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Implement trivial DSE. If two stores are neighbors and store to the same

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location, replace them with a new store of the last value.  This occurs
in the same neighborhood in 197.parser, speeding it up about 1.5%


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23691 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-10-10 22:31:19 +00:00
parent 01a2202138
commit 87514ca04c
1 changed files with 29 additions and 0 deletions
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29
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -77,6 +77,7 @@ namespace {
}
SDOperand CombineTo(SDNode *N, const std::vector<SDOperand> &To) {
++NodesCombined;
DEBUG(std::cerr << "\nReplacing "; N->dump();
std::cerr << "\nWith: "; To[0].Val->dump();
std::cerr << " and " << To.size()-1 << " other values\n");
@ -99,6 +100,12 @@ namespace {
DAG.DeleteNode(N);
return SDOperand(N, 0);
}
SDOperand CombineTo(SDNode *N, SDOperand Res) {
std::vector<SDOperand> To;
To.push_back(Res);
return CombineTo(N, To);
}
SDOperand CombineTo(SDNode *N, SDOperand Res0, SDOperand Res1) {
std::vector<SDOperand> To;
@ -165,6 +172,7 @@ namespace {
SDOperand visitBRTWOWAY_CC(SDNode *N);
SDOperand visitLOAD(SDNode *N);
SDOperand visitSTORE(SDNode *N);
SDOperand SimplifySelect(SDOperand N0, SDOperand N1, SDOperand N2);
SDOperand SimplifySelectCC(SDOperand N0, SDOperand N1, SDOperand N2,
@ -439,6 +447,7 @@ SDOperand DAGCombiner::visit(SDNode *N) {
case ISD::BR_CC: return visitBR_CC(N);
case ISD::BRTWOWAY_CC: return visitBRTWOWAY_CC(N);
case ISD::LOAD: return visitLOAD(N);
case ISD::STORE: return visitSTORE(N);
}
return SDOperand();
}
@ -1567,6 +1576,26 @@ SDOperand DAGCombiner::visitLOAD(SDNode *N) {
return SDOperand();
}
SDOperand DAGCombiner::visitSTORE(SDNode *N) {
SDOperand Chain = N->getOperand(0);
SDOperand Value = N->getOperand(1);
SDOperand Ptr = N->getOperand(2);
SDOperand SrcValue = N->getOperand(3);
// If this is a store that kills a previous store, remove the previous store.
if (Chain.getOpcode() == ISD::STORE && Chain.getOperand(2) == Ptr) {
// Create a new store of Value that replaces both stores.
SDNode *PrevStore = Chain.Val;
SDOperand NewStore = DAG.getNode(ISD::STORE, MVT::Other,
PrevStore->getOperand(0), Value, Ptr,
SrcValue);
CombineTo(PrevStore, NewStore); // Nuke the previous store.
return NewStore; // Replace this store with NewStore.
}
return SDOperand();
}
SDOperand DAGCombiner::SimplifySelect(SDOperand N0, SDOperand N1, SDOperand N2){
assert(N0.getOpcode() ==ISD::SETCC && "First argument must be a SetCC node!");