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Fix a serious X86 instruction selection bug. In
X86DAGToDAGISel::PreprocessISelDAG(), isel is moving load inside callseq_start / callseq_end so it can be folded into a call. This can create a cycle in the DAG when the call is glued to a copytoreg. We have been lucky this hasn't caused too many issues because the pre-ra scheduler has special handling of call sequences. However, it has caused a crash in a specific tailcall case. rdar://12393897 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165072 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -362,7 +362,7 @@ X86DAGToDAGISel::IsProfitableToFold(SDValue N, SDNode *U, SDNode *Root) const {
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/// MoveBelowCallOrigChain - Replace the original chain operand of the call with
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/// load's chain operand and move load below the call's chain operand.
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static void MoveBelowOrigChain(SelectionDAG *CurDAG, SDValue Load,
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SDValue Call, SDValue OrigChain) {
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SDValue Call, SDValue OrigChain) {
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SmallVector<SDValue, 8> Ops;
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SDValue Chain = OrigChain.getOperand(0);
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if (Chain.getNode() == Load.getNode())
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@ -386,11 +386,22 @@ static void MoveBelowOrigChain(SelectionDAG *CurDAG, SDValue Load,
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CurDAG->UpdateNodeOperands(OrigChain.getNode(), &Ops[0], Ops.size());
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CurDAG->UpdateNodeOperands(Load.getNode(), Call.getOperand(0),
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Load.getOperand(1), Load.getOperand(2));
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bool IsGlued = Call.getOperand(0).getNode()->getGluedUser() == Call.getNode();
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unsigned NumOps = Call.getNode()->getNumOperands();
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Ops.clear();
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Ops.push_back(SDValue(Load.getNode(), 1));
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for (unsigned i = 1, e = Call.getNode()->getNumOperands(); i != e; ++i)
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for (unsigned i = 1, e = NumOps; i != e; ++i)
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Ops.push_back(Call.getOperand(i));
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CurDAG->UpdateNodeOperands(Call.getNode(), &Ops[0], Ops.size());
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if (!IsGlued)
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CurDAG->UpdateNodeOperands(Call.getNode(), &Ops[0], NumOps);
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else
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// If call's chain was glued to the call (tailcall), and now the load
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// is moved between them. Remove the glue to avoid a cycle (where the
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// call is glued to its old chain and the load is using the old chain
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// as its new chain).
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CurDAG->MorphNodeTo(Call.getNode(), Call.getOpcode(),
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Call.getNode()->getVTList(), &Ops[0], NumOps-1);
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}
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/// isCalleeLoad - Return true if call address is a load and it can be
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16
test/CodeGen/X86/2012-10-02-DAGCycle.ll
Normal file
16
test/CodeGen/X86/2012-10-02-DAGCycle.ll
Normal file
@ -0,0 +1,16 @@
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; RUN: llc -mtriple=i386-apple-macosx -relocation-model=pic < %s
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; rdar://12393897
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%TRp = type { i32, %TRH*, i32, i32 }
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%TRH = type { i8*, i8*, i8*, i8*, {}* }
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define i32 @t(%TRp* inreg %rp) nounwind optsize ssp {
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entry:
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%handler = getelementptr inbounds %TRp* %rp, i32 0, i32 1
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%0 = load %TRH** %handler, align 4
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%sync = getelementptr inbounds %TRH* %0, i32 0, i32 4
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%sync12 = load {}** %sync, align 4
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%1 = bitcast {}* %sync12 to i32 (%TRp*)*
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%call = tail call i32 %1(%TRp* inreg %rp) nounwind optsize
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ret i32 %call
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}
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