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When doing the very-late shift-and address-mode optimization,

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create a new DAG node to represent the new shift to keep the
DAG consistent, even though it'll almost always be folded into
the address.

If a user of the resulting address has multiple uses, the
nodes may get revisited by a later MatchAddress call, in which
case DAG inconsistencies do matter.

This fixes PR2849.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57465 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2008-10-13 20:52:04 +00:00
parent b82eb06faf
commit 7b8e96401c
2 changed files with 41 additions and 0 deletions
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3
lib/Target/X86/X86ISelDAGToDAG.cpp
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@@ -989,8 +989,11 @@ DOUT << "AlreadySelected " << AlreadySelected << "\n";
SDValue(C2, 0), SDValue(C1, 0));
SDValue NewAND = CurDAG->getNode(ISD::AND, N.getValueType(),
Shift.getOperand(0), NewANDMask);
SDValue NewSHIFT = CurDAG->getNode(ISD::SHL, N.getValueType(),
NewAND, SDValue(C1, 0));
NewANDMask.getNode()->setNodeId(Shift.getNode()->getNodeId());
NewAND.getNode()->setNodeId(N.getNode()->getNodeId());
CurDAG->ReplaceAllUsesWith(N, NewSHIFT);
AM.Scale = 1 << ShiftCst;
AM.IndexReg = NewAND;