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//===-- StructuralHash.cpp - IR Hashing -------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/IR/StructuralHash.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Module.h"
using namespace llvm;
namespace {
// Basic hashing mechanism to detect structural change to the IR, used to verify
// pass return status consistency with actual change. Loosely copied from
// llvm/lib/Transforms/Utils/FunctionComparator.cpp
class StructuralHashImpl {
hash_code Hash;
template <typename T> void hash(const T &V) { Hash = hash_combine(Hash, V); }
public:
StructuralHashImpl() : Hash(4) {}
void update(const Function &F) {
// Declarations don't affect analyses.
if (F.isDeclaration())
return;
hash(12345); // Function header
hash(F.isVarArg());
hash(F.arg_size());
SmallVector<const BasicBlock *, 8> BBs;
SmallPtrSet<const BasicBlock *, 16> VisitedBBs;
BBs.push_back(&F.getEntryBlock());
VisitedBBs.insert(BBs[0]);
while (!BBs.empty()) {
const BasicBlock *BB = BBs.pop_back_val();
hash(45798); // Block header
for (auto &Inst : *BB)
hash(Inst.getOpcode());
const Instruction *Term = BB->getTerminator();
for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
if (!VisitedBBs.insert(Term->getSuccessor(i)).second)
continue;
BBs.push_back(Term->getSuccessor(i));
}
}
}
void update(const GlobalVariable &GV) {
// Declarations and used/compiler.used don't affect analyses.
// Since there are several `llvm.*` metadata, like `llvm.embedded.object`,
// we ignore anything with the `.llvm` prefix
if (GV.isDeclaration() || GV.getName().starts_with("llvm."))
return;
hash(23456); // Global header
hash(GV.getValueType()->getTypeID());
}
void update(const Module &M) {
for (const GlobalVariable &GV : M.globals())
update(GV);
for (const Function &F : M)
update(F);
}
uint64_t getHash() const { return Hash; }
};
} // namespace
uint64_t llvm::StructuralHash(const Function &F) {
StructuralHashImpl H;
H.update(F);
return H.getHash();
}
uint64_t llvm::StructuralHash(const Module &M) {
StructuralHashImpl H;
H.update(M);
return H.getHash();
}
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