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[DAGCombiner] Move or/xor/and opcode check in ReduceLoadOpStoreWidth before hasOneUse check. 

hasOneUse is not cheap on nodes with chain results that might have
many uses. By checking the opcode first, we can avoid a costly walk
of the use list on nodes we aren't interested in.

Found by investigating calls to hasNUsesOfValue from the example
provided in D123857.
This commit is contained in:
Craig Topper 2022-04-15 16:33:12 -07:00
parent 81143b69dd
commit a7b9d75e7a
1 changed files with 6 additions and 3 deletions
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9
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -17375,11 +17375,15 @@ SDValue DAGCombiner::ReduceLoadOpStoreWidth(SDNode *N) {
SDValue Ptr = ST->getBasePtr();
EVT VT = Value.getValueType();
if (ST->isTruncatingStore() || VT.isVector() || !Value.hasOneUse())
if (ST->isTruncatingStore() || VT.isVector())
return SDValue();
unsigned Opc = Value.getOpcode();
if ((Opc != ISD::OR && Opc != ISD::XOR && Opc != ISD::AND) ||
!Value.hasOneUse())
return SDValue();
// If this is "store (or X, Y), P" and X is "(and (load P), cst)", where cst
// is a byte mask indicating a consecutive number of bytes, check to see if
// Y is known to provide just those bytes. If so, we try to replace the
@ -17404,8 +17408,7 @@ SDValue DAGCombiner::ReduceLoadOpStoreWidth(SDNode *N) {
if (!EnableReduceLoadOpStoreWidth)
return SDValue();
if ((Opc != ISD::OR && Opc != ISD::XOR && Opc != ISD::AND) ||
Value.getOperand(1).getOpcode() != ISD::Constant)
if (Value.getOperand(1).getOpcode() != ISD::Constant)
return SDValue();
SDValue N0 = Value.getOperand(0);