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//=== InstructionWorklist.h - Worklist for InstCombine & others -*- 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
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_UTILS_INSTRUCTIONWORKLIST_H
#define LLVM_TRANSFORMS_UTILS_INSTRUCTIONWORKLIST_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/Instruction.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
namespace llvm {
/// InstructionWorklist - This is the worklist management logic for
/// InstCombine and other simplification passes.
class InstructionWorklist {
SmallVector<Instruction *, 256> Worklist;
DenseMap<Instruction *, unsigned> WorklistMap;
/// These instructions will be added in reverse order after the current
/// combine has finished. This means that these instructions will be visited
/// in the order they have been added.
SmallSetVector<Instruction *, 16> Deferred;
public:
InstructionWorklist() = default;
InstructionWorklist(InstructionWorklist &&) = default;
InstructionWorklist &operator=(InstructionWorklist &&) = default;
bool isEmpty() const { return Worklist.empty() && Deferred.empty(); }
/// Add instruction to the worklist.
/// Instructions will be visited in the order they are added.
/// You likely want to use this method.
void add(Instruction *I) {
if (Deferred.insert(I))
LLVM_DEBUG(dbgs() << "ADD DEFERRED: " << *I << '\n');
}
/// Add value to the worklist if it is an instruction.
/// Instructions will be visited in the order they are added.
void addValue(Value *V) {
if (Instruction *I = dyn_cast<Instruction>(V))
add(I);
}
/// Push the instruction onto the worklist stack.
/// Instructions that have been added first will be visited last.
void push(Instruction *I) {
assert(I);
assert(I->getParent() && "Instruction not inserted yet?");
if (WorklistMap.insert(std::make_pair(I, Worklist.size())).second) {
LLVM_DEBUG(dbgs() << "ADD: " << *I << '\n');
Worklist.push_back(I);
}
}
void pushValue(Value *V) {
if (Instruction *I = dyn_cast<Instruction>(V))
push(I);
}
Instruction *popDeferred() {
if (Deferred.empty())
return nullptr;
return Deferred.pop_back_val();
}
void reserve(size_t Size) {
Worklist.reserve(Size + 16);
WorklistMap.reserve(Size);
}
/// Remove I from the worklist if it exists.
void remove(Instruction *I) {
DenseMap<Instruction *, unsigned>::iterator It = WorklistMap.find(I);
if (It != WorklistMap.end()) {
// Don't bother moving everything down, just null out the slot.
Worklist[It->second] = nullptr;
WorklistMap.erase(It);
}
Deferred.remove(I);
}
Instruction *removeOne() {
if (Worklist.empty())
return nullptr;
Instruction *I = Worklist.pop_back_val();
WorklistMap.erase(I);
return I;
}
/// When an instruction is simplified, add all users of the instruction
/// to the work lists because they might get more simplified now.
void pushUsersToWorkList(Instruction &I) {
for (User *U : I.users())
push(cast<Instruction>(U));
}
/// Should be called *after* decrementing the use-count on V.
void handleUseCountDecrement(Value *V) {
if (auto *I = dyn_cast<Instruction>(V)) {
add(I);
// Many folds have one-use limitations. If there's only one use left,
// revisit that use.
if (I->hasOneUse())
add(cast<Instruction>(*I->user_begin()));
}
}
/// Check that the worklist is empty and nuke the backing store for the map.
void zap() {
assert(WorklistMap.empty() && "Worklist empty, but map not?");
assert(Deferred.empty() && "Deferred instructions left over");
// Do an explicit clear, this shrinks the map if needed.
WorklistMap.clear();
}
};
} // end namespace llvm.
#endif
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