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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/ADT/STLExtras.h"
17 : #include "llvm/ADT/SmallPtrSet.h"
18 : #include "llvm/ADT/SmallVector.h"
19 : #include "llvm/IR/BasicBlock.h"
20 : #include "llvm/IR/Function.h"
21 : #include "llvm/IR/InstrTypes.h"
22 : #include "llvm/IR/Instruction.h"
23 : #include "llvm/IR/Instructions.h"
24 : #include "llvm/IR/Intrinsics.h"
25 : #include "llvm/IR/PassManager.h"
26 : #include "llvm/IR/PatternMatch.h"
27 : #include "llvm/Pass.h"
28 : #include "llvm/Support/Casting.h"
29 : #include "llvm/Support/CommandLine.h"
30 : #include "llvm/Support/ErrorHandling.h"
31 : #include "llvm/Support/raw_ostream.h"
32 : #include <algorithm>
33 : #include <cassert>
34 : #include <utility>
35 :
36 : using namespace llvm;
37 : using namespace llvm::PatternMatch;
38 :
39 : static cl::opt<bool>
40 : VerifyAssumptionCache("verify-assumption-cache", cl::Hidden,
41 : cl::desc("Enable verification of assumption cache"),
42 : cl::init(false));
43 :
44 : SmallVector<WeakTrackingVH, 1> &
45 7490 : AssumptionCache::getOrInsertAffectedValues(Value *V) {
46 : // Try using find_as first to avoid creating extra value handles just for the
47 : // purpose of doing the lookup.
48 7490 : auto AVI = AffectedValues.find_as(V);
49 7490 : if (AVI != AffectedValues.end())
50 3556 : return AVI->second;
51 :
52 : auto AVIP = AffectedValues.insert(
53 11802 : {AffectedValueCallbackVH(V, this), SmallVector<WeakTrackingVH, 1>()});
54 3934 : return AVIP.first->second;
55 : }
56 :
57 3675 : void AssumptionCache::updateAffectedValues(CallInst *CI) {
58 : // Note: This code must be kept in-sync with the code in
59 : // computeKnownBitsFromAssume in ValueTracking.
60 :
61 : SmallVector<Value *, 16> Affected;
62 : auto AddAffected = [&Affected](Value *V) {
63 : if (isa<Argument>(V)) {
64 : Affected.push_back(V);
65 : } else if (auto *I = dyn_cast<Instruction>(V)) {
66 : Affected.push_back(I);
67 :
68 : // Peek through unary operators to find the source of the condition.
69 : Value *Op;
70 : if (match(I, m_BitCast(m_Value(Op))) ||
71 : match(I, m_PtrToInt(m_Value(Op))) ||
72 : match(I, m_Not(m_Value(Op)))) {
73 : if (isa<Instruction>(Op) || isa<Argument>(Op))
74 : Affected.push_back(Op);
75 : }
76 : }
77 3675 : };
78 :
79 3675 : Value *Cond = CI->getArgOperand(0), *A, *B;
80 3675 : AddAffected(Cond);
81 :
82 : CmpInst::Predicate Pred;
83 : if (match(Cond, m_ICmp(Pred, m_Value(A), m_Value(B)))) {
84 3524 : AddAffected(A);
85 3524 : AddAffected(B);
86 :
87 3524 : if (Pred == ICmpInst::ICMP_EQ) {
88 : // For equality comparisons, we handle the case of bit inversion.
89 : auto AddAffectedFromEq = [&AddAffected](Value *V) {
90 : Value *A;
91 : if (match(V, m_Not(m_Value(A)))) {
92 : AddAffected(A);
93 : V = A;
94 : }
95 :
96 : Value *B;
97 : ConstantInt *C;
98 : // (A & B) or (A | B) or (A ^ B).
99 : if (match(V, m_BitwiseLogic(m_Value(A), m_Value(B)))) {
100 : AddAffected(A);
101 : AddAffected(B);
102 : // (A << C) or (A >>_s C) or (A >>_u C) where C is some constant.
103 : } else if (match(V, m_Shift(m_Value(A), m_ConstantInt(C)))) {
104 : AddAffected(A);
105 : }
106 204 : };
107 :
108 204 : AddAffectedFromEq(A);
109 204 : AddAffectedFromEq(B);
110 : }
111 : }
112 :
113 11141 : for (auto &AV : Affected) {
114 7466 : auto &AVV = getOrInsertAffectedValues(AV);
115 7466 : if (std::find(AVV.begin(), AVV.end(), CI) == AVV.end())
116 21420 : AVV.push_back(CI);
117 : }
118 3675 : }
119 :
120 92 : void AssumptionCache::AffectedValueCallbackVH::deleted() {
121 184 : auto AVI = AC->AffectedValues.find(getValPtr());
122 184 : if (AVI != AC->AffectedValues.end())
123 92 : AC->AffectedValues.erase(AVI);
124 : // 'this' now dangles!
125 92 : }
126 :
127 24 : void AssumptionCache::copyAffectedValuesInCache(Value *OV, Value *NV) {
128 24 : auto &NAVV = getOrInsertAffectedValues(NV);
129 72 : auto AVI = AffectedValues.find(OV);
130 24 : if (AVI == AffectedValues.end())
131 0 : return;
132 :
133 49 : for (auto &A : AVI->second)
134 25 : if (std::find(NAVV.begin(), NAVV.end(), A) == NAVV.end())
135 25 : NAVV.push_back(A);
136 : }
137 :
138 69 : void AssumptionCache::AffectedValueCallbackVH::allUsesReplacedWith(Value *NV) {
139 69 : if (!isa<Instruction>(NV) && !isa<Argument>(NV))
140 : return;
141 :
142 : // Any assumptions that affected this value now affect the new value.
143 :
144 24 : AC->copyAffectedValuesInCache(getValPtr(), NV);
145 : // 'this' now might dangle! If the AffectedValues map was resized to add an
146 : // entry for NV then this object might have been destroyed in favor of some
147 : // copy in the grown map.
148 : }
149 :
150 111296 : void AssumptionCache::scanFunction() {
151 : assert(!Scanned && "Tried to scan the function twice!");
152 : assert(AssumeHandles.empty() && "Already have assumes when scanning!");
153 :
154 : // Go through all instructions in all blocks, add all calls to @llvm.assume
155 : // to this cache.
156 641505 : for (BasicBlock &B : F)
157 4065878 : for (Instruction &II : B)
158 569654 : if (match(&II, m_Intrinsic<Intrinsic::assume>()))
159 10281 : AssumeHandles.push_back(&II);
160 :
161 : // Mark the scan as complete.
162 111296 : Scanned = true;
163 :
164 : // Update affected values.
165 114723 : for (auto &A : AssumeHandles)
166 3427 : updateAffectedValues(cast<CallInst>(A));
167 111296 : }
168 :
169 7099 : void AssumptionCache::registerAssumption(CallInst *CI) {
170 : assert(match(CI, m_Intrinsic<Intrinsic::assume>()) &&
171 : "Registered call does not call @llvm.assume");
172 :
173 : // If we haven't scanned the function yet, just drop this assumption. It will
174 : // be found when we scan later.
175 7099 : if (!Scanned)
176 : return;
177 :
178 138 : AssumeHandles.push_back(CI);
179 :
180 : #ifndef NDEBUG
181 : assert(CI->getParent() &&
182 : "Cannot register @llvm.assume call not in a basic block");
183 : assert(&F == CI->getParent()->getParent() &&
184 : "Cannot register @llvm.assume call not in this function");
185 :
186 : // We expect the number of assumptions to be small, so in an asserts build
187 : // check that we don't accumulate duplicates and that all assumptions point
188 : // to the same function.
189 : SmallPtrSet<Value *, 16> AssumptionSet;
190 : for (auto &VH : AssumeHandles) {
191 : if (!VH)
192 : continue;
193 :
194 : assert(&F == cast<Instruction>(VH)->getParent()->getParent() &&
195 : "Cached assumption not inside this function!");
196 : assert(match(cast<CallInst>(VH), m_Intrinsic<Intrinsic::assume>()) &&
197 : "Cached something other than a call to @llvm.assume!");
198 : assert(AssumptionSet.insert(VH).second &&
199 : "Cache contains multiple copies of a call!");
200 : }
201 : #endif
202 :
203 69 : updateAffectedValues(CI);
204 : }
205 :
206 : AnalysisKey AssumptionAnalysis::Key;
207 :
208 1 : PreservedAnalyses AssumptionPrinterPass::run(Function &F,
209 : FunctionAnalysisManager &AM) {
210 : AssumptionCache &AC = AM.getResult<AssumptionAnalysis>(F);
211 :
212 1 : OS << "Cached assumptions for function: " << F.getName() << "\n";
213 4 : for (auto &VH : AC.assumptions())
214 3 : if (VH)
215 6 : OS << " " << *cast<CallInst>(VH)->getArgOperand(0) << "\n";
216 :
217 1 : return PreservedAnalyses::all();
218 : }
219 :
220 559539 : void AssumptionCacheTracker::FunctionCallbackVH::deleted() {
221 559539 : auto I = ACT->AssumptionCaches.find_as(cast<Function>(getValPtr()));
222 1119078 : if (I != ACT->AssumptionCaches.end())
223 559539 : ACT->AssumptionCaches.erase(I);
224 : // 'this' now dangles!
225 559539 : }
226 :
227 7279611 : AssumptionCache &AssumptionCacheTracker::getAssumptionCache(Function &F) {
228 : // We probe the function map twice to try and avoid creating a value handle
229 : // around the function in common cases. This makes insertion a bit slower,
230 : // but if we have to insert we're going to scan the whole function so that
231 : // shouldn't matter.
232 7279611 : auto I = AssumptionCaches.find_as(&F);
233 7279614 : if (I != AssumptionCaches.end())
234 6134225 : return *I->second;
235 :
236 : // Ok, build a new cache by scanning the function, insert it and the value
237 : // handle into our map, and return the newly populated cache.
238 1145389 : auto IP = AssumptionCaches.insert(std::make_pair(
239 2290778 : FunctionCallbackVH(&F, this), llvm::make_unique<AssumptionCache>(F)));
240 : assert(IP.second && "Scanning function already in the map?");
241 2290778 : return *IP.first->second;
242 : }
243 :
244 127350 : void AssumptionCacheTracker::verifyAnalysis() const {
245 : // FIXME: In the long term the verifier should not be controllable with a
246 : // flag. We should either fix all passes to correctly update the assumption
247 : // cache and enable the verifier unconditionally or somehow arrange for the
248 : // assumption list to be updated automatically by passes.
249 127350 : if (!VerifyAssumptionCache)
250 127349 : return;
251 :
252 : SmallPtrSet<const CallInst *, 4> AssumptionSet;
253 3 : for (const auto &I : AssumptionCaches) {
254 3 : for (auto &VH : I.second->assumptions())
255 2 : if (VH)
256 2 : AssumptionSet.insert(cast<CallInst>(VH));
257 :
258 6 : for (const BasicBlock &B : cast<Function>(*I.first))
259 26 : for (const Instruction &II : B)
260 10 : if (match(&II, m_Intrinsic<Intrinsic::assume>()) &&
261 2 : !AssumptionSet.count(cast<CallInst>(&II)))
262 0 : report_fatal_error("Assumption in scanned function not in cache");
263 : }
264 : }
265 :
266 102754 : AssumptionCacheTracker::AssumptionCacheTracker() : ImmutablePass(ID) {
267 51377 : initializeAssumptionCacheTrackerPass(*PassRegistry::getPassRegistry());
268 51377 : }
269 :
270 : AssumptionCacheTracker::~AssumptionCacheTracker() = default;
271 :
272 : char AssumptionCacheTracker::ID = 0;
273 :
274 1590771 : INITIALIZE_PASS(AssumptionCacheTracker, "assumption-cache-tracker",
275 : "Assumption Cache Tracker", false, true)
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