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[IR2Vec] Scale embeddings once in vocab analysis instead of repetitive scaling #143986

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[IR2Vec] Scale embeddings once in vocab analysis instead of repetitive scaling #143986

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5 changes: 4 additions & 1 deletion llvm/docs/MLGO.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -448,7 +448,10 @@ downstream tasks, including ML-guided compiler optimizations.

The core components are:
- **Vocabulary**: A mapping from IR entities (opcodes, types, etc.) to their
vector representations. This is managed by ``IR2VecVocabAnalysis``.
vector representations. This is managed by ``IR2VecVocabAnalysis``. The
vocabulary (.json file) contains three sections -- Opcodes, Types, and
Arguments, each containing the representations of the corresponding
entities.
- **Embedder**: A class (``ir2vec::Embedder``) that uses the vocabulary to
compute embeddings for instructions, basic blocks, and functions.

Expand Down
16 changes: 15 additions & 1 deletion llvm/include/llvm/Analysis/IR2Vec.h
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Expand Up @@ -108,6 +108,7 @@ struct Embedding {
/// Arithmetic operators
Embedding &operator+=(const Embedding &RHS);
Embedding &operator-=(const Embedding &RHS);
Embedding &operator*=(double Factor);

/// Adds Src Embedding scaled by Factor with the called Embedding.
/// Called_Embedding += Src * Factor
Expand All @@ -116,6 +117,8 @@ struct Embedding {
/// Returns true if the embedding is approximately equal to the RHS embedding
/// within the specified tolerance.
bool approximatelyEquals(const Embedding &RHS, double Tolerance = 1e-6) const;

void print(raw_ostream &OS) const;
};

using InstEmbeddingsMap = DenseMap<const Instruction *, Embedding>;
Expand Down Expand Up @@ -234,6 +237,8 @@ class IR2VecVocabResult {
class IR2VecVocabAnalysis : public AnalysisInfoMixin<IR2VecVocabAnalysis> {
ir2vec::Vocab Vocabulary;
Error readVocabulary();
Error parseVocabSection(StringRef Key, const json::Value &ParsedVocabValue,
ir2vec::Vocab &TargetVocab, unsigned &Dim);
void emitError(Error Err, LLVMContext &Ctx);

public:
Expand All @@ -249,14 +254,23 @@ class IR2VecVocabAnalysis : public AnalysisInfoMixin<IR2VecVocabAnalysis> {
/// functions.
class IR2VecPrinterPass : public PassInfoMixin<IR2VecPrinterPass> {
raw_ostream &OS;
void printVector(const ir2vec::Embedding &Vec) const;

public:
explicit IR2VecPrinterPass(raw_ostream &OS) : OS(OS) {}
PreservedAnalyses run(Module &M, ModuleAnalysisManager &MAM);
static bool isRequired() { return true; }
};

/// This pass prints the embeddings in the vocabulary
class IR2VecVocabPrinterPass : public PassInfoMixin<IR2VecVocabPrinterPass> {
raw_ostream &OS;

public:
explicit IR2VecVocabPrinterPass(raw_ostream &OS) : OS(OS) {}
PreservedAnalyses run(Module &M, ModuleAnalysisManager &MAM);
static bool isRequired() { return true; }
};

} // namespace llvm

#endif // LLVM_ANALYSIS_IR2VEC_H
136 changes: 97 additions & 39 deletions llvm/lib/Analysis/IR2Vec.cpp
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Expand Up @@ -85,6 +85,12 @@ Embedding &Embedding::operator-=(const Embedding &RHS) {
return *this;
}

Embedding &Embedding::operator*=(double Factor) {
std::transform(this->begin(), this->end(), this->begin(),
[Factor](double Elem) { return Elem * Factor; });
return *this;
}

Embedding &Embedding::scaleAndAdd(const Embedding &Src, float Factor) {
assert(this->size() == Src.size() && "Vectors must have the same dimension");
for (size_t Itr = 0; Itr < this->size(); ++Itr)
Expand All @@ -101,6 +107,13 @@ bool Embedding::approximatelyEquals(const Embedding &RHS,
return true;
}

void Embedding::print(raw_ostream &OS) const {
OS << " [";
for (const auto &Elem : Data)
OS << " " << format("%.2f", Elem) << " ";
OS << "]\n";
}

// ==----------------------------------------------------------------------===//
// Embedder and its subclasses
//===----------------------------------------------------------------------===//
Expand Down Expand Up @@ -196,18 +209,12 @@ void SymbolicEmbedder::computeEmbeddings(const BasicBlock &BB) const {
for (const auto &I : BB.instructionsWithoutDebug()) {
Embedding InstVector(Dimension, 0);

const auto OpcVec = lookupVocab(I.getOpcodeName());
InstVector.scaleAndAdd(OpcVec, OpcWeight);

// FIXME: Currently lookups are string based. Use numeric Keys
// for efficiency.
const auto Type = I.getType();
const auto TypeVec = getTypeEmbedding(Type);
InstVector.scaleAndAdd(TypeVec, TypeWeight);

InstVector += lookupVocab(I.getOpcodeName());
InstVector += getTypeEmbedding(I.getType());
for (const auto &Op : I.operands()) {
const auto OperandVec = getOperandEmbedding(Op.get());
InstVector.scaleAndAdd(OperandVec, ArgWeight);
InstVector += getOperandEmbedding(Op.get());
}
InstVecMap[&I] = InstVector;
BBVector += InstVector;
Expand Down Expand Up @@ -251,6 +258,43 @@ bool IR2VecVocabResult::invalidate(
return !(PAC.preservedWhenStateless());
}

Error IR2VecVocabAnalysis::parseVocabSection(
StringRef Key, const json::Value &ParsedVocabValue,
ir2vec::Vocab &TargetVocab, unsigned &Dim) {
json::Path::Root Path("");
const json::Object *RootObj = ParsedVocabValue.getAsObject();
if (!RootObj)
return createStringError(errc::invalid_argument,
"JSON root is not an object");

const json::Value *SectionValue = RootObj->get(Key);
if (!SectionValue)
return createStringError(errc::invalid_argument,
"Missing '" + std::string(Key) +
"' section in vocabulary file");
if (!json::fromJSON(*SectionValue, TargetVocab, Path))
return createStringError(errc::illegal_byte_sequence,
"Unable to parse '" + std::string(Key) +
"' section from vocabulary");

Dim = TargetVocab.begin()->second.size();
if (Dim == 0)
return createStringError(errc::illegal_byte_sequence,
"Dimension of '" + std::string(Key) +
"' section of the vocabulary is zero");

if (!std::all_of(TargetVocab.begin(), TargetVocab.end(),
[Dim](const std::pair<StringRef, Embedding> &Entry) {
return Entry.second.size() == Dim;
}))
return createStringError(
errc::illegal_byte_sequence,
"All vectors in the '" + std::string(Key) +
"' section of the vocabulary are not of the same dimension");

return Error::success();
};

// FIXME: Make this optional. We can avoid file reads
// by auto-generating a default vocabulary during the build time.
Error IR2VecVocabAnalysis::readVocabulary() {
Expand All @@ -259,32 +303,40 @@ Error IR2VecVocabAnalysis::readVocabulary() {
return createFileError(VocabFile, BufOrError.getError());

auto Content = BufOrError.get()->getBuffer();
json::Path::Root Path("");

Expected<json::Value> ParsedVocabValue = json::parse(Content);
if (!ParsedVocabValue)
return ParsedVocabValue.takeError();

bool Res = json::fromJSON(*ParsedVocabValue, Vocabulary, Path);
if (!Res)
return createStringError(errc::illegal_byte_sequence,
"Unable to parse the vocabulary");
ir2vec::Vocab OpcodeVocab, TypeVocab, ArgVocab;
unsigned OpcodeDim = 0, TypeDim = 0, ArgDim = 0;
if (auto Err = parseVocabSection("Opcodes", *ParsedVocabValue, OpcodeVocab,
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@mtrofin mtrofin Jun 13, 2025 •
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This changes the format, best to also update the doc.

Also, this means the sections must all be present (in any order), even if empty, correct? SGTM, just something worth spelling out.

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Correct. Will put it in the doc.

OpcodeDim))
return Err;

if (Vocabulary.empty())
return createStringError(errc::illegal_byte_sequence,
"Vocabulary is empty");
if (auto Err =
parseVocabSection("Types", *ParsedVocabValue, TypeVocab, TypeDim))
return Err;

unsigned Dim = Vocabulary.begin()->second.size();
if (Dim == 0)
if (auto Err =
parseVocabSection("Arguments", *ParsedVocabValue, ArgVocab, ArgDim))
return Err;

if (!(OpcodeDim == TypeDim && TypeDim == ArgDim))
return createStringError(errc::illegal_byte_sequence,
"Dimension of vocabulary is zero");
"Vocabulary sections have different dimensions");

if (!std::all_of(Vocabulary.begin(), Vocabulary.end(),
[Dim](const std::pair<StringRef, Embedding> &Entry) {
return Entry.second.size() == Dim;
}))
return createStringError(
errc::illegal_byte_sequence,
"All vectors in the vocabulary are not of the same dimension");
auto scaleVocabSection = [](ir2vec::Vocab &Vocab, double Weight) {
for (auto &Entry : Vocab)
Entry.second *= Weight;
};
scaleVocabSection(OpcodeVocab, OpcWeight);
scaleVocabSection(TypeVocab, TypeWeight);
scaleVocabSection(ArgVocab, ArgWeight);

Vocabulary.insert(OpcodeVocab.begin(), OpcodeVocab.end());
Vocabulary.insert(TypeVocab.begin(), TypeVocab.end());
Vocabulary.insert(ArgVocab.begin(), ArgVocab.end());

return Error::success();
}
Expand All @@ -304,7 +356,6 @@ void IR2VecVocabAnalysis::emitError(Error Err, LLVMContext &Ctx) {
IR2VecVocabAnalysis::Result
IR2VecVocabAnalysis::run(Module &M, ModuleAnalysisManager &AM) {
auto Ctx = &M.getContext();
// FIXME: Scale the vocabulary once. This would avoid scaling per use later.
// If vocabulary is already populated by the constructor, use it.
if (!Vocabulary.empty())
return IR2VecVocabResult(std::move(Vocabulary));
Expand All @@ -323,16 +374,9 @@ IR2VecVocabAnalysis::run(Module &M, ModuleAnalysisManager &AM) {
}

// ==----------------------------------------------------------------------===//
// IR2VecPrinterPass
// Printer Passes
//===----------------------------------------------------------------------===//

void IR2VecPrinterPass::printVector(const Embedding &Vec) const {
OS << " [";
for (const auto &Elem : Vec)
OS << " " << format("%.2f", Elem) << " ";
OS << "]\n";
}

PreservedAnalyses IR2VecPrinterPass::run(Module &M,
ModuleAnalysisManager &MAM) {
auto IR2VecVocabResult = MAM.getResult<IR2VecVocabAnalysis>(M);
Expand All @@ -353,15 +397,15 @@ PreservedAnalyses IR2VecPrinterPass::run(Module &M,

OS << "IR2Vec embeddings for function " << F.getName() << ":\n";
OS << "Function vector: ";
printVector(Emb->getFunctionVector());
Emb->getFunctionVector().print(OS);

OS << "Basic block vectors:\n";
const auto &BBMap = Emb->getBBVecMap();
for (const BasicBlock &BB : F) {
auto It = BBMap.find(&BB);
if (It != BBMap.end()) {
OS << "Basic block: " << BB.getName() << ":\n";
printVector(It->second);
It->second.print(OS);
}
}

Expand All @@ -373,10 +417,24 @@ PreservedAnalyses IR2VecPrinterPass::run(Module &M,
if (It != InstMap.end()) {
OS << "Instruction: ";
I.print(OS);
printVector(It->second);
It->second.print(OS);
}
}
}
}
return PreservedAnalyses::all();
}

PreservedAnalyses IR2VecVocabPrinterPass::run(Module &M,
ModuleAnalysisManager &MAM) {
auto IR2VecVocabResult = MAM.getResult<IR2VecVocabAnalysis>(M);
assert(IR2VecVocabResult.isValid() && "IR2Vec Vocabulary is invalid");

auto Vocab = IR2VecVocabResult.getVocabulary();
for (const auto &Entry : Vocab) {
OS << "Key: " << Entry.first << ": ";
Entry.second.print(OS);
}

return PreservedAnalyses::all();
}
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