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//===- GISelWorkList.h - Worklist for GISel passes ----*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
namespace llvm {
class MachineInstr;
// Worklist which mostly works similar to InstCombineWorkList, but on
// MachineInstrs. The main difference with something like a SetVector is that
// erasing an element doesn't move all elements over one place - instead just
// nulls out the element of the vector.
// FIXME: Does it make sense to factor out common code with the
// instcombinerWorkList?
template<unsigned N>
class GISelWorkList {
SmallVector<MachineInstr *, N> Worklist;
DenseMap<MachineInstr *, unsigned> WorklistMap;
bool Finalized = true;
GISelWorkList() : WorklistMap(N) {}
bool empty() const { return WorklistMap.empty(); }
unsigned size() const { return WorklistMap.size(); }
// Since we don't know ahead of time how many instructions we're going to add
// to the worklist, and migrating densemap's elements is quite expensive
// everytime we resize, only insert to the smallvector (typically during the
// initial phase of populating lists). Before the worklist can be used,
// finalize should be called. Also assert with NDEBUG if list is ever used
// without finalizing. Note that unlike insert, we won't check for duplicates
// - so the ideal place to use this is during the initial prepopulating phase
// of most passes.
void deferred_insert(MachineInstr *I) {
Finalized = false;
// This should only be called when using deferred_insert.
// This asserts that the WorklistMap is empty, and then
// inserts all the elements in the Worklist into the map.
// It also asserts if there are any duplicate elements found.
void finalize() {
assert(WorklistMap.empty() && "Expecting empty worklistmap");
if (Worklist.size() > N)
for (unsigned i = 0; i < Worklist.size(); ++i)
if (!WorklistMap.try_emplace(Worklist[i], i).second)
llvm_unreachable("Duplicate elements in the list");
Finalized = true;
/// Add the specified instruction to the worklist if it isn't already in it.
void insert(MachineInstr *I) {
assert(Finalized && "GISelWorkList used without finalizing");
if (WorklistMap.try_emplace(I, Worklist.size()).second)
/// Remove I from the worklist if it exists.
void remove(const MachineInstr *I) {
assert((Finalized || WorklistMap.empty()) && "Neither finalized nor empty");
auto It = WorklistMap.find(I);
if (It == WorklistMap.end())
return; // Not in worklist.
// Don't bother moving everything down, just null out the slot.
Worklist[It->second] = nullptr;
void clear() {
MachineInstr *pop_back_val() {
assert(Finalized && "GISelWorkList used without finalizing");
MachineInstr *I;
do {
I = Worklist.pop_back_val();
} while(!I);
assert(I && "Pop back on empty worklist");
return I;
} // end namespace llvm.