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[BOLT][heatmap] Add synthetic hot text section #139824

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Merged
merged 1 commit into from
May 14, 2025
Merged

[BOLT][heatmap] Add synthetic hot text section #139824

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3 changes: 3 additions & 0 deletions bolt/include/bolt/Profile/Heatmap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,9 @@ class Heatmap {
: BucketSize(BucketSize), MinAddress(MinAddress), MaxAddress(MaxAddress),
TextSections(TextSections) {}

uint64_t HotStart{0};
uint64_t HotEnd{0};

inline bool ignoreAddress(uint64_t Address) const {
return (Address > MaxAddress) || (Address < MinAddress);
}
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8 changes: 8 additions & 0 deletions bolt/lib/Profile/DataAggregator.cpp
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Expand Up @@ -1316,6 +1316,14 @@ std::error_code DataAggregator::printLBRHeatMap() {
}
Heatmap HM(opts::HeatmapBlock, opts::HeatmapMinAddress,
opts::HeatmapMaxAddress, getTextSections(BC));
auto getSymbolValue = [&](const MCSymbol *Symbol) -> uint64_t {
if (Symbol)
if (ErrorOr<uint64_t> SymValue = BC->getSymbolValue(*Symbol))
return SymValue.get();
return 0;
};
HM.HotStart = getSymbolValue(BC->getHotTextStartSymbol());
HM.HotEnd = getSymbolValue(BC->getHotTextEndSymbol());

if (!NumTotalSamples) {
if (opts::BasicAggregation) {
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15 changes: 14 additions & 1 deletion bolt/lib/Profile/Heatmap.cpp
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Expand Up @@ -8,6 +8,7 @@

#include "bolt/Profile/Heatmap.h"
#include "bolt/Utils/CommandLineOpts.h"
#include "llvm/ADT/AddressRanges.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/Debug.h"
Expand Down Expand Up @@ -313,6 +314,9 @@ void Heatmap::printSectionHotness(raw_ostream &OS) const {
UnmappedHotness += Frequency;
};

AddressRange HotTextRange(HotStart, HotEnd);
StringRef HotTextName = "[hot text]";

for (const std::pair<const uint64_t, uint64_t> &KV : Map) {
NumTotalCounts += KV.second;
// We map an address bucket to the first section (lowest address)
Expand All @@ -328,15 +332,24 @@ void Heatmap::printSectionHotness(raw_ostream &OS) const {
}
SectionHotness[TextSections[TextSectionIndex].Name] += KV.second;
++BucketUtilization[TextSections[TextSectionIndex].Name];
if (HotTextRange.contains(Address)) {
SectionHotness[HotTextName] += KV.second;
++BucketUtilization[HotTextName];
}
}

std::vector<SectionNameAndRange> Sections(TextSections);
// Append synthetic hot text section to TextSections
if (!HotTextRange.empty())
Sections.emplace_back(SectionNameAndRange{HotTextName, HotStart, HotEnd});

assert(NumTotalCounts > 0 &&
"total number of heatmap buckets should be greater than 0");

OS << "Section Name, Begin Address, End Address, Percentage Hotness, "
<< "Utilization Pct, Partition Score\n";
const uint64_t MappedCounts = NumTotalCounts - UnmappedHotness;
for (const auto [Name, Begin, End] : TextSections) {
for (const auto [Name, Begin, End] : Sections) {
const float Hotness = 1. * SectionHotness[Name] / NumTotalCounts;
const float MappedHotness =
MappedCounts ? 1. * SectionHotness[Name] / MappedCounts : 0;
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5 changes: 3 additions & 2 deletions bolt/lib/Rewrite/RewriteInstance.cpp
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Expand Up @@ -968,8 +968,9 @@ void RewriteInstance::discoverFileObjects() {
continue;
}

// Ignore input hot markers
if (SymName == "__hot_start" || SymName == "__hot_end")
// Ignore input hot markers unless in heatmap mode
if ((SymName == "__hot_start" || SymName == "__hot_end") &&
!opts::HeatmapMode)
continue;

FileSymRefs.emplace(SymbolAddress, Symbol);
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4 changes: 4 additions & 0 deletions bolt/test/X86/heatmap-preagg.test
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Expand Up @@ -13,6 +13,7 @@ RUN: --reorder-functions=cdsort --enable-bat --dyno-stats --skip-funcs=main
RUN: llvm-bolt-heatmap %t.out -o %t2 --pa -p %p/Inputs/blarge_new_bat.preagg.txt \
RUN: 2>&1 | FileCheck --check-prefix CHECK-HEATMAP-BAT %s
RUN: FileCheck %s --check-prefix CHECK-SEC-HOT-BAT --input-file %t2-section-hotness.csv
RUN: llvm-nm -n %t.out | FileCheck %s --check-prefix=CHECK-HOT-SYMS

CHECK-HEATMAP: PERF2BOLT: read 81 aggregated LBR entries
CHECK-HEATMAP: HEATMAP: invalid traces: 1
Expand All @@ -33,3 +34,6 @@ CHECK-SEC-HOT-BAT-NEXT: .bolt.org.text, 0x4010b0, 0x401c25, 38.3385, 51.0638, 0.
CHECK-SEC-HOT-BAT-NEXT: .fini, 0x401c28, 0x401c35, 0.0000, 0.0000, 0.0000
CHECK-SEC-HOT-BAT-NEXT: .text, 0x800000, 0x8002cc, 38.7595, 91.6667, 0.3553
CHECK-SEC-HOT-BAT-NEXT: .text.cold, 0x800300, 0x800415, 0.0000, 0.0000, 0.0000
CHECK-SEC-HOT-BAT-NEXT: [hot text], 0x800000, 0x8002cc, 38.7595, 91.6667, 0.3553
CHECK-HOT-SYMS: 800000 W __hot_start
CHECK-HOT-SYMS: 8002cc W __hot_end
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