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223e47cc LB |
1 | //===- PromoteMemoryToRegister.cpp - Convert allocas to registers ---------===// |
2 | // | |
3 | // The LLVM Compiler Infrastructure | |
4 | // | |
5 | // This file is distributed under the University of Illinois Open Source | |
6 | // License. See LICENSE.TXT for details. | |
7 | // | |
8 | //===----------------------------------------------------------------------===// | |
9 | // | |
10 | // This file promotes memory references to be register references. It promotes | |
11 | // alloca instructions which only have loads and stores as uses. An alloca is | |
12 | // transformed by using iterated dominator frontiers to place PHI nodes, then | |
13 | // traversing the function in depth-first order to rewrite loads and stores as | |
14 | // appropriate. | |
15 | // | |
16 | // The algorithm used here is based on: | |
17 | // | |
18 | // Sreedhar and Gao. A linear time algorithm for placing phi-nodes. | |
19 | // In Proceedings of the 22nd ACM SIGPLAN-SIGACT Symposium on Principles of | |
20 | // Programming Languages | |
21 | // POPL '95. ACM, New York, NY, 62-73. | |
22 | // | |
23 | // It has been modified to not explicitly use the DJ graph data structure and to | |
24 | // directly compute pruned SSA using per-variable liveness information. | |
25 | // | |
26 | //===----------------------------------------------------------------------===// | |
27 | ||
223e47cc | 28 | #include "llvm/Transforms/Utils/PromoteMemToReg.h" |
1a4d82fc | 29 | #include "llvm/ADT/ArrayRef.h" |
223e47cc | 30 | #include "llvm/ADT/DenseMap.h" |
970d7e83 | 31 | #include "llvm/ADT/STLExtras.h" |
223e47cc LB |
32 | #include "llvm/ADT/SmallPtrSet.h" |
33 | #include "llvm/ADT/SmallVector.h" | |
34 | #include "llvm/ADT/Statistic.h" | |
970d7e83 | 35 | #include "llvm/Analysis/AliasSetTracker.h" |
970d7e83 LB |
36 | #include "llvm/Analysis/InstructionSimplify.h" |
37 | #include "llvm/Analysis/ValueTracking.h" | |
1a4d82fc | 38 | #include "llvm/IR/CFG.h" |
970d7e83 | 39 | #include "llvm/IR/Constants.h" |
1a4d82fc JJ |
40 | #include "llvm/IR/DIBuilder.h" |
41 | #include "llvm/IR/DebugInfo.h" | |
970d7e83 | 42 | #include "llvm/IR/DerivedTypes.h" |
1a4d82fc | 43 | #include "llvm/IR/Dominators.h" |
970d7e83 LB |
44 | #include "llvm/IR/Function.h" |
45 | #include "llvm/IR/Instructions.h" | |
46 | #include "llvm/IR/IntrinsicInst.h" | |
47 | #include "llvm/IR/Metadata.h" | |
970d7e83 | 48 | #include "llvm/Transforms/Utils/Local.h" |
223e47cc LB |
49 | #include <algorithm> |
50 | #include <queue> | |
51 | using namespace llvm; | |
52 | ||
1a4d82fc JJ |
53 | #define DEBUG_TYPE "mem2reg" |
54 | ||
223e47cc LB |
55 | STATISTIC(NumLocalPromoted, "Number of alloca's promoted within one block"); |
56 | STATISTIC(NumSingleStore, "Number of alloca's promoted with a single store"); | |
57 | STATISTIC(NumDeadAlloca, "Number of dead alloca's removed"); | |
58 | STATISTIC(NumPHIInsert, "Number of PHI nodes inserted"); | |
59 | ||
223e47cc LB |
60 | bool llvm::isAllocaPromotable(const AllocaInst *AI) { |
61 | // FIXME: If the memory unit is of pointer or integer type, we can permit | |
62 | // assignments to subsections of the memory unit. | |
1a4d82fc | 63 | unsigned AS = AI->getType()->getAddressSpace(); |
223e47cc LB |
64 | |
65 | // Only allow direct and non-volatile loads and stores... | |
1a4d82fc | 66 | for (const User *U : AI->users()) { |
223e47cc LB |
67 | if (const LoadInst *LI = dyn_cast<LoadInst>(U)) { |
68 | // Note that atomic loads can be transformed; atomic semantics do | |
69 | // not have any meaning for a local alloca. | |
70 | if (LI->isVolatile()) | |
71 | return false; | |
72 | } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) { | |
73 | if (SI->getOperand(0) == AI) | |
1a4d82fc | 74 | return false; // Don't allow a store OF the AI, only INTO the AI. |
223e47cc LB |
75 | // Note that atomic stores can be transformed; atomic semantics do |
76 | // not have any meaning for a local alloca. | |
77 | if (SI->isVolatile()) | |
78 | return false; | |
79 | } else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) { | |
80 | if (II->getIntrinsicID() != Intrinsic::lifetime_start && | |
81 | II->getIntrinsicID() != Intrinsic::lifetime_end) | |
82 | return false; | |
83 | } else if (const BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { | |
1a4d82fc | 84 | if (BCI->getType() != Type::getInt8PtrTy(U->getContext(), AS)) |
223e47cc LB |
85 | return false; |
86 | if (!onlyUsedByLifetimeMarkers(BCI)) | |
87 | return false; | |
88 | } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { | |
1a4d82fc | 89 | if (GEPI->getType() != Type::getInt8PtrTy(U->getContext(), AS)) |
223e47cc LB |
90 | return false; |
91 | if (!GEPI->hasAllZeroIndices()) | |
92 | return false; | |
93 | if (!onlyUsedByLifetimeMarkers(GEPI)) | |
94 | return false; | |
95 | } else { | |
96 | return false; | |
97 | } | |
98 | } | |
99 | ||
100 | return true; | |
101 | } | |
102 | ||
103 | namespace { | |
1a4d82fc JJ |
104 | |
105 | struct AllocaInfo { | |
106 | SmallVector<BasicBlock *, 32> DefiningBlocks; | |
107 | SmallVector<BasicBlock *, 32> UsingBlocks; | |
108 | ||
109 | StoreInst *OnlyStore; | |
110 | BasicBlock *OnlyBlock; | |
111 | bool OnlyUsedInOneBlock; | |
112 | ||
113 | Value *AllocaPointerVal; | |
114 | DbgDeclareInst *DbgDeclare; | |
115 | ||
116 | void clear() { | |
117 | DefiningBlocks.clear(); | |
118 | UsingBlocks.clear(); | |
119 | OnlyStore = nullptr; | |
120 | OnlyBlock = nullptr; | |
121 | OnlyUsedInOneBlock = true; | |
122 | AllocaPointerVal = nullptr; | |
123 | DbgDeclare = nullptr; | |
124 | } | |
125 | ||
126 | /// Scan the uses of the specified alloca, filling in the AllocaInfo used | |
127 | /// by the rest of the pass to reason about the uses of this alloca. | |
128 | void AnalyzeAlloca(AllocaInst *AI) { | |
129 | clear(); | |
130 | ||
131 | // As we scan the uses of the alloca instruction, keep track of stores, | |
132 | // and decide whether all of the loads and stores to the alloca are within | |
133 | // the same basic block. | |
134 | for (auto UI = AI->user_begin(), E = AI->user_end(); UI != E;) { | |
135 | Instruction *User = cast<Instruction>(*UI++); | |
136 | ||
137 | if (StoreInst *SI = dyn_cast<StoreInst>(User)) { | |
138 | // Remember the basic blocks which define new values for the alloca | |
139 | DefiningBlocks.push_back(SI->getParent()); | |
140 | AllocaPointerVal = SI->getOperand(0); | |
141 | OnlyStore = SI; | |
142 | } else { | |
143 | LoadInst *LI = cast<LoadInst>(User); | |
144 | // Otherwise it must be a load instruction, keep track of variable | |
145 | // reads. | |
146 | UsingBlocks.push_back(LI->getParent()); | |
147 | AllocaPointerVal = LI; | |
148 | } | |
149 | ||
150 | if (OnlyUsedInOneBlock) { | |
151 | if (!OnlyBlock) | |
152 | OnlyBlock = User->getParent(); | |
153 | else if (OnlyBlock != User->getParent()) | |
154 | OnlyUsedInOneBlock = false; | |
155 | } | |
223e47cc | 156 | } |
1a4d82fc JJ |
157 | |
158 | DbgDeclare = FindAllocaDbgDeclare(AI); | |
159 | } | |
160 | }; | |
161 | ||
162 | // Data package used by RenamePass() | |
163 | class RenamePassData { | |
164 | public: | |
165 | typedef std::vector<Value *> ValVector; | |
166 | ||
167 | RenamePassData() : BB(nullptr), Pred(nullptr), Values() {} | |
168 | RenamePassData(BasicBlock *B, BasicBlock *P, const ValVector &V) | |
169 | : BB(B), Pred(P), Values(V) {} | |
170 | BasicBlock *BB; | |
171 | BasicBlock *Pred; | |
172 | ValVector Values; | |
173 | ||
174 | void swap(RenamePassData &RHS) { | |
175 | std::swap(BB, RHS.BB); | |
176 | std::swap(Pred, RHS.Pred); | |
177 | Values.swap(RHS.Values); | |
178 | } | |
179 | }; | |
180 | ||
181 | /// \brief This assigns and keeps a per-bb relative ordering of load/store | |
182 | /// instructions in the block that directly load or store an alloca. | |
183 | /// | |
184 | /// This functionality is important because it avoids scanning large basic | |
185 | /// blocks multiple times when promoting many allocas in the same block. | |
186 | class LargeBlockInfo { | |
187 | /// \brief For each instruction that we track, keep the index of the | |
188 | /// instruction. | |
223e47cc | 189 | /// |
1a4d82fc JJ |
190 | /// The index starts out as the number of the instruction from the start of |
191 | /// the block. | |
192 | DenseMap<const Instruction *, unsigned> InstNumbers; | |
193 | ||
194 | public: | |
195 | ||
196 | /// This code only looks at accesses to allocas. | |
197 | static bool isInterestingInstruction(const Instruction *I) { | |
198 | return (isa<LoadInst>(I) && isa<AllocaInst>(I->getOperand(0))) || | |
199 | (isa<StoreInst>(I) && isa<AllocaInst>(I->getOperand(1))); | |
200 | } | |
201 | ||
202 | /// Get or calculate the index of the specified instruction. | |
203 | unsigned getInstructionIndex(const Instruction *I) { | |
204 | assert(isInterestingInstruction(I) && | |
205 | "Not a load/store to/from an alloca?"); | |
206 | ||
207 | // If we already have this instruction number, return it. | |
208 | DenseMap<const Instruction *, unsigned>::iterator It = InstNumbers.find(I); | |
209 | if (It != InstNumbers.end()) | |
223e47cc | 210 | return It->second; |
223e47cc | 211 | |
1a4d82fc JJ |
212 | // Scan the whole block to get the instruction. This accumulates |
213 | // information for every interesting instruction in the block, in order to | |
214 | // avoid gratuitus rescans. | |
215 | const BasicBlock *BB = I->getParent(); | |
216 | unsigned InstNo = 0; | |
217 | for (BasicBlock::const_iterator BBI = BB->begin(), E = BB->end(); BBI != E; | |
218 | ++BBI) | |
219 | if (isInterestingInstruction(BBI)) | |
220 | InstNumbers[BBI] = InstNo++; | |
221 | It = InstNumbers.find(I); | |
222 | ||
223 | assert(It != InstNumbers.end() && "Didn't insert instruction?"); | |
224 | return It->second; | |
225 | } | |
223e47cc | 226 | |
1a4d82fc | 227 | void deleteValue(const Instruction *I) { InstNumbers.erase(I); } |
223e47cc | 228 | |
1a4d82fc JJ |
229 | void clear() { InstNumbers.clear(); } |
230 | }; | |
223e47cc | 231 | |
1a4d82fc JJ |
232 | struct PromoteMem2Reg { |
233 | /// The alloca instructions being promoted. | |
234 | std::vector<AllocaInst *> Allocas; | |
235 | DominatorTree &DT; | |
236 | DIBuilder DIB; | |
223e47cc | 237 | |
1a4d82fc JJ |
238 | /// An AliasSetTracker object to update. If null, don't update it. |
239 | AliasSetTracker *AST; | |
223e47cc | 240 | |
1a4d82fc | 241 | /// A cache of @llvm.assume intrinsics used by SimplifyInstruction. |
85aaf69f | 242 | AssumptionCache *AC; |
223e47cc | 243 | |
1a4d82fc JJ |
244 | /// Reverse mapping of Allocas. |
245 | DenseMap<AllocaInst *, unsigned> AllocaLookup; | |
246 | ||
247 | /// \brief The PhiNodes we're adding. | |
248 | /// | |
249 | /// That map is used to simplify some Phi nodes as we iterate over it, so | |
250 | /// it should have deterministic iterators. We could use a MapVector, but | |
251 | /// since we already maintain a map from BasicBlock* to a stable numbering | |
252 | /// (BBNumbers), the DenseMap is more efficient (also supports removal). | |
253 | DenseMap<std::pair<unsigned, unsigned>, PHINode *> NewPhiNodes; | |
254 | ||
255 | /// For each PHI node, keep track of which entry in Allocas it corresponds | |
256 | /// to. | |
257 | DenseMap<PHINode *, unsigned> PhiToAllocaMap; | |
258 | ||
259 | /// If we are updating an AliasSetTracker, then for each alloca that is of | |
260 | /// pointer type, we keep track of what to copyValue to the inserted PHI | |
261 | /// nodes here. | |
262 | std::vector<Value *> PointerAllocaValues; | |
263 | ||
264 | /// For each alloca, we keep track of the dbg.declare intrinsic that | |
265 | /// describes it, if any, so that we can convert it to a dbg.value | |
266 | /// intrinsic if the alloca gets promoted. | |
267 | SmallVector<DbgDeclareInst *, 8> AllocaDbgDeclares; | |
268 | ||
269 | /// The set of basic blocks the renamer has already visited. | |
270 | /// | |
271 | SmallPtrSet<BasicBlock *, 16> Visited; | |
272 | ||
273 | /// Contains a stable numbering of basic blocks to avoid non-determinstic | |
274 | /// behavior. | |
275 | DenseMap<BasicBlock *, unsigned> BBNumbers; | |
276 | ||
277 | /// Maps DomTreeNodes to their level in the dominator tree. | |
278 | DenseMap<DomTreeNode *, unsigned> DomLevels; | |
279 | ||
280 | /// Lazily compute the number of predecessors a block has. | |
281 | DenseMap<const BasicBlock *, unsigned> BBNumPreds; | |
282 | ||
283 | public: | |
284 | PromoteMem2Reg(ArrayRef<AllocaInst *> Allocas, DominatorTree &DT, | |
85aaf69f | 285 | AliasSetTracker *AST, AssumptionCache *AC) |
1a4d82fc | 286 | : Allocas(Allocas.begin(), Allocas.end()), DT(DT), |
85aaf69f SL |
287 | DIB(*DT.getRoot()->getParent()->getParent(), /*AllowUnresolved*/ false), |
288 | AST(AST), AC(AC) {} | |
1a4d82fc JJ |
289 | |
290 | void run(); | |
291 | ||
292 | private: | |
293 | void RemoveFromAllocasList(unsigned &AllocaIdx) { | |
294 | Allocas[AllocaIdx] = Allocas.back(); | |
295 | Allocas.pop_back(); | |
296 | --AllocaIdx; | |
297 | } | |
298 | ||
299 | unsigned getNumPreds(const BasicBlock *BB) { | |
300 | unsigned &NP = BBNumPreds[BB]; | |
301 | if (NP == 0) | |
302 | NP = std::distance(pred_begin(BB), pred_end(BB)) + 1; | |
303 | return NP - 1; | |
304 | } | |
305 | ||
306 | void DetermineInsertionPoint(AllocaInst *AI, unsigned AllocaNum, | |
307 | AllocaInfo &Info); | |
308 | void ComputeLiveInBlocks(AllocaInst *AI, AllocaInfo &Info, | |
309 | const SmallPtrSetImpl<BasicBlock *> &DefBlocks, | |
310 | SmallPtrSetImpl<BasicBlock *> &LiveInBlocks); | |
311 | void RenamePass(BasicBlock *BB, BasicBlock *Pred, | |
312 | RenamePassData::ValVector &IncVals, | |
313 | std::vector<RenamePassData> &Worklist); | |
314 | bool QueuePhiNode(BasicBlock *BB, unsigned AllocaIdx, unsigned &Version); | |
315 | }; | |
316 | ||
317 | } // end of anonymous namespace | |
223e47cc LB |
318 | |
319 | static void removeLifetimeIntrinsicUsers(AllocaInst *AI) { | |
320 | // Knowing that this alloca is promotable, we know that it's safe to kill all | |
321 | // instructions except for load and store. | |
322 | ||
1a4d82fc | 323 | for (auto UI = AI->user_begin(), UE = AI->user_end(); UI != UE;) { |
223e47cc LB |
324 | Instruction *I = cast<Instruction>(*UI); |
325 | ++UI; | |
326 | if (isa<LoadInst>(I) || isa<StoreInst>(I)) | |
327 | continue; | |
328 | ||
329 | if (!I->getType()->isVoidTy()) { | |
330 | // The only users of this bitcast/GEP instruction are lifetime intrinsics. | |
331 | // Follow the use/def chain to erase them now instead of leaving it for | |
332 | // dead code elimination later. | |
1a4d82fc JJ |
333 | for (auto UUI = I->user_begin(), UUE = I->user_end(); UUI != UUE;) { |
334 | Instruction *Inst = cast<Instruction>(*UUI); | |
335 | ++UUI; | |
223e47cc LB |
336 | Inst->eraseFromParent(); |
337 | } | |
338 | } | |
339 | I->eraseFromParent(); | |
340 | } | |
341 | } | |
342 | ||
1a4d82fc JJ |
343 | /// \brief Rewrite as many loads as possible given a single store. |
344 | /// | |
345 | /// When there is only a single store, we can use the domtree to trivially | |
346 | /// replace all of the dominated loads with the stored value. Do so, and return | |
347 | /// true if this has successfully promoted the alloca entirely. If this returns | |
348 | /// false there were some loads which were not dominated by the single store | |
349 | /// and thus must be phi-ed with undef. We fall back to the standard alloca | |
350 | /// promotion algorithm in that case. | |
351 | static bool rewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info, | |
352 | LargeBlockInfo &LBI, | |
353 | DominatorTree &DT, | |
354 | AliasSetTracker *AST) { | |
355 | StoreInst *OnlyStore = Info.OnlyStore; | |
356 | bool StoringGlobalVal = !isa<Instruction>(OnlyStore->getOperand(0)); | |
357 | BasicBlock *StoreBB = OnlyStore->getParent(); | |
358 | int StoreIndex = -1; | |
359 | ||
360 | // Clear out UsingBlocks. We will reconstruct it here if needed. | |
361 | Info.UsingBlocks.clear(); | |
362 | ||
363 | for (auto UI = AI->user_begin(), E = AI->user_end(); UI != E;) { | |
364 | Instruction *UserInst = cast<Instruction>(*UI++); | |
365 | if (!isa<LoadInst>(UserInst)) { | |
366 | assert(UserInst == OnlyStore && "Should only have load/stores"); | |
367 | continue; | |
368 | } | |
369 | LoadInst *LI = cast<LoadInst>(UserInst); | |
370 | ||
371 | // Okay, if we have a load from the alloca, we want to replace it with the | |
372 | // only value stored to the alloca. We can do this if the value is | |
373 | // dominated by the store. If not, we use the rest of the mem2reg machinery | |
374 | // to insert the phi nodes as needed. | |
375 | if (!StoringGlobalVal) { // Non-instructions are always dominated. | |
376 | if (LI->getParent() == StoreBB) { | |
377 | // If we have a use that is in the same block as the store, compare the | |
378 | // indices of the two instructions to see which one came first. If the | |
379 | // load came before the store, we can't handle it. | |
380 | if (StoreIndex == -1) | |
381 | StoreIndex = LBI.getInstructionIndex(OnlyStore); | |
382 | ||
383 | if (unsigned(StoreIndex) > LBI.getInstructionIndex(LI)) { | |
384 | // Can't handle this load, bail out. | |
385 | Info.UsingBlocks.push_back(StoreBB); | |
386 | continue; | |
387 | } | |
388 | ||
389 | } else if (LI->getParent() != StoreBB && | |
390 | !DT.dominates(StoreBB, LI->getParent())) { | |
391 | // If the load and store are in different blocks, use BB dominance to | |
392 | // check their relationships. If the store doesn't dom the use, bail | |
393 | // out. | |
394 | Info.UsingBlocks.push_back(LI->getParent()); | |
395 | continue; | |
396 | } | |
397 | } | |
398 | ||
399 | // Otherwise, we *can* safely rewrite this load. | |
400 | Value *ReplVal = OnlyStore->getOperand(0); | |
401 | // If the replacement value is the load, this must occur in unreachable | |
402 | // code. | |
403 | if (ReplVal == LI) | |
404 | ReplVal = UndefValue::get(LI->getType()); | |
405 | LI->replaceAllUsesWith(ReplVal); | |
406 | if (AST && LI->getType()->isPointerTy()) | |
407 | AST->deleteValue(LI); | |
408 | LI->eraseFromParent(); | |
409 | LBI.deleteValue(LI); | |
410 | } | |
411 | ||
412 | // Finally, after the scan, check to see if the store is all that is left. | |
413 | if (!Info.UsingBlocks.empty()) | |
414 | return false; // If not, we'll have to fall back for the remainder. | |
415 | ||
416 | // Record debuginfo for the store and remove the declaration's | |
417 | // debuginfo. | |
418 | if (DbgDeclareInst *DDI = Info.DbgDeclare) { | |
85aaf69f SL |
419 | DIBuilder DIB(*AI->getParent()->getParent()->getParent(), |
420 | /*AllowUnresolved*/ false); | |
1a4d82fc JJ |
421 | ConvertDebugDeclareToDebugValue(DDI, Info.OnlyStore, DIB); |
422 | DDI->eraseFromParent(); | |
423 | LBI.deleteValue(DDI); | |
424 | } | |
425 | // Remove the (now dead) store and alloca. | |
426 | Info.OnlyStore->eraseFromParent(); | |
427 | LBI.deleteValue(Info.OnlyStore); | |
428 | ||
429 | if (AST) | |
430 | AST->deleteValue(AI); | |
431 | AI->eraseFromParent(); | |
432 | LBI.deleteValue(AI); | |
433 | return true; | |
434 | } | |
435 | ||
436 | /// Many allocas are only used within a single basic block. If this is the | |
437 | /// case, avoid traversing the CFG and inserting a lot of potentially useless | |
438 | /// PHI nodes by just performing a single linear pass over the basic block | |
439 | /// using the Alloca. | |
440 | /// | |
441 | /// If we cannot promote this alloca (because it is read before it is written), | |
442 | /// return true. This is necessary in cases where, due to control flow, the | |
443 | /// alloca is potentially undefined on some control flow paths. e.g. code like | |
444 | /// this is potentially correct: | |
445 | /// | |
446 | /// for (...) { if (c) { A = undef; undef = B; } } | |
447 | /// | |
448 | /// ... so long as A is not used before undef is set. | |
449 | static void promoteSingleBlockAlloca(AllocaInst *AI, const AllocaInfo &Info, | |
450 | LargeBlockInfo &LBI, | |
451 | AliasSetTracker *AST) { | |
452 | // The trickiest case to handle is when we have large blocks. Because of this, | |
453 | // this code is optimized assuming that large blocks happen. This does not | |
454 | // significantly pessimize the small block case. This uses LargeBlockInfo to | |
455 | // make it efficient to get the index of various operations in the block. | |
456 | ||
457 | // Walk the use-def list of the alloca, getting the locations of all stores. | |
458 | typedef SmallVector<std::pair<unsigned, StoreInst *>, 64> StoresByIndexTy; | |
459 | StoresByIndexTy StoresByIndex; | |
460 | ||
461 | for (User *U : AI->users()) | |
462 | if (StoreInst *SI = dyn_cast<StoreInst>(U)) | |
463 | StoresByIndex.push_back(std::make_pair(LBI.getInstructionIndex(SI), SI)); | |
464 | ||
465 | // Sort the stores by their index, making it efficient to do a lookup with a | |
466 | // binary search. | |
467 | std::sort(StoresByIndex.begin(), StoresByIndex.end(), less_first()); | |
468 | ||
469 | // Walk all of the loads from this alloca, replacing them with the nearest | |
470 | // store above them, if any. | |
471 | for (auto UI = AI->user_begin(), E = AI->user_end(); UI != E;) { | |
472 | LoadInst *LI = dyn_cast<LoadInst>(*UI++); | |
473 | if (!LI) | |
474 | continue; | |
475 | ||
476 | unsigned LoadIdx = LBI.getInstructionIndex(LI); | |
477 | ||
478 | // Find the nearest store that has a lower index than this load. | |
479 | StoresByIndexTy::iterator I = | |
480 | std::lower_bound(StoresByIndex.begin(), StoresByIndex.end(), | |
481 | std::make_pair(LoadIdx, | |
482 | static_cast<StoreInst *>(nullptr)), | |
483 | less_first()); | |
484 | ||
485 | if (I == StoresByIndex.begin()) | |
486 | // If there is no store before this load, the load takes the undef value. | |
487 | LI->replaceAllUsesWith(UndefValue::get(LI->getType())); | |
488 | else | |
489 | // Otherwise, there was a store before this load, the load takes its value. | |
490 | LI->replaceAllUsesWith(std::prev(I)->second->getOperand(0)); | |
491 | ||
492 | if (AST && LI->getType()->isPointerTy()) | |
493 | AST->deleteValue(LI); | |
494 | LI->eraseFromParent(); | |
495 | LBI.deleteValue(LI); | |
496 | } | |
497 | ||
498 | // Remove the (now dead) stores and alloca. | |
499 | while (!AI->use_empty()) { | |
500 | StoreInst *SI = cast<StoreInst>(AI->user_back()); | |
501 | // Record debuginfo for the store before removing it. | |
502 | if (DbgDeclareInst *DDI = Info.DbgDeclare) { | |
85aaf69f SL |
503 | DIBuilder DIB(*AI->getParent()->getParent()->getParent(), |
504 | /*AllowUnresolved*/ false); | |
1a4d82fc JJ |
505 | ConvertDebugDeclareToDebugValue(DDI, SI, DIB); |
506 | } | |
507 | SI->eraseFromParent(); | |
508 | LBI.deleteValue(SI); | |
509 | } | |
510 | ||
511 | if (AST) | |
512 | AST->deleteValue(AI); | |
513 | AI->eraseFromParent(); | |
514 | LBI.deleteValue(AI); | |
515 | ||
516 | // The alloca's debuginfo can be removed as well. | |
517 | if (DbgDeclareInst *DDI = Info.DbgDeclare) { | |
518 | DDI->eraseFromParent(); | |
519 | LBI.deleteValue(DDI); | |
520 | } | |
521 | ||
522 | ++NumLocalPromoted; | |
523 | } | |
524 | ||
223e47cc LB |
525 | void PromoteMem2Reg::run() { |
526 | Function &F = *DT.getRoot()->getParent(); | |
527 | ||
1a4d82fc JJ |
528 | if (AST) |
529 | PointerAllocaValues.resize(Allocas.size()); | |
223e47cc LB |
530 | AllocaDbgDeclares.resize(Allocas.size()); |
531 | ||
532 | AllocaInfo Info; | |
533 | LargeBlockInfo LBI; | |
534 | ||
535 | for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) { | |
536 | AllocaInst *AI = Allocas[AllocaNum]; | |
537 | ||
1a4d82fc | 538 | assert(isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!"); |
223e47cc LB |
539 | assert(AI->getParent()->getParent() == &F && |
540 | "All allocas should be in the same function, which is same as DF!"); | |
541 | ||
542 | removeLifetimeIntrinsicUsers(AI); | |
543 | ||
544 | if (AI->use_empty()) { | |
545 | // If there are no uses of the alloca, just delete it now. | |
1a4d82fc JJ |
546 | if (AST) |
547 | AST->deleteValue(AI); | |
223e47cc LB |
548 | AI->eraseFromParent(); |
549 | ||
550 | // Remove the alloca from the Allocas list, since it has been processed | |
551 | RemoveFromAllocasList(AllocaNum); | |
552 | ++NumDeadAlloca; | |
553 | continue; | |
554 | } | |
1a4d82fc | 555 | |
223e47cc LB |
556 | // Calculate the set of read and write-locations for each alloca. This is |
557 | // analogous to finding the 'uses' and 'definitions' of each variable. | |
558 | Info.AnalyzeAlloca(AI); | |
559 | ||
560 | // If there is only a single store to this value, replace any loads of | |
561 | // it that are directly dominated by the definition with the value stored. | |
562 | if (Info.DefiningBlocks.size() == 1) { | |
1a4d82fc | 563 | if (rewriteSingleStoreAlloca(AI, Info, LBI, DT, AST)) { |
223e47cc LB |
564 | // The alloca has been processed, move on. |
565 | RemoveFromAllocasList(AllocaNum); | |
223e47cc LB |
566 | ++NumSingleStore; |
567 | continue; | |
568 | } | |
569 | } | |
1a4d82fc | 570 | |
223e47cc LB |
571 | // If the alloca is only read and written in one basic block, just perform a |
572 | // linear sweep over the block to eliminate it. | |
573 | if (Info.OnlyUsedInOneBlock) { | |
1a4d82fc | 574 | promoteSingleBlockAlloca(AI, Info, LBI, AST); |
223e47cc | 575 | |
1a4d82fc JJ |
576 | // The alloca has been processed, move on. |
577 | RemoveFromAllocasList(AllocaNum); | |
578 | continue; | |
223e47cc LB |
579 | } |
580 | ||
581 | // If we haven't computed dominator tree levels, do so now. | |
582 | if (DomLevels.empty()) { | |
1a4d82fc | 583 | SmallVector<DomTreeNode *, 32> Worklist; |
223e47cc LB |
584 | |
585 | DomTreeNode *Root = DT.getRootNode(); | |
586 | DomLevels[Root] = 0; | |
587 | Worklist.push_back(Root); | |
588 | ||
589 | while (!Worklist.empty()) { | |
590 | DomTreeNode *Node = Worklist.pop_back_val(); | |
591 | unsigned ChildLevel = DomLevels[Node] + 1; | |
592 | for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end(); | |
593 | CI != CE; ++CI) { | |
594 | DomLevels[*CI] = ChildLevel; | |
595 | Worklist.push_back(*CI); | |
596 | } | |
597 | } | |
598 | } | |
599 | ||
600 | // If we haven't computed a numbering for the BB's in the function, do so | |
601 | // now. | |
602 | if (BBNumbers.empty()) { | |
603 | unsigned ID = 0; | |
604 | for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) | |
605 | BBNumbers[I] = ID++; | |
606 | } | |
607 | ||
608 | // If we have an AST to keep updated, remember some pointer value that is | |
609 | // stored into the alloca. | |
610 | if (AST) | |
611 | PointerAllocaValues[AllocaNum] = Info.AllocaPointerVal; | |
1a4d82fc | 612 | |
223e47cc | 613 | // Remember the dbg.declare intrinsic describing this alloca, if any. |
1a4d82fc JJ |
614 | if (Info.DbgDeclare) |
615 | AllocaDbgDeclares[AllocaNum] = Info.DbgDeclare; | |
616 | ||
223e47cc LB |
617 | // Keep the reverse mapping of the 'Allocas' array for the rename pass. |
618 | AllocaLookup[Allocas[AllocaNum]] = AllocaNum; | |
619 | ||
620 | // At this point, we're committed to promoting the alloca using IDF's, and | |
621 | // the standard SSA construction algorithm. Determine which blocks need PHI | |
622 | // nodes and see if we can optimize out some work by avoiding insertion of | |
623 | // dead phi nodes. | |
624 | DetermineInsertionPoint(AI, AllocaNum, Info); | |
625 | } | |
626 | ||
627 | if (Allocas.empty()) | |
628 | return; // All of the allocas must have been trivial! | |
629 | ||
630 | LBI.clear(); | |
1a4d82fc | 631 | |
223e47cc LB |
632 | // Set the incoming values for the basic block to be null values for all of |
633 | // the alloca's. We do this in case there is a load of a value that has not | |
634 | // been stored yet. In this case, it will get this null value. | |
635 | // | |
636 | RenamePassData::ValVector Values(Allocas.size()); | |
637 | for (unsigned i = 0, e = Allocas.size(); i != e; ++i) | |
638 | Values[i] = UndefValue::get(Allocas[i]->getAllocatedType()); | |
639 | ||
640 | // Walks all basic blocks in the function performing the SSA rename algorithm | |
641 | // and inserting the phi nodes we marked as necessary | |
642 | // | |
643 | std::vector<RenamePassData> RenamePassWorkList; | |
1a4d82fc | 644 | RenamePassWorkList.push_back(RenamePassData(F.begin(), nullptr, Values)); |
223e47cc LB |
645 | do { |
646 | RenamePassData RPD; | |
647 | RPD.swap(RenamePassWorkList.back()); | |
648 | RenamePassWorkList.pop_back(); | |
649 | // RenamePass may add new worklist entries. | |
650 | RenamePass(RPD.BB, RPD.Pred, RPD.Values, RenamePassWorkList); | |
651 | } while (!RenamePassWorkList.empty()); | |
1a4d82fc | 652 | |
223e47cc LB |
653 | // The renamer uses the Visited set to avoid infinite loops. Clear it now. |
654 | Visited.clear(); | |
655 | ||
656 | // Remove the allocas themselves from the function. | |
657 | for (unsigned i = 0, e = Allocas.size(); i != e; ++i) { | |
658 | Instruction *A = Allocas[i]; | |
659 | ||
660 | // If there are any uses of the alloca instructions left, they must be in | |
661 | // unreachable basic blocks that were not processed by walking the dominator | |
662 | // tree. Just delete the users now. | |
663 | if (!A->use_empty()) | |
664 | A->replaceAllUsesWith(UndefValue::get(A->getType())); | |
1a4d82fc JJ |
665 | if (AST) |
666 | AST->deleteValue(A); | |
223e47cc LB |
667 | A->eraseFromParent(); |
668 | } | |
669 | ||
670 | // Remove alloca's dbg.declare instrinsics from the function. | |
671 | for (unsigned i = 0, e = AllocaDbgDeclares.size(); i != e; ++i) | |
672 | if (DbgDeclareInst *DDI = AllocaDbgDeclares[i]) | |
673 | DDI->eraseFromParent(); | |
674 | ||
675 | // Loop over all of the PHI nodes and see if there are any that we can get | |
676 | // rid of because they merge all of the same incoming values. This can | |
677 | // happen due to undef values coming into the PHI nodes. This process is | |
678 | // iterative, because eliminating one PHI node can cause others to be removed. | |
679 | bool EliminatedAPHI = true; | |
680 | while (EliminatedAPHI) { | |
681 | EliminatedAPHI = false; | |
1a4d82fc | 682 | |
970d7e83 LB |
683 | // Iterating over NewPhiNodes is deterministic, so it is safe to try to |
684 | // simplify and RAUW them as we go. If it was not, we could add uses to | |
1a4d82fc JJ |
685 | // the values we replace with in a non-deterministic order, thus creating |
686 | // non-deterministic def->use chains. | |
687 | for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator | |
688 | I = NewPhiNodes.begin(), | |
689 | E = NewPhiNodes.end(); | |
690 | I != E;) { | |
223e47cc LB |
691 | PHINode *PN = I->second; |
692 | ||
693 | // If this PHI node merges one value and/or undefs, get the value. | |
85aaf69f | 694 | if (Value *V = SimplifyInstruction(PN, nullptr, nullptr, &DT, AC)) { |
223e47cc LB |
695 | if (AST && PN->getType()->isPointerTy()) |
696 | AST->deleteValue(PN); | |
697 | PN->replaceAllUsesWith(V); | |
698 | PN->eraseFromParent(); | |
699 | NewPhiNodes.erase(I++); | |
700 | EliminatedAPHI = true; | |
701 | continue; | |
702 | } | |
703 | ++I; | |
704 | } | |
705 | } | |
1a4d82fc | 706 | |
223e47cc LB |
707 | // At this point, the renamer has added entries to PHI nodes for all reachable |
708 | // code. Unfortunately, there may be unreachable blocks which the renamer | |
709 | // hasn't traversed. If this is the case, the PHI nodes may not | |
710 | // have incoming values for all predecessors. Loop over all PHI nodes we have | |
711 | // created, inserting undef values if they are missing any incoming values. | |
712 | // | |
1a4d82fc JJ |
713 | for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator |
714 | I = NewPhiNodes.begin(), | |
715 | E = NewPhiNodes.end(); | |
716 | I != E; ++I) { | |
223e47cc LB |
717 | // We want to do this once per basic block. As such, only process a block |
718 | // when we find the PHI that is the first entry in the block. | |
719 | PHINode *SomePHI = I->second; | |
720 | BasicBlock *BB = SomePHI->getParent(); | |
721 | if (&BB->front() != SomePHI) | |
722 | continue; | |
723 | ||
724 | // Only do work here if there the PHI nodes are missing incoming values. We | |
725 | // know that all PHI nodes that were inserted in a block will have the same | |
726 | // number of incoming values, so we can just check any of them. | |
727 | if (SomePHI->getNumIncomingValues() == getNumPreds(BB)) | |
728 | continue; | |
729 | ||
730 | // Get the preds for BB. | |
1a4d82fc JJ |
731 | SmallVector<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB)); |
732 | ||
223e47cc LB |
733 | // Ok, now we know that all of the PHI nodes are missing entries for some |
734 | // basic blocks. Start by sorting the incoming predecessors for efficient | |
735 | // access. | |
736 | std::sort(Preds.begin(), Preds.end()); | |
1a4d82fc | 737 | |
223e47cc LB |
738 | // Now we loop through all BB's which have entries in SomePHI and remove |
739 | // them from the Preds list. | |
740 | for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i) { | |
741 | // Do a log(n) search of the Preds list for the entry we want. | |
1a4d82fc JJ |
742 | SmallVectorImpl<BasicBlock *>::iterator EntIt = std::lower_bound( |
743 | Preds.begin(), Preds.end(), SomePHI->getIncomingBlock(i)); | |
744 | assert(EntIt != Preds.end() && *EntIt == SomePHI->getIncomingBlock(i) && | |
223e47cc LB |
745 | "PHI node has entry for a block which is not a predecessor!"); |
746 | ||
747 | // Remove the entry | |
748 | Preds.erase(EntIt); | |
749 | } | |
750 | ||
751 | // At this point, the blocks left in the preds list must have dummy | |
752 | // entries inserted into every PHI nodes for the block. Update all the phi | |
753 | // nodes in this block that we are inserting (there could be phis before | |
754 | // mem2reg runs). | |
755 | unsigned NumBadPreds = SomePHI->getNumIncomingValues(); | |
756 | BasicBlock::iterator BBI = BB->begin(); | |
757 | while ((SomePHI = dyn_cast<PHINode>(BBI++)) && | |
758 | SomePHI->getNumIncomingValues() == NumBadPreds) { | |
759 | Value *UndefVal = UndefValue::get(SomePHI->getType()); | |
760 | for (unsigned pred = 0, e = Preds.size(); pred != e; ++pred) | |
761 | SomePHI->addIncoming(UndefVal, Preds[pred]); | |
762 | } | |
763 | } | |
1a4d82fc | 764 | |
223e47cc LB |
765 | NewPhiNodes.clear(); |
766 | } | |
767 | ||
1a4d82fc JJ |
768 | /// \brief Determine which blocks the value is live in. |
769 | /// | |
770 | /// These are blocks which lead to uses. Knowing this allows us to avoid | |
771 | /// inserting PHI nodes into blocks which don't lead to uses (thus, the | |
772 | /// inserted phi nodes would be dead). | |
773 | void PromoteMem2Reg::ComputeLiveInBlocks( | |
774 | AllocaInst *AI, AllocaInfo &Info, | |
775 | const SmallPtrSetImpl<BasicBlock *> &DefBlocks, | |
776 | SmallPtrSetImpl<BasicBlock *> &LiveInBlocks) { | |
223e47cc | 777 | |
223e47cc LB |
778 | // To determine liveness, we must iterate through the predecessors of blocks |
779 | // where the def is live. Blocks are added to the worklist if we need to | |
780 | // check their predecessors. Start with all the using blocks. | |
1a4d82fc JJ |
781 | SmallVector<BasicBlock *, 64> LiveInBlockWorklist(Info.UsingBlocks.begin(), |
782 | Info.UsingBlocks.end()); | |
783 | ||
223e47cc LB |
784 | // If any of the using blocks is also a definition block, check to see if the |
785 | // definition occurs before or after the use. If it happens before the use, | |
786 | // the value isn't really live-in. | |
787 | for (unsigned i = 0, e = LiveInBlockWorklist.size(); i != e; ++i) { | |
788 | BasicBlock *BB = LiveInBlockWorklist[i]; | |
1a4d82fc JJ |
789 | if (!DefBlocks.count(BB)) |
790 | continue; | |
791 | ||
223e47cc LB |
792 | // Okay, this is a block that both uses and defines the value. If the first |
793 | // reference to the alloca is a def (store), then we know it isn't live-in. | |
1a4d82fc | 794 | for (BasicBlock::iterator I = BB->begin();; ++I) { |
223e47cc | 795 | if (StoreInst *SI = dyn_cast<StoreInst>(I)) { |
1a4d82fc JJ |
796 | if (SI->getOperand(1) != AI) |
797 | continue; | |
798 | ||
223e47cc LB |
799 | // We found a store to the alloca before a load. The alloca is not |
800 | // actually live-in here. | |
801 | LiveInBlockWorklist[i] = LiveInBlockWorklist.back(); | |
802 | LiveInBlockWorklist.pop_back(); | |
803 | --i, --e; | |
804 | break; | |
805 | } | |
1a4d82fc | 806 | |
223e47cc | 807 | if (LoadInst *LI = dyn_cast<LoadInst>(I)) { |
1a4d82fc JJ |
808 | if (LI->getOperand(0) != AI) |
809 | continue; | |
810 | ||
223e47cc LB |
811 | // Okay, we found a load before a store to the alloca. It is actually |
812 | // live into this block. | |
813 | break; | |
814 | } | |
815 | } | |
816 | } | |
1a4d82fc | 817 | |
223e47cc LB |
818 | // Now that we have a set of blocks where the phi is live-in, recursively add |
819 | // their predecessors until we find the full region the value is live. | |
820 | while (!LiveInBlockWorklist.empty()) { | |
821 | BasicBlock *BB = LiveInBlockWorklist.pop_back_val(); | |
1a4d82fc | 822 | |
223e47cc LB |
823 | // The block really is live in here, insert it into the set. If already in |
824 | // the set, then it has already been processed. | |
85aaf69f | 825 | if (!LiveInBlocks.insert(BB).second) |
223e47cc | 826 | continue; |
1a4d82fc | 827 | |
223e47cc LB |
828 | // Since the value is live into BB, it is either defined in a predecessor or |
829 | // live into it to. Add the preds to the worklist unless they are a | |
830 | // defining block. | |
831 | for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { | |
832 | BasicBlock *P = *PI; | |
1a4d82fc | 833 | |
223e47cc LB |
834 | // The value is not live into a predecessor if it defines the value. |
835 | if (DefBlocks.count(P)) | |
836 | continue; | |
1a4d82fc | 837 | |
223e47cc LB |
838 | // Otherwise it is, add to the worklist. |
839 | LiveInBlockWorklist.push_back(P); | |
840 | } | |
841 | } | |
842 | } | |
843 | ||
1a4d82fc JJ |
844 | /// At this point, we're committed to promoting the alloca using IDF's, and the |
845 | /// standard SSA construction algorithm. Determine which blocks need phi nodes | |
846 | /// and see if we can optimize out some work by avoiding insertion of dead phi | |
847 | /// nodes. | |
223e47cc LB |
848 | void PromoteMem2Reg::DetermineInsertionPoint(AllocaInst *AI, unsigned AllocaNum, |
849 | AllocaInfo &Info) { | |
850 | // Unique the set of defining blocks for efficient lookup. | |
1a4d82fc | 851 | SmallPtrSet<BasicBlock *, 32> DefBlocks; |
223e47cc LB |
852 | DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end()); |
853 | ||
854 | // Determine which blocks the value is live in. These are blocks which lead | |
855 | // to uses. | |
1a4d82fc | 856 | SmallPtrSet<BasicBlock *, 32> LiveInBlocks; |
223e47cc LB |
857 | ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks); |
858 | ||
859 | // Use a priority queue keyed on dominator tree level so that inserted nodes | |
860 | // are handled from the bottom of the dominator tree upwards. | |
1a4d82fc | 861 | typedef std::pair<DomTreeNode *, unsigned> DomTreeNodePair; |
223e47cc | 862 | typedef std::priority_queue<DomTreeNodePair, SmallVector<DomTreeNodePair, 32>, |
1a4d82fc | 863 | less_second> IDFPriorityQueue; |
223e47cc LB |
864 | IDFPriorityQueue PQ; |
865 | ||
1a4d82fc JJ |
866 | for (BasicBlock *BB : DefBlocks) { |
867 | if (DomTreeNode *Node = DT.getNode(BB)) | |
223e47cc LB |
868 | PQ.push(std::make_pair(Node, DomLevels[Node])); |
869 | } | |
870 | ||
1a4d82fc JJ |
871 | SmallVector<std::pair<unsigned, BasicBlock *>, 32> DFBlocks; |
872 | SmallPtrSet<DomTreeNode *, 32> Visited; | |
873 | SmallVector<DomTreeNode *, 32> Worklist; | |
223e47cc LB |
874 | while (!PQ.empty()) { |
875 | DomTreeNodePair RootPair = PQ.top(); | |
876 | PQ.pop(); | |
877 | DomTreeNode *Root = RootPair.first; | |
878 | unsigned RootLevel = RootPair.second; | |
879 | ||
880 | // Walk all dominator tree children of Root, inspecting their CFG edges with | |
881 | // targets elsewhere on the dominator tree. Only targets whose level is at | |
882 | // most Root's level are added to the iterated dominance frontier of the | |
883 | // definition set. | |
884 | ||
885 | Worklist.clear(); | |
886 | Worklist.push_back(Root); | |
887 | ||
888 | while (!Worklist.empty()) { | |
889 | DomTreeNode *Node = Worklist.pop_back_val(); | |
890 | BasicBlock *BB = Node->getBlock(); | |
891 | ||
892 | for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; | |
893 | ++SI) { | |
894 | DomTreeNode *SuccNode = DT.getNode(*SI); | |
895 | ||
896 | // Quickly skip all CFG edges that are also dominator tree edges instead | |
897 | // of catching them below. | |
898 | if (SuccNode->getIDom() == Node) | |
899 | continue; | |
900 | ||
901 | unsigned SuccLevel = DomLevels[SuccNode]; | |
902 | if (SuccLevel > RootLevel) | |
903 | continue; | |
904 | ||
85aaf69f | 905 | if (!Visited.insert(SuccNode).second) |
223e47cc LB |
906 | continue; |
907 | ||
908 | BasicBlock *SuccBB = SuccNode->getBlock(); | |
909 | if (!LiveInBlocks.count(SuccBB)) | |
910 | continue; | |
911 | ||
912 | DFBlocks.push_back(std::make_pair(BBNumbers[SuccBB], SuccBB)); | |
913 | if (!DefBlocks.count(SuccBB)) | |
914 | PQ.push(std::make_pair(SuccNode, SuccLevel)); | |
915 | } | |
916 | ||
917 | for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end(); CI != CE; | |
918 | ++CI) { | |
919 | if (!Visited.count(*CI)) | |
920 | Worklist.push_back(*CI); | |
921 | } | |
922 | } | |
923 | } | |
924 | ||
925 | if (DFBlocks.size() > 1) | |
926 | std::sort(DFBlocks.begin(), DFBlocks.end()); | |
927 | ||
928 | unsigned CurrentVersion = 0; | |
929 | for (unsigned i = 0, e = DFBlocks.size(); i != e; ++i) | |
930 | QueuePhiNode(DFBlocks[i].second, AllocaNum, CurrentVersion); | |
931 | } | |
932 | ||
1a4d82fc | 933 | /// \brief Queue a phi-node to be added to a basic-block for a specific Alloca. |
223e47cc | 934 | /// |
1a4d82fc | 935 | /// Returns true if there wasn't already a phi-node for that variable |
223e47cc LB |
936 | bool PromoteMem2Reg::QueuePhiNode(BasicBlock *BB, unsigned AllocaNo, |
937 | unsigned &Version) { | |
938 | // Look up the basic-block in question. | |
970d7e83 | 939 | PHINode *&PN = NewPhiNodes[std::make_pair(BBNumbers[BB], AllocaNo)]; |
223e47cc LB |
940 | |
941 | // If the BB already has a phi node added for the i'th alloca then we're done! | |
1a4d82fc JJ |
942 | if (PN) |
943 | return false; | |
223e47cc LB |
944 | |
945 | // Create a PhiNode using the dereferenced type... and add the phi-node to the | |
946 | // BasicBlock. | |
947 | PN = PHINode::Create(Allocas[AllocaNo]->getAllocatedType(), getNumPreds(BB), | |
1a4d82fc | 948 | Allocas[AllocaNo]->getName() + "." + Twine(Version++), |
223e47cc LB |
949 | BB->begin()); |
950 | ++NumPHIInsert; | |
951 | PhiToAllocaMap[PN] = AllocaNo; | |
952 | ||
953 | if (AST && PN->getType()->isPointerTy()) | |
954 | AST->copyValue(PointerAllocaValues[AllocaNo], PN); | |
955 | ||
956 | return true; | |
957 | } | |
958 | ||
1a4d82fc JJ |
959 | /// \brief Recursively traverse the CFG of the function, renaming loads and |
960 | /// stores to the allocas which we are promoting. | |
961 | /// | |
962 | /// IncomingVals indicates what value each Alloca contains on exit from the | |
963 | /// predecessor block Pred. | |
223e47cc LB |
964 | void PromoteMem2Reg::RenamePass(BasicBlock *BB, BasicBlock *Pred, |
965 | RenamePassData::ValVector &IncomingVals, | |
966 | std::vector<RenamePassData> &Worklist) { | |
967 | NextIteration: | |
968 | // If we are inserting any phi nodes into this BB, they will already be in the | |
969 | // block. | |
970 | if (PHINode *APN = dyn_cast<PHINode>(BB->begin())) { | |
971 | // If we have PHI nodes to update, compute the number of edges from Pred to | |
972 | // BB. | |
973 | if (PhiToAllocaMap.count(APN)) { | |
974 | // We want to be able to distinguish between PHI nodes being inserted by | |
975 | // this invocation of mem2reg from those phi nodes that already existed in | |
976 | // the IR before mem2reg was run. We determine that APN is being inserted | |
977 | // because it is missing incoming edges. All other PHI nodes being | |
978 | // inserted by this pass of mem2reg will have the same number of incoming | |
979 | // operands so far. Remember this count. | |
980 | unsigned NewPHINumOperands = APN->getNumOperands(); | |
1a4d82fc JJ |
981 | |
982 | unsigned NumEdges = std::count(succ_begin(Pred), succ_end(Pred), BB); | |
223e47cc | 983 | assert(NumEdges && "Must be at least one edge from Pred to BB!"); |
1a4d82fc | 984 | |
223e47cc LB |
985 | // Add entries for all the phis. |
986 | BasicBlock::iterator PNI = BB->begin(); | |
987 | do { | |
988 | unsigned AllocaNo = PhiToAllocaMap[APN]; | |
1a4d82fc | 989 | |
223e47cc LB |
990 | // Add N incoming values to the PHI node. |
991 | for (unsigned i = 0; i != NumEdges; ++i) | |
992 | APN->addIncoming(IncomingVals[AllocaNo], Pred); | |
1a4d82fc | 993 | |
223e47cc LB |
994 | // The currently active variable for this block is now the PHI. |
995 | IncomingVals[AllocaNo] = APN; | |
1a4d82fc | 996 | |
223e47cc LB |
997 | // Get the next phi node. |
998 | ++PNI; | |
999 | APN = dyn_cast<PHINode>(PNI); | |
1a4d82fc JJ |
1000 | if (!APN) |
1001 | break; | |
1002 | ||
223e47cc LB |
1003 | // Verify that it is missing entries. If not, it is not being inserted |
1004 | // by this mem2reg invocation so we want to ignore it. | |
1005 | } while (APN->getNumOperands() == NewPHINumOperands); | |
1006 | } | |
1007 | } | |
1a4d82fc | 1008 | |
223e47cc | 1009 | // Don't revisit blocks. |
85aaf69f | 1010 | if (!Visited.insert(BB).second) |
1a4d82fc | 1011 | return; |
223e47cc | 1012 | |
1a4d82fc | 1013 | for (BasicBlock::iterator II = BB->begin(); !isa<TerminatorInst>(II);) { |
223e47cc LB |
1014 | Instruction *I = II++; // get the instruction, increment iterator |
1015 | ||
1016 | if (LoadInst *LI = dyn_cast<LoadInst>(I)) { | |
1017 | AllocaInst *Src = dyn_cast<AllocaInst>(LI->getPointerOperand()); | |
1a4d82fc JJ |
1018 | if (!Src) |
1019 | continue; | |
1020 | ||
1021 | DenseMap<AllocaInst *, unsigned>::iterator AI = AllocaLookup.find(Src); | |
1022 | if (AI == AllocaLookup.end()) | |
1023 | continue; | |
223e47cc LB |
1024 | |
1025 | Value *V = IncomingVals[AI->second]; | |
1026 | ||
1027 | // Anything using the load now uses the current value. | |
1028 | LI->replaceAllUsesWith(V); | |
1029 | if (AST && LI->getType()->isPointerTy()) | |
1030 | AST->deleteValue(LI); | |
1031 | BB->getInstList().erase(LI); | |
1032 | } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { | |
1033 | // Delete this instruction and mark the name as the current holder of the | |
1034 | // value | |
1035 | AllocaInst *Dest = dyn_cast<AllocaInst>(SI->getPointerOperand()); | |
1a4d82fc JJ |
1036 | if (!Dest) |
1037 | continue; | |
1038 | ||
223e47cc LB |
1039 | DenseMap<AllocaInst *, unsigned>::iterator ai = AllocaLookup.find(Dest); |
1040 | if (ai == AllocaLookup.end()) | |
1041 | continue; | |
1a4d82fc | 1042 | |
223e47cc LB |
1043 | // what value were we writing? |
1044 | IncomingVals[ai->second] = SI->getOperand(0); | |
1045 | // Record debuginfo for the store before removing it. | |
1a4d82fc JJ |
1046 | if (DbgDeclareInst *DDI = AllocaDbgDeclares[ai->second]) |
1047 | ConvertDebugDeclareToDebugValue(DDI, SI, DIB); | |
223e47cc LB |
1048 | BB->getInstList().erase(SI); |
1049 | } | |
1050 | } | |
1051 | ||
1052 | // 'Recurse' to our successors. | |
1053 | succ_iterator I = succ_begin(BB), E = succ_end(BB); | |
1a4d82fc JJ |
1054 | if (I == E) |
1055 | return; | |
223e47cc LB |
1056 | |
1057 | // Keep track of the successors so we don't visit the same successor twice | |
1a4d82fc | 1058 | SmallPtrSet<BasicBlock *, 8> VisitedSuccs; |
223e47cc LB |
1059 | |
1060 | // Handle the first successor without using the worklist. | |
1061 | VisitedSuccs.insert(*I); | |
1062 | Pred = BB; | |
1063 | BB = *I; | |
1064 | ++I; | |
1065 | ||
1066 | for (; I != E; ++I) | |
85aaf69f | 1067 | if (VisitedSuccs.insert(*I).second) |
223e47cc LB |
1068 | Worklist.push_back(RenamePassData(*I, Pred, IncomingVals)); |
1069 | ||
1070 | goto NextIteration; | |
1071 | } | |
1072 | ||
1a4d82fc | 1073 | void llvm::PromoteMemToReg(ArrayRef<AllocaInst *> Allocas, DominatorTree &DT, |
85aaf69f | 1074 | AliasSetTracker *AST, AssumptionCache *AC) { |
223e47cc | 1075 | // If there is nothing to do, bail out... |
1a4d82fc JJ |
1076 | if (Allocas.empty()) |
1077 | return; | |
223e47cc | 1078 | |
85aaf69f | 1079 | PromoteMem2Reg(Allocas, DT, AST, AC).run(); |
223e47cc | 1080 | } |