 17:09:26 +0000 |
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committer | Daniel Dunbar <daniel@zuster.org> | 2010-06-23 17:09:26 +0000 |
commit | cbe762b5d165c565feb98b745e93b71d208a1e36 (patch) | |
tree | 0f6f0b75c5f50a24a09c41e4224b54fc1c4c0123 /lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp | |
parent | f1ab49e83abccd9f7b885e74172419249bd5fd8a (diff) | |
download | external_llvm-cbe762b5d165c565feb98b745e93b71d208a1e36.zip external_llvm-cbe762b5d165c565feb98b745e93b71d208a1e36.tar.gz external_llvm-cbe762b5d165c565feb98b745e93b71d208a1e36.tar.bz2 |
Revert r106263, "Fold the ShrinkDemandedOps pass into the regular DAGCombiner pass,"... it was causing both 'file' (with clang) and 176.gcc (with llvm-gcc) to be miscompiled.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106634 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp')
-rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp | 100 |
1 files changed, 99 insertions, 1 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp index 3b0ef18..15c1ae5 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp @@ -372,6 +372,102 @@ public: }; } +/// TrivialTruncElim - Eliminate some trivial nops that can result from +/// ShrinkDemandedOps: (trunc (ext n)) -> n. +static bool TrivialTruncElim(SDValue Op, + TargetLowering::TargetLoweringOpt &TLO) { + SDValue N0 = Op.getOperand(0); + EVT VT = Op.getValueType(); + if ((N0.getOpcode() == ISD::ZERO_EXTEND || + N0.getOpcode() == ISD::SIGN_EXTEND || + N0.getOpcode() == ISD::ANY_EXTEND) && + N0.getOperand(0).getValueType() == VT) { + return TLO.CombineTo(Op, N0.getOperand(0)); + } + return false; +} + +/// ShrinkDemandedOps - A late transformation pass that shrink expressions +/// using TargetLowering::TargetLoweringOpt::ShrinkDemandedOp. It converts +/// x+y to (VT)((SmallVT)x+(SmallVT)y) if the casts are free. +void SelectionDAGISel::ShrinkDemandedOps() { + SmallVector<SDNode*, 128> Worklist; + SmallPtrSet<SDNode*, 128> InWorklist; + + // Add all the dag nodes to the worklist. + Worklist.reserve(CurDAG->allnodes_size()); + for (SelectionDAG::allnodes_iterator I = CurDAG->allnodes_begin(), + E = CurDAG->allnodes_end(); I != E; ++I) { + Worklist.push_back(I); + InWorklist.insert(I); + } + + TargetLowering::TargetLoweringOpt TLO(*CurDAG, true, true, true); + while (!Worklist.empty()) { + SDNode *N = Worklist.pop_back_val(); + InWorklist.erase(N); + + if (N->use_empty() && N != CurDAG->getRoot().getNode()) { + // Deleting this node may make its operands dead, add them to the worklist + // if they aren't already there. + for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) + if (InWorklist.insert(N->getOperand(i).getNode())) + Worklist.push_back(N->getOperand(i).getNode()); + + CurDAG->DeleteNode(N); + continue; + } + + // Run ShrinkDemandedOp on scalar binary operations. + if (N->getNumValues() != 1 || + !N->getValueType(0).isSimple() || !N->getValueType(0).isInteger()) + continue; + + unsigned BitWidth = N->getValueType(0).getScalarType().getSizeInBits(); + APInt Demanded = APInt::getAllOnesValue(BitWidth); + APInt KnownZero, KnownOne; + if (!TLI.SimplifyDemandedBits(SDValue(N, 0), Demanded, + KnownZero, KnownOne, TLO) && + (N->getOpcode() != ISD::TRUNCATE || + !TrivialTruncElim(SDValue(N, 0), TLO))) + continue; + + // Revisit the node. + assert(!InWorklist.count(N) && "Already in worklist"); + Worklist.push_back(N); + InWorklist.insert(N); + + // Replace the old value with the new one. + DEBUG(errs() << "\nShrinkDemandedOps replacing "; + TLO.Old.getNode()->dump(CurDAG); + errs() << "\nWith: "; + TLO.New.getNode()->dump(CurDAG); + errs() << '\n'); + + if (InWorklist.insert(TLO.New.getNode())) + Worklist.push_back(TLO.New.getNode()); + + SDOPsWorkListRemover DeadNodes(Worklist, InWorklist); + CurDAG->ReplaceAllUsesOfValueWith(TLO.Old, TLO.New, &DeadNodes); + + if (!TLO.Old.getNode()->use_empty()) continue; + + for (unsigned i = 0, e = TLO.Old.getNode()->getNumOperands(); + i != e; ++i) { + SDNode *OpNode = TLO.Old.getNode()->getOperand(i).getNode(); + if (OpNode->hasOneUse()) { + // Add OpNode to the end of the list to revisit. + DeadNodes.RemoveFromWorklist(OpNode); + Worklist.push_back(OpNode); + InWorklist.insert(OpNode); + } + } + + DeadNodes.RemoveFromWorklist(TLO.Old.getNode()); + CurDAG->DeleteNode(TLO.Old.getNode()); + } +} + void SelectionDAGISel::ComputeLiveOutVRegInfo() { SmallPtrSet<SDNode*, 128> VisitedNodes; SmallVector<SDNode*, 128> Worklist; @@ -521,8 +617,10 @@ MachineBasicBlock *SelectionDAGISel::CodeGenAndEmitDAG(MachineBasicBlock *BB) { DEBUG(dbgs() << "Optimized legalized selection DAG:\n"; CurDAG->dump()); - if (OptLevel != CodeGenOpt::None) + if (OptLevel != CodeGenOpt::None) { + ShrinkDemandedOps(); ComputeLiveOutVRegInfo(); + } if (ViewISelDAGs) CurDAG->viewGraph("isel input for " + BlockName); |