File: | llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp |
Warning: | line 1330, column 11 Called C++ object pointer is null |
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1 | //===- DeadStoreElimination.cpp - MemorySSA Backed Dead Store Elimination -===// | |||
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 | // The code below implements dead store elimination using MemorySSA. It uses | |||
10 | // the following general approach: given a MemoryDef, walk upwards to find | |||
11 | // clobbering MemoryDefs that may be killed by the starting def. Then check | |||
12 | // that there are no uses that may read the location of the original MemoryDef | |||
13 | // in between both MemoryDefs. A bit more concretely: | |||
14 | // | |||
15 | // For all MemoryDefs StartDef: | |||
16 | // 1. Get the next dominating clobbering MemoryDef (EarlierAccess) by walking | |||
17 | // upwards. | |||
18 | // 2. Check that there are no reads between EarlierAccess and the StartDef by | |||
19 | // checking all uses starting at EarlierAccess and walking until we see | |||
20 | // StartDef. | |||
21 | // 3. For each found CurrentDef, check that: | |||
22 | // 1. There are no barrier instructions between CurrentDef and StartDef (like | |||
23 | // throws or stores with ordering constraints). | |||
24 | // 2. StartDef is executed whenever CurrentDef is executed. | |||
25 | // 3. StartDef completely overwrites CurrentDef. | |||
26 | // 4. Erase CurrentDef from the function and MemorySSA. | |||
27 | // | |||
28 | //===----------------------------------------------------------------------===// | |||
29 | ||||
30 | #include "llvm/Transforms/Scalar/DeadStoreElimination.h" | |||
31 | #include "llvm/ADT/APInt.h" | |||
32 | #include "llvm/ADT/DenseMap.h" | |||
33 | #include "llvm/ADT/MapVector.h" | |||
34 | #include "llvm/ADT/PostOrderIterator.h" | |||
35 | #include "llvm/ADT/SetVector.h" | |||
36 | #include "llvm/ADT/SmallPtrSet.h" | |||
37 | #include "llvm/ADT/SmallVector.h" | |||
38 | #include "llvm/ADT/Statistic.h" | |||
39 | #include "llvm/ADT/StringRef.h" | |||
40 | #include "llvm/Analysis/AliasAnalysis.h" | |||
41 | #include "llvm/Analysis/CaptureTracking.h" | |||
42 | #include "llvm/Analysis/GlobalsModRef.h" | |||
43 | #include "llvm/Analysis/LoopInfo.h" | |||
44 | #include "llvm/Analysis/MemoryBuiltins.h" | |||
45 | #include "llvm/Analysis/MemoryLocation.h" | |||
46 | #include "llvm/Analysis/MemorySSA.h" | |||
47 | #include "llvm/Analysis/MemorySSAUpdater.h" | |||
48 | #include "llvm/Analysis/MustExecute.h" | |||
49 | #include "llvm/Analysis/PostDominators.h" | |||
50 | #include "llvm/Analysis/TargetLibraryInfo.h" | |||
51 | #include "llvm/Analysis/ValueTracking.h" | |||
52 | #include "llvm/IR/Argument.h" | |||
53 | #include "llvm/IR/BasicBlock.h" | |||
54 | #include "llvm/IR/Constant.h" | |||
55 | #include "llvm/IR/Constants.h" | |||
56 | #include "llvm/IR/DataLayout.h" | |||
57 | #include "llvm/IR/Dominators.h" | |||
58 | #include "llvm/IR/Function.h" | |||
59 | #include "llvm/IR/IRBuilder.h" | |||
60 | #include "llvm/IR/InstIterator.h" | |||
61 | #include "llvm/IR/InstrTypes.h" | |||
62 | #include "llvm/IR/Instruction.h" | |||
63 | #include "llvm/IR/Instructions.h" | |||
64 | #include "llvm/IR/IntrinsicInst.h" | |||
65 | #include "llvm/IR/Intrinsics.h" | |||
66 | #include "llvm/IR/LLVMContext.h" | |||
67 | #include "llvm/IR/Module.h" | |||
68 | #include "llvm/IR/PassManager.h" | |||
69 | #include "llvm/IR/PatternMatch.h" | |||
70 | #include "llvm/IR/Value.h" | |||
71 | #include "llvm/InitializePasses.h" | |||
72 | #include "llvm/Pass.h" | |||
73 | #include "llvm/Support/Casting.h" | |||
74 | #include "llvm/Support/CommandLine.h" | |||
75 | #include "llvm/Support/Debug.h" | |||
76 | #include "llvm/Support/DebugCounter.h" | |||
77 | #include "llvm/Support/ErrorHandling.h" | |||
78 | #include "llvm/Support/MathExtras.h" | |||
79 | #include "llvm/Support/raw_ostream.h" | |||
80 | #include "llvm/Transforms/Scalar.h" | |||
81 | #include "llvm/Transforms/Utils/AssumeBundleBuilder.h" | |||
82 | #include "llvm/Transforms/Utils/BuildLibCalls.h" | |||
83 | #include "llvm/Transforms/Utils/Local.h" | |||
84 | #include <algorithm> | |||
85 | #include <cassert> | |||
86 | #include <cstddef> | |||
87 | #include <cstdint> | |||
88 | #include <iterator> | |||
89 | #include <map> | |||
90 | #include <utility> | |||
91 | ||||
92 | using namespace llvm; | |||
93 | using namespace PatternMatch; | |||
94 | ||||
95 | #define DEBUG_TYPE"dse" "dse" | |||
96 | ||||
97 | STATISTIC(NumRemainingStores, "Number of stores remaining after DSE")static llvm::Statistic NumRemainingStores = {"dse", "NumRemainingStores" , "Number of stores remaining after DSE"}; | |||
98 | STATISTIC(NumRedundantStores, "Number of redundant stores deleted")static llvm::Statistic NumRedundantStores = {"dse", "NumRedundantStores" , "Number of redundant stores deleted"}; | |||
99 | STATISTIC(NumFastStores, "Number of stores deleted")static llvm::Statistic NumFastStores = {"dse", "NumFastStores" , "Number of stores deleted"}; | |||
100 | STATISTIC(NumFastOther, "Number of other instrs removed")static llvm::Statistic NumFastOther = {"dse", "NumFastOther", "Number of other instrs removed"}; | |||
101 | STATISTIC(NumCompletePartials, "Number of stores dead by later partials")static llvm::Statistic NumCompletePartials = {"dse", "NumCompletePartials" , "Number of stores dead by later partials"}; | |||
102 | STATISTIC(NumModifiedStores, "Number of stores modified")static llvm::Statistic NumModifiedStores = {"dse", "NumModifiedStores" , "Number of stores modified"}; | |||
103 | STATISTIC(NumCFGChecks, "Number of stores modified")static llvm::Statistic NumCFGChecks = {"dse", "NumCFGChecks", "Number of stores modified"}; | |||
104 | STATISTIC(NumCFGTries, "Number of stores modified")static llvm::Statistic NumCFGTries = {"dse", "NumCFGTries", "Number of stores modified" }; | |||
105 | STATISTIC(NumCFGSuccess, "Number of stores modified")static llvm::Statistic NumCFGSuccess = {"dse", "NumCFGSuccess" , "Number of stores modified"}; | |||
106 | STATISTIC(NumGetDomMemoryDefPassed,static llvm::Statistic NumGetDomMemoryDefPassed = {"dse", "NumGetDomMemoryDefPassed" , "Number of times a valid candidate is returned from getDomMemoryDef" } | |||
107 | "Number of times a valid candidate is returned from getDomMemoryDef")static llvm::Statistic NumGetDomMemoryDefPassed = {"dse", "NumGetDomMemoryDefPassed" , "Number of times a valid candidate is returned from getDomMemoryDef" }; | |||
108 | STATISTIC(NumDomMemDefChecks,static llvm::Statistic NumDomMemDefChecks = {"dse", "NumDomMemDefChecks" , "Number iterations check for reads in getDomMemoryDef"} | |||
109 | "Number iterations check for reads in getDomMemoryDef")static llvm::Statistic NumDomMemDefChecks = {"dse", "NumDomMemDefChecks" , "Number iterations check for reads in getDomMemoryDef"}; | |||
110 | ||||
111 | DEBUG_COUNTER(MemorySSACounter, "dse-memoryssa",static const unsigned MemorySSACounter = DebugCounter::registerCounter ("dse-memoryssa", "Controls which MemoryDefs are eliminated." ) | |||
112 | "Controls which MemoryDefs are eliminated.")static const unsigned MemorySSACounter = DebugCounter::registerCounter ("dse-memoryssa", "Controls which MemoryDefs are eliminated." ); | |||
113 | ||||
114 | static cl::opt<bool> | |||
115 | EnablePartialOverwriteTracking("enable-dse-partial-overwrite-tracking", | |||
116 | cl::init(true), cl::Hidden, | |||
117 | cl::desc("Enable partial-overwrite tracking in DSE")); | |||
118 | ||||
119 | static cl::opt<bool> | |||
120 | EnablePartialStoreMerging("enable-dse-partial-store-merging", | |||
121 | cl::init(true), cl::Hidden, | |||
122 | cl::desc("Enable partial store merging in DSE")); | |||
123 | ||||
124 | static cl::opt<unsigned> | |||
125 | MemorySSAScanLimit("dse-memoryssa-scanlimit", cl::init(150), cl::Hidden, | |||
126 | cl::desc("The number of memory instructions to scan for " | |||
127 | "dead store elimination (default = 150)")); | |||
128 | static cl::opt<unsigned> MemorySSAUpwardsStepLimit( | |||
129 | "dse-memoryssa-walklimit", cl::init(90), cl::Hidden, | |||
130 | cl::desc("The maximum number of steps while walking upwards to find " | |||
131 | "MemoryDefs that may be killed (default = 90)")); | |||
132 | ||||
133 | static cl::opt<unsigned> MemorySSAPartialStoreLimit( | |||
134 | "dse-memoryssa-partial-store-limit", cl::init(5), cl::Hidden, | |||
135 | cl::desc("The maximum number candidates that only partially overwrite the " | |||
136 | "killing MemoryDef to consider" | |||
137 | " (default = 5)")); | |||
138 | ||||
139 | static cl::opt<unsigned> MemorySSADefsPerBlockLimit( | |||
140 | "dse-memoryssa-defs-per-block-limit", cl::init(5000), cl::Hidden, | |||
141 | cl::desc("The number of MemoryDefs we consider as candidates to eliminated " | |||
142 | "other stores per basic block (default = 5000)")); | |||
143 | ||||
144 | static cl::opt<unsigned> MemorySSASameBBStepCost( | |||
145 | "dse-memoryssa-samebb-cost", cl::init(1), cl::Hidden, | |||
146 | cl::desc( | |||
147 | "The cost of a step in the same basic block as the killing MemoryDef" | |||
148 | "(default = 1)")); | |||
149 | ||||
150 | static cl::opt<unsigned> | |||
151 | MemorySSAOtherBBStepCost("dse-memoryssa-otherbb-cost", cl::init(5), | |||
152 | cl::Hidden, | |||
153 | cl::desc("The cost of a step in a different basic " | |||
154 | "block than the killing MemoryDef" | |||
155 | "(default = 5)")); | |||
156 | ||||
157 | static cl::opt<unsigned> MemorySSAPathCheckLimit( | |||
158 | "dse-memoryssa-path-check-limit", cl::init(50), cl::Hidden, | |||
159 | cl::desc("The maximum number of blocks to check when trying to prove that " | |||
160 | "all paths to an exit go through a killing block (default = 50)")); | |||
161 | ||||
162 | //===----------------------------------------------------------------------===// | |||
163 | // Helper functions | |||
164 | //===----------------------------------------------------------------------===// | |||
165 | using OverlapIntervalsTy = std::map<int64_t, int64_t>; | |||
166 | using InstOverlapIntervalsTy = DenseMap<Instruction *, OverlapIntervalsTy>; | |||
167 | ||||
168 | /// Does this instruction write some memory? This only returns true for things | |||
169 | /// that we can analyze with other helpers below. | |||
170 | static bool hasAnalyzableMemoryWrite(Instruction *I, | |||
171 | const TargetLibraryInfo &TLI) { | |||
172 | if (isa<StoreInst>(I)) | |||
173 | return true; | |||
174 | if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { | |||
175 | switch (II->getIntrinsicID()) { | |||
176 | default: | |||
177 | return false; | |||
178 | case Intrinsic::memset: | |||
179 | case Intrinsic::memmove: | |||
180 | case Intrinsic::memcpy: | |||
181 | case Intrinsic::memcpy_inline: | |||
182 | case Intrinsic::memcpy_element_unordered_atomic: | |||
183 | case Intrinsic::memmove_element_unordered_atomic: | |||
184 | case Intrinsic::memset_element_unordered_atomic: | |||
185 | case Intrinsic::init_trampoline: | |||
186 | case Intrinsic::lifetime_end: | |||
187 | case Intrinsic::masked_store: | |||
188 | return true; | |||
189 | } | |||
190 | } | |||
191 | if (auto *CB = dyn_cast<CallBase>(I)) { | |||
192 | LibFunc LF; | |||
193 | if (TLI.getLibFunc(*CB, LF) && TLI.has(LF)) { | |||
194 | switch (LF) { | |||
195 | case LibFunc_strcpy: | |||
196 | case LibFunc_strncpy: | |||
197 | case LibFunc_strcat: | |||
198 | case LibFunc_strncat: | |||
199 | return true; | |||
200 | default: | |||
201 | return false; | |||
202 | } | |||
203 | } | |||
204 | } | |||
205 | return false; | |||
206 | } | |||
207 | ||||
208 | /// Return a Location stored to by the specified instruction. If isRemovable | |||
209 | /// returns true, this function and getLocForRead completely describe the memory | |||
210 | /// operations for this instruction. | |||
211 | static MemoryLocation getLocForWrite(Instruction *Inst, | |||
212 | const TargetLibraryInfo &TLI) { | |||
213 | if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) | |||
214 | return MemoryLocation::get(SI); | |||
215 | ||||
216 | // memcpy/memmove/memset. | |||
217 | if (auto *MI = dyn_cast<AnyMemIntrinsic>(Inst)) | |||
218 | return MemoryLocation::getForDest(MI); | |||
219 | ||||
220 | if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { | |||
221 | switch (II->getIntrinsicID()) { | |||
222 | default: | |||
223 | return MemoryLocation(); // Unhandled intrinsic. | |||
224 | case Intrinsic::init_trampoline: | |||
225 | return MemoryLocation::getAfter(II->getArgOperand(0)); | |||
226 | case Intrinsic::masked_store: | |||
227 | return MemoryLocation::getForArgument(II, 1, TLI); | |||
228 | case Intrinsic::lifetime_end: { | |||
229 | uint64_t Len = cast<ConstantInt>(II->getArgOperand(0))->getZExtValue(); | |||
230 | return MemoryLocation(II->getArgOperand(1), Len); | |||
231 | } | |||
232 | } | |||
233 | } | |||
234 | if (auto *CB = dyn_cast<CallBase>(Inst)) | |||
235 | // All the supported TLI functions so far happen to have dest as their | |||
236 | // first argument. | |||
237 | return MemoryLocation::getAfter(CB->getArgOperand(0)); | |||
238 | return MemoryLocation(); | |||
239 | } | |||
240 | ||||
241 | /// If the value of this instruction and the memory it writes to is unused, may | |||
242 | /// we delete this instruction? | |||
243 | static bool isRemovable(Instruction *I) { | |||
244 | // Don't remove volatile/atomic stores. | |||
245 | if (StoreInst *SI = dyn_cast<StoreInst>(I)) | |||
246 | return SI->isUnordered(); | |||
247 | ||||
248 | if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { | |||
249 | switch (II->getIntrinsicID()) { | |||
250 | default: llvm_unreachable("doesn't pass 'hasAnalyzableMemoryWrite' predicate")__builtin_unreachable(); | |||
251 | case Intrinsic::lifetime_end: | |||
252 | // Never remove dead lifetime_end's, e.g. because it is followed by a | |||
253 | // free. | |||
254 | return false; | |||
255 | case Intrinsic::init_trampoline: | |||
256 | // Always safe to remove init_trampoline. | |||
257 | return true; | |||
258 | case Intrinsic::memset: | |||
259 | case Intrinsic::memmove: | |||
260 | case Intrinsic::memcpy: | |||
261 | case Intrinsic::memcpy_inline: | |||
262 | // Don't remove volatile memory intrinsics. | |||
263 | return !cast<MemIntrinsic>(II)->isVolatile(); | |||
264 | case Intrinsic::memcpy_element_unordered_atomic: | |||
265 | case Intrinsic::memmove_element_unordered_atomic: | |||
266 | case Intrinsic::memset_element_unordered_atomic: | |||
267 | case Intrinsic::masked_store: | |||
268 | return true; | |||
269 | } | |||
270 | } | |||
271 | ||||
272 | // note: only get here for calls with analyzable writes - i.e. libcalls | |||
273 | if (auto *CB = dyn_cast<CallBase>(I)) | |||
274 | return CB->use_empty(); | |||
275 | ||||
276 | return false; | |||
277 | } | |||
278 | ||||
279 | /// Returns true if the end of this instruction can be safely shortened in | |||
280 | /// length. | |||
281 | static bool isShortenableAtTheEnd(Instruction *I) { | |||
282 | // Don't shorten stores for now | |||
283 | if (isa<StoreInst>(I)) | |||
284 | return false; | |||
285 | ||||
286 | if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { | |||
287 | switch (II->getIntrinsicID()) { | |||
288 | default: return false; | |||
289 | case Intrinsic::memset: | |||
290 | case Intrinsic::memcpy: | |||
291 | case Intrinsic::memcpy_element_unordered_atomic: | |||
292 | case Intrinsic::memset_element_unordered_atomic: | |||
293 | // Do shorten memory intrinsics. | |||
294 | // FIXME: Add memmove if it's also safe to transform. | |||
295 | return true; | |||
296 | } | |||
297 | } | |||
298 | ||||
299 | // Don't shorten libcalls calls for now. | |||
300 | ||||
301 | return false; | |||
302 | } | |||
303 | ||||
304 | /// Returns true if the beginning of this instruction can be safely shortened | |||
305 | /// in length. | |||
306 | static bool isShortenableAtTheBeginning(Instruction *I) { | |||
307 | // FIXME: Handle only memset for now. Supporting memcpy/memmove should be | |||
308 | // easily done by offsetting the source address. | |||
309 | return isa<AnyMemSetInst>(I); | |||
310 | } | |||
311 | ||||
312 | static uint64_t getPointerSize(const Value *V, const DataLayout &DL, | |||
313 | const TargetLibraryInfo &TLI, | |||
314 | const Function *F) { | |||
315 | uint64_t Size; | |||
316 | ObjectSizeOpts Opts; | |||
317 | Opts.NullIsUnknownSize = NullPointerIsDefined(F); | |||
318 | ||||
319 | if (getObjectSize(V, Size, DL, &TLI, Opts)) | |||
320 | return Size; | |||
321 | return MemoryLocation::UnknownSize; | |||
322 | } | |||
323 | ||||
324 | namespace { | |||
325 | ||||
326 | enum OverwriteResult { | |||
327 | OW_Begin, | |||
328 | OW_Complete, | |||
329 | OW_End, | |||
330 | OW_PartialEarlierWithFullLater, | |||
331 | OW_MaybePartial, | |||
332 | OW_Unknown | |||
333 | }; | |||
334 | ||||
335 | } // end anonymous namespace | |||
336 | ||||
337 | /// Check if two instruction are masked stores that completely | |||
338 | /// overwrite one another. More specifically, \p Later has to | |||
339 | /// overwrite \p Earlier. | |||
340 | static OverwriteResult isMaskedStoreOverwrite(const Instruction *Later, | |||
341 | const Instruction *Earlier, | |||
342 | BatchAAResults &AA) { | |||
343 | const auto *IIL = dyn_cast<IntrinsicInst>(Later); | |||
344 | const auto *IIE = dyn_cast<IntrinsicInst>(Earlier); | |||
345 | if (IIL == nullptr || IIE == nullptr) | |||
346 | return OW_Unknown; | |||
347 | if (IIL->getIntrinsicID() != Intrinsic::masked_store || | |||
348 | IIE->getIntrinsicID() != Intrinsic::masked_store) | |||
349 | return OW_Unknown; | |||
350 | // Pointers. | |||
351 | Value *LP = IIL->getArgOperand(1)->stripPointerCasts(); | |||
352 | Value *EP = IIE->getArgOperand(1)->stripPointerCasts(); | |||
353 | if (LP != EP && !AA.isMustAlias(LP, EP)) | |||
354 | return OW_Unknown; | |||
355 | // Masks. | |||
356 | // TODO: check that Later's mask is a superset of the Earlier's mask. | |||
357 | if (IIL->getArgOperand(3) != IIE->getArgOperand(3)) | |||
358 | return OW_Unknown; | |||
359 | return OW_Complete; | |||
360 | } | |||
361 | ||||
362 | /// Return 'OW_Complete' if a store to the 'Later' location completely | |||
363 | /// overwrites a store to the 'Earlier' location, 'OW_End' if the end of the | |||
364 | /// 'Earlier' location is completely overwritten by 'Later', 'OW_Begin' if the | |||
365 | /// beginning of the 'Earlier' location is overwritten by 'Later'. | |||
366 | /// 'OW_PartialEarlierWithFullLater' means that an earlier (big) store was | |||
367 | /// overwritten by a latter (smaller) store which doesn't write outside the big | |||
368 | /// store's memory locations. Returns 'OW_Unknown' if nothing can be determined. | |||
369 | /// NOTE: This function must only be called if both \p Later and \p Earlier | |||
370 | /// write to the same underlying object with valid \p EarlierOff and \p | |||
371 | /// LaterOff. | |||
372 | static OverwriteResult isPartialOverwrite(const MemoryLocation &Later, | |||
373 | const MemoryLocation &Earlier, | |||
374 | int64_t EarlierOff, int64_t LaterOff, | |||
375 | Instruction *DepWrite, | |||
376 | InstOverlapIntervalsTy &IOL) { | |||
377 | const uint64_t LaterSize = Later.Size.getValue(); | |||
378 | const uint64_t EarlierSize = Earlier.Size.getValue(); | |||
379 | // We may now overlap, although the overlap is not complete. There might also | |||
380 | // be other incomplete overlaps, and together, they might cover the complete | |||
381 | // earlier write. | |||
382 | // Note: The correctness of this logic depends on the fact that this function | |||
383 | // is not even called providing DepWrite when there are any intervening reads. | |||
384 | if (EnablePartialOverwriteTracking && | |||
385 | LaterOff < int64_t(EarlierOff + EarlierSize) && | |||
386 | int64_t(LaterOff + LaterSize) >= EarlierOff) { | |||
387 | ||||
388 | // Insert our part of the overlap into the map. | |||
389 | auto &IM = IOL[DepWrite]; | |||
390 | LLVM_DEBUG(dbgs() << "DSE: Partial overwrite: Earlier [" << EarlierOffdo { } while (false) | |||
391 | << ", " << int64_t(EarlierOff + EarlierSize)do { } while (false) | |||
392 | << ") Later [" << LaterOff << ", "do { } while (false) | |||
393 | << int64_t(LaterOff + LaterSize) << ")\n")do { } while (false); | |||
394 | ||||
395 | // Make sure that we only insert non-overlapping intervals and combine | |||
396 | // adjacent intervals. The intervals are stored in the map with the ending | |||
397 | // offset as the key (in the half-open sense) and the starting offset as | |||
398 | // the value. | |||
399 | int64_t LaterIntStart = LaterOff, LaterIntEnd = LaterOff + LaterSize; | |||
400 | ||||
401 | // Find any intervals ending at, or after, LaterIntStart which start | |||
402 | // before LaterIntEnd. | |||
403 | auto ILI = IM.lower_bound(LaterIntStart); | |||
404 | if (ILI != IM.end() && ILI->second <= LaterIntEnd) { | |||
405 | // This existing interval is overlapped with the current store somewhere | |||
406 | // in [LaterIntStart, LaterIntEnd]. Merge them by erasing the existing | |||
407 | // intervals and adjusting our start and end. | |||
408 | LaterIntStart = std::min(LaterIntStart, ILI->second); | |||
409 | LaterIntEnd = std::max(LaterIntEnd, ILI->first); | |||
410 | ILI = IM.erase(ILI); | |||
411 | ||||
412 | // Continue erasing and adjusting our end in case other previous | |||
413 | // intervals are also overlapped with the current store. | |||
414 | // | |||
415 | // |--- ealier 1 ---| |--- ealier 2 ---| | |||
416 | // |------- later---------| | |||
417 | // | |||
418 | while (ILI != IM.end() && ILI->second <= LaterIntEnd) { | |||
419 | assert(ILI->second > LaterIntStart && "Unexpected interval")(static_cast<void> (0)); | |||
420 | LaterIntEnd = std::max(LaterIntEnd, ILI->first); | |||
421 | ILI = IM.erase(ILI); | |||
422 | } | |||
423 | } | |||
424 | ||||
425 | IM[LaterIntEnd] = LaterIntStart; | |||
426 | ||||
427 | ILI = IM.begin(); | |||
428 | if (ILI->second <= EarlierOff && | |||
429 | ILI->first >= int64_t(EarlierOff + EarlierSize)) { | |||
430 | LLVM_DEBUG(dbgs() << "DSE: Full overwrite from partials: Earlier ["do { } while (false) | |||
431 | << EarlierOff << ", "do { } while (false) | |||
432 | << int64_t(EarlierOff + EarlierSize)do { } while (false) | |||
433 | << ") Composite Later [" << ILI->second << ", "do { } while (false) | |||
434 | << ILI->first << ")\n")do { } while (false); | |||
435 | ++NumCompletePartials; | |||
436 | return OW_Complete; | |||
437 | } | |||
438 | } | |||
439 | ||||
440 | // Check for an earlier store which writes to all the memory locations that | |||
441 | // the later store writes to. | |||
442 | if (EnablePartialStoreMerging && LaterOff >= EarlierOff && | |||
443 | int64_t(EarlierOff + EarlierSize) > LaterOff && | |||
444 | uint64_t(LaterOff - EarlierOff) + LaterSize <= EarlierSize) { | |||
445 | LLVM_DEBUG(dbgs() << "DSE: Partial overwrite an earlier load ["do { } while (false) | |||
446 | << EarlierOff << ", "do { } while (false) | |||
447 | << int64_t(EarlierOff + EarlierSize)do { } while (false) | |||
448 | << ") by a later store [" << LaterOff << ", "do { } while (false) | |||
449 | << int64_t(LaterOff + LaterSize) << ")\n")do { } while (false); | |||
450 | // TODO: Maybe come up with a better name? | |||
451 | return OW_PartialEarlierWithFullLater; | |||
452 | } | |||
453 | ||||
454 | // Another interesting case is if the later store overwrites the end of the | |||
455 | // earlier store. | |||
456 | // | |||
457 | // |--earlier--| | |||
458 | // |-- later --| | |||
459 | // | |||
460 | // In this case we may want to trim the size of earlier to avoid generating | |||
461 | // writes to addresses which will definitely be overwritten later | |||
462 | if (!EnablePartialOverwriteTracking && | |||
463 | (LaterOff > EarlierOff && LaterOff < int64_t(EarlierOff + EarlierSize) && | |||
464 | int64_t(LaterOff + LaterSize) >= int64_t(EarlierOff + EarlierSize))) | |||
465 | return OW_End; | |||
466 | ||||
467 | // Finally, we also need to check if the later store overwrites the beginning | |||
468 | // of the earlier store. | |||
469 | // | |||
470 | // |--earlier--| | |||
471 | // |-- later --| | |||
472 | // | |||
473 | // In this case we may want to move the destination address and trim the size | |||
474 | // of earlier to avoid generating writes to addresses which will definitely | |||
475 | // be overwritten later. | |||
476 | if (!EnablePartialOverwriteTracking && | |||
477 | (LaterOff <= EarlierOff && int64_t(LaterOff + LaterSize) > EarlierOff)) { | |||
478 | assert(int64_t(LaterOff + LaterSize) < int64_t(EarlierOff + EarlierSize) &&(static_cast<void> (0)) | |||
479 | "Expect to be handled as OW_Complete")(static_cast<void> (0)); | |||
480 | return OW_Begin; | |||
481 | } | |||
482 | // Otherwise, they don't completely overlap. | |||
483 | return OW_Unknown; | |||
484 | } | |||
485 | ||||
486 | /// Returns true if the memory which is accessed by the second instruction is not | |||
487 | /// modified between the first and the second instruction. | |||
488 | /// Precondition: Second instruction must be dominated by the first | |||
489 | /// instruction. | |||
490 | static bool | |||
491 | memoryIsNotModifiedBetween(Instruction *FirstI, Instruction *SecondI, | |||
492 | BatchAAResults &AA, const DataLayout &DL, | |||
493 | DominatorTree *DT) { | |||
494 | // Do a backwards scan through the CFG from SecondI to FirstI. Look for | |||
495 | // instructions which can modify the memory location accessed by SecondI. | |||
496 | // | |||
497 | // While doing the walk keep track of the address to check. It might be | |||
498 | // different in different basic blocks due to PHI translation. | |||
499 | using BlockAddressPair = std::pair<BasicBlock *, PHITransAddr>; | |||
500 | SmallVector<BlockAddressPair, 16> WorkList; | |||
501 | // Keep track of the address we visited each block with. Bail out if we | |||
502 | // visit a block with different addresses. | |||
503 | DenseMap<BasicBlock *, Value *> Visited; | |||
504 | ||||
505 | BasicBlock::iterator FirstBBI(FirstI); | |||
506 | ++FirstBBI; | |||
507 | BasicBlock::iterator SecondBBI(SecondI); | |||
508 | BasicBlock *FirstBB = FirstI->getParent(); | |||
509 | BasicBlock *SecondBB = SecondI->getParent(); | |||
510 | MemoryLocation MemLoc; | |||
511 | if (auto *MemSet = dyn_cast<MemSetInst>(SecondI)) | |||
512 | MemLoc = MemoryLocation::getForDest(MemSet); | |||
513 | else | |||
514 | MemLoc = MemoryLocation::get(SecondI); | |||
515 | ||||
516 | auto *MemLocPtr = const_cast<Value *>(MemLoc.Ptr); | |||
517 | ||||
518 | // Start checking the SecondBB. | |||
519 | WorkList.push_back( | |||
520 | std::make_pair(SecondBB, PHITransAddr(MemLocPtr, DL, nullptr))); | |||
521 | bool isFirstBlock = true; | |||
522 | ||||
523 | // Check all blocks going backward until we reach the FirstBB. | |||
524 | while (!WorkList.empty()) { | |||
525 | BlockAddressPair Current = WorkList.pop_back_val(); | |||
526 | BasicBlock *B = Current.first; | |||
527 | PHITransAddr &Addr = Current.second; | |||
528 | Value *Ptr = Addr.getAddr(); | |||
529 | ||||
530 | // Ignore instructions before FirstI if this is the FirstBB. | |||
531 | BasicBlock::iterator BI = (B == FirstBB ? FirstBBI : B->begin()); | |||
532 | ||||
533 | BasicBlock::iterator EI; | |||
534 | if (isFirstBlock) { | |||
535 | // Ignore instructions after SecondI if this is the first visit of SecondBB. | |||
536 | assert(B == SecondBB && "first block is not the store block")(static_cast<void> (0)); | |||
537 | EI = SecondBBI; | |||
538 | isFirstBlock = false; | |||
539 | } else { | |||
540 | // It's not SecondBB or (in case of a loop) the second visit of SecondBB. | |||
541 | // In this case we also have to look at instructions after SecondI. | |||
542 | EI = B->end(); | |||
543 | } | |||
544 | for (; BI != EI; ++BI) { | |||
545 | Instruction *I = &*BI; | |||
546 | if (I->mayWriteToMemory() && I != SecondI) | |||
547 | if (isModSet(AA.getModRefInfo(I, MemLoc.getWithNewPtr(Ptr)))) | |||
548 | return false; | |||
549 | } | |||
550 | if (B != FirstBB) { | |||
551 | assert(B != &FirstBB->getParent()->getEntryBlock() &&(static_cast<void> (0)) | |||
552 | "Should not hit the entry block because SI must be dominated by LI")(static_cast<void> (0)); | |||
553 | for (BasicBlock *Pred : predecessors(B)) { | |||
554 | PHITransAddr PredAddr = Addr; | |||
555 | if (PredAddr.NeedsPHITranslationFromBlock(B)) { | |||
556 | if (!PredAddr.IsPotentiallyPHITranslatable()) | |||
557 | return false; | |||
558 | if (PredAddr.PHITranslateValue(B, Pred, DT, false)) | |||
559 | return false; | |||
560 | } | |||
561 | Value *TranslatedPtr = PredAddr.getAddr(); | |||
562 | auto Inserted = Visited.insert(std::make_pair(Pred, TranslatedPtr)); | |||
563 | if (!Inserted.second) { | |||
564 | // We already visited this block before. If it was with a different | |||
565 | // address - bail out! | |||
566 | if (TranslatedPtr != Inserted.first->second) | |||
567 | return false; | |||
568 | // ... otherwise just skip it. | |||
569 | continue; | |||
570 | } | |||
571 | WorkList.push_back(std::make_pair(Pred, PredAddr)); | |||
572 | } | |||
573 | } | |||
574 | } | |||
575 | return true; | |||
576 | } | |||
577 | ||||
578 | static bool tryToShorten(Instruction *EarlierWrite, int64_t &EarlierStart, | |||
579 | uint64_t &EarlierSize, int64_t LaterStart, | |||
580 | uint64_t LaterSize, bool IsOverwriteEnd) { | |||
581 | auto *EarlierIntrinsic = cast<AnyMemIntrinsic>(EarlierWrite); | |||
582 | Align PrefAlign = EarlierIntrinsic->getDestAlign().valueOrOne(); | |||
583 | ||||
584 | // We assume that memet/memcpy operates in chunks of the "largest" native | |||
585 | // type size and aligned on the same value. That means optimal start and size | |||
586 | // of memset/memcpy should be modulo of preferred alignment of that type. That | |||
587 | // is it there is no any sense in trying to reduce store size any further | |||
588 | // since any "extra" stores comes for free anyway. | |||
589 | // On the other hand, maximum alignment we can achieve is limited by alignment | |||
590 | // of initial store. | |||
591 | ||||
592 | // TODO: Limit maximum alignment by preferred (or abi?) alignment of the | |||
593 | // "largest" native type. | |||
594 | // Note: What is the proper way to get that value? | |||
595 | // Should TargetTransformInfo::getRegisterBitWidth be used or anything else? | |||
596 | // PrefAlign = std::min(DL.getPrefTypeAlign(LargestType), PrefAlign); | |||
597 | ||||
598 | int64_t ToRemoveStart = 0; | |||
599 | uint64_t ToRemoveSize = 0; | |||
600 | // Compute start and size of the region to remove. Make sure 'PrefAlign' is | |||
601 | // maintained on the remaining store. | |||
602 | if (IsOverwriteEnd) { | |||
603 | // Calculate required adjustment for 'LaterStart'in order to keep remaining | |||
604 | // store size aligned on 'PerfAlign'. | |||
605 | uint64_t Off = | |||
606 | offsetToAlignment(uint64_t(LaterStart - EarlierStart), PrefAlign); | |||
607 | ToRemoveStart = LaterStart + Off; | |||
608 | if (EarlierSize <= uint64_t(ToRemoveStart - EarlierStart)) | |||
609 | return false; | |||
610 | ToRemoveSize = EarlierSize - uint64_t(ToRemoveStart - EarlierStart); | |||
611 | } else { | |||
612 | ToRemoveStart = EarlierStart; | |||
613 | assert(LaterSize >= uint64_t(EarlierStart - LaterStart) &&(static_cast<void> (0)) | |||
614 | "Not overlapping accesses?")(static_cast<void> (0)); | |||
615 | ToRemoveSize = LaterSize - uint64_t(EarlierStart - LaterStart); | |||
616 | // Calculate required adjustment for 'ToRemoveSize'in order to keep | |||
617 | // start of the remaining store aligned on 'PerfAlign'. | |||
618 | uint64_t Off = offsetToAlignment(ToRemoveSize, PrefAlign); | |||
619 | if (Off != 0) { | |||
620 | if (ToRemoveSize <= (PrefAlign.value() - Off)) | |||
621 | return false; | |||
622 | ToRemoveSize -= PrefAlign.value() - Off; | |||
623 | } | |||
624 | assert(isAligned(PrefAlign, ToRemoveSize) &&(static_cast<void> (0)) | |||
625 | "Should preserve selected alignment")(static_cast<void> (0)); | |||
626 | } | |||
627 | ||||
628 | assert(ToRemoveSize > 0 && "Shouldn't reach here if nothing to remove")(static_cast<void> (0)); | |||
629 | assert(EarlierSize > ToRemoveSize && "Can't remove more than original size")(static_cast<void> (0)); | |||
630 | ||||
631 | uint64_t NewSize = EarlierSize - ToRemoveSize; | |||
632 | if (auto *AMI = dyn_cast<AtomicMemIntrinsic>(EarlierWrite)) { | |||
633 | // When shortening an atomic memory intrinsic, the newly shortened | |||
634 | // length must remain an integer multiple of the element size. | |||
635 | const uint32_t ElementSize = AMI->getElementSizeInBytes(); | |||
636 | if (0 != NewSize % ElementSize) | |||
637 | return false; | |||
638 | } | |||
639 | ||||
640 | LLVM_DEBUG(dbgs() << "DSE: Remove Dead Store:\n OW "do { } while (false) | |||
641 | << (IsOverwriteEnd ? "END" : "BEGIN") << ": "do { } while (false) | |||
642 | << *EarlierWrite << "\n KILLER [" << ToRemoveStart << ", "do { } while (false) | |||
643 | << int64_t(ToRemoveStart + ToRemoveSize) << ")\n")do { } while (false); | |||
644 | ||||
645 | Value *EarlierWriteLength = EarlierIntrinsic->getLength(); | |||
646 | Value *TrimmedLength = | |||
647 | ConstantInt::get(EarlierWriteLength->getType(), NewSize); | |||
648 | EarlierIntrinsic->setLength(TrimmedLength); | |||
649 | EarlierIntrinsic->setDestAlignment(PrefAlign); | |||
650 | ||||
651 | if (!IsOverwriteEnd) { | |||
652 | Value *OrigDest = EarlierIntrinsic->getRawDest(); | |||
653 | Type *Int8PtrTy = | |||
654 | Type::getInt8PtrTy(EarlierIntrinsic->getContext(), | |||
655 | OrigDest->getType()->getPointerAddressSpace()); | |||
656 | Value *Dest = OrigDest; | |||
657 | if (OrigDest->getType() != Int8PtrTy) | |||
658 | Dest = CastInst::CreatePointerCast(OrigDest, Int8PtrTy, "", EarlierWrite); | |||
659 | Value *Indices[1] = { | |||
660 | ConstantInt::get(EarlierWriteLength->getType(), ToRemoveSize)}; | |||
661 | Instruction *NewDestGEP = GetElementPtrInst::CreateInBounds( | |||
662 | Type::getInt8Ty(EarlierIntrinsic->getContext()), | |||
663 | Dest, Indices, "", EarlierWrite); | |||
664 | NewDestGEP->setDebugLoc(EarlierIntrinsic->getDebugLoc()); | |||
665 | if (NewDestGEP->getType() != OrigDest->getType()) | |||
666 | NewDestGEP = CastInst::CreatePointerCast(NewDestGEP, OrigDest->getType(), | |||
667 | "", EarlierWrite); | |||
668 | EarlierIntrinsic->setDest(NewDestGEP); | |||
669 | } | |||
670 | ||||
671 | // Finally update start and size of earlier access. | |||
672 | if (!IsOverwriteEnd) | |||
673 | EarlierStart += ToRemoveSize; | |||
674 | EarlierSize = NewSize; | |||
675 | ||||
676 | return true; | |||
677 | } | |||
678 | ||||
679 | static bool tryToShortenEnd(Instruction *EarlierWrite, | |||
680 | OverlapIntervalsTy &IntervalMap, | |||
681 | int64_t &EarlierStart, uint64_t &EarlierSize) { | |||
682 | if (IntervalMap.empty() || !isShortenableAtTheEnd(EarlierWrite)) | |||
683 | return false; | |||
684 | ||||
685 | OverlapIntervalsTy::iterator OII = --IntervalMap.end(); | |||
686 | int64_t LaterStart = OII->second; | |||
687 | uint64_t LaterSize = OII->first - LaterStart; | |||
688 | ||||
689 | assert(OII->first - LaterStart >= 0 && "Size expected to be positive")(static_cast<void> (0)); | |||
690 | ||||
691 | if (LaterStart > EarlierStart && | |||
692 | // Note: "LaterStart - EarlierStart" is known to be positive due to | |||
693 | // preceding check. | |||
694 | (uint64_t)(LaterStart - EarlierStart) < EarlierSize && | |||
695 | // Note: "EarlierSize - (uint64_t)(LaterStart - EarlierStart)" is known to | |||
696 | // be non negative due to preceding checks. | |||
697 | LaterSize >= EarlierSize - (uint64_t)(LaterStart - EarlierStart)) { | |||
698 | if (tryToShorten(EarlierWrite, EarlierStart, EarlierSize, LaterStart, | |||
699 | LaterSize, true)) { | |||
700 | IntervalMap.erase(OII); | |||
701 | return true; | |||
702 | } | |||
703 | } | |||
704 | return false; | |||
705 | } | |||
706 | ||||
707 | static bool tryToShortenBegin(Instruction *EarlierWrite, | |||
708 | OverlapIntervalsTy &IntervalMap, | |||
709 | int64_t &EarlierStart, uint64_t &EarlierSize) { | |||
710 | if (IntervalMap.empty() || !isShortenableAtTheBeginning(EarlierWrite)) | |||
711 | return false; | |||
712 | ||||
713 | OverlapIntervalsTy::iterator OII = IntervalMap.begin(); | |||
714 | int64_t LaterStart = OII->second; | |||
715 | uint64_t LaterSize = OII->first - LaterStart; | |||
716 | ||||
717 | assert(OII->first - LaterStart >= 0 && "Size expected to be positive")(static_cast<void> (0)); | |||
718 | ||||
719 | if (LaterStart <= EarlierStart && | |||
720 | // Note: "EarlierStart - LaterStart" is known to be non negative due to | |||
721 | // preceding check. | |||
722 | LaterSize > (uint64_t)(EarlierStart - LaterStart)) { | |||
723 | // Note: "LaterSize - (uint64_t)(EarlierStart - LaterStart)" is known to be | |||
724 | // positive due to preceding checks. | |||
725 | assert(LaterSize - (uint64_t)(EarlierStart - LaterStart) < EarlierSize &&(static_cast<void> (0)) | |||
726 | "Should have been handled as OW_Complete")(static_cast<void> (0)); | |||
727 | if (tryToShorten(EarlierWrite, EarlierStart, EarlierSize, LaterStart, | |||
728 | LaterSize, false)) { | |||
729 | IntervalMap.erase(OII); | |||
730 | return true; | |||
731 | } | |||
732 | } | |||
733 | return false; | |||
734 | } | |||
735 | ||||
736 | static bool removePartiallyOverlappedStores(const DataLayout &DL, | |||
737 | InstOverlapIntervalsTy &IOL, | |||
738 | const TargetLibraryInfo &TLI) { | |||
739 | bool Changed = false; | |||
740 | for (auto OI : IOL) { | |||
741 | Instruction *EarlierWrite = OI.first; | |||
742 | MemoryLocation Loc = getLocForWrite(EarlierWrite, TLI); | |||
743 | assert(isRemovable(EarlierWrite) && "Expect only removable instruction")(static_cast<void> (0)); | |||
744 | ||||
745 | const Value *Ptr = Loc.Ptr->stripPointerCasts(); | |||
746 | int64_t EarlierStart = 0; | |||
747 | uint64_t EarlierSize = Loc.Size.getValue(); | |||
748 | GetPointerBaseWithConstantOffset(Ptr, EarlierStart, DL); | |||
749 | OverlapIntervalsTy &IntervalMap = OI.second; | |||
750 | Changed |= | |||
751 | tryToShortenEnd(EarlierWrite, IntervalMap, EarlierStart, EarlierSize); | |||
752 | if (IntervalMap.empty()) | |||
753 | continue; | |||
754 | Changed |= | |||
755 | tryToShortenBegin(EarlierWrite, IntervalMap, EarlierStart, EarlierSize); | |||
756 | } | |||
757 | return Changed; | |||
758 | } | |||
759 | ||||
760 | static Constant *tryToMergePartialOverlappingStores( | |||
761 | StoreInst *Earlier, StoreInst *Later, int64_t InstWriteOffset, | |||
762 | int64_t DepWriteOffset, const DataLayout &DL, BatchAAResults &AA, | |||
763 | DominatorTree *DT) { | |||
764 | ||||
765 | if (Earlier && isa<ConstantInt>(Earlier->getValueOperand()) && | |||
766 | DL.typeSizeEqualsStoreSize(Earlier->getValueOperand()->getType()) && | |||
767 | Later && isa<ConstantInt>(Later->getValueOperand()) && | |||
768 | DL.typeSizeEqualsStoreSize(Later->getValueOperand()->getType()) && | |||
769 | memoryIsNotModifiedBetween(Earlier, Later, AA, DL, DT)) { | |||
770 | // If the store we find is: | |||
771 | // a) partially overwritten by the store to 'Loc' | |||
772 | // b) the later store is fully contained in the earlier one and | |||
773 | // c) they both have a constant value | |||
774 | // d) none of the two stores need padding | |||
775 | // Merge the two stores, replacing the earlier store's value with a | |||
776 | // merge of both values. | |||
777 | // TODO: Deal with other constant types (vectors, etc), and probably | |||
778 | // some mem intrinsics (if needed) | |||
779 | ||||
780 | APInt EarlierValue = | |||
781 | cast<ConstantInt>(Earlier->getValueOperand())->getValue(); | |||
782 | APInt LaterValue = cast<ConstantInt>(Later->getValueOperand())->getValue(); | |||
783 | unsigned LaterBits = LaterValue.getBitWidth(); | |||
784 | assert(EarlierValue.getBitWidth() > LaterValue.getBitWidth())(static_cast<void> (0)); | |||
785 | LaterValue = LaterValue.zext(EarlierValue.getBitWidth()); | |||
786 | ||||
787 | // Offset of the smaller store inside the larger store | |||
788 | unsigned BitOffsetDiff = (InstWriteOffset - DepWriteOffset) * 8; | |||
789 | unsigned LShiftAmount = DL.isBigEndian() ? EarlierValue.getBitWidth() - | |||
790 | BitOffsetDiff - LaterBits | |||
791 | : BitOffsetDiff; | |||
792 | APInt Mask = APInt::getBitsSet(EarlierValue.getBitWidth(), LShiftAmount, | |||
793 | LShiftAmount + LaterBits); | |||
794 | // Clear the bits we'll be replacing, then OR with the smaller | |||
795 | // store, shifted appropriately. | |||
796 | APInt Merged = (EarlierValue & ~Mask) | (LaterValue << LShiftAmount); | |||
797 | LLVM_DEBUG(dbgs() << "DSE: Merge Stores:\n Earlier: " << *Earlierdo { } while (false) | |||
798 | << "\n Later: " << *Laterdo { } while (false) | |||
799 | << "\n Merged Value: " << Merged << '\n')do { } while (false); | |||
800 | return ConstantInt::get(Earlier->getValueOperand()->getType(), Merged); | |||
801 | } | |||
802 | return nullptr; | |||
803 | } | |||
804 | ||||
805 | namespace { | |||
806 | // Returns true if \p I is an intrisnic that does not read or write memory. | |||
807 | bool isNoopIntrinsic(Instruction *I) { | |||
808 | if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { | |||
809 | switch (II->getIntrinsicID()) { | |||
810 | case Intrinsic::lifetime_start: | |||
811 | case Intrinsic::lifetime_end: | |||
812 | case Intrinsic::invariant_end: | |||
813 | case Intrinsic::launder_invariant_group: | |||
814 | case Intrinsic::assume: | |||
815 | return true; | |||
816 | case Intrinsic::dbg_addr: | |||
817 | case Intrinsic::dbg_declare: | |||
818 | case Intrinsic::dbg_label: | |||
819 | case Intrinsic::dbg_value: | |||
820 | llvm_unreachable("Intrinsic should not be modeled in MemorySSA")__builtin_unreachable(); | |||
821 | default: | |||
822 | return false; | |||
823 | } | |||
824 | } | |||
825 | return false; | |||
826 | } | |||
827 | ||||
828 | // Check if we can ignore \p D for DSE. | |||
829 | bool canSkipDef(MemoryDef *D, bool DefVisibleToCaller, | |||
830 | const TargetLibraryInfo &TLI) { | |||
831 | Instruction *DI = D->getMemoryInst(); | |||
832 | // Calls that only access inaccessible memory cannot read or write any memory | |||
833 | // locations we consider for elimination. | |||
834 | if (auto *CB = dyn_cast<CallBase>(DI)) | |||
835 | if (CB->onlyAccessesInaccessibleMemory()) { | |||
836 | if (isAllocLikeFn(DI, &TLI)) | |||
837 | return false; | |||
838 | return true; | |||
839 | } | |||
840 | // We can eliminate stores to locations not visible to the caller across | |||
841 | // throwing instructions. | |||
842 | if (DI->mayThrow() && !DefVisibleToCaller) | |||
843 | return true; | |||
844 | ||||
845 | // We can remove the dead stores, irrespective of the fence and its ordering | |||
846 | // (release/acquire/seq_cst). Fences only constraints the ordering of | |||
847 | // already visible stores, it does not make a store visible to other | |||
848 | // threads. So, skipping over a fence does not change a store from being | |||
849 | // dead. | |||
850 | if (isa<FenceInst>(DI)) | |||
851 | return true; | |||
852 | ||||
853 | // Skip intrinsics that do not really read or modify memory. | |||
854 | if (isNoopIntrinsic(DI)) | |||
855 | return true; | |||
856 | ||||
857 | return false; | |||
858 | } | |||
859 | ||||
860 | struct DSEState { | |||
861 | Function &F; | |||
862 | AliasAnalysis &AA; | |||
863 | ||||
864 | /// The single BatchAA instance that is used to cache AA queries. It will | |||
865 | /// not be invalidated over the whole run. This is safe, because: | |||
866 | /// 1. Only memory writes are removed, so the alias cache for memory | |||
867 | /// locations remains valid. | |||
868 | /// 2. No new instructions are added (only instructions removed), so cached | |||
869 | /// information for a deleted value cannot be accessed by a re-used new | |||
870 | /// value pointer. | |||
871 | BatchAAResults BatchAA; | |||
872 | ||||
873 | MemorySSA &MSSA; | |||
874 | DominatorTree &DT; | |||
875 | PostDominatorTree &PDT; | |||
876 | const TargetLibraryInfo &TLI; | |||
877 | const DataLayout &DL; | |||
878 | const LoopInfo &LI; | |||
879 | ||||
880 | // Whether the function contains any irreducible control flow, useful for | |||
881 | // being accurately able to detect loops. | |||
882 | bool ContainsIrreducibleLoops; | |||
883 | ||||
884 | // All MemoryDefs that potentially could kill other MemDefs. | |||
885 | SmallVector<MemoryDef *, 64> MemDefs; | |||
886 | // Any that should be skipped as they are already deleted | |||
887 | SmallPtrSet<MemoryAccess *, 4> SkipStores; | |||
888 | // Keep track of all of the objects that are invisible to the caller before | |||
889 | // the function returns. | |||
890 | // SmallPtrSet<const Value *, 16> InvisibleToCallerBeforeRet; | |||
891 | DenseMap<const Value *, bool> InvisibleToCallerBeforeRet; | |||
892 | // Keep track of all of the objects that are invisible to the caller after | |||
893 | // the function returns. | |||
894 | DenseMap<const Value *, bool> InvisibleToCallerAfterRet; | |||
895 | // Keep track of blocks with throwing instructions not modeled in MemorySSA. | |||
896 | SmallPtrSet<BasicBlock *, 16> ThrowingBlocks; | |||
897 | // Post-order numbers for each basic block. Used to figure out if memory | |||
898 | // accesses are executed before another access. | |||
899 | DenseMap<BasicBlock *, unsigned> PostOrderNumbers; | |||
900 | ||||
901 | /// Keep track of instructions (partly) overlapping with killing MemoryDefs per | |||
902 | /// basic block. | |||
903 | DenseMap<BasicBlock *, InstOverlapIntervalsTy> IOLs; | |||
904 | ||||
905 | DSEState(Function &F, AliasAnalysis &AA, MemorySSA &MSSA, DominatorTree &DT, | |||
906 | PostDominatorTree &PDT, const TargetLibraryInfo &TLI, | |||
907 | const LoopInfo &LI) | |||
908 | : F(F), AA(AA), BatchAA(AA), MSSA(MSSA), DT(DT), PDT(PDT), TLI(TLI), | |||
909 | DL(F.getParent()->getDataLayout()), LI(LI) {} | |||
910 | ||||
911 | static DSEState get(Function &F, AliasAnalysis &AA, MemorySSA &MSSA, | |||
912 | DominatorTree &DT, PostDominatorTree &PDT, | |||
913 | const TargetLibraryInfo &TLI, const LoopInfo &LI) { | |||
914 | DSEState State(F, AA, MSSA, DT, PDT, TLI, LI); | |||
915 | // Collect blocks with throwing instructions not modeled in MemorySSA and | |||
916 | // alloc-like objects. | |||
917 | unsigned PO = 0; | |||
918 | for (BasicBlock *BB : post_order(&F)) { | |||
919 | State.PostOrderNumbers[BB] = PO++; | |||
920 | for (Instruction &I : *BB) { | |||
921 | MemoryAccess *MA = MSSA.getMemoryAccess(&I); | |||
922 | if (I.mayThrow() && !MA) | |||
923 | State.ThrowingBlocks.insert(I.getParent()); | |||
924 | ||||
925 | auto *MD = dyn_cast_or_null<MemoryDef>(MA); | |||
926 | if (MD && State.MemDefs.size() < MemorySSADefsPerBlockLimit && | |||
927 | (State.getLocForWriteEx(&I) || State.isMemTerminatorInst(&I))) | |||
928 | State.MemDefs.push_back(MD); | |||
929 | } | |||
930 | } | |||
931 | ||||
932 | // Treat byval or inalloca arguments the same as Allocas, stores to them are | |||
933 | // dead at the end of the function. | |||
934 | for (Argument &AI : F.args()) | |||
935 | if (AI.hasPassPointeeByValueCopyAttr()) { | |||
936 | // For byval, the caller doesn't know the address of the allocation. | |||
937 | if (AI.hasByValAttr()) | |||
938 | State.InvisibleToCallerBeforeRet.insert({&AI, true}); | |||
939 | State.InvisibleToCallerAfterRet.insert({&AI, true}); | |||
940 | } | |||
941 | ||||
942 | // Collect whether there is any irreducible control flow in the function. | |||
943 | State.ContainsIrreducibleLoops = mayContainIrreducibleControl(F, &LI); | |||
944 | ||||
945 | return State; | |||
946 | } | |||
947 | ||||
948 | /// Return 'OW_Complete' if a store to the 'Later' location (by \p LaterI | |||
949 | /// instruction) completely overwrites a store to the 'Earlier' location. | |||
950 | /// (by \p EarlierI instruction). | |||
951 | /// Return OW_MaybePartial if \p Later does not completely overwrite | |||
952 | /// \p Earlier, but they both write to the same underlying object. In that | |||
953 | /// case, use isPartialOverwrite to check if \p Later partially overwrites | |||
954 | /// \p Earlier. Returns 'OW_Unknown' if nothing can be determined. | |||
955 | OverwriteResult | |||
956 | isOverwrite(const Instruction *LaterI, const Instruction *EarlierI, | |||
957 | const MemoryLocation &Later, const MemoryLocation &Earlier, | |||
958 | int64_t &EarlierOff, int64_t &LaterOff) { | |||
959 | // AliasAnalysis does not always account for loops. Limit overwrite checks | |||
960 | // to dependencies for which we can guarantee they are independant of any | |||
961 | // loops they are in. | |||
962 | if (!isGuaranteedLoopIndependent(EarlierI, LaterI, Earlier)) | |||
963 | return OW_Unknown; | |||
964 | ||||
965 | // FIXME: Vet that this works for size upper-bounds. Seems unlikely that we'll | |||
966 | // get imprecise values here, though (except for unknown sizes). | |||
967 | if (!Later.Size.isPrecise() || !Earlier.Size.isPrecise()) { | |||
968 | // In case no constant size is known, try to an IR values for the number | |||
969 | // of bytes written and check if they match. | |||
970 | const auto *LaterMemI = dyn_cast<MemIntrinsic>(LaterI); | |||
971 | const auto *EarlierMemI = dyn_cast<MemIntrinsic>(EarlierI); | |||
972 | if (LaterMemI && EarlierMemI) { | |||
973 | const Value *LaterV = LaterMemI->getLength(); | |||
974 | const Value *EarlierV = EarlierMemI->getLength(); | |||
975 | if (LaterV == EarlierV && BatchAA.isMustAlias(Earlier, Later)) | |||
976 | return OW_Complete; | |||
977 | } | |||
978 | ||||
979 | // Masked stores have imprecise locations, but we can reason about them | |||
980 | // to some extent. | |||
981 | return isMaskedStoreOverwrite(LaterI, EarlierI, BatchAA); | |||
982 | } | |||
983 | ||||
984 | const uint64_t LaterSize = Later.Size.getValue(); | |||
985 | const uint64_t EarlierSize = Earlier.Size.getValue(); | |||
986 | ||||
987 | // Query the alias information | |||
988 | AliasResult AAR = BatchAA.alias(Later, Earlier); | |||
989 | ||||
990 | // If the start pointers are the same, we just have to compare sizes to see if | |||
991 | // the later store was larger than the earlier store. | |||
992 | if (AAR == AliasResult::MustAlias) { | |||
993 | // Make sure that the Later size is >= the Earlier size. | |||
994 | if (LaterSize >= EarlierSize) | |||
995 | return OW_Complete; | |||
996 | } | |||
997 | ||||
998 | // If we hit a partial alias we may have a full overwrite | |||
999 | if (AAR == AliasResult::PartialAlias && AAR.hasOffset()) { | |||
1000 | int32_t Off = AAR.getOffset(); | |||
1001 | if (Off >= 0 && (uint64_t)Off + EarlierSize <= LaterSize) | |||
1002 | return OW_Complete; | |||
1003 | } | |||
1004 | ||||
1005 | // Check to see if the later store is to the entire object (either a global, | |||
1006 | // an alloca, or a byval/inalloca argument). If so, then it clearly | |||
1007 | // overwrites any other store to the same object. | |||
1008 | const Value *P1 = Earlier.Ptr->stripPointerCasts(); | |||
1009 | const Value *P2 = Later.Ptr->stripPointerCasts(); | |||
1010 | const Value *UO1 = getUnderlyingObject(P1), *UO2 = getUnderlyingObject(P2); | |||
1011 | ||||
1012 | // If we can't resolve the same pointers to the same object, then we can't | |||
1013 | // analyze them at all. | |||
1014 | if (UO1 != UO2) | |||
1015 | return OW_Unknown; | |||
1016 | ||||
1017 | // If the "Later" store is to a recognizable object, get its size. | |||
1018 | uint64_t ObjectSize = getPointerSize(UO2, DL, TLI, &F); | |||
1019 | if (ObjectSize != MemoryLocation::UnknownSize) | |||
1020 | if (ObjectSize == LaterSize && ObjectSize >= EarlierSize) | |||
1021 | return OW_Complete; | |||
1022 | ||||
1023 | // Okay, we have stores to two completely different pointers. Try to | |||
1024 | // decompose the pointer into a "base + constant_offset" form. If the base | |||
1025 | // pointers are equal, then we can reason about the two stores. | |||
1026 | EarlierOff = 0; | |||
1027 | LaterOff = 0; | |||
1028 | const Value *BP1 = GetPointerBaseWithConstantOffset(P1, EarlierOff, DL); | |||
1029 | const Value *BP2 = GetPointerBaseWithConstantOffset(P2, LaterOff, DL); | |||
1030 | ||||
1031 | // If the base pointers still differ, we have two completely different stores. | |||
1032 | if (BP1 != BP2) | |||
1033 | return OW_Unknown; | |||
1034 | ||||
1035 | // The later access completely overlaps the earlier store if and only if | |||
1036 | // both start and end of the earlier one is "inside" the later one: | |||
1037 | // |<->|--earlier--|<->| | |||
1038 | // |-------later-------| | |||
1039 | // Accesses may overlap if and only if start of one of them is "inside" | |||
1040 | // another one: | |||
1041 | // |<->|--earlier--|<----->| | |||
1042 | // |-------later-------| | |||
1043 | // OR | |||
1044 | // |----- earlier -----| | |||
1045 | // |<->|---later---|<----->| | |||
1046 | // | |||
1047 | // We have to be careful here as *Off is signed while *.Size is unsigned. | |||
1048 | ||||
1049 | // Check if the earlier access starts "not before" the later one. | |||
1050 | if (EarlierOff >= LaterOff) { | |||
1051 | // If the earlier access ends "not after" the later access then the earlier | |||
1052 | // one is completely overwritten by the later one. | |||
1053 | if (uint64_t(EarlierOff - LaterOff) + EarlierSize <= LaterSize) | |||
1054 | return OW_Complete; | |||
1055 | // If start of the earlier access is "before" end of the later access then | |||
1056 | // accesses overlap. | |||
1057 | else if ((uint64_t)(EarlierOff - LaterOff) < LaterSize) | |||
1058 | return OW_MaybePartial; | |||
1059 | } | |||
1060 | // If start of the later access is "before" end of the earlier access then | |||
1061 | // accesses overlap. | |||
1062 | else if ((uint64_t)(LaterOff - EarlierOff) < EarlierSize) { | |||
1063 | return OW_MaybePartial; | |||
1064 | } | |||
1065 | ||||
1066 | // Can reach here only if accesses are known not to overlap. There is no | |||
1067 | // dedicated code to indicate no overlap so signal "unknown". | |||
1068 | return OW_Unknown; | |||
1069 | } | |||
1070 | ||||
1071 | bool isInvisibleToCallerAfterRet(const Value *V) { | |||
1072 | if (isa<AllocaInst>(V)) | |||
1073 | return true; | |||
1074 | auto I = InvisibleToCallerAfterRet.insert({V, false}); | |||
1075 | if (I.second) { | |||
1076 | if (!isInvisibleToCallerBeforeRet(V)) { | |||
1077 | I.first->second = false; | |||
1078 | } else { | |||
1079 | auto *Inst = dyn_cast<Instruction>(V); | |||
1080 | if (Inst && isAllocLikeFn(Inst, &TLI)) | |||
1081 | I.first->second = !PointerMayBeCaptured(V, true, false); | |||
1082 | } | |||
1083 | } | |||
1084 | return I.first->second; | |||
1085 | } | |||
1086 | ||||
1087 | bool isInvisibleToCallerBeforeRet(const Value *V) { | |||
1088 | if (isa<AllocaInst>(V)) | |||
1089 | return true; | |||
1090 | auto I = InvisibleToCallerBeforeRet.insert({V, false}); | |||
1091 | if (I.second) { | |||
1092 | auto *Inst = dyn_cast<Instruction>(V); | |||
1093 | if (Inst && isAllocLikeFn(Inst, &TLI)) | |||
1094 | // NOTE: This could be made more precise by PointerMayBeCapturedBefore | |||
1095 | // with the killing MemoryDef. But we refrain from doing so for now to | |||
1096 | // limit compile-time and this does not cause any changes to the number | |||
1097 | // of stores removed on a large test set in practice. | |||
1098 | I.first->second = !PointerMayBeCaptured(V, false, true); | |||
1099 | } | |||
1100 | return I.first->second; | |||
1101 | } | |||
1102 | ||||
1103 | Optional<MemoryLocation> getLocForWriteEx(Instruction *I) const { | |||
1104 | if (!I->mayWriteToMemory()) | |||
1105 | return None; | |||
1106 | ||||
1107 | if (auto *MTI = dyn_cast<AnyMemIntrinsic>(I)) | |||
1108 | return {MemoryLocation::getForDest(MTI)}; | |||
1109 | ||||
1110 | if (auto *CB = dyn_cast<CallBase>(I)) { | |||
1111 | // If the functions may write to memory we do not know about, bail out. | |||
1112 | if (!CB->onlyAccessesArgMemory() && | |||
1113 | !CB->onlyAccessesInaccessibleMemOrArgMem()) | |||
1114 | return None; | |||
1115 | ||||
1116 | LibFunc LF; | |||
1117 | if (TLI.getLibFunc(*CB, LF) && TLI.has(LF)) { | |||
1118 | switch (LF) { | |||
1119 | case LibFunc_strcpy: | |||
1120 | case LibFunc_strncpy: | |||
1121 | case LibFunc_strcat: | |||
1122 | case LibFunc_strncat: | |||
1123 | return {MemoryLocation::getAfter(CB->getArgOperand(0))}; | |||
1124 | default: | |||
1125 | break; | |||
1126 | } | |||
1127 | } | |||
1128 | switch (CB->getIntrinsicID()) { | |||
1129 | case Intrinsic::init_trampoline: | |||
1130 | return {MemoryLocation::getAfter(CB->getArgOperand(0))}; | |||
1131 | case Intrinsic::masked_store: | |||
1132 | return {MemoryLocation::getForArgument(CB, 1, TLI)}; | |||
1133 | default: | |||
1134 | break; | |||
1135 | } | |||
1136 | return None; | |||
1137 | } | |||
1138 | ||||
1139 | return MemoryLocation::getOrNone(I); | |||
1140 | } | |||
1141 | ||||
1142 | /// Returns true if \p UseInst completely overwrites \p DefLoc | |||
1143 | /// (stored by \p DefInst). | |||
1144 | bool isCompleteOverwrite(const MemoryLocation &DefLoc, Instruction *DefInst, | |||
1145 | Instruction *UseInst) { | |||
1146 | // UseInst has a MemoryDef associated in MemorySSA. It's possible for a | |||
1147 | // MemoryDef to not write to memory, e.g. a volatile load is modeled as a | |||
1148 | // MemoryDef. | |||
1149 | if (!UseInst->mayWriteToMemory()) | |||
1150 | return false; | |||
1151 | ||||
1152 | if (auto *CB = dyn_cast<CallBase>(UseInst)) | |||
1153 | if (CB->onlyAccessesInaccessibleMemory()) | |||
1154 | return false; | |||
1155 | ||||
1156 | int64_t InstWriteOffset, DepWriteOffset; | |||
1157 | if (auto CC = getLocForWriteEx(UseInst)) | |||
1158 | return isOverwrite(UseInst, DefInst, *CC, DefLoc, DepWriteOffset, | |||
1159 | InstWriteOffset) == OW_Complete; | |||
1160 | return false; | |||
1161 | } | |||
1162 | ||||
1163 | /// Returns true if \p Def is not read before returning from the function. | |||
1164 | bool isWriteAtEndOfFunction(MemoryDef *Def) { | |||
1165 | LLVM_DEBUG(dbgs() << " Check if def " << *Def << " ("do { } while (false) | |||
1166 | << *Def->getMemoryInst()do { } while (false) | |||
1167 | << ") is at the end the function \n")do { } while (false); | |||
1168 | ||||
1169 | auto MaybeLoc = getLocForWriteEx(Def->getMemoryInst()); | |||
1170 | if (!MaybeLoc) { | |||
1171 | LLVM_DEBUG(dbgs() << " ... could not get location for write.\n")do { } while (false); | |||
1172 | return false; | |||
1173 | } | |||
1174 | ||||
1175 | SmallVector<MemoryAccess *, 4> WorkList; | |||
1176 | SmallPtrSet<MemoryAccess *, 8> Visited; | |||
1177 | auto PushMemUses = [&WorkList, &Visited](MemoryAccess *Acc) { | |||
1178 | if (!Visited.insert(Acc).second) | |||
1179 | return; | |||
1180 | for (Use &U : Acc->uses()) | |||
1181 | WorkList.push_back(cast<MemoryAccess>(U.getUser())); | |||
1182 | }; | |||
1183 | PushMemUses(Def); | |||
1184 | for (unsigned I = 0; I < WorkList.size(); I++) { | |||
1185 | if (WorkList.size() >= MemorySSAScanLimit) { | |||
1186 | LLVM_DEBUG(dbgs() << " ... hit exploration limit.\n")do { } while (false); | |||
1187 | return false; | |||
1188 | } | |||
1189 | ||||
1190 | MemoryAccess *UseAccess = WorkList[I]; | |||
1191 | // Simply adding the users of MemoryPhi to the worklist is not enough, | |||
1192 | // because we might miss read clobbers in different iterations of a loop, | |||
1193 | // for example. | |||
1194 | // TODO: Add support for phi translation to handle the loop case. | |||
1195 | if (isa<MemoryPhi>(UseAccess)) | |||
1196 | return false; | |||
1197 | ||||
1198 | // TODO: Checking for aliasing is expensive. Consider reducing the amount | |||
1199 | // of times this is called and/or caching it. | |||
1200 | Instruction *UseInst = cast<MemoryUseOrDef>(UseAccess)->getMemoryInst(); | |||
1201 | if (isReadClobber(*MaybeLoc, UseInst)) { | |||
1202 | LLVM_DEBUG(dbgs() << " ... hit read clobber " << *UseInst << ".\n")do { } while (false); | |||
1203 | return false; | |||
1204 | } | |||
1205 | ||||
1206 | if (MemoryDef *UseDef = dyn_cast<MemoryDef>(UseAccess)) | |||
1207 | PushMemUses(UseDef); | |||
1208 | } | |||
1209 | return true; | |||
1210 | } | |||
1211 | ||||
1212 | /// If \p I is a memory terminator like llvm.lifetime.end or free, return a | |||
1213 | /// pair with the MemoryLocation terminated by \p I and a boolean flag | |||
1214 | /// indicating whether \p I is a free-like call. | |||
1215 | Optional<std::pair<MemoryLocation, bool>> | |||
1216 | getLocForTerminator(Instruction *I) const { | |||
1217 | uint64_t Len; | |||
1218 | Value *Ptr; | |||
1219 | if (match(I, m_Intrinsic<Intrinsic::lifetime_end>(m_ConstantInt(Len), | |||
1220 | m_Value(Ptr)))) | |||
1221 | return {std::make_pair(MemoryLocation(Ptr, Len), false)}; | |||
1222 | ||||
1223 | if (auto *CB = dyn_cast<CallBase>(I)) { | |||
1224 | if (isFreeCall(I, &TLI)) | |||
1225 | return {std::make_pair(MemoryLocation::getAfter(CB->getArgOperand(0)), | |||
1226 | true)}; | |||
1227 | } | |||
1228 | ||||
1229 | return None; | |||
1230 | } | |||
1231 | ||||
1232 | /// Returns true if \p I is a memory terminator instruction like | |||
1233 | /// llvm.lifetime.end or free. | |||
1234 | bool isMemTerminatorInst(Instruction *I) const { | |||
1235 | IntrinsicInst *II = dyn_cast<IntrinsicInst>(I); | |||
1236 | return (II && II->getIntrinsicID() == Intrinsic::lifetime_end) || | |||
1237 | isFreeCall(I, &TLI); | |||
1238 | } | |||
1239 | ||||
1240 | /// Returns true if \p MaybeTerm is a memory terminator for \p Loc from | |||
1241 | /// instruction \p AccessI. | |||
1242 | bool isMemTerminator(const MemoryLocation &Loc, Instruction *AccessI, | |||
1243 | Instruction *MaybeTerm) { | |||
1244 | Optional<std::pair<MemoryLocation, bool>> MaybeTermLoc = | |||
1245 | getLocForTerminator(MaybeTerm); | |||
1246 | ||||
1247 | if (!MaybeTermLoc) | |||
1248 | return false; | |||
1249 | ||||
1250 | // If the terminator is a free-like call, all accesses to the underlying | |||
1251 | // object can be considered terminated. | |||
1252 | if (getUnderlyingObject(Loc.Ptr) != | |||
1253 | getUnderlyingObject(MaybeTermLoc->first.Ptr)) | |||
1254 | return false; | |||
1255 | ||||
1256 | auto TermLoc = MaybeTermLoc->first; | |||
1257 | if (MaybeTermLoc->second) { | |||
1258 | const Value *LocUO = getUnderlyingObject(Loc.Ptr); | |||
1259 | return BatchAA.isMustAlias(TermLoc.Ptr, LocUO); | |||
1260 | } | |||
1261 | int64_t InstWriteOffset, DepWriteOffset; | |||
1262 | return isOverwrite(MaybeTerm, AccessI, TermLoc, Loc, DepWriteOffset, | |||
1263 | InstWriteOffset) == OW_Complete; | |||
1264 | } | |||
1265 | ||||
1266 | // Returns true if \p Use may read from \p DefLoc. | |||
1267 | bool isReadClobber(const MemoryLocation &DefLoc, Instruction *UseInst) { | |||
1268 | if (isNoopIntrinsic(UseInst)) | |||
1269 | return false; | |||
1270 | ||||
1271 | // Monotonic or weaker atomic stores can be re-ordered and do not need to be | |||
1272 | // treated as read clobber. | |||
1273 | if (auto SI = dyn_cast<StoreInst>(UseInst)) | |||
1274 | return isStrongerThan(SI->getOrdering(), AtomicOrdering::Monotonic); | |||
1275 | ||||
1276 | if (!UseInst->mayReadFromMemory()) | |||
1277 | return false; | |||
1278 | ||||
1279 | if (auto *CB = dyn_cast<CallBase>(UseInst)) | |||
1280 | if (CB->onlyAccessesInaccessibleMemory()) | |||
1281 | return false; | |||
1282 | ||||
1283 | // NOTE: For calls, the number of stores removed could be slightly improved | |||
1284 | // by using AA.callCapturesBefore(UseInst, DefLoc, &DT), but that showed to | |||
1285 | // be expensive compared to the benefits in practice. For now, avoid more | |||
1286 | // expensive analysis to limit compile-time. | |||
1287 | return isRefSet(BatchAA.getModRefInfo(UseInst, DefLoc)); | |||
1288 | } | |||
1289 | ||||
1290 | /// Returns true if a dependency between \p Current and \p KillingDef is | |||
1291 | /// guaranteed to be loop invariant for the loops that they are in. Either | |||
1292 | /// because they are known to be in the same block, in the same loop level or | |||
1293 | /// by guaranteeing that \p CurrentLoc only references a single MemoryLocation | |||
1294 | /// during execution of the containing function. | |||
1295 | bool isGuaranteedLoopIndependent(const Instruction *Current, | |||
1296 | const Instruction *KillingDef, | |||
1297 | const MemoryLocation &CurrentLoc) { | |||
1298 | // If the dependency is within the same block or loop level (being careful | |||
1299 | // of irreducible loops), we know that AA will return a valid result for the | |||
1300 | // memory dependency. (Both at the function level, outside of any loop, | |||
1301 | // would also be valid but we currently disable that to limit compile time). | |||
1302 | if (Current->getParent() == KillingDef->getParent()) | |||
1303 | return true; | |||
1304 | const Loop *CurrentLI = LI.getLoopFor(Current->getParent()); | |||
1305 | if (!ContainsIrreducibleLoops && CurrentLI && | |||
1306 | CurrentLI == LI.getLoopFor(KillingDef->getParent())) | |||
1307 | return true; | |||
1308 | // Otherwise check the memory location is invariant to any loops. | |||
1309 | return isGuaranteedLoopInvariant(CurrentLoc.Ptr); | |||
1310 | } | |||
1311 | ||||
1312 | /// Returns true if \p Ptr is guaranteed to be loop invariant for any possible | |||
1313 | /// loop. In particular, this guarantees that it only references a single | |||
1314 | /// MemoryLocation during execution of the containing function. | |||
1315 | bool isGuaranteedLoopInvariant(const Value *Ptr) { | |||
1316 | auto IsGuaranteedLoopInvariantBase = [this](const Value *Ptr) { | |||
1317 | Ptr = Ptr->stripPointerCasts(); | |||
1318 | if (auto *I = dyn_cast<Instruction>(Ptr)) { | |||
1319 | if (isa<AllocaInst>(Ptr)) | |||
1320 | return true; | |||
1321 | ||||
1322 | if (isAllocLikeFn(I, &TLI)) | |||
1323 | return true; | |||
1324 | ||||
1325 | return false; | |||
1326 | } | |||
1327 | return true; | |||
1328 | }; | |||
1329 | ||||
1330 | Ptr = Ptr->stripPointerCasts(); | |||
| ||||
1331 | if (auto *I = dyn_cast<Instruction>(Ptr)) { | |||
1332 | if (I->getParent()->isEntryBlock()) | |||
1333 | return true; | |||
1334 | } | |||
1335 | if (auto *GEP = dyn_cast<GEPOperator>(Ptr)) { | |||
1336 | return IsGuaranteedLoopInvariantBase(GEP->getPointerOperand()) && | |||
1337 | GEP->hasAllConstantIndices(); | |||
1338 | } | |||
1339 | return IsGuaranteedLoopInvariantBase(Ptr); | |||
1340 | } | |||
1341 | ||||
1342 | // Find a MemoryDef writing to \p DefLoc and dominating \p StartAccess, with | |||
1343 | // no read access between them or on any other path to a function exit block | |||
1344 | // if \p DefLoc is not accessible after the function returns. If there is no | |||
1345 | // such MemoryDef, return None. The returned value may not (completely) | |||
1346 | // overwrite \p DefLoc. Currently we bail out when we encounter an aliasing | |||
1347 | // MemoryUse (read). | |||
1348 | Optional<MemoryAccess *> | |||
1349 | getDomMemoryDef(MemoryDef *KillingDef, MemoryAccess *StartAccess, | |||
1350 | const MemoryLocation &DefLoc, const Value *DefUO, | |||
1351 | unsigned &ScanLimit, unsigned &WalkerStepLimit, | |||
1352 | bool IsMemTerm, unsigned &PartialLimit) { | |||
1353 | if (ScanLimit == 0 || WalkerStepLimit == 0) { | |||
1354 | LLVM_DEBUG(dbgs() << "\n ... hit scan limit\n")do { } while (false); | |||
1355 | return None; | |||
1356 | } | |||
1357 | ||||
1358 | MemoryAccess *Current = StartAccess; | |||
1359 | Instruction *KillingI = KillingDef->getMemoryInst(); | |||
1360 | LLVM_DEBUG(dbgs() << " trying to get dominating access\n")do { } while (false); | |||
1361 | ||||
1362 | // Find the next clobbering Mod access for DefLoc, starting at StartAccess. | |||
1363 | Optional<MemoryLocation> CurrentLoc; | |||
1364 | for (;; Current = cast<MemoryDef>(Current)->getDefiningAccess()) { | |||
1365 | LLVM_DEBUG({do { } while (false) | |||
1366 | dbgs() << " visiting " << *Current;do { } while (false) | |||
1367 | if (!MSSA.isLiveOnEntryDef(Current) && isa<MemoryUseOrDef>(Current))do { } while (false) | |||
1368 | dbgs() << " (" << *cast<MemoryUseOrDef>(Current)->getMemoryInst()do { } while (false) | |||
1369 | << ")";do { } while (false) | |||
1370 | dbgs() << "\n";do { } while (false) | |||
1371 | })do { } while (false); | |||
1372 | ||||
1373 | // Reached TOP. | |||
1374 | if (MSSA.isLiveOnEntryDef(Current)) { | |||
1375 | LLVM_DEBUG(dbgs() << " ... found LiveOnEntryDef\n")do { } while (false); | |||
1376 | return None; | |||
1377 | } | |||
1378 | ||||
1379 | // Cost of a step. Accesses in the same block are more likely to be valid | |||
1380 | // candidates for elimination, hence consider them cheaper. | |||
1381 | unsigned StepCost = KillingDef->getBlock() == Current->getBlock() | |||
1382 | ? MemorySSASameBBStepCost | |||
1383 | : MemorySSAOtherBBStepCost; | |||
1384 | if (WalkerStepLimit <= StepCost) { | |||
1385 | LLVM_DEBUG(dbgs() << " ... hit walker step limit\n")do { } while (false); | |||
1386 | return None; | |||
1387 | } | |||
1388 | WalkerStepLimit -= StepCost; | |||
1389 | ||||
1390 | // Return for MemoryPhis. They cannot be eliminated directly and the | |||
1391 | // caller is responsible for traversing them. | |||
1392 | if (isa<MemoryPhi>(Current)) { | |||
1393 | LLVM_DEBUG(dbgs() << " ... found MemoryPhi\n")do { } while (false); | |||
1394 | return Current; | |||
1395 | } | |||
1396 | ||||
1397 | // Below, check if CurrentDef is a valid candidate to be eliminated by | |||
1398 | // KillingDef. If it is not, check the next candidate. | |||
1399 | MemoryDef *CurrentDef = cast<MemoryDef>(Current); | |||
1400 | Instruction *CurrentI = CurrentDef->getMemoryInst(); | |||
1401 | ||||
1402 | if (canSkipDef(CurrentDef, !isInvisibleToCallerBeforeRet(DefUO), TLI)) | |||
1403 | continue; | |||
1404 | ||||
1405 | // Before we try to remove anything, check for any extra throwing | |||
1406 | // instructions that block us from DSEing | |||
1407 | if (mayThrowBetween(KillingI, CurrentI, DefUO)) { | |||
1408 | LLVM_DEBUG(dbgs() << " ... skip, may throw!\n")do { } while (false); | |||
1409 | return None; | |||
1410 | } | |||
1411 | ||||
1412 | // Check for anything that looks like it will be a barrier to further | |||
1413 | // removal | |||
1414 | if (isDSEBarrier(DefUO, CurrentI)) { | |||
1415 | LLVM_DEBUG(dbgs() << " ... skip, barrier\n")do { } while (false); | |||
1416 | return None; | |||
1417 | } | |||
1418 | ||||
1419 | // If Current is known to be on path that reads DefLoc or is a read | |||
1420 | // clobber, bail out, as the path is not profitable. We skip this check | |||
1421 | // for intrinsic calls, because the code knows how to handle memcpy | |||
1422 | // intrinsics. | |||
1423 | if (!isa<IntrinsicInst>(CurrentI) && isReadClobber(DefLoc, CurrentI)) | |||
1424 | return None; | |||
1425 | ||||
1426 | // Quick check if there are direct uses that are read-clobbers. | |||
1427 | if (any_of(Current->uses(), [this, &DefLoc, StartAccess](Use &U) { | |||
1428 | if (auto *UseOrDef = dyn_cast<MemoryUseOrDef>(U.getUser())) | |||
1429 | return !MSSA.dominates(StartAccess, UseOrDef) && | |||
1430 | isReadClobber(DefLoc, UseOrDef->getMemoryInst()); | |||
1431 | return false; | |||
1432 | })) { | |||
1433 | LLVM_DEBUG(dbgs() << " ... found a read clobber\n")do { } while (false); | |||
1434 | return None; | |||
1435 | } | |||
1436 | ||||
1437 | // If Current cannot be analyzed or is not removable, check the next | |||
1438 | // candidate. | |||
1439 | if (!hasAnalyzableMemoryWrite(CurrentI, TLI) || !isRemovable(CurrentI)) | |||
1440 | continue; | |||
1441 | ||||
1442 | // If Current does not have an analyzable write location, skip it | |||
1443 | CurrentLoc = getLocForWriteEx(CurrentI); | |||
1444 | if (!CurrentLoc) | |||
1445 | continue; | |||
1446 | ||||
1447 | // AliasAnalysis does not account for loops. Limit elimination to | |||
1448 | // candidates for which we can guarantee they always store to the same | |||
1449 | // memory location and not located in different loops. | |||
1450 | if (!isGuaranteedLoopIndependent(CurrentI, KillingI, *CurrentLoc)) { | |||
1451 | LLVM_DEBUG(dbgs() << " ... not guaranteed loop independent\n")do { } while (false); | |||
1452 | WalkerStepLimit -= 1; | |||
1453 | continue; | |||
1454 | } | |||
1455 | ||||
1456 | if (IsMemTerm) { | |||
1457 | // If the killing def is a memory terminator (e.g. lifetime.end), check | |||
1458 | // the next candidate if the current Current does not write the same | |||
1459 | // underlying object as the terminator. | |||
1460 | if (!isMemTerminator(*CurrentLoc, CurrentI, KillingI)) | |||
1461 | continue; | |||
1462 | } else { | |||
1463 | int64_t InstWriteOffset, DepWriteOffset; | |||
1464 | auto OR = isOverwrite(KillingI, CurrentI, DefLoc, *CurrentLoc, | |||
1465 | DepWriteOffset, InstWriteOffset); | |||
1466 | // If Current does not write to the same object as KillingDef, check | |||
1467 | // the next candidate. | |||
1468 | if (OR == OW_Unknown) | |||
1469 | continue; | |||
1470 | else if (OR == OW_MaybePartial) { | |||
1471 | // If KillingDef only partially overwrites Current, check the next | |||
1472 | // candidate if the partial step limit is exceeded. This aggressively | |||
1473 | // limits the number of candidates for partial store elimination, | |||
1474 | // which are less likely to be removable in the end. | |||
1475 | if (PartialLimit <= 1) { | |||
1476 | WalkerStepLimit -= 1; | |||
1477 | continue; | |||
1478 | } | |||
1479 | PartialLimit -= 1; | |||
1480 | } | |||
1481 | } | |||
1482 | break; | |||
1483 | }; | |||
1484 | ||||
1485 | // Accesses to objects accessible after the function returns can only be | |||
1486 | // eliminated if the access is killed along all paths to the exit. Collect | |||
1487 | // the blocks with killing (=completely overwriting MemoryDefs) and check if | |||
1488 | // they cover all paths from EarlierAccess to any function exit. | |||
1489 | SmallPtrSet<Instruction *, 16> KillingDefs; | |||
1490 | KillingDefs.insert(KillingDef->getMemoryInst()); | |||
1491 | MemoryAccess *EarlierAccess = Current; | |||
1492 | Instruction *EarlierMemInst = | |||
1493 | cast<MemoryDef>(EarlierAccess)->getMemoryInst(); | |||
1494 | LLVM_DEBUG(dbgs() << " Checking for reads of " << *EarlierAccess << " ("do { } while (false) | |||
1495 | << *EarlierMemInst << ")\n")do { } while (false); | |||
1496 | ||||
1497 | SmallSetVector<MemoryAccess *, 32> WorkList; | |||
1498 | auto PushMemUses = [&WorkList](MemoryAccess *Acc) { | |||
1499 | for (Use &U : Acc->uses()) | |||
1500 | WorkList.insert(cast<MemoryAccess>(U.getUser())); | |||
1501 | }; | |||
1502 | PushMemUses(EarlierAccess); | |||
1503 | ||||
1504 | // Check if EarlierDef may be read. | |||
1505 | for (unsigned I = 0; I < WorkList.size(); I++) { | |||
1506 | MemoryAccess *UseAccess = WorkList[I]; | |||
1507 | ||||
1508 | LLVM_DEBUG(dbgs() << " " << *UseAccess)do { } while (false); | |||
1509 | // Bail out if the number of accesses to check exceeds the scan limit. | |||
1510 | if (ScanLimit < (WorkList.size() - I)) { | |||
1511 | LLVM_DEBUG(dbgs() << "\n ... hit scan limit\n")do { } while (false); | |||
1512 | return None; | |||
1513 | } | |||
1514 | --ScanLimit; | |||
1515 | NumDomMemDefChecks++; | |||
1516 | ||||
1517 | if (isa<MemoryPhi>(UseAccess)) { | |||
1518 | if (any_of(KillingDefs, [this, UseAccess](Instruction *KI) { | |||
1519 | return DT.properlyDominates(KI->getParent(), | |||
1520 | UseAccess->getBlock()); | |||
1521 | })) { | |||
1522 | LLVM_DEBUG(dbgs() << " ... skipping, dominated by killing block\n")do { } while (false); | |||
1523 | continue; | |||
1524 | } | |||
1525 | LLVM_DEBUG(dbgs() << "\n ... adding PHI uses\n")do { } while (false); | |||
1526 | PushMemUses(UseAccess); | |||
1527 | continue; | |||
1528 | } | |||
1529 | ||||
1530 | Instruction *UseInst = cast<MemoryUseOrDef>(UseAccess)->getMemoryInst(); | |||
1531 | LLVM_DEBUG(dbgs() << " (" << *UseInst << ")\n")do { } while (false); | |||
1532 | ||||
1533 | if (any_of(KillingDefs, [this, UseInst](Instruction *KI) { | |||
1534 | return DT.dominates(KI, UseInst); | |||
1535 | })) { | |||
1536 | LLVM_DEBUG(dbgs() << " ... skipping, dominated by killing def\n")do { } while (false); | |||
1537 | continue; | |||
1538 | } | |||
1539 | ||||
1540 | // A memory terminator kills all preceeding MemoryDefs and all succeeding | |||
1541 | // MemoryAccesses. We do not have to check it's users. | |||
1542 | if (isMemTerminator(*CurrentLoc, EarlierMemInst, UseInst)) { | |||
1543 | LLVM_DEBUG(do { } while (false) | |||
1544 | dbgs()do { } while (false) | |||
1545 | << " ... skipping, memterminator invalidates following accesses\n")do { } while (false); | |||
1546 | continue; | |||
1547 | } | |||
1548 | ||||
1549 | if (isNoopIntrinsic(cast<MemoryUseOrDef>(UseAccess)->getMemoryInst())) { | |||
1550 | LLVM_DEBUG(dbgs() << " ... adding uses of intrinsic\n")do { } while (false); | |||
1551 | PushMemUses(UseAccess); | |||
1552 | continue; | |||
1553 | } | |||
1554 | ||||
1555 | if (UseInst->mayThrow() && !isInvisibleToCallerBeforeRet(DefUO)) { | |||
1556 | LLVM_DEBUG(dbgs() << " ... found throwing instruction\n")do { } while (false); | |||
1557 | return None; | |||
1558 | } | |||
1559 | ||||
1560 | // Uses which may read the original MemoryDef mean we cannot eliminate the | |||
1561 | // original MD. Stop walk. | |||
1562 | if (isReadClobber(*CurrentLoc, UseInst)) { | |||
1563 | LLVM_DEBUG(dbgs() << " ... found read clobber\n")do { } while (false); | |||
1564 | return None; | |||
1565 | } | |||
1566 | ||||
1567 | // If this worklist walks back to the original memory access (and the | |||
1568 | // pointer is not guarenteed loop invariant) then we cannot assume that a | |||
1569 | // store kills itself. | |||
1570 | if (EarlierAccess == UseAccess && | |||
1571 | !isGuaranteedLoopInvariant(CurrentLoc->Ptr)) { | |||
1572 | LLVM_DEBUG(dbgs() << " ... found not loop invariant self access\n")do { } while (false); | |||
1573 | return None; | |||
1574 | } | |||
1575 | // Otherwise, for the KillingDef and EarlierAccess we only have to check | |||
1576 | // if it reads the memory location. | |||
1577 | // TODO: It would probably be better to check for self-reads before | |||
1578 | // calling the function. | |||
1579 | if (KillingDef == UseAccess || EarlierAccess == UseAccess) { | |||
1580 | LLVM_DEBUG(dbgs() << " ... skipping killing def/dom access\n")do { } while (false); | |||
1581 | continue; | |||
1582 | } | |||
1583 | ||||
1584 | // Check all uses for MemoryDefs, except for defs completely overwriting | |||
1585 | // the original location. Otherwise we have to check uses of *all* | |||
1586 | // MemoryDefs we discover, including non-aliasing ones. Otherwise we might | |||
1587 | // miss cases like the following | |||
1588 | // 1 = Def(LoE) ; <----- EarlierDef stores [0,1] | |||
1589 | // 2 = Def(1) ; (2, 1) = NoAlias, stores [2,3] | |||
1590 | // Use(2) ; MayAlias 2 *and* 1, loads [0, 3]. | |||
1591 | // (The Use points to the *first* Def it may alias) | |||
1592 | // 3 = Def(1) ; <---- Current (3, 2) = NoAlias, (3,1) = MayAlias, | |||
1593 | // stores [0,1] | |||
1594 | if (MemoryDef *UseDef = dyn_cast<MemoryDef>(UseAccess)) { | |||
1595 | if (isCompleteOverwrite(*CurrentLoc, EarlierMemInst, UseInst)) { | |||
1596 | BasicBlock *MaybeKillingBlock = UseInst->getParent(); | |||
1597 | if (PostOrderNumbers.find(MaybeKillingBlock)->second < | |||
1598 | PostOrderNumbers.find(EarlierAccess->getBlock())->second) { | |||
1599 | if (!isInvisibleToCallerAfterRet(DefUO)) { | |||
1600 | LLVM_DEBUG(dbgs()do { } while (false) | |||
1601 | << " ... found killing def " << *UseInst << "\n")do { } while (false); | |||
1602 | KillingDefs.insert(UseInst); | |||
1603 | } | |||
1604 | } else { | |||
1605 | LLVM_DEBUG(dbgs()do { } while (false) | |||
1606 | << " ... found preceeding def " << *UseInst << "\n")do { } while (false); | |||
1607 | return None; | |||
1608 | } | |||
1609 | } else | |||
1610 | PushMemUses(UseDef); | |||
1611 | } | |||
1612 | } | |||
1613 | ||||
1614 | // For accesses to locations visible after the function returns, make sure | |||
1615 | // that the location is killed (=overwritten) along all paths from | |||
1616 | // EarlierAccess to the exit. | |||
1617 | if (!isInvisibleToCallerAfterRet(DefUO)) { | |||
1618 | SmallPtrSet<BasicBlock *, 16> KillingBlocks; | |||
1619 | for (Instruction *KD : KillingDefs) | |||
1620 | KillingBlocks.insert(KD->getParent()); | |||
1621 | assert(!KillingBlocks.empty() &&(static_cast<void> (0)) | |||
1622 | "Expected at least a single killing block")(static_cast<void> (0)); | |||
1623 | ||||
1624 | // Find the common post-dominator of all killing blocks. | |||
1625 | BasicBlock *CommonPred = *KillingBlocks.begin(); | |||
1626 | for (auto I = std::next(KillingBlocks.begin()), E = KillingBlocks.end(); | |||
1627 | I != E; I++) { | |||
1628 | if (!CommonPred) | |||
1629 | break; | |||
1630 | CommonPred = PDT.findNearestCommonDominator(CommonPred, *I); | |||
1631 | } | |||
1632 | ||||
1633 | // If CommonPred is in the set of killing blocks, just check if it | |||
1634 | // post-dominates EarlierAccess. | |||
1635 | if (KillingBlocks.count(CommonPred)) { | |||
1636 | if (PDT.dominates(CommonPred, EarlierAccess->getBlock())) | |||
1637 | return {EarlierAccess}; | |||
1638 | return None; | |||
1639 | } | |||
1640 | ||||
1641 | // If the common post-dominator does not post-dominate EarlierAccess, | |||
1642 | // there is a path from EarlierAccess to an exit not going through a | |||
1643 | // killing block. | |||
1644 | if (PDT.dominates(CommonPred, EarlierAccess->getBlock())) { | |||
1645 | SetVector<BasicBlock *> WorkList; | |||
1646 | ||||
1647 | // If CommonPred is null, there are multiple exits from the function. | |||
1648 | // They all have to be added to the worklist. | |||
1649 | if (CommonPred) | |||
1650 | WorkList.insert(CommonPred); | |||
1651 | else | |||
1652 | for (BasicBlock *R : PDT.roots()) | |||
1653 | WorkList.insert(R); | |||
1654 | ||||
1655 | NumCFGTries++; | |||
1656 | // Check if all paths starting from an exit node go through one of the | |||
1657 | // killing blocks before reaching EarlierAccess. | |||
1658 | for (unsigned I = 0; I < WorkList.size(); I++) { | |||
1659 | NumCFGChecks++; | |||
1660 | BasicBlock *Current = WorkList[I]; | |||
1661 | if (KillingBlocks.count(Current)) | |||
1662 | continue; | |||
1663 | if (Current == EarlierAccess->getBlock()) | |||
1664 | return None; | |||
1665 | ||||
1666 | // EarlierAccess is reachable from the entry, so we don't have to | |||
1667 | // explore unreachable blocks further. | |||
1668 | if (!DT.isReachableFromEntry(Current)) | |||
1669 | continue; | |||
1670 | ||||
1671 | for (BasicBlock *Pred : predecessors(Current)) | |||
1672 | WorkList.insert(Pred); | |||
1673 | ||||
1674 | if (WorkList.size() >= MemorySSAPathCheckLimit) | |||
1675 | return None; | |||
1676 | } | |||
1677 | NumCFGSuccess++; | |||
1678 | return {EarlierAccess}; | |||
1679 | } | |||
1680 | return None; | |||
1681 | } | |||
1682 | ||||
1683 | // No aliasing MemoryUses of EarlierAccess found, EarlierAccess is | |||
1684 | // potentially dead. | |||
1685 | return {EarlierAccess}; | |||
1686 | } | |||
1687 | ||||
1688 | // Delete dead memory defs | |||
1689 | void deleteDeadInstruction(Instruction *SI) { | |||
1690 | MemorySSAUpdater Updater(&MSSA); | |||
1691 | SmallVector<Instruction *, 32> NowDeadInsts; | |||
1692 | NowDeadInsts.push_back(SI); | |||
1693 | --NumFastOther; | |||
1694 | ||||
1695 | while (!NowDeadInsts.empty()) { | |||
1696 | Instruction *DeadInst = NowDeadInsts.pop_back_val(); | |||
1697 | ++NumFastOther; | |||
1698 | ||||
1699 | // Try to preserve debug information attached to the dead instruction. | |||
1700 | salvageDebugInfo(*DeadInst); | |||
1701 | salvageKnowledge(DeadInst); | |||
1702 | ||||
1703 | // Remove the Instruction from MSSA. | |||
1704 | if (MemoryAccess *MA = MSSA.getMemoryAccess(DeadInst)) { | |||
1705 | if (MemoryDef *MD = dyn_cast<MemoryDef>(MA)) { | |||
1706 | SkipStores.insert(MD); | |||
1707 | } | |||
1708 | Updater.removeMemoryAccess(MA); | |||
1709 | } | |||
1710 | ||||
1711 | auto I = IOLs.find(DeadInst->getParent()); | |||
1712 | if (I != IOLs.end()) | |||
1713 | I->second.erase(DeadInst); | |||
1714 | // Remove its operands | |||
1715 | for (Use &O : DeadInst->operands()) | |||
1716 | if (Instruction *OpI = dyn_cast<Instruction>(O)) { | |||
1717 | O = nullptr; | |||
1718 | if (isInstructionTriviallyDead(OpI, &TLI)) | |||
1719 | NowDeadInsts.push_back(OpI); | |||
1720 | } | |||
1721 | ||||
1722 | DeadInst->eraseFromParent(); | |||
1723 | } | |||
1724 | } | |||
1725 | ||||
1726 | // Check for any extra throws between SI and NI that block DSE. This only | |||
1727 | // checks extra maythrows (those that aren't MemoryDef's). MemoryDef that may | |||
1728 | // throw are handled during the walk from one def to the next. | |||
1729 | bool mayThrowBetween(Instruction *SI, Instruction *NI, | |||
1730 | const Value *SILocUnd) { | |||
1731 | // First see if we can ignore it by using the fact that SI is an | |||
1732 | // alloca/alloca like object that is not visible to the caller during | |||
1733 | // execution of the function. | |||
1734 | if (SILocUnd && isInvisibleToCallerBeforeRet(SILocUnd)) | |||
1735 | return false; | |||
1736 | ||||
1737 | if (SI->getParent() == NI->getParent()) | |||
1738 | return ThrowingBlocks.count(SI->getParent()); | |||
1739 | return !ThrowingBlocks.empty(); | |||
1740 | } | |||
1741 | ||||
1742 | // Check if \p NI acts as a DSE barrier for \p SI. The following instructions | |||
1743 | // act as barriers: | |||
1744 | // * A memory instruction that may throw and \p SI accesses a non-stack | |||
1745 | // object. | |||
1746 | // * Atomic stores stronger that monotonic. | |||
1747 | bool isDSEBarrier(const Value *SILocUnd, Instruction *NI) { | |||
1748 | // If NI may throw it acts as a barrier, unless we are to an alloca/alloca | |||
1749 | // like object that does not escape. | |||
1750 | if (NI->mayThrow() && !isInvisibleToCallerBeforeRet(SILocUnd)) | |||
1751 | return true; | |||
1752 | ||||
1753 | // If NI is an atomic load/store stronger than monotonic, do not try to | |||
1754 | // eliminate/reorder it. | |||
1755 | if (NI->isAtomic()) { | |||
1756 | if (auto *LI = dyn_cast<LoadInst>(NI)) | |||
1757 | return isStrongerThanMonotonic(LI->getOrdering()); | |||
1758 | if (auto *SI = dyn_cast<StoreInst>(NI)) | |||
1759 | return isStrongerThanMonotonic(SI->getOrdering()); | |||
1760 | if (auto *ARMW = dyn_cast<AtomicRMWInst>(NI)) | |||
1761 | return isStrongerThanMonotonic(ARMW->getOrdering()); | |||
1762 | if (auto *CmpXchg = dyn_cast<AtomicCmpXchgInst>(NI)) | |||
1763 | return isStrongerThanMonotonic(CmpXchg->getSuccessOrdering()) || | |||
1764 | isStrongerThanMonotonic(CmpXchg->getFailureOrdering()); | |||
1765 | llvm_unreachable("other instructions should be skipped in MemorySSA")__builtin_unreachable(); | |||
1766 | } | |||
1767 | return false; | |||
1768 | } | |||
1769 | ||||
1770 | /// Eliminate writes to objects that are not visible in the caller and are not | |||
1771 | /// accessed before returning from the function. | |||
1772 | bool eliminateDeadWritesAtEndOfFunction() { | |||
1773 | bool MadeChange = false; | |||
1774 | LLVM_DEBUG(do { } while (false) | |||
1775 | dbgs()do { } while (false) | |||
1776 | << "Trying to eliminate MemoryDefs at the end of the function\n")do { } while (false); | |||
1777 | for (int I = MemDefs.size() - 1; I >= 0; I--) { | |||
1778 | MemoryDef *Def = MemDefs[I]; | |||
1779 | if (SkipStores.contains(Def) || !isRemovable(Def->getMemoryInst())) | |||
1780 | continue; | |||
1781 | ||||
1782 | Instruction *DefI = Def->getMemoryInst(); | |||
1783 | auto DefLoc = getLocForWriteEx(DefI); | |||
1784 | if (!DefLoc) | |||
1785 | continue; | |||
1786 | ||||
1787 | // NOTE: Currently eliminating writes at the end of a function is limited | |||
1788 | // to MemoryDefs with a single underlying object, to save compile-time. In | |||
1789 | // practice it appears the case with multiple underlying objects is very | |||
1790 | // uncommon. If it turns out to be important, we can use | |||
1791 | // getUnderlyingObjects here instead. | |||
1792 | const Value *UO = getUnderlyingObject(DefLoc->Ptr); | |||
1793 | if (!UO || !isInvisibleToCallerAfterRet(UO)) | |||
1794 | continue; | |||
1795 | ||||
1796 | if (isWriteAtEndOfFunction(Def)) { | |||
1797 | // See through pointer-to-pointer bitcasts | |||
1798 | LLVM_DEBUG(dbgs() << " ... MemoryDef is not accessed until the end "do { } while (false) | |||
1799 | "of the function\n")do { } while (false); | |||
1800 | deleteDeadInstruction(DefI); | |||
1801 | ++NumFastStores; | |||
1802 | MadeChange = true; | |||
1803 | } | |||
1804 | } | |||
1805 | return MadeChange; | |||
1806 | } | |||
1807 | ||||
1808 | /// \returns true if \p Def is a no-op store, either because it | |||
1809 | /// directly stores back a loaded value or stores zero to a calloced object. | |||
1810 | bool storeIsNoop(MemoryDef *Def, const Value *DefUO) { | |||
1811 | StoreInst *Store = dyn_cast<StoreInst>(Def->getMemoryInst()); | |||
1812 | MemSetInst *MemSet = dyn_cast<MemSetInst>(Def->getMemoryInst()); | |||
1813 | Constant *StoredConstant = nullptr; | |||
1814 | if (Store) | |||
1815 | StoredConstant = dyn_cast<Constant>(Store->getOperand(0)); | |||
1816 | if (MemSet) | |||
1817 | StoredConstant = dyn_cast<Constant>(MemSet->getValue()); | |||
1818 | ||||
1819 | if (StoredConstant && StoredConstant->isNullValue()) { | |||
1820 | auto *DefUOInst = dyn_cast<Instruction>(DefUO); | |||
1821 | if (DefUOInst) { | |||
1822 | if (isCallocLikeFn(DefUOInst, &TLI)) { | |||
1823 | auto *UnderlyingDef = | |||
1824 | cast<MemoryDef>(MSSA.getMemoryAccess(DefUOInst)); | |||
1825 | // If UnderlyingDef is the clobbering access of Def, no instructions | |||
1826 | // between them can modify the memory location. | |||
1827 | auto *ClobberDef = | |||
1828 | MSSA.getSkipSelfWalker()->getClobberingMemoryAccess(Def); | |||
1829 | return UnderlyingDef == ClobberDef; | |||
1830 | } | |||
1831 | ||||
1832 | if (MemSet) { | |||
1833 | if (F.hasFnAttribute(Attribute::SanitizeMemory) || | |||
1834 | F.hasFnAttribute(Attribute::SanitizeAddress) || | |||
1835 | F.hasFnAttribute(Attribute::SanitizeHWAddress) || | |||
1836 | F.getName() == "calloc") | |||
1837 | return false; | |||
1838 | auto *Malloc = const_cast<CallInst *>(dyn_cast<CallInst>(DefUOInst)); | |||
1839 | if (!Malloc) | |||
1840 | return false; | |||
1841 | auto *InnerCallee = Malloc->getCalledFunction(); | |||
1842 | if (!InnerCallee) | |||
1843 | return false; | |||
1844 | LibFunc Func; | |||
1845 | if (!TLI.getLibFunc(*InnerCallee, Func) || !TLI.has(Func) || | |||
1846 | Func != LibFunc_malloc) | |||
1847 | return false; | |||
1848 | if (Malloc->getOperand(0) == MemSet->getLength()) { | |||
1849 | if (DT.dominates(Malloc, MemSet) && PDT.dominates(MemSet, Malloc) && | |||
1850 | memoryIsNotModifiedBetween(Malloc, MemSet, BatchAA, DL, &DT)) { | |||
1851 | IRBuilder<> IRB(Malloc); | |||
1852 | const auto &DL = Malloc->getModule()->getDataLayout(); | |||
1853 | if (auto *Calloc = | |||
1854 | emitCalloc(ConstantInt::get(IRB.getIntPtrTy(DL), 1), | |||
1855 | Malloc->getArgOperand(0), IRB, TLI)) { | |||
1856 | MemorySSAUpdater Updater(&MSSA); | |||
1857 | auto *LastDef = cast<MemoryDef>( | |||
1858 | Updater.getMemorySSA()->getMemoryAccess(Malloc)); | |||
1859 | auto *NewAccess = Updater.createMemoryAccessAfter( | |||
1860 | cast<Instruction>(Calloc), LastDef, LastDef); | |||
1861 | auto *NewAccessMD = cast<MemoryDef>(NewAccess); | |||
1862 | Updater.insertDef(NewAccessMD, /*RenameUses=*/true); | |||
1863 | Updater.removeMemoryAccess(Malloc); | |||
1864 | Malloc->replaceAllUsesWith(Calloc); | |||
1865 | Malloc->eraseFromParent(); | |||
1866 | return true; | |||
1867 | } | |||
1868 | return false; | |||
1869 | } | |||
1870 | } | |||
1871 | } | |||
1872 | } | |||
1873 | } | |||
1874 | ||||
1875 | if (!Store) | |||
1876 | return false; | |||
1877 | ||||
1878 | if (auto *LoadI = dyn_cast<LoadInst>(Store->getOperand(0))) { | |||
1879 | if (LoadI->getPointerOperand() == Store->getOperand(1)) { | |||
1880 | // Get the defining access for the load. | |||
1881 | auto *LoadAccess = MSSA.getMemoryAccess(LoadI)->getDefiningAccess(); | |||
1882 | // Fast path: the defining accesses are the same. | |||
1883 | if (LoadAccess == Def->getDefiningAccess()) | |||
1884 | return true; | |||
1885 | ||||
1886 | // Look through phi accesses. Recursively scan all phi accesses by | |||
1887 | // adding them to a worklist. Bail when we run into a memory def that | |||
1888 | // does not match LoadAccess. | |||
1889 | SetVector<MemoryAccess *> ToCheck; | |||
1890 | MemoryAccess *Current = | |||
1891 | MSSA.getWalker()->getClobberingMemoryAccess(Def); | |||
1892 | // We don't want to bail when we run into the store memory def. But, | |||
1893 | // the phi access may point to it. So, pretend like we've already | |||
1894 | // checked it. | |||
1895 | ToCheck.insert(Def); | |||
1896 | ToCheck.insert(Current); | |||
1897 | // Start at current (1) to simulate already having checked Def. | |||
1898 | for (unsigned I = 1; I < ToCheck.size(); ++I) { | |||
1899 | Current = ToCheck[I]; | |||
1900 | if (auto PhiAccess = dyn_cast<MemoryPhi>(Current)) { | |||
1901 | // Check all the operands. | |||
1902 | for (auto &Use : PhiAccess->incoming_values()) | |||
1903 | ToCheck.insert(cast<MemoryAccess>(&Use)); | |||
1904 | continue; | |||
1905 | } | |||
1906 | ||||
1907 | // If we found a memory def, bail. This happens when we have an | |||
1908 | // unrelated write in between an otherwise noop store. | |||
1909 | assert(isa<MemoryDef>(Current) &&(static_cast<void> (0)) | |||
1910 | "Only MemoryDefs should reach here.")(static_cast<void> (0)); | |||
1911 | // TODO: Skip no alias MemoryDefs that have no aliasing reads. | |||
1912 | // We are searching for the definition of the store's destination. | |||
1913 | // So, if that is the same definition as the load, then this is a | |||
1914 | // noop. Otherwise, fail. | |||
1915 | if (LoadAccess != Current) | |||
1916 | return false; | |||
1917 | } | |||
1918 | return true; | |||
1919 | } | |||
1920 | } | |||
1921 | ||||
1922 | return false; | |||
1923 | } | |||
1924 | }; | |||
1925 | ||||
1926 | static bool eliminateDeadStores(Function &F, AliasAnalysis &AA, MemorySSA &MSSA, | |||
1927 | DominatorTree &DT, PostDominatorTree &PDT, | |||
1928 | const TargetLibraryInfo &TLI, | |||
1929 | const LoopInfo &LI) { | |||
1930 | bool MadeChange = false; | |||
1931 | ||||
1932 | DSEState State = DSEState::get(F, AA, MSSA, DT, PDT, TLI, LI); | |||
1933 | // For each store: | |||
1934 | for (unsigned I = 0; I < State.MemDefs.size(); I++) { | |||
1935 | MemoryDef *KillingDef = State.MemDefs[I]; | |||
1936 | if (State.SkipStores.count(KillingDef)) | |||
1937 | continue; | |||
1938 | Instruction *SI = KillingDef->getMemoryInst(); | |||
1939 | ||||
1940 | Optional<MemoryLocation> MaybeSILoc; | |||
1941 | if (State.isMemTerminatorInst(SI)) | |||
1942 | MaybeSILoc = State.getLocForTerminator(SI).map( | |||
1943 | [](const std::pair<MemoryLocation, bool> &P) { return P.first; }); | |||
1944 | else | |||
1945 | MaybeSILoc = State.getLocForWriteEx(SI); | |||
1946 | ||||
1947 | if (!MaybeSILoc) { | |||
1948 | LLVM_DEBUG(dbgs() << "Failed to find analyzable write location for "do { } while (false) | |||
1949 | << *SI << "\n")do { } while (false); | |||
1950 | continue; | |||
1951 | } | |||
1952 | MemoryLocation SILoc = *MaybeSILoc; | |||
1953 | assert(SILoc.Ptr && "SILoc should not be null")(static_cast<void> (0)); | |||
1954 | const Value *SILocUnd = getUnderlyingObject(SILoc.Ptr); | |||
1955 | ||||
1956 | MemoryAccess *Current = KillingDef; | |||
1957 | LLVM_DEBUG(dbgs() << "Trying to eliminate MemoryDefs killed by "do { } while (false) | |||
1958 | << *Current << " (" << *SI << ")\n")do { } while (false); | |||
1959 | ||||
1960 | unsigned ScanLimit = MemorySSAScanLimit; | |||
1961 | unsigned WalkerStepLimit = MemorySSAUpwardsStepLimit; | |||
1962 | unsigned PartialLimit = MemorySSAPartialStoreLimit; | |||
1963 | // Worklist of MemoryAccesses that may be killed by KillingDef. | |||
1964 | SetVector<MemoryAccess *> ToCheck; | |||
1965 | ||||
1966 | if (SILocUnd) | |||
1967 | ToCheck.insert(KillingDef->getDefiningAccess()); | |||
1968 | ||||
1969 | bool Shortend = false; | |||
1970 | bool IsMemTerm = State.isMemTerminatorInst(SI); | |||
1971 | // Check if MemoryAccesses in the worklist are killed by KillingDef. | |||
1972 | for (unsigned I = 0; I < ToCheck.size(); I++) { | |||
1973 | Current = ToCheck[I]; | |||
1974 | if (State.SkipStores.count(Current)) | |||
1975 | continue; | |||
1976 | ||||
1977 | Optional<MemoryAccess *> Next = State.getDomMemoryDef( | |||
1978 | KillingDef, Current, SILoc, SILocUnd, ScanLimit, WalkerStepLimit, | |||
1979 | IsMemTerm, PartialLimit); | |||
1980 | ||||
1981 | if (!Next) { | |||
1982 | LLVM_DEBUG(dbgs() << " finished walk\n")do { } while (false); | |||
1983 | continue; | |||
1984 | } | |||
1985 | ||||
1986 | MemoryAccess *EarlierAccess = *Next; | |||
1987 | LLVM_DEBUG(dbgs() << " Checking if we can kill " << *EarlierAccess)do { } while (false); | |||
1988 | if (isa<MemoryPhi>(EarlierAccess)) { | |||
1989 | LLVM_DEBUG(dbgs() << "\n ... adding incoming values to worklist\n")do { } while (false); | |||
1990 | for (Value *V : cast<MemoryPhi>(EarlierAccess)->incoming_values()) { | |||
1991 | MemoryAccess *IncomingAccess = cast<MemoryAccess>(V); | |||
1992 | BasicBlock *IncomingBlock = IncomingAccess->getBlock(); | |||
1993 | BasicBlock *PhiBlock = EarlierAccess->getBlock(); | |||
1994 | ||||
1995 | // We only consider incoming MemoryAccesses that come before the | |||
1996 | // MemoryPhi. Otherwise we could discover candidates that do not | |||
1997 | // strictly dominate our starting def. | |||
1998 | if (State.PostOrderNumbers[IncomingBlock] > | |||
1999 | State.PostOrderNumbers[PhiBlock]) | |||
2000 | ToCheck.insert(IncomingAccess); | |||
2001 | } | |||
2002 | continue; | |||
2003 | } | |||
2004 | auto *NextDef = cast<MemoryDef>(EarlierAccess); | |||
2005 | Instruction *NI = NextDef->getMemoryInst(); | |||
2006 | LLVM_DEBUG(dbgs() << " (" << *NI << ")\n")do { } while (false); | |||
2007 | ToCheck.insert(NextDef->getDefiningAccess()); | |||
2008 | NumGetDomMemoryDefPassed++; | |||
2009 | ||||
2010 | if (!DebugCounter::shouldExecute(MemorySSACounter)) | |||
2011 | continue; | |||
2012 | ||||
2013 | MemoryLocation NILoc = *State.getLocForWriteEx(NI); | |||
2014 | ||||
2015 | if (IsMemTerm) { | |||
2016 | const Value *NIUnd = getUnderlyingObject(NILoc.Ptr); | |||
2017 | if (SILocUnd != NIUnd) | |||
2018 | continue; | |||
2019 | LLVM_DEBUG(dbgs() << "DSE: Remove Dead Store:\n DEAD: " << *NIdo { } while (false) | |||
2020 | << "\n KILLER: " << *SI << '\n')do { } while (false); | |||
2021 | State.deleteDeadInstruction(NI); | |||
2022 | ++NumFastStores; | |||
2023 | MadeChange = true; | |||
2024 | } else { | |||
2025 | // Check if NI overwrites SI. | |||
2026 | int64_t InstWriteOffset, DepWriteOffset; | |||
2027 | OverwriteResult OR = State.isOverwrite(SI, NI, SILoc, NILoc, | |||
2028 | DepWriteOffset, InstWriteOffset); | |||
2029 | if (OR == OW_MaybePartial) { | |||
2030 | auto Iter = State.IOLs.insert( | |||
2031 | std::make_pair<BasicBlock *, InstOverlapIntervalsTy>( | |||
2032 | NI->getParent(), InstOverlapIntervalsTy())); | |||
2033 | auto &IOL = Iter.first->second; | |||
2034 | OR = isPartialOverwrite(SILoc, NILoc, DepWriteOffset, InstWriteOffset, | |||
2035 | NI, IOL); | |||
2036 | } | |||
2037 | ||||
2038 | if (EnablePartialStoreMerging && OR == OW_PartialEarlierWithFullLater) { | |||
2039 | auto *Earlier = dyn_cast<StoreInst>(NI); | |||
2040 | auto *Later = dyn_cast<StoreInst>(SI); | |||
2041 | // We are re-using tryToMergePartialOverlappingStores, which requires | |||
2042 | // Earlier to domiante Later. | |||
2043 | // TODO: implement tryToMergeParialOverlappingStores using MemorySSA. | |||
2044 | if (Earlier && Later && DT.dominates(Earlier, Later)) { | |||
2045 | if (Constant *Merged = tryToMergePartialOverlappingStores( | |||
2046 | Earlier, Later, InstWriteOffset, DepWriteOffset, State.DL, | |||
2047 | State.BatchAA, &DT)) { | |||
2048 | ||||
2049 | // Update stored value of earlier store to merged constant. | |||
2050 | Earlier->setOperand(0, Merged); | |||
2051 | ++NumModifiedStores; | |||
2052 | MadeChange = true; | |||
2053 | ||||
2054 | Shortend = true; | |||
2055 | // Remove later store and remove any outstanding overlap intervals | |||
2056 | // for the updated store. | |||
2057 | State.deleteDeadInstruction(Later); | |||
2058 | auto I = State.IOLs.find(Earlier->getParent()); | |||
2059 | if (I != State.IOLs.end()) | |||
2060 | I->second.erase(Earlier); | |||
2061 | break; | |||
2062 | } | |||
2063 | } | |||
2064 | } | |||
2065 | ||||
2066 | if (OR == OW_Complete) { | |||
2067 | LLVM_DEBUG(dbgs() << "DSE: Remove Dead Store:\n DEAD: " << *NIdo { } while (false) | |||
2068 | << "\n KILLER: " << *SI << '\n')do { } while (false); | |||
2069 | State.deleteDeadInstruction(NI); | |||
2070 | ++NumFastStores; | |||
2071 | MadeChange = true; | |||
2072 | } | |||
2073 | } | |||
2074 | } | |||
2075 | ||||
2076 | // Check if the store is a no-op. | |||
2077 | if (!Shortend && isRemovable(SI) && | |||
2078 | State.storeIsNoop(KillingDef, SILocUnd)) { | |||
2079 | LLVM_DEBUG(dbgs() << "DSE: Remove No-Op Store:\n DEAD: " << *SI << '\n')do { } while (false); | |||
2080 | State.deleteDeadInstruction(SI); | |||
2081 | NumRedundantStores++; | |||
2082 | MadeChange = true; | |||
2083 | continue; | |||
2084 | } | |||
2085 | } | |||
2086 | ||||
2087 | if (EnablePartialOverwriteTracking) | |||
2088 | for (auto &KV : State.IOLs) | |||
2089 | MadeChange |= removePartiallyOverlappedStores(State.DL, KV.second, TLI); | |||
2090 | ||||
2091 | MadeChange |= State.eliminateDeadWritesAtEndOfFunction(); | |||
2092 | return MadeChange; | |||
2093 | } | |||
2094 | } // end anonymous namespace | |||
2095 | ||||
2096 | //===----------------------------------------------------------------------===// | |||
2097 | // DSE Pass | |||
2098 | //===----------------------------------------------------------------------===// | |||
2099 | PreservedAnalyses DSEPass::run(Function &F, FunctionAnalysisManager &AM) { | |||
2100 | AliasAnalysis &AA = AM.getResult<AAManager>(F); | |||
2101 | const TargetLibraryInfo &TLI = AM.getResult<TargetLibraryAnalysis>(F); | |||
2102 | DominatorTree &DT = AM.getResult<DominatorTreeAnalysis>(F); | |||
2103 | MemorySSA &MSSA = AM.getResult<MemorySSAAnalysis>(F).getMSSA(); | |||
2104 | PostDominatorTree &PDT = AM.getResult<PostDominatorTreeAnalysis>(F); | |||
2105 | LoopInfo &LI = AM.getResult<LoopAnalysis>(F); | |||
2106 | ||||
2107 | bool Changed = eliminateDeadStores(F, AA, MSSA, DT, PDT, TLI, LI); | |||
| ||||
2108 | ||||
2109 | #ifdef LLVM_ENABLE_STATS0 | |||
2110 | if (AreStatisticsEnabled()) | |||
2111 | for (auto &I : instructions(F)) | |||
2112 | NumRemainingStores += isa<StoreInst>(&I); | |||
2113 | #endif | |||
2114 | ||||
2115 | if (!Changed) | |||
2116 | return PreservedAnalyses::all(); | |||
2117 | ||||
2118 | PreservedAnalyses PA; | |||
2119 | PA.preserveSet<CFGAnalyses>(); | |||
2120 | PA.preserve<MemorySSAAnalysis>(); | |||
2121 | PA.preserve<LoopAnalysis>(); | |||
2122 | return PA; | |||
2123 | } | |||
2124 | ||||
2125 | namespace { | |||
2126 | ||||
2127 | /// A legacy pass for the legacy pass manager that wraps \c DSEPass. | |||
2128 | class DSELegacyPass : public FunctionPass { | |||
2129 | public: | |||
2130 | static char ID; // Pass identification, replacement for typeid | |||
2131 | ||||
2132 | DSELegacyPass() : FunctionPass(ID) { | |||
2133 | initializeDSELegacyPassPass(*PassRegistry::getPassRegistry()); | |||
2134 | } | |||
2135 | ||||
2136 | bool runOnFunction(Function &F) override { | |||
2137 | if (skipFunction(F)) | |||
2138 | return false; | |||
2139 | ||||
2140 | AliasAnalysis &AA = getAnalysis<AAResultsWrapperPass>().getAAResults(); | |||
2141 | DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); | |||
2142 | const TargetLibraryInfo &TLI = | |||
2143 | getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F); | |||
2144 | MemorySSA &MSSA = getAnalysis<MemorySSAWrapperPass>().getMSSA(); | |||
2145 | PostDominatorTree &PDT = | |||
2146 | getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree(); | |||
2147 | LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); | |||
2148 | ||||
2149 | bool Changed = eliminateDeadStores(F, AA, MSSA, DT, PDT, TLI, LI); | |||
2150 | ||||
2151 | #ifdef LLVM_ENABLE_STATS0 | |||
2152 | if (AreStatisticsEnabled()) | |||
2153 | for (auto &I : instructions(F)) | |||
2154 | NumRemainingStores += isa<StoreInst>(&I); | |||
2155 | #endif | |||
2156 | ||||
2157 | return Changed; | |||
2158 | } | |||
2159 | ||||
2160 | void getAnalysisUsage(AnalysisUsage &AU) const override { | |||
2161 | AU.setPreservesCFG(); | |||
2162 | AU.addRequired<AAResultsWrapperPass>(); | |||
2163 | AU.addRequired<TargetLibraryInfoWrapperPass>(); | |||
2164 | AU.addPreserved<GlobalsAAWrapperPass>(); | |||
2165 | AU.addRequired<DominatorTreeWrapperPass>(); | |||
2166 | AU.addPreserved<DominatorTreeWrapperPass>(); | |||
2167 | AU.addRequired<PostDominatorTreeWrapperPass>(); | |||
2168 | AU.addRequired<MemorySSAWrapperPass>(); | |||
2169 | AU.addPreserved<PostDominatorTreeWrapperPass>(); | |||
2170 | AU.addPreserved<MemorySSAWrapperPass>(); | |||
2171 | AU.addRequired<LoopInfoWrapperPass>(); | |||
2172 | AU.addPreserved<LoopInfoWrapperPass>(); | |||
2173 | } | |||
2174 | }; | |||
2175 | ||||
2176 | } // end anonymous namespace | |||
2177 | ||||
2178 | char DSELegacyPass::ID = 0; | |||
2179 | ||||
2180 | INITIALIZE_PASS_BEGIN(DSELegacyPass, "dse", "Dead Store Elimination", false,static void *initializeDSELegacyPassPassOnce(PassRegistry & Registry) { | |||
2181 | false)static void *initializeDSELegacyPassPassOnce(PassRegistry & Registry) { | |||
2182 | INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry); | |||
2183 | INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)initializePostDominatorTreeWrapperPassPass(Registry); | |||
2184 | INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)initializeAAResultsWrapperPassPass(Registry); | |||
2185 | INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)initializeGlobalsAAWrapperPassPass(Registry); | |||
2186 | INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry); | |||
2187 | INITIALIZE_PASS_DEPENDENCY(MemoryDependenceWrapperPass)initializeMemoryDependenceWrapperPassPass(Registry); | |||
2188 | INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry); | |||
2189 | INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry); | |||
2190 | INITIALIZE_PASS_END(DSELegacyPass, "dse", "Dead Store Elimination", false,PassInfo *PI = new PassInfo( "Dead Store Elimination", "dse", &DSELegacyPass::ID, PassInfo::NormalCtor_t(callDefaultCtor <DSELegacyPass>), false, false); Registry.registerPass( *PI, true); return PI; } static llvm::once_flag InitializeDSELegacyPassPassFlag ; void llvm::initializeDSELegacyPassPass(PassRegistry &Registry ) { llvm::call_once(InitializeDSELegacyPassPassFlag, initializeDSELegacyPassPassOnce , std::ref(Registry)); } | |||
2191 | false)PassInfo *PI = new PassInfo( "Dead Store Elimination", "dse", &DSELegacyPass::ID, PassInfo::NormalCtor_t(callDefaultCtor <DSELegacyPass>), false, false); Registry.registerPass( *PI, true); return PI; } static llvm::once_flag InitializeDSELegacyPassPassFlag ; void llvm::initializeDSELegacyPassPass(PassRegistry &Registry ) { llvm::call_once(InitializeDSELegacyPassPassFlag, initializeDSELegacyPassPassOnce , std::ref(Registry)); } | |||
2192 | ||||
2193 | FunctionPass *llvm::createDeadStoreEliminationPass() { | |||
2194 | return new DSELegacyPass(); | |||
2195 | } |