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Fix PR1114 and CodeGen/Generic/2007-01-15-LoadSelectCycle.ll by being

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careful when folding "c ? load p : load q" that C doesn't reach either load.
If so, folding this into load (c ? p : q) will induce a cycle in the graph.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33251 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-01-16 05:59:59 +00:00
parent 232b8ad8c1
commit c4e664bb9d
1 changed files with 41 additions and 25 deletions
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66
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -3709,36 +3709,52 @@ bool DAGCombiner::SimplifySelectOps(SDNode *TheSelect, SDOperand LHS,
// the right thing to do, but nothing uses srcvalues now. When they do,
// turn SrcValue into a list of locations.
SDOperand Addr;
if (TheSelect->getOpcode() == ISD::SELECT)
Addr = DAG.getNode(ISD::SELECT, LLD->getBasePtr().getValueType(),
TheSelect->getOperand(0), LLD->getBasePtr(),
RLD->getBasePtr());
else
Addr = DAG.getNode(ISD::SELECT_CC, LLD->getBasePtr().getValueType(),
if (TheSelect->getOpcode() == ISD::SELECT) {
// Check that the condition doesn't reach either load. If so, folding
// this will induce a cycle into the DAG.
if (!LLD->isPredecessor(TheSelect->getOperand(0).Val) &&
!RLD->isPredecessor(TheSelect->getOperand(0).Val)) {
Addr = DAG.getNode(ISD::SELECT, LLD->getBasePtr().getValueType(),
TheSelect->getOperand(0), LLD->getBasePtr(),
RLD->getBasePtr());
}
} else {
// Check that the condition doesn't reach either load. If so, folding
// this will induce a cycle into the DAG.
if (!LLD->isPredecessor(TheSelect->getOperand(0).Val) &&
!RLD->isPredecessor(TheSelect->getOperand(0).Val) &&
!LLD->isPredecessor(TheSelect->getOperand(1).Val) &&
!RLD->isPredecessor(TheSelect->getOperand(1).Val)) {
Addr = DAG.getNode(ISD::SELECT_CC, LLD->getBasePtr().getValueType(),
TheSelect->getOperand(0),
TheSelect->getOperand(1),
LLD->getBasePtr(), RLD->getBasePtr(),
TheSelect->getOperand(4));
SDOperand Load;
if (LLD->getExtensionType() == ISD::NON_EXTLOAD)
Load = DAG.getLoad(TheSelect->getValueType(0), LLD->getChain(),
Addr,LLD->getSrcValue(), LLD->getSrcValueOffset());
else {
Load = DAG.getExtLoad(LLD->getExtensionType(),
TheSelect->getValueType(0),
LLD->getChain(), Addr, LLD->getSrcValue(),
LLD->getSrcValueOffset(),
LLD->getLoadedVT());
}
}
if (Addr.Val) {
SDOperand Load;
if (LLD->getExtensionType() == ISD::NON_EXTLOAD)
Load = DAG.getLoad(TheSelect->getValueType(0), LLD->getChain(),
Addr,LLD->getSrcValue(),
LLD->getSrcValueOffset());
else {
Load = DAG.getExtLoad(LLD->getExtensionType(),
TheSelect->getValueType(0),
LLD->getChain(), Addr, LLD->getSrcValue(),
LLD->getSrcValueOffset(),
LLD->getLoadedVT());
}
// Users of the select now use the result of the load.
CombineTo(TheSelect, Load);
// Users of the old loads now use the new load's chain. We know the
// old-load value is dead now.
CombineTo(LHS.Val, Load.getValue(0), Load.getValue(1));
CombineTo(RHS.Val, Load.getValue(0), Load.getValue(1));
return true;
}
// Users of the select now use the result of the load.
CombineTo(TheSelect, Load);
// Users of the old loads now use the new load's chain. We know the
// old-load value is dead now.
CombineTo(LHS.Val, Load.getValue(0), Load.getValue(1));
CombineTo(RHS.Val, Load.getValue(0), Load.getValue(1));
return true;
}
}
}