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IR: Reduce RAUW traffic in ConstantVector 

Avoid creating a new `ConstantVector` on an RAUW of one of its members.
This reduces RAUW traffic on any containing constant.

This is part of PR20515.

llvm-svn: 215966
This commit is contained in:
Duncan P. N. Exon Smith 2014-08-19 02:24:46 +00:00
parent b11cd6fbc5
commit 687744d011
1 changed files with 27 additions and 3 deletions
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30
llvm/lib/IR/Constants.cpp
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@ -2810,17 +2810,41 @@ void ConstantStruct::replaceUsesOfWithOnConstant(Value *From, Value *To,
void ConstantVector::replaceUsesOfWithOnConstant(Value *From, Value *To,
Use *U) {
assert(isa<Constant>(To) && "Cannot make Constant refer to non-constant!");
Constant *ToC = cast<Constant>(To);
SmallVector<Constant*, 8> Values;
Values.reserve(getNumOperands()); // Build replacement array...
unsigned NumUpdated = 0;
for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
Constant *Val = getOperand(i);
if (Val == From) Val = cast<Constant>(To);
if (Val == From) {
++NumUpdated;
Val = ToC;
}
Values.push_back(Val);
}
Constant *Replacement = get(Values);
replaceUsesOfWithOnConstantImpl(Replacement);
if (Constant *C = getImpl(Values)) {
replaceUsesOfWithOnConstantImpl(C);
return;
}
// Update to the new value. Optimize for the case when we have a single
// operand that we're changing, but handle bulk updates efficiently.
auto &pImpl = getType()->getContext().pImpl;
pImpl->VectorConstants.remove(this);
if (NumUpdated == 1) {
unsigned OperandToUpdate = U - OperandList;
assert(getOperand(OperandToUpdate) == From && "ReplaceAllUsesWith broken!");
setOperand(OperandToUpdate, ToC);
} else {
for (unsigned I = 0, E = getNumOperands(); I != E; ++I)
if (getOperand(I) == From)
setOperand(I, ToC);
}
pImpl->VectorConstants.insert(this);
}
void ConstantExpr::replaceUsesOfWithOnConstant(Value *From, Value *ToV,