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[BOLT] Refactor SplitFunctions for function reuse. NFC. #73078

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[BOLT] Refactor SplitFunctions for function reuse. NFC. #73078

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4d47f05
[BOLT] Refactor SplitFunctions for function reuse. NFC.
ShatianWang Nov 8, 2023
c85461f
fixup! [BOLT] Refactor SplitFunctions for function reuse. NFC.
ShatianWang Nov 25, 2023
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7 changes: 7 additions & 0 deletions bolt/include/bolt/Core/BinaryFunction.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1272,6 +1272,13 @@ class BinaryFunction {
/// otherwise processed.
bool isPseudo() const { return IsPseudo; }

/// Return true if every block in the function has a zero execution count.
bool allBlocksCold() const {
return llvm::all_of(blocks(), [](const BinaryBasicBlock &BB) {
return BB.getExecutionCount() == 0;
});
}

/// Return true if the function contains explicit or implicit indirect branch
/// to its split fragments, e.g., split jump table, landing pad in split
/// fragment.
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32 changes: 16 additions & 16 deletions bolt/include/bolt/Passes/SplitFunctions.h
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Expand Up @@ -50,6 +50,19 @@ class SplitFunctions : public BinaryFunctionPass {
/// Split function body into fragments.
void splitFunction(BinaryFunction &Function, SplitStrategy &Strategy);

std::atomic<uint64_t> SplitBytesHot{0ull};
std::atomic<uint64_t> SplitBytesCold{0ull};

public:
explicit SplitFunctions(const cl::opt<bool> &PrintPass)
: BinaryFunctionPass(PrintPass) {}

bool shouldOptimize(const BinaryFunction &BF) const override;

const char *getName() const override { return "split-functions"; }

void runOnFunctions(BinaryContext &BC) override;

struct TrampolineKey {
FragmentNum SourceFN = FragmentNum::main();
const MCSymbol *Target = nullptr;
Expand Down Expand Up @@ -81,27 +94,14 @@ class SplitFunctions : public BinaryFunctionPass {
/// corresponding thrower block. The trampoline landing pad, when created,
/// will redirect the execution to the real landing pad in a different
/// fragment.
TrampolineSetType createEHTrampolines(BinaryFunction &Function) const;
static TrampolineSetType createEHTrampolines(BinaryFunction &Function);

/// Merge trampolines into \p Layout without trampolines. The merge will place
/// a trampoline immediately before its destination. Used to revert the effect
/// of trampolines after createEHTrampolines().
BasicBlockOrderType
static BasicBlockOrderType
mergeEHTrampolines(BinaryFunction &BF, BasicBlockOrderType &Layout,
const TrampolineSetType &Trampolines) const;

std::atomic<uint64_t> SplitBytesHot{0ull};
std::atomic<uint64_t> SplitBytesCold{0ull};

public:
explicit SplitFunctions(const cl::opt<bool> &PrintPass)
: BinaryFunctionPass(PrintPass) {}

bool shouldOptimize(const BinaryFunction &BF) const override;

const char *getName() const override { return "split-functions"; }

void runOnFunctions(BinaryContext &BC) override;
const TrampolineSetType &Trampolines);
};

} // namespace bolt
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12 changes: 3 additions & 9 deletions bolt/lib/Passes/SplitFunctions.cpp
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Expand Up @@ -115,15 +115,9 @@ bool hasFullProfile(const BinaryFunction &BF) {
});
}

bool allBlocksCold(const BinaryFunction &BF) {
return llvm::all_of(BF.blocks(), [](const BinaryBasicBlock &BB) {
return BB.getExecutionCount() == 0;
});
}

struct SplitProfile2 final : public SplitStrategy {
bool canSplit(const BinaryFunction &BF) override {
return BF.hasValidProfile() && hasFullProfile(BF) && !allBlocksCold(BF);
return BF.hasValidProfile() && hasFullProfile(BF) && !BF.allBlocksCold();
}

bool keepEmpty() override { return false; }
Expand Down Expand Up @@ -434,7 +428,7 @@ void SplitFunctions::splitFunction(BinaryFunction &BF, SplitStrategy &S) {
}

SplitFunctions::TrampolineSetType
SplitFunctions::createEHTrampolines(BinaryFunction &BF) const {
SplitFunctions::createEHTrampolines(BinaryFunction &BF) {
const auto &MIB = BF.getBinaryContext().MIB;

// Map real landing pads to the corresponding trampolines.
Expand Down Expand Up @@ -501,7 +495,7 @@ SplitFunctions::createEHTrampolines(BinaryFunction &BF) const {

SplitFunctions::BasicBlockOrderType SplitFunctions::mergeEHTrampolines(
BinaryFunction &BF, SplitFunctions::BasicBlockOrderType &Layout,
const SplitFunctions::TrampolineSetType &Trampolines) const {
const SplitFunctions::TrampolineSetType &Trampolines) {
DenseMap<const MCSymbol *, SmallVector<const MCSymbol *, 0>>
IncomingTrampolines;
for (const auto &Entry : Trampolines) {
Expand Down