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[PGO][InstrProf] Do not promote count if the exit blocks contains ret instruction 

Skip profile count promotion if any of the ExitBlocks contains a ret
instruction. This is to prevent dumping of incomplete profile -- if the
the loop is a long running loop and dump is called in the middle
of the loop, the result profile is incomplete.

ExitBlocks containing a ret instruction is an indication of a long running
loop -- early exit to error handling code.

Differential Revision: https://reviews.llvm.org/D84379
This commit is contained in:
Rong Xu 2020-07-24 17:13:58 -07:00
parent 4b53072ee5
commit 6fdc6f6c7d
1 changed files with 12 additions and 1 deletions
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13
llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
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@ -1131,11 +1131,18 @@ bool PGOUseFunc::setInstrumentedCounts(
if (NumCounters != CountFromProfile.size()) {
return false;
}
auto *FuncEntry = &*F.begin();
// Set the profile count to the Instrumented BBs.
uint32_t I = 0;
for (BasicBlock *InstrBB : InstrumentBBs) {
uint64_t CountValue = CountFromProfile[I++];
UseBBInfo &Info = getBBInfo(InstrBB);
// If we reach here, we know that we have some nonzero count
// values in this function. The entry count should not be 0.
// Fix it if necessary.
if (InstrBB == FuncEntry && CountValue == 0)
CountValue = 1;
Info.setBBInfoCount(CountValue);
}
ProfileCountSize = CountFromProfile.size();
@ -1326,7 +1333,6 @@ void PGOUseFunc::populateCounters() {
}
#endif
uint64_t FuncEntryCount = getBBInfo(&*F.begin()).CountValue;
F.setEntryCount(ProfileCount(FuncEntryCount, Function::PCT_Real));
uint64_t FuncMaxCount = FuncEntryCount;
for (auto &BB : F) {
auto BI = findBBInfo(&BB);
@ -1334,6 +1340,11 @@ void PGOUseFunc::populateCounters() {
continue;
FuncMaxCount = std::max(FuncMaxCount, BI->CountValue);
}
// Fix the obviously inconsistent entry count.
if (FuncMaxCount > 0 && FuncEntryCount == 0)
FuncEntryCount = 1;
F.setEntryCount(ProfileCount(FuncEntryCount, Function::PCT_Real));
markFunctionAttributes(FuncEntryCount, FuncMaxCount);
// Now annotate select instructions