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Teach DAG combiner to commute commutable binary nodes in order to achieve sdisel CSE.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48673 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2008-03-22 01:55:50 +00:00
parent 641dae19eb
commit 08b1173971
4 changed files with 63 additions and 0 deletions
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17
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@@ -758,6 +758,23 @@ SDOperand DAGCombiner::combine(SDNode *N) {
}
}
// If N is a commutative binary node, try commuting it to enable more
// sdisel CSE.
if (RV.Val == 0 &&
SelectionDAG::isCommutativeBinOp(N->getOpcode()) &&
N->getNumValues() == 1) {
SDOperand N0 = N->getOperand(0);
SDOperand N1 = N->getOperand(1);
// Constant operands are canonicalized to RHS.
if (isa<ConstantSDNode>(N0) || !isa<ConstantSDNode>(N1)) {
SDOperand Ops[] = { N1, N0 };
SDNode *CSENode = DAG.getNodeIfExists(N->getOpcode(), N->getVTList(),
Ops, 2);
if (CSENode && CSENode->use_size() <= N->use_size())
return SDOperand(CSENode, 0);
}
}
return RV;
}

14
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@@ -3291,6 +3291,20 @@ SDNode *SelectionDAG::getTargetNode(unsigned Opcode,
Ops, NumOps).Val;
}
/// getNodeIfExists - Get the specified node if it's already available, or
/// else return NULL.
SDNode *SelectionDAG::getNodeIfExists(unsigned Opcode, SDVTList VTList,
const SDOperand *Ops, unsigned NumOps) {
if (VTList.VTs[VTList.NumVTs-1] != MVT::Flag) {
FoldingSetNodeID ID;
AddNodeIDNode(ID, Opcode, VTList, Ops, NumOps);
void *IP = 0;
if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
return E;
}
return NULL;
}
/// ReplaceAllUsesWith - Modify anything using 'From' to use 'To' instead.
/// This can cause recursive merging of nodes in the DAG.