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Code Issues 2 Packages Projects Releases 7 Wiki Activity

[Bitcode] Drop invalid branch_weight in BitcodeReader

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Summary:
If bitcode reader gets an invalid branch weight, drop that from the
inputs. This allows us to read the broken modules we generated before
the verifier was able to catch this.

rdar://64870641

Reviewers: yrouban, t.p.northover, dexonsmith, arphaman, aprantl

Reviewed By: aprantl

Subscribers: aprantl, hiraditya, jkorous, ributzka, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D83699
This commit is contained in:
Steven Wu
2020-07-23 09:06:47 -07:00
parent 3840199d04
commit 7e7fa937e3
3 changed files with 49 additions and 0 deletions
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lib/Bitcode/Reader/BitcodeReader.cpp
+30
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@@ -5394,6 +5394,36 @@ Error BitcodeReader::materialize(GlobalValue *GV) {
}
}
// "Upgrade" older incorrect branch weights by dropping them.
for (auto &I : instructions(F)) {
if (auto *MD = I.getMetadata(LLVMContext::MD_prof)) {
if (MD->getOperand(0) != nullptr && isa<MDString>(MD->getOperand(0))) {
MDString *MDS = cast<MDString>(MD->getOperand(0));
StringRef ProfName = MDS->getString();
// Check consistency of !prof branch_weights metadata.
if (!ProfName.equals("branch_weights"))
continue;
unsigned ExpectedNumOperands = 0;
if (BranchInst *BI = dyn_cast<BranchInst>(&I))
ExpectedNumOperands = BI->getNumSuccessors();
else if (SwitchInst *SI = dyn_cast<SwitchInst>(&I))
ExpectedNumOperands = SI->getNumSuccessors();
else if (isa<CallInst>(&I))
ExpectedNumOperands = 1;
else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(&I))
ExpectedNumOperands = IBI->getNumDestinations();
else if (isa<SelectInst>(&I))
ExpectedNumOperands = 2;
else
continue; // ignore and continue.
// If branch weight doesn't match, just strip branch weight.
if (MD->getNumOperands() != 1 + ExpectedNumOperands)
I.setMetadata(LLVMContext::MD_prof, nullptr);
}
}
}
// Look for functions that rely on old function attribute behavior.
UpgradeFunctionAttributes(*F);