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[Utils] Avoid a hash table lookup in salvageDI, NFC 

According to the current coverage report salvageDebugInfo() is called
5.12 million times during testing and almost always returns early.

The early return depends on LocalAsMetadata::getIfExists returning null,
which involves a DenseMap lookup in an LLVMContextImpl. We can probably
speed this up by simply checking the IsUsedByMD bit in Value.

llvm-svn: 325738
This commit is contained in:
Vedant Kumar 2018-02-22 01:29:41 +00:00
parent 55b7e01116
commit 1ceabcf080
1 changed files with 5 additions and 0 deletions
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5
llvm/lib/Transforms/Utils/Local.cpp
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@ -1486,6 +1486,11 @@ void llvm::replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
}
void llvm::salvageDebugInfo(Instruction &I) {
// This function is hot. An early check to determine whether the instruction
// has any metadata to save allows it to return earlier on average.
if (!I.isUsedByMetadata())
return;
SmallVector<DbgInfoIntrinsic *, 1> DbgUsers;
findDbgUsers(DbgUsers, &I);
if (DbgUsers.empty())