1//- CFLAndersAliasAnalysis.cpp - Unification-based Alias Analysis ---*- C++-*-//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements a CFL-based, summary-based alias analysis algorithm. It
11// differs from CFLSteensAliasAnalysis in its inclusion-based nature while
12// CFLSteensAliasAnalysis is unification-based. This pass has worse performance
13// than CFLSteensAliasAnalysis (the worst case complexity of
14// CFLAndersAliasAnalysis is cubic, while the worst case complexity of
15// CFLSteensAliasAnalysis is almost linear), but it is able to yield more
16// precise analysis result. The precision of this analysis is roughly the same
17// as that of an one level context-sensitive Andersen's algorithm.
18//
19//===----------------------------------------------------------------------===//
20
21// N.B. AliasAnalysis as a whole is phrased as a FunctionPass at the moment, and
22// CFLAndersAA is interprocedural. This is *technically* A Bad Thing, because
23// FunctionPasses are only allowed to inspect the Function that they're being
24// run on. Realistically, this likely isn't a problem until we allow
25// FunctionPasses to run concurrently.
26
27#include "llvm/Analysis/CFLAndersAliasAnalysis.h"
28#include "CFLGraph.h"
29#include "llvm/Pass.h"
30
31using namespace llvm;
32using namespace llvm::cflaa;
33
34#define DEBUG_TYPE "cfl-anders-aa"
35
36CFLAndersAAResult::CFLAndersAAResult() = default;
37
38char CFLAndersAA::PassID;
39
40CFLAndersAAResult CFLAndersAA::run(Function &F, AnalysisManager<Function> &AM) {
41  return CFLAndersAAResult();
42}
43
44char CFLAndersAAWrapperPass::ID = 0;
45INITIALIZE_PASS(CFLAndersAAWrapperPass, "cfl-anders-aa",
46                "Inclusion-Based CFL Alias Analysis", false, true)
47
48ImmutablePass *llvm::createCFLAndersAAWrapperPass() {
49  return new CFLAndersAAWrapperPass();
50}
51
52CFLAndersAAWrapperPass::CFLAndersAAWrapperPass() : ImmutablePass(ID) {
53  initializeCFLAndersAAWrapperPassPass(*PassRegistry::getPassRegistry());
54}
55
56void CFLAndersAAWrapperPass::initializePass() {}
57
58void CFLAndersAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
59  AU.setPreservesAll();
60}
61