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[Coverage] Ignore 'unused' functions with non-zero execution counts

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Frontends emit 'unused' coverage mapping records for functions which are
provably unused in a TU. These unused records contain a single counter
with CounterKind::Zero. However, a function may be unused in one TU and
used in another. When this happens, prefer the records with a full set
of counters instead of arbitrarily picking the first loaded record.

There is no impact on the single-TU case. In the multiple-TU case, this
resolves issues causing a function to appear unused when it's not.

Testing: check-{llvm,clang,compiler-rt}

rdar://42981322

llvm-svn: 339194
This commit is contained in:
Vedant Kumar 2018-08-07 22:25:36 +00:00
parent b57ad60b6e
commit 4be2fef14a
1 changed files with 15 additions and 6 deletions
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21
lib/ProfileData/Coverage/CoverageMapping.cpp
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@ -207,12 +207,6 @@ Error CoverageMapping::loadFunctionRecord(
else
OrigFuncName = getFuncNameWithoutPrefix(OrigFuncName, Record.Filenames[0]);
// Don't load records for (filenames, function) pairs we've already seen.
auto FilenamesHash = hash_combine_range(Record.Filenames.begin(),
Record.Filenames.end());
if (!RecordProvenance[FilenamesHash].insert(hash_value(OrigFuncName)).second)
return Error::success();
CounterMappingContext Ctx(Record.Expressions);
std::vector<uint64_t> Counts;
@ -230,6 +224,15 @@ Error CoverageMapping::loadFunctionRecord(
assert(!Record.MappingRegions.empty() && "Function has no regions");
// This coverage record is a zero region for a function that's unused in
// some TU, but used in a different TU. Ignore it. The coverage maps from the
// the other TU will either be loaded (providing full region counts) or they
// won't (in which case we don't unintuitively report functions as uncovered
// when they have non-zero counts in the profile).
if (Record.MappingRegions.size() == 1 &&
Record.MappingRegions[0].Count.isZero() && Counts[0] > 0)
return Error::success();
FunctionRecord Function(OrigFuncName, Record.Filenames);
for (const auto &Region : Record.MappingRegions) {
Expected<int64_t> ExecutionCount = Ctx.evaluate(Region.Count);
@ -240,6 +243,12 @@ Error CoverageMapping::loadFunctionRecord(
Function.pushRegion(Region, *ExecutionCount);
}
// Don't create records for (filenames, function) pairs we've already seen.
auto FilenamesHash = hash_combine_range(Record.Filenames.begin(),
Record.Filenames.end());
if (!RecordProvenance[FilenamesHash].insert(hash_value(OrigFuncName)).second)
return Error::success();
Functions.push_back(std::move(Function));
return Error::success();
}