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
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 @@
};
}
+/// 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 @@
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);