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Use the last 7 bits to represent the discriminator to fit it in 1 byte ULEB128 (NFC). 

From experiments, discriminator is rarely greater than 127. Here we enforce it to be no greater than 127 so that it will always fit in 1 byte.

llvm-svn: 286245
This commit is contained in:
Dehao Chen 2016-11-08 16:32:32 +00:00
parent 825e538559
commit 2ca9be330b
1 changed files with 7 additions and 5 deletions
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12
llvm/lib/Transforms/Utils/AddDiscriminators.cpp
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@ -188,12 +188,13 @@ static bool addDiscriminators(Function &F) {
continue;
// If we could insert more than one block with the same line+file, a
// discriminator is needed to distinguish both instructions.
unsigned Discriminator = R.second ? ++LDM[L] : LDM[L];
// Only the lowest 7 bits are used to represent a discriminator to fit
// it in 1 byte ULEB128 representation.
unsigned Discriminator = (R.second ? ++LDM[L] : LDM[L]) & 0x7f;
I.setDebugLoc(DIL->cloneWithDiscriminator(Discriminator));
DEBUG(dbgs() << DIL->getFilename() << ":" << DIL->getLine() << ":"
<< DIL->getColumn() << ":"
<< Discriminator << " "
<< I << "\n");
<< DIL->getColumn() << ":" << Discriminator << " " << I
<< "\n");
Changed = true;
}
}
@ -215,7 +216,8 @@ static bool addDiscriminators(Function &F) {
Location L =
std::make_pair(CurrentDIL->getFilename(), CurrentDIL->getLine());
if (!CallLocations.insert(L).second) {
Current->setDebugLoc(CurrentDIL->cloneWithDiscriminator(++LDM[L]));
Current->setDebugLoc(
CurrentDIL->cloneWithDiscriminator((++LDM[L]) & 0x7f));
Changed = true;
}
}