1//===- AssumptionCache.cpp - Cache finding @llvm.assume calls -------------===//
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 contains a pass that keeps track of @llvm.assume intrinsics in
11// the functions of a module.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/Analysis/AssumptionCache.h"
16#include "llvm/IR/CallSite.h"
17#include "llvm/IR/Dominators.h"
18#include "llvm/IR/Function.h"
19#include "llvm/IR/Instructions.h"
20#include "llvm/IR/IntrinsicInst.h"
21#include "llvm/IR/PassManager.h"
22#include "llvm/IR/PatternMatch.h"
23#include "llvm/Support/Debug.h"
24using namespace llvm;
25using namespace llvm::PatternMatch;
26
27void AssumptionCache::scanFunction() {
28  assert(!Scanned && "Tried to scan the function twice!");
29  assert(AssumeHandles.empty() && "Already have assumes when scanning!");
30
31  // Go through all instructions in all blocks, add all calls to @llvm.assume
32  // to this cache.
33  for (BasicBlock &B : F)
34    for (Instruction &II : B)
35      if (match(&II, m_Intrinsic<Intrinsic::assume>()))
36        AssumeHandles.push_back(&II);
37
38  // Mark the scan as complete.
39  Scanned = true;
40}
41
42void AssumptionCache::registerAssumption(CallInst *CI) {
43  assert(match(CI, m_Intrinsic<Intrinsic::assume>()) &&
44         "Registered call does not call @llvm.assume");
45
46  // If we haven't scanned the function yet, just drop this assumption. It will
47  // be found when we scan later.
48  if (!Scanned)
49    return;
50
51  AssumeHandles.push_back(CI);
52
53#ifndef NDEBUG
54  assert(CI->getParent() &&
55         "Cannot register @llvm.assume call not in a basic block");
56  assert(&F == CI->getParent()->getParent() &&
57         "Cannot register @llvm.assume call not in this function");
58
59  // We expect the number of assumptions to be small, so in an asserts build
60  // check that we don't accumulate duplicates and that all assumptions point
61  // to the same function.
62  SmallPtrSet<Value *, 16> AssumptionSet;
63  for (auto &VH : AssumeHandles) {
64    if (!VH)
65      continue;
66
67    assert(&F == cast<Instruction>(VH)->getParent()->getParent() &&
68           "Cached assumption not inside this function!");
69    assert(match(cast<CallInst>(VH), m_Intrinsic<Intrinsic::assume>()) &&
70           "Cached something other than a call to @llvm.assume!");
71    assert(AssumptionSet.insert(VH).second &&
72           "Cache contains multiple copies of a call!");
73  }
74#endif
75}
76
77char AssumptionAnalysis::PassID;
78
79PreservedAnalyses AssumptionPrinterPass::run(Function &F,
80                                             AnalysisManager<Function> &AM) {
81  AssumptionCache &AC = AM.getResult<AssumptionAnalysis>(F);
82
83  OS << "Cached assumptions for function: " << F.getName() << "\n";
84  for (auto &VH : AC.assumptions())
85    if (VH)
86      OS << "  " << *cast<CallInst>(VH)->getArgOperand(0) << "\n";
87
88  return PreservedAnalyses::all();
89}
90
91void AssumptionCacheTracker::FunctionCallbackVH::deleted() {
92  auto I = ACT->AssumptionCaches.find_as(cast<Function>(getValPtr()));
93  if (I != ACT->AssumptionCaches.end())
94    ACT->AssumptionCaches.erase(I);
95  // 'this' now dangles!
96}
97
98AssumptionCache &AssumptionCacheTracker::getAssumptionCache(Function &F) {
99  // We probe the function map twice to try and avoid creating a value handle
100  // around the function in common cases. This makes insertion a bit slower,
101  // but if we have to insert we're going to scan the whole function so that
102  // shouldn't matter.
103  auto I = AssumptionCaches.find_as(&F);
104  if (I != AssumptionCaches.end())
105    return *I->second;
106
107  // Ok, build a new cache by scanning the function, insert it and the value
108  // handle into our map, and return the newly populated cache.
109  auto IP = AssumptionCaches.insert(std::make_pair(
110      FunctionCallbackVH(&F, this), llvm::make_unique<AssumptionCache>(F)));
111  assert(IP.second && "Scanning function already in the map?");
112  return *IP.first->second;
113}
114
115void AssumptionCacheTracker::verifyAnalysis() const {
116#ifndef NDEBUG
117  SmallPtrSet<const CallInst *, 4> AssumptionSet;
118  for (const auto &I : AssumptionCaches) {
119    for (auto &VH : I.second->assumptions())
120      if (VH)
121        AssumptionSet.insert(cast<CallInst>(VH));
122
123    for (const BasicBlock &B : cast<Function>(*I.first))
124      for (const Instruction &II : B)
125        if (match(&II, m_Intrinsic<Intrinsic::assume>()))
126          assert(AssumptionSet.count(cast<CallInst>(&II)) &&
127                 "Assumption in scanned function not in cache");
128  }
129#endif
130}
131
132AssumptionCacheTracker::AssumptionCacheTracker() : ImmutablePass(ID) {
133  initializeAssumptionCacheTrackerPass(*PassRegistry::getPassRegistry());
134}
135
136AssumptionCacheTracker::~AssumptionCacheTracker() {}
137
138INITIALIZE_PASS(AssumptionCacheTracker, "assumption-cache-tracker",
139                "Assumption Cache Tracker", false, true)
140char AssumptionCacheTracker::ID = 0;
141