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make the common case of a single store (which clearly shouldn't be turned 

into a memset!) faster by avoiding an allocation of an std::list node.

llvm-svn: 48939
This commit is contained in:
Chris Lattner 2008-03-29 04:52:12 +00:00
parent 28e7b57605
commit ac95515741
1 changed files with 12 additions and 3 deletions
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15
llvm/lib/Transforms/Scalar/GVN.cpp
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@ -1182,7 +1182,7 @@ public:
typedef std::list<MemsetRange>::const_iterator const_iterator; typedef std::list<MemsetRange>::const_iterator const_iterator;
const_iterator begin() const { return Ranges.begin(); } const_iterator begin() const { return Ranges.begin(); }
const_iterator end() const { return Ranges.end(); } const_iterator end() const { return Ranges.end(); }
bool empty() const { return Ranges.empty(); }
void addStore(int64_t OffsetFromFirst, StoreInst *SI); void addStore(int64_t OffsetFromFirst, StoreInst *SI);
}; };
@ -1281,8 +1281,6 @@ bool GVN::processStore(StoreInst *SI, SmallVectorImpl<Instruction*> &toErase) {
// are stored. // are stored.
MemsetRanges Ranges(TD); MemsetRanges Ranges(TD);
// Add our first pointer.
Ranges.addStore(0, SI);
Value *StartPtr = SI->getPointerOperand(); Value *StartPtr = SI->getPointerOperand();
BasicBlock::iterator BI = SI; BasicBlock::iterator BI = SI;
@ -1319,6 +1317,17 @@ bool GVN::processStore(StoreInst *SI, SmallVectorImpl<Instruction*> &toErase) {
Ranges.addStore(Offset, NextStore); Ranges.addStore(Offset, NextStore);
} }
// If we have no ranges, then we just had a single store with nothing that
// could be merged in. This is a very common case of course.
if (Ranges.empty())
return false;
// If we had at least one store that could be merged in, add the starting
// store as well. We try to avoid this unless there is at least something
// interesting as a small compile-time optimization.
Ranges.addStore(0, SI);
Function *MemSetF = 0; Function *MemSetF = 0;