1 | //===- AssumptionCache.cpp - Cache finding @llvm.assume calls -------------===// |
2 | // |
3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | // See https://llvm.org/LICENSE.txt for license information. |
5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | // |
7 | //===----------------------------------------------------------------------===// |
8 | // |
9 | // This file contains a pass that keeps track of @llvm.assume intrinsics in |
10 | // the functions of a module. |
11 | // |
12 | //===----------------------------------------------------------------------===// |
13 | |
14 | #include "llvm/Analysis/AssumptionCache.h" |
15 | #include "llvm/ADT/STLExtras.h" |
16 | #include "llvm/ADT/SmallPtrSet.h" |
17 | #include "llvm/ADT/SmallVector.h" |
18 | #include "llvm/Analysis/AssumeBundleQueries.h" |
19 | #include "llvm/Analysis/TargetTransformInfo.h" |
20 | #include "llvm/Analysis/ValueTracking.h" |
21 | #include "llvm/IR/BasicBlock.h" |
22 | #include "llvm/IR/Function.h" |
23 | #include "llvm/IR/InstrTypes.h" |
24 | #include "llvm/IR/Instruction.h" |
25 | #include "llvm/IR/Instructions.h" |
26 | #include "llvm/IR/PassManager.h" |
27 | #include "llvm/IR/PatternMatch.h" |
28 | #include "llvm/InitializePasses.h" |
29 | #include "llvm/Pass.h" |
30 | #include "llvm/Support/Casting.h" |
31 | #include "llvm/Support/CommandLine.h" |
32 | #include "llvm/Support/ErrorHandling.h" |
33 | #include "llvm/Support/raw_ostream.h" |
34 | #include <cassert> |
35 | #include <utility> |
36 | |
37 | using namespace llvm; |
38 | using namespace llvm::PatternMatch; |
39 | |
40 | static cl::opt<bool> |
41 | VerifyAssumptionCache("verify-assumption-cache" , cl::Hidden, |
42 | cl::desc("Enable verification of assumption cache" ), |
43 | cl::init(Val: false)); |
44 | |
45 | SmallVector<AssumptionCache::ResultElem, 1> & |
46 | AssumptionCache::getOrInsertAffectedValues(Value *V) { |
47 | // Try using find_as first to avoid creating extra value handles just for the |
48 | // purpose of doing the lookup. |
49 | auto AVI = AffectedValues.find_as(Val: V); |
50 | if (AVI != AffectedValues.end()) |
51 | return AVI->second; |
52 | |
53 | auto AVIP = AffectedValues.insert( |
54 | KV: {AffectedValueCallbackVH(V, this), SmallVector<ResultElem, 1>()}); |
55 | return AVIP.first->second; |
56 | } |
57 | |
58 | static void |
59 | findAffectedValues(CallBase *CI, TargetTransformInfo *TTI, |
60 | SmallVectorImpl<AssumptionCache::ResultElem> &Affected) { |
61 | // Note: This code must be kept in-sync with the code in |
62 | // computeKnownBitsFromAssume in ValueTracking. |
63 | |
64 | auto AddAffected = [&Affected](Value *V, unsigned Idx = |
65 | AssumptionCache::ExprResultIdx) { |
66 | if (isa<Argument>(Val: V) || isa<GlobalValue>(Val: V)) { |
67 | Affected.push_back(Elt: {.Assume: V, .Index: Idx}); |
68 | } else if (auto *I = dyn_cast<Instruction>(Val: V)) { |
69 | Affected.push_back(Elt: {.Assume: I, .Index: Idx}); |
70 | |
71 | // Peek through unary operators to find the source of the condition. |
72 | Value *Op; |
73 | if (match(V: I, P: m_PtrToInt(Op: m_Value(V&: Op)))) { |
74 | if (isa<Instruction>(Val: Op) || isa<Argument>(Val: Op)) |
75 | Affected.push_back(Elt: {.Assume: Op, .Index: Idx}); |
76 | } |
77 | } |
78 | }; |
79 | |
80 | for (unsigned Idx = 0; Idx != CI->getNumOperandBundles(); Idx++) { |
81 | OperandBundleUse Bundle = CI->getOperandBundleAt(Index: Idx); |
82 | if (Bundle.getTagName() == "separate_storage" ) { |
83 | assert(Bundle.Inputs.size() == 2 && |
84 | "separate_storage must have two args" ); |
85 | AddAffected(getUnderlyingObject(V: Bundle.Inputs[0]), Idx); |
86 | AddAffected(getUnderlyingObject(V: Bundle.Inputs[1]), Idx); |
87 | } else if (Bundle.Inputs.size() > ABA_WasOn && |
88 | Bundle.getTagName() != IgnoreBundleTag) |
89 | AddAffected(Bundle.Inputs[ABA_WasOn], Idx); |
90 | } |
91 | |
92 | Value *Cond = CI->getArgOperand(i: 0), *A, *B; |
93 | AddAffected(Cond); |
94 | if (match(V: Cond, P: m_Not(V: m_Value(V&: A)))) |
95 | AddAffected(A); |
96 | |
97 | CmpInst::Predicate Pred; |
98 | if (match(V: Cond, P: m_Cmp(Pred, L: m_Value(V&: A), R: m_Value(V&: B)))) { |
99 | AddAffected(A); |
100 | AddAffected(B); |
101 | |
102 | if (Pred == ICmpInst::ICMP_EQ) { |
103 | if (match(V: B, P: m_ConstantInt())) { |
104 | Value *X; |
105 | // (X & C) or (X | C) or (X ^ C). |
106 | // (X << C) or (X >>_s C) or (X >>_u C). |
107 | if (match(V: A, P: m_BitwiseLogic(L: m_Value(V&: X), R: m_ConstantInt())) || |
108 | match(V: A, P: m_Shift(L: m_Value(V&: X), R: m_ConstantInt()))) |
109 | AddAffected(X); |
110 | } |
111 | } else if (Pred == ICmpInst::ICMP_NE) { |
112 | Value *X; |
113 | // Handle (X & pow2 != 0). |
114 | if (match(V: A, P: m_And(L: m_Value(V&: X), R: m_Power2())) && match(V: B, P: m_Zero())) |
115 | AddAffected(X); |
116 | } else if (Pred == ICmpInst::ICMP_ULT) { |
117 | Value *X; |
118 | // Handle (A + C1) u< C2, which is the canonical form of A > C3 && A < C4, |
119 | // and recognized by LVI at least. |
120 | if (match(V: A, P: m_Add(L: m_Value(V&: X), R: m_ConstantInt())) && |
121 | match(V: B, P: m_ConstantInt())) |
122 | AddAffected(X); |
123 | } else if (CmpInst::isFPPredicate(P: Pred)) { |
124 | // fcmp fneg(x), y |
125 | // fcmp fabs(x), y |
126 | // fcmp fneg(fabs(x)), y |
127 | if (match(V: A, P: m_FNeg(X: m_Value(V&: A)))) |
128 | AddAffected(A); |
129 | if (match(V: A, P: m_FAbs(Op0: m_Value(V&: A)))) |
130 | AddAffected(A); |
131 | } |
132 | } else if (match(Cond, m_Intrinsic<Intrinsic::is_fpclass>(m_Value(V&: A), |
133 | m_Value(V&: B)))) { |
134 | AddAffected(A); |
135 | } |
136 | |
137 | if (TTI) { |
138 | const Value *Ptr; |
139 | unsigned AS; |
140 | std::tie(args&: Ptr, args&: AS) = TTI->getPredicatedAddrSpace(V: Cond); |
141 | if (Ptr) |
142 | AddAffected(const_cast<Value *>(Ptr->stripInBoundsOffsets())); |
143 | } |
144 | } |
145 | |
146 | void AssumptionCache::updateAffectedValues(AssumeInst *CI) { |
147 | SmallVector<AssumptionCache::ResultElem, 16> Affected; |
148 | findAffectedValues(CI, TTI, Affected); |
149 | |
150 | for (auto &AV : Affected) { |
151 | auto &AVV = getOrInsertAffectedValues(V: AV.Assume); |
152 | if (llvm::none_of(Range&: AVV, P: [&](ResultElem &Elem) { |
153 | return Elem.Assume == CI && Elem.Index == AV.Index; |
154 | })) |
155 | AVV.push_back(Elt: {.Assume: CI, .Index: AV.Index}); |
156 | } |
157 | } |
158 | |
159 | void AssumptionCache::unregisterAssumption(AssumeInst *CI) { |
160 | SmallVector<AssumptionCache::ResultElem, 16> Affected; |
161 | findAffectedValues(CI, TTI, Affected); |
162 | |
163 | for (auto &AV : Affected) { |
164 | auto AVI = AffectedValues.find_as(Val: AV.Assume); |
165 | if (AVI == AffectedValues.end()) |
166 | continue; |
167 | bool Found = false; |
168 | bool HasNonnull = false; |
169 | for (ResultElem &Elem : AVI->second) { |
170 | if (Elem.Assume == CI) { |
171 | Found = true; |
172 | Elem.Assume = nullptr; |
173 | } |
174 | HasNonnull |= !!Elem.Assume; |
175 | if (HasNonnull && Found) |
176 | break; |
177 | } |
178 | assert(Found && "already unregistered or incorrect cache state" ); |
179 | if (!HasNonnull) |
180 | AffectedValues.erase(I: AVI); |
181 | } |
182 | |
183 | llvm::erase(C&: AssumeHandles, V: CI); |
184 | } |
185 | |
186 | void AssumptionCache::AffectedValueCallbackVH::deleted() { |
187 | AC->AffectedValues.erase(Val: getValPtr()); |
188 | // 'this' now dangles! |
189 | } |
190 | |
191 | void AssumptionCache::transferAffectedValuesInCache(Value *OV, Value *NV) { |
192 | auto &NAVV = getOrInsertAffectedValues(V: NV); |
193 | auto AVI = AffectedValues.find(Val: OV); |
194 | if (AVI == AffectedValues.end()) |
195 | return; |
196 | |
197 | for (auto &A : AVI->second) |
198 | if (!llvm::is_contained(Range&: NAVV, Element: A)) |
199 | NAVV.push_back(Elt: A); |
200 | AffectedValues.erase(Val: OV); |
201 | } |
202 | |
203 | void AssumptionCache::AffectedValueCallbackVH::allUsesReplacedWith(Value *NV) { |
204 | if (!isa<Instruction>(Val: NV) && !isa<Argument>(Val: NV)) |
205 | return; |
206 | |
207 | // Any assumptions that affected this value now affect the new value. |
208 | |
209 | AC->transferAffectedValuesInCache(OV: getValPtr(), NV); |
210 | // 'this' now might dangle! If the AffectedValues map was resized to add an |
211 | // entry for NV then this object might have been destroyed in favor of some |
212 | // copy in the grown map. |
213 | } |
214 | |
215 | void AssumptionCache::scanFunction() { |
216 | assert(!Scanned && "Tried to scan the function twice!" ); |
217 | assert(AssumeHandles.empty() && "Already have assumes when scanning!" ); |
218 | |
219 | // Go through all instructions in all blocks, add all calls to @llvm.assume |
220 | // to this cache. |
221 | for (BasicBlock &B : F) |
222 | for (Instruction &I : B) |
223 | if (isa<AssumeInst>(Val: &I)) |
224 | AssumeHandles.push_back(Elt: {.Assume: &I, .Index: ExprResultIdx}); |
225 | |
226 | // Mark the scan as complete. |
227 | Scanned = true; |
228 | |
229 | // Update affected values. |
230 | for (auto &A : AssumeHandles) |
231 | updateAffectedValues(CI: cast<AssumeInst>(Val&: A)); |
232 | } |
233 | |
234 | void AssumptionCache::registerAssumption(AssumeInst *CI) { |
235 | // If we haven't scanned the function yet, just drop this assumption. It will |
236 | // be found when we scan later. |
237 | if (!Scanned) |
238 | return; |
239 | |
240 | AssumeHandles.push_back(Elt: {.Assume: CI, .Index: ExprResultIdx}); |
241 | |
242 | #ifndef NDEBUG |
243 | assert(CI->getParent() && |
244 | "Cannot register @llvm.assume call not in a basic block" ); |
245 | assert(&F == CI->getParent()->getParent() && |
246 | "Cannot register @llvm.assume call not in this function" ); |
247 | |
248 | // We expect the number of assumptions to be small, so in an asserts build |
249 | // check that we don't accumulate duplicates and that all assumptions point |
250 | // to the same function. |
251 | SmallPtrSet<Value *, 16> AssumptionSet; |
252 | for (auto &VH : AssumeHandles) { |
253 | if (!VH) |
254 | continue; |
255 | |
256 | assert(&F == cast<Instruction>(VH)->getParent()->getParent() && |
257 | "Cached assumption not inside this function!" ); |
258 | assert(match(cast<CallInst>(VH), m_Intrinsic<Intrinsic::assume>()) && |
259 | "Cached something other than a call to @llvm.assume!" ); |
260 | assert(AssumptionSet.insert(VH).second && |
261 | "Cache contains multiple copies of a call!" ); |
262 | } |
263 | #endif |
264 | |
265 | updateAffectedValues(CI); |
266 | } |
267 | |
268 | AssumptionCache AssumptionAnalysis::run(Function &F, |
269 | FunctionAnalysisManager &FAM) { |
270 | auto &TTI = FAM.getResult<TargetIRAnalysis>(IR&: F); |
271 | return AssumptionCache(F, &TTI); |
272 | } |
273 | |
274 | AnalysisKey AssumptionAnalysis::Key; |
275 | |
276 | PreservedAnalyses AssumptionPrinterPass::run(Function &F, |
277 | FunctionAnalysisManager &AM) { |
278 | AssumptionCache &AC = AM.getResult<AssumptionAnalysis>(IR&: F); |
279 | |
280 | OS << "Cached assumptions for function: " << F.getName() << "\n" ; |
281 | for (auto &VH : AC.assumptions()) |
282 | if (VH) |
283 | OS << " " << *cast<CallInst>(Val&: VH)->getArgOperand(i: 0) << "\n" ; |
284 | |
285 | return PreservedAnalyses::all(); |
286 | } |
287 | |
288 | void AssumptionCacheTracker::FunctionCallbackVH::deleted() { |
289 | auto I = ACT->AssumptionCaches.find_as(Val: cast<Function>(Val: getValPtr())); |
290 | if (I != ACT->AssumptionCaches.end()) |
291 | ACT->AssumptionCaches.erase(I); |
292 | // 'this' now dangles! |
293 | } |
294 | |
295 | AssumptionCache &AssumptionCacheTracker::getAssumptionCache(Function &F) { |
296 | // We probe the function map twice to try and avoid creating a value handle |
297 | // around the function in common cases. This makes insertion a bit slower, |
298 | // but if we have to insert we're going to scan the whole function so that |
299 | // shouldn't matter. |
300 | auto I = AssumptionCaches.find_as(Val: &F); |
301 | if (I != AssumptionCaches.end()) |
302 | return *I->second; |
303 | |
304 | auto *TTIWP = getAnalysisIfAvailable<TargetTransformInfoWrapperPass>(); |
305 | auto *TTI = TTIWP ? &TTIWP->getTTI(F) : nullptr; |
306 | |
307 | // Ok, build a new cache by scanning the function, insert it and the value |
308 | // handle into our map, and return the newly populated cache. |
309 | auto IP = AssumptionCaches.insert(KV: std::make_pair( |
310 | x: FunctionCallbackVH(&F, this), y: std::make_unique<AssumptionCache>(args&: F, args&: TTI))); |
311 | assert(IP.second && "Scanning function already in the map?" ); |
312 | return *IP.first->second; |
313 | } |
314 | |
315 | AssumptionCache *AssumptionCacheTracker::lookupAssumptionCache(Function &F) { |
316 | auto I = AssumptionCaches.find_as(Val: &F); |
317 | if (I != AssumptionCaches.end()) |
318 | return I->second.get(); |
319 | return nullptr; |
320 | } |
321 | |
322 | void AssumptionCacheTracker::verifyAnalysis() const { |
323 | // FIXME: In the long term the verifier should not be controllable with a |
324 | // flag. We should either fix all passes to correctly update the assumption |
325 | // cache and enable the verifier unconditionally or somehow arrange for the |
326 | // assumption list to be updated automatically by passes. |
327 | if (!VerifyAssumptionCache) |
328 | return; |
329 | |
330 | SmallPtrSet<const CallInst *, 4> AssumptionSet; |
331 | for (const auto &I : AssumptionCaches) { |
332 | for (auto &VH : I.second->assumptions()) |
333 | if (VH) |
334 | AssumptionSet.insert(Ptr: cast<CallInst>(Val&: VH)); |
335 | |
336 | for (const BasicBlock &B : cast<Function>(Val&: *I.first)) |
337 | for (const Instruction &II : B) |
338 | if (match(&II, m_Intrinsic<Intrinsic::assume>()) && |
339 | !AssumptionSet.count(cast<CallInst>(&II))) |
340 | report_fatal_error(reason: "Assumption in scanned function not in cache" ); |
341 | } |
342 | } |
343 | |
344 | AssumptionCacheTracker::AssumptionCacheTracker() : ImmutablePass(ID) { |
345 | initializeAssumptionCacheTrackerPass(*PassRegistry::getPassRegistry()); |
346 | } |
347 | |
348 | AssumptionCacheTracker::~AssumptionCacheTracker() = default; |
349 | |
350 | char AssumptionCacheTracker::ID = 0; |
351 | |
352 | INITIALIZE_PASS(AssumptionCacheTracker, "assumption-cache-tracker" , |
353 | "Assumption Cache Tracker" , false, true) |
354 | |