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[ThinLTO] Represent relative BF using a scaled representation .

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Summary:
The current integer representation of relative block frequency prevents
representing relative block frequencies below 1. This change uses a 8 of
the 29 bits to represent the decimal part by using a fixed scale of -8.

Reviewers: tejohnson, davidxl

Subscribers: mehdi_amini, inglorion, llvm-commits

Differential Revision: https://reviews.llvm.org/D43520

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325823 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Easwaran Raman
2018-02-22 19:44:08 +00:00
parent 1e23b92b96
commit 95d34a2e59
3 changed files with 23 additions and 16 deletions
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lib/Analysis/ModuleSummaryAnalysis.cpp
+3 -11
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@@ -279,17 +279,9 @@ computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
// Add the relative block frequency to CalleeInfo if there is no profile
// information.
if (BFI != nullptr && Hotness == CalleeInfo::HotnessType::Unknown) {
auto BBFreq = BFI->getBlockFreq(&BB).getFrequency();
// FIXME: This might need some scaling to prevent BBFreq values from
// being rounded down to 0.
auto EntryFreq = BFI->getEntryFreq();
// Block frequencies can be directly set for a block and so we need to
// handle the case of entry frequency being 0.
if (EntryFreq)
BBFreq /= EntryFreq;
else
BBFreq = 0;
ValueInfo.updateRelBlockFreq(BBFreq);
uint64_t BBFreq = BFI->getBlockFreq(&BB).getFrequency();
uint64_t EntryFreq = BFI->getEntryFreq();
ValueInfo.updateRelBlockFreq(BBFreq, EntryFreq);
}
} else {
// Skip inline assembly calls.