Bug Summary

File:lib/Transforms/Utils/MemorySSA.cpp
Warning:line 852, column 37
Called C++ object pointer is null

Annotated Source Code

1//===-- MemorySSA.cpp - Memory SSA Builder---------------------------===//
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 implements the MemorySSA class.
11//
12//===----------------------------------------------------------------===//
13#include "llvm/Transforms/Utils/MemorySSA.h"
14#include "llvm/ADT/DenseMap.h"
15#include "llvm/ADT/DenseSet.h"
16#include "llvm/ADT/DepthFirstIterator.h"
17#include "llvm/ADT/GraphTraits.h"
18#include "llvm/ADT/PostOrderIterator.h"
19#include "llvm/ADT/STLExtras.h"
20#include "llvm/ADT/SmallBitVector.h"
21#include "llvm/ADT/SmallPtrSet.h"
22#include "llvm/ADT/SmallSet.h"
23#include "llvm/ADT/Statistic.h"
24#include "llvm/Analysis/AliasAnalysis.h"
25#include "llvm/Analysis/CFG.h"
26#include "llvm/Analysis/GlobalsModRef.h"
27#include "llvm/Analysis/IteratedDominanceFrontier.h"
28#include "llvm/Analysis/MemoryLocation.h"
29#include "llvm/Analysis/PHITransAddr.h"
30#include "llvm/IR/AssemblyAnnotationWriter.h"
31#include "llvm/IR/DataLayout.h"
32#include "llvm/IR/Dominators.h"
33#include "llvm/IR/GlobalVariable.h"
34#include "llvm/IR/IRBuilder.h"
35#include "llvm/IR/IntrinsicInst.h"
36#include "llvm/IR/LLVMContext.h"
37#include "llvm/IR/Metadata.h"
38#include "llvm/IR/Module.h"
39#include "llvm/IR/PatternMatch.h"
40#include "llvm/Support/Debug.h"
41#include "llvm/Support/FormattedStream.h"
42#include "llvm/Transforms/Scalar.h"
43#include <algorithm>
44
45#define DEBUG_TYPE"memoryssa" "memoryssa"
46using namespace llvm;
47STATISTIC(NumClobberCacheLookups, "Number of Memory SSA version cache lookups")static llvm::Statistic NumClobberCacheLookups = {"memoryssa",
"NumClobberCacheLookups", "Number of Memory SSA version cache lookups"
, {0}, false};
48STATISTIC(NumClobberCacheHits, "Number of Memory SSA version cache hits")static llvm::Statistic NumClobberCacheHits = {"memoryssa", "NumClobberCacheHits"
, "Number of Memory SSA version cache hits", {0}, false};
49STATISTIC(NumClobberCacheInserts, "Number of MemorySSA version cache inserts")static llvm::Statistic NumClobberCacheInserts = {"memoryssa",
"NumClobberCacheInserts", "Number of MemorySSA version cache inserts"
, {0}, false};
50
51INITIALIZE_PASS_BEGIN(MemorySSAWrapperPass, "memoryssa", "Memory SSA", false,static void *initializeMemorySSAWrapperPassPassOnce(PassRegistry
&Registry) {
52 true)static void *initializeMemorySSAWrapperPassPassOnce(PassRegistry
&Registry) {
53INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
54INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)initializeAAResultsWrapperPassPass(Registry);
55INITIALIZE_PASS_END(MemorySSAWrapperPass, "memoryssa", "Memory SSA", false,PassInfo *PI = new PassInfo( "Memory SSA", "memoryssa", &
MemorySSAWrapperPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<MemorySSAWrapperPass>), false, true); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeMemorySSAWrapperPassPassFlag
; void llvm::initializeMemorySSAWrapperPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemorySSAWrapperPassPassFlag
, initializeMemorySSAWrapperPassPassOnce, std::ref(Registry))
; }
56 true)PassInfo *PI = new PassInfo( "Memory SSA", "memoryssa", &
MemorySSAWrapperPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<MemorySSAWrapperPass>), false, true); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeMemorySSAWrapperPassPassFlag
; void llvm::initializeMemorySSAWrapperPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemorySSAWrapperPassPassFlag
, initializeMemorySSAWrapperPassPassOnce, std::ref(Registry))
; }
57
58INITIALIZE_PASS_BEGIN(MemorySSAPrinterLegacyPass, "print-memoryssa",static void *initializeMemorySSAPrinterLegacyPassPassOnce(PassRegistry
&Registry) {
59 "Memory SSA Printer", false, false)static void *initializeMemorySSAPrinterLegacyPassPassOnce(PassRegistry
&Registry) {
60INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry);
61INITIALIZE_PASS_END(MemorySSAPrinterLegacyPass, "print-memoryssa",PassInfo *PI = new PassInfo( "Memory SSA Printer", "print-memoryssa"
, &MemorySSAPrinterLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<MemorySSAPrinterLegacyPass>), false, false
); Registry.registerPass(*PI, true); return PI; } static llvm
::once_flag InitializeMemorySSAPrinterLegacyPassPassFlag; void
llvm::initializeMemorySSAPrinterLegacyPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemorySSAPrinterLegacyPassPassFlag
, initializeMemorySSAPrinterLegacyPassPassOnce, std::ref(Registry
)); }
62 "Memory SSA Printer", false, false)PassInfo *PI = new PassInfo( "Memory SSA Printer", "print-memoryssa"
, &MemorySSAPrinterLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<MemorySSAPrinterLegacyPass>), false, false
); Registry.registerPass(*PI, true); return PI; } static llvm
::once_flag InitializeMemorySSAPrinterLegacyPassPassFlag; void
llvm::initializeMemorySSAPrinterLegacyPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeMemorySSAPrinterLegacyPassPassFlag
, initializeMemorySSAPrinterLegacyPassPassOnce, std::ref(Registry
)); }
63
64static cl::opt<unsigned> MaxCheckLimit(
65 "memssa-check-limit", cl::Hidden, cl::init(100),
66 cl::desc("The maximum number of stores/phis MemorySSA"
67 "will consider trying to walk past (default = 100)"));
68
69static cl::opt<bool>
70 VerifyMemorySSA("verify-memoryssa", cl::init(false), cl::Hidden,
71 cl::desc("Verify MemorySSA in legacy printer pass."));
72
73namespace llvm {
74/// \brief An assembly annotator class to print Memory SSA information in
75/// comments.
76class MemorySSAAnnotatedWriter : public AssemblyAnnotationWriter {
77 friend class MemorySSA;
78 const MemorySSA *MSSA;
79
80public:
81 MemorySSAAnnotatedWriter(const MemorySSA *M) : MSSA(M) {}
82
83 virtual void emitBasicBlockStartAnnot(const BasicBlock *BB,
84 formatted_raw_ostream &OS) {
85 if (MemoryAccess *MA = MSSA->getMemoryAccess(BB))
86 OS << "; " << *MA << "\n";
87 }
88
89 virtual void emitInstructionAnnot(const Instruction *I,
90 formatted_raw_ostream &OS) {
91 if (MemoryAccess *MA = MSSA->getMemoryAccess(I))
92 OS << "; " << *MA << "\n";
93 }
94};
95}
96
97namespace {
98/// Our current alias analysis API differentiates heavily between calls and
99/// non-calls, and functions called on one usually assert on the other.
100/// This class encapsulates the distinction to simplify other code that wants
101/// "Memory affecting instructions and related data" to use as a key.
102/// For example, this class is used as a densemap key in the use optimizer.
103class MemoryLocOrCall {
104public:
105 MemoryLocOrCall() : IsCall(false) {}
106 MemoryLocOrCall(MemoryUseOrDef *MUD)
107 : MemoryLocOrCall(MUD->getMemoryInst()) {}
108 MemoryLocOrCall(const MemoryUseOrDef *MUD)
109 : MemoryLocOrCall(MUD->getMemoryInst()) {}
110
111 MemoryLocOrCall(Instruction *Inst) {
112 if (ImmutableCallSite(Inst)) {
113 IsCall = true;
114 CS = ImmutableCallSite(Inst);
115 } else {
116 IsCall = false;
117 // There is no such thing as a memorylocation for a fence inst, and it is
118 // unique in that regard.
119 if (!isa<FenceInst>(Inst))
120 Loc = MemoryLocation::get(Inst);
121 }
122 }
123
124 explicit MemoryLocOrCall(const MemoryLocation &Loc)
125 : IsCall(false), Loc(Loc) {}
126
127 bool IsCall;
128 ImmutableCallSite getCS() const {
129 assert(IsCall)((IsCall) ? static_cast<void> (0) : __assert_fail ("IsCall"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 129, __PRETTY_FUNCTION__));
130 return CS;
131 }
132 MemoryLocation getLoc() const {
133 assert(!IsCall)((!IsCall) ? static_cast<void> (0) : __assert_fail ("!IsCall"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 133, __PRETTY_FUNCTION__));
134 return Loc;
135 }
136
137 bool operator==(const MemoryLocOrCall &Other) const {
138 if (IsCall != Other.IsCall)
139 return false;
140
141 if (IsCall)
142 return CS.getCalledValue() == Other.CS.getCalledValue();
143 return Loc == Other.Loc;
144 }
145
146private:
147 union {
148 ImmutableCallSite CS;
149 MemoryLocation Loc;
150 };
151};
152}
153
154namespace llvm {
155template <> struct DenseMapInfo<MemoryLocOrCall> {
156 static inline MemoryLocOrCall getEmptyKey() {
157 return MemoryLocOrCall(DenseMapInfo<MemoryLocation>::getEmptyKey());
158 }
159 static inline MemoryLocOrCall getTombstoneKey() {
160 return MemoryLocOrCall(DenseMapInfo<MemoryLocation>::getTombstoneKey());
161 }
162 static unsigned getHashValue(const MemoryLocOrCall &MLOC) {
163 if (MLOC.IsCall)
164 return hash_combine(MLOC.IsCall,
165 DenseMapInfo<const Value *>::getHashValue(
166 MLOC.getCS().getCalledValue()));
167 return hash_combine(
168 MLOC.IsCall, DenseMapInfo<MemoryLocation>::getHashValue(MLOC.getLoc()));
169 }
170 static bool isEqual(const MemoryLocOrCall &LHS, const MemoryLocOrCall &RHS) {
171 return LHS == RHS;
172 }
173};
174
175enum class Reorderability { Always, IfNoAlias, Never };
176
177/// This does one-way checks to see if Use could theoretically be hoisted above
178/// MayClobber. This will not check the other way around.
179///
180/// This assumes that, for the purposes of MemorySSA, Use comes directly after
181/// MayClobber, with no potentially clobbering operations in between them.
182/// (Where potentially clobbering ops are memory barriers, aliased stores, etc.)
183static Reorderability getLoadReorderability(const LoadInst *Use,
184 const LoadInst *MayClobber) {
185 bool VolatileUse = Use->isVolatile();
186 bool VolatileClobber = MayClobber->isVolatile();
187 // Volatile operations may never be reordered with other volatile operations.
188 if (VolatileUse && VolatileClobber)
189 return Reorderability::Never;
190
191 // The lang ref allows reordering of volatile and non-volatile operations.
192 // Whether an aliasing nonvolatile load and volatile load can be reordered,
193 // though, is ambiguous. Because it may not be best to exploit this ambiguity,
194 // we only allow volatile/non-volatile reordering if the volatile and
195 // non-volatile operations don't alias.
196 Reorderability Result = VolatileUse || VolatileClobber
197 ? Reorderability::IfNoAlias
198 : Reorderability::Always;
199
200 // If a load is seq_cst, it cannot be moved above other loads. If its ordering
201 // is weaker, it can be moved above other loads. We just need to be sure that
202 // MayClobber isn't an acquire load, because loads can't be moved above
203 // acquire loads.
204 //
205 // Note that this explicitly *does* allow the free reordering of monotonic (or
206 // weaker) loads of the same address.
207 bool SeqCstUse = Use->getOrdering() == AtomicOrdering::SequentiallyConsistent;
208 bool MayClobberIsAcquire = isAtLeastOrStrongerThan(MayClobber->getOrdering(),
209 AtomicOrdering::Acquire);
210 if (SeqCstUse || MayClobberIsAcquire)
211 return Reorderability::Never;
212 return Result;
213}
214
215static bool instructionClobbersQuery(MemoryDef *MD,
216 const MemoryLocation &UseLoc,
217 const Instruction *UseInst,
218 AliasAnalysis &AA) {
219 Instruction *DefInst = MD->getMemoryInst();
220 assert(DefInst && "Defining instruction not actually an instruction")((DefInst && "Defining instruction not actually an instruction"
) ? static_cast<void> (0) : __assert_fail ("DefInst && \"Defining instruction not actually an instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 220, __PRETTY_FUNCTION__));
221
222 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) {
223 // These intrinsics will show up as affecting memory, but they are just
224 // markers.
225 switch (II->getIntrinsicID()) {
226 case Intrinsic::lifetime_start:
227 case Intrinsic::lifetime_end:
228 case Intrinsic::invariant_start:
229 case Intrinsic::invariant_end:
230 case Intrinsic::assume:
231 return false;
232 default:
233 break;
234 }
235 }
236
237 ImmutableCallSite UseCS(UseInst);
238 if (UseCS) {
239 ModRefInfo I = AA.getModRefInfo(DefInst, UseCS);
240 return I != MRI_NoModRef;
241 }
242
243 if (auto *DefLoad = dyn_cast<LoadInst>(DefInst)) {
244 if (auto *UseLoad = dyn_cast<LoadInst>(UseInst)) {
245 switch (getLoadReorderability(UseLoad, DefLoad)) {
246 case Reorderability::Always:
247 return false;
248 case Reorderability::Never:
249 return true;
250 case Reorderability::IfNoAlias:
251 return !AA.isNoAlias(UseLoc, MemoryLocation::get(DefLoad));
252 }
253 }
254 }
255
256 return AA.getModRefInfo(DefInst, UseLoc) & MRI_Mod;
257}
258
259static bool instructionClobbersQuery(MemoryDef *MD, const MemoryUseOrDef *MU,
260 const MemoryLocOrCall &UseMLOC,
261 AliasAnalysis &AA) {
262 // FIXME: This is a temporary hack to allow a single instructionClobbersQuery
263 // to exist while MemoryLocOrCall is pushed through places.
264 if (UseMLOC.IsCall)
265 return instructionClobbersQuery(MD, MemoryLocation(), MU->getMemoryInst(),
266 AA);
267 return instructionClobbersQuery(MD, UseMLOC.getLoc(), MU->getMemoryInst(),
268 AA);
269}
270
271// Return true when MD may alias MU, return false otherwise.
272bool MemorySSAUtil::defClobbersUseOrDef(MemoryDef *MD, const MemoryUseOrDef *MU,
273 AliasAnalysis &AA) {
274 return instructionClobbersQuery(MD, MU, MemoryLocOrCall(MU), AA);
275}
276}
277
278namespace {
279struct UpwardsMemoryQuery {
280 // True if our original query started off as a call
281 bool IsCall;
282 // The pointer location we started the query with. This will be empty if
283 // IsCall is true.
284 MemoryLocation StartingLoc;
285 // This is the instruction we were querying about.
286 const Instruction *Inst;
287 // The MemoryAccess we actually got called with, used to test local domination
288 const MemoryAccess *OriginalAccess;
289
290 UpwardsMemoryQuery()
291 : IsCall(false), Inst(nullptr), OriginalAccess(nullptr) {}
292
293 UpwardsMemoryQuery(const Instruction *Inst, const MemoryAccess *Access)
294 : IsCall(ImmutableCallSite(Inst)), Inst(Inst), OriginalAccess(Access) {
295 if (!IsCall)
296 StartingLoc = MemoryLocation::get(Inst);
297 }
298};
299
300static bool lifetimeEndsAt(MemoryDef *MD, const MemoryLocation &Loc,
301 AliasAnalysis &AA) {
302 Instruction *Inst = MD->getMemoryInst();
303 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
304 switch (II->getIntrinsicID()) {
305 case Intrinsic::lifetime_start:
306 case Intrinsic::lifetime_end:
307 return AA.isMustAlias(MemoryLocation(II->getArgOperand(1)), Loc);
308 default:
309 return false;
310 }
311 }
312 return false;
313}
314
315static bool isUseTriviallyOptimizableToLiveOnEntry(AliasAnalysis &AA,
316 const Instruction *I) {
317 // If the memory can't be changed, then loads of the memory can't be
318 // clobbered.
319 //
320 // FIXME: We should handle invariant groups, as well. It's a bit harder,
321 // because we need to pay close attention to invariant group barriers.
322 return isa<LoadInst>(I) && (I->getMetadata(LLVMContext::MD_invariant_load) ||
323 AA.pointsToConstantMemory(I));
324}
325
326/// Cache for our caching MemorySSA walker.
327class WalkerCache {
328 DenseMap<ConstMemoryAccessPair, MemoryAccess *> Accesses;
329 DenseMap<const MemoryAccess *, MemoryAccess *> Calls;
330
331public:
332 MemoryAccess *lookup(const MemoryAccess *MA, const MemoryLocation &Loc,
333 bool IsCall) const {
334 ++NumClobberCacheLookups;
335 MemoryAccess *R = IsCall ? Calls.lookup(MA) : Accesses.lookup({MA, Loc});
336 if (R)
337 ++NumClobberCacheHits;
338 return R;
339 }
340
341 bool insert(const MemoryAccess *MA, MemoryAccess *To,
342 const MemoryLocation &Loc, bool IsCall) {
343 // This is fine for Phis, since there are times where we can't optimize
344 // them. Making a def its own clobber is never correct, though.
345 assert((MA != To || isa<MemoryPhi>(MA)) &&(((MA != To || isa<MemoryPhi>(MA)) && "Something can't clobber itself!"
) ? static_cast<void> (0) : __assert_fail ("(MA != To || isa<MemoryPhi>(MA)) && \"Something can't clobber itself!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 346, __PRETTY_FUNCTION__))
346 "Something can't clobber itself!")(((MA != To || isa<MemoryPhi>(MA)) && "Something can't clobber itself!"
) ? static_cast<void> (0) : __assert_fail ("(MA != To || isa<MemoryPhi>(MA)) && \"Something can't clobber itself!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 346, __PRETTY_FUNCTION__));
347
348 ++NumClobberCacheInserts;
349 bool Inserted;
350 if (IsCall)
351 Inserted = Calls.insert({MA, To}).second;
352 else
353 Inserted = Accesses.insert({{MA, Loc}, To}).second;
354
355 return Inserted;
356 }
357
358 bool remove(const MemoryAccess *MA, const MemoryLocation &Loc, bool IsCall) {
359 return IsCall ? Calls.erase(MA) : Accesses.erase({MA, Loc});
360 }
361
362 void clear() {
363 Accesses.clear();
364 Calls.clear();
365 }
366
367 bool contains(const MemoryAccess *MA) const {
368 for (auto &P : Accesses)
369 if (P.first.first == MA || P.second == MA)
370 return true;
371 for (auto &P : Calls)
372 if (P.first == MA || P.second == MA)
373 return true;
374 return false;
375 }
376};
377
378/// Verifies that `Start` is clobbered by `ClobberAt`, and that nothing
379/// inbetween `Start` and `ClobberAt` can clobbers `Start`.
380///
381/// This is meant to be as simple and self-contained as possible. Because it
382/// uses no cache, etc., it can be relatively expensive.
383///
384/// \param Start The MemoryAccess that we want to walk from.
385/// \param ClobberAt A clobber for Start.
386/// \param StartLoc The MemoryLocation for Start.
387/// \param MSSA The MemorySSA isntance that Start and ClobberAt belong to.
388/// \param Query The UpwardsMemoryQuery we used for our search.
389/// \param AA The AliasAnalysis we used for our search.
390static void LLVM_ATTRIBUTE_UNUSED__attribute__((__unused__))
391checkClobberSanity(MemoryAccess *Start, MemoryAccess *ClobberAt,
392 const MemoryLocation &StartLoc, const MemorySSA &MSSA,
393 const UpwardsMemoryQuery &Query, AliasAnalysis &AA) {
394 assert(MSSA.dominates(ClobberAt, Start) && "Clobber doesn't dominate start?")((MSSA.dominates(ClobberAt, Start) && "Clobber doesn't dominate start?"
) ? static_cast<void> (0) : __assert_fail ("MSSA.dominates(ClobberAt, Start) && \"Clobber doesn't dominate start?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 394, __PRETTY_FUNCTION__));
395
396 if (MSSA.isLiveOnEntryDef(Start)) {
397 assert(MSSA.isLiveOnEntryDef(ClobberAt) &&((MSSA.isLiveOnEntryDef(ClobberAt) && "liveOnEntry must clobber itself"
) ? static_cast<void> (0) : __assert_fail ("MSSA.isLiveOnEntryDef(ClobberAt) && \"liveOnEntry must clobber itself\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 398, __PRETTY_FUNCTION__))
398 "liveOnEntry must clobber itself")((MSSA.isLiveOnEntryDef(ClobberAt) && "liveOnEntry must clobber itself"
) ? static_cast<void> (0) : __assert_fail ("MSSA.isLiveOnEntryDef(ClobberAt) && \"liveOnEntry must clobber itself\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 398, __PRETTY_FUNCTION__));
399 return;
400 }
401
402 bool FoundClobber = false;
403 DenseSet<MemoryAccessPair> VisitedPhis;
404 SmallVector<MemoryAccessPair, 8> Worklist;
405 Worklist.emplace_back(Start, StartLoc);
406 // Walk all paths from Start to ClobberAt, while looking for clobbers. If one
407 // is found, complain.
408 while (!Worklist.empty()) {
409 MemoryAccessPair MAP = Worklist.pop_back_val();
410 // All we care about is that nothing from Start to ClobberAt clobbers Start.
411 // We learn nothing from revisiting nodes.
412 if (!VisitedPhis.insert(MAP).second)
413 continue;
414
415 for (MemoryAccess *MA : def_chain(MAP.first)) {
416 if (MA == ClobberAt) {
417 if (auto *MD = dyn_cast<MemoryDef>(MA)) {
418 // instructionClobbersQuery isn't essentially free, so don't use `|=`,
419 // since it won't let us short-circuit.
420 //
421 // Also, note that this can't be hoisted out of the `Worklist` loop,
422 // since MD may only act as a clobber for 1 of N MemoryLocations.
423 FoundClobber =
424 FoundClobber || MSSA.isLiveOnEntryDef(MD) ||
425 instructionClobbersQuery(MD, MAP.second, Query.Inst, AA);
426 }
427 break;
428 }
429
430 // We should never hit liveOnEntry, unless it's the clobber.
431 assert(!MSSA.isLiveOnEntryDef(MA) && "Hit liveOnEntry before clobber?")((!MSSA.isLiveOnEntryDef(MA) && "Hit liveOnEntry before clobber?"
) ? static_cast<void> (0) : __assert_fail ("!MSSA.isLiveOnEntryDef(MA) && \"Hit liveOnEntry before clobber?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 431, __PRETTY_FUNCTION__));
432
433 if (auto *MD = dyn_cast<MemoryDef>(MA)) {
434 (void)MD;
435 assert(!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA) &&((!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA) &&
"Found clobber before reaching ClobberAt!") ? static_cast<
void> (0) : __assert_fail ("!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA) && \"Found clobber before reaching ClobberAt!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 436, __PRETTY_FUNCTION__))
436 "Found clobber before reaching ClobberAt!")((!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA) &&
"Found clobber before reaching ClobberAt!") ? static_cast<
void> (0) : __assert_fail ("!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA) && \"Found clobber before reaching ClobberAt!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 436, __PRETTY_FUNCTION__));
437 continue;
438 }
439
440 assert(isa<MemoryPhi>(MA))((isa<MemoryPhi>(MA)) ? static_cast<void> (0) : __assert_fail
("isa<MemoryPhi>(MA)", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 440, __PRETTY_FUNCTION__));
441 Worklist.append(upward_defs_begin({MA, MAP.second}), upward_defs_end());
442 }
443 }
444
445 // If ClobberAt is a MemoryPhi, we can assume something above it acted as a
446 // clobber. Otherwise, `ClobberAt` should've acted as a clobber at some point.
447 assert((isa<MemoryPhi>(ClobberAt) || FoundClobber) &&(((isa<MemoryPhi>(ClobberAt) || FoundClobber) &&
"ClobberAt never acted as a clobber") ? static_cast<void>
(0) : __assert_fail ("(isa<MemoryPhi>(ClobberAt) || FoundClobber) && \"ClobberAt never acted as a clobber\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 448, __PRETTY_FUNCTION__))
448 "ClobberAt never acted as a clobber")(((isa<MemoryPhi>(ClobberAt) || FoundClobber) &&
"ClobberAt never acted as a clobber") ? static_cast<void>
(0) : __assert_fail ("(isa<MemoryPhi>(ClobberAt) || FoundClobber) && \"ClobberAt never acted as a clobber\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 448, __PRETTY_FUNCTION__));
449}
450
451/// Our algorithm for walking (and trying to optimize) clobbers, all wrapped up
452/// in one class.
453class ClobberWalker {
454 /// Save a few bytes by using unsigned instead of size_t.
455 using ListIndex = unsigned;
456
457 /// Represents a span of contiguous MemoryDefs, potentially ending in a
458 /// MemoryPhi.
459 struct DefPath {
460 MemoryLocation Loc;
461 // Note that, because we always walk in reverse, Last will always dominate
462 // First. Also note that First and Last are inclusive.
463 MemoryAccess *First;
464 MemoryAccess *Last;
465 Optional<ListIndex> Previous;
466
467 DefPath(const MemoryLocation &Loc, MemoryAccess *First, MemoryAccess *Last,
468 Optional<ListIndex> Previous)
469 : Loc(Loc), First(First), Last(Last), Previous(Previous) {}
470
471 DefPath(const MemoryLocation &Loc, MemoryAccess *Init,
472 Optional<ListIndex> Previous)
473 : DefPath(Loc, Init, Init, Previous) {}
474 };
475
476 const MemorySSA &MSSA;
477 AliasAnalysis &AA;
478 DominatorTree &DT;
479 WalkerCache &WC;
480 UpwardsMemoryQuery *Query;
481 bool UseCache;
482
483 // Phi optimization bookkeeping
484 SmallVector<DefPath, 32> Paths;
485 DenseSet<ConstMemoryAccessPair> VisitedPhis;
486
487 void setUseCache(bool Use) { UseCache = Use; }
488 bool shouldIgnoreCache() const {
489 // UseCache will only be false when we're debugging, or when expensive
490 // checks are enabled. In either case, we don't care deeply about speed.
491 return LLVM_UNLIKELY(!UseCache)__builtin_expect((bool)(!UseCache), false);
492 }
493
494 void addCacheEntry(const MemoryAccess *What, MemoryAccess *To,
495 const MemoryLocation &Loc) const {
496// EXPENSIVE_CHECKS because most of these queries are redundant.
497#ifdef EXPENSIVE_CHECKS
498 assert(MSSA.dominates(To, What))((MSSA.dominates(To, What)) ? static_cast<void> (0) : __assert_fail
("MSSA.dominates(To, What)", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 498, __PRETTY_FUNCTION__));
499#endif
500 if (shouldIgnoreCache())
501 return;
502 WC.insert(What, To, Loc, Query->IsCall);
503 }
504
505 MemoryAccess *lookupCache(const MemoryAccess *MA,
506 const MemoryLocation &Loc) const {
507 return shouldIgnoreCache() ? nullptr : WC.lookup(MA, Loc, Query->IsCall);
508 }
509
510 void cacheDefPath(const DefPath &DN, MemoryAccess *Target) const {
511 if (shouldIgnoreCache())
512 return;
513
514 for (MemoryAccess *MA : def_chain(DN.First, DN.Last))
515 addCacheEntry(MA, Target, DN.Loc);
516
517 // DefPaths only express the path we walked. So, DN.Last could either be a
518 // thing we want to cache, or not.
519 if (DN.Last != Target)
520 addCacheEntry(DN.Last, Target, DN.Loc);
521 }
522
523 /// Find the nearest def or phi that `From` can legally be optimized to.
524 const MemoryAccess *getWalkTarget(const MemoryPhi *From) const {
525 assert(From->getNumOperands() && "Phi with no operands?")((From->getNumOperands() && "Phi with no operands?"
) ? static_cast<void> (0) : __assert_fail ("From->getNumOperands() && \"Phi with no operands?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 525, __PRETTY_FUNCTION__));
526
527 BasicBlock *BB = From->getBlock();
528 MemoryAccess *Result = MSSA.getLiveOnEntryDef();
529 DomTreeNode *Node = DT.getNode(BB);
530 while ((Node = Node->getIDom())) {
531 auto *Defs = MSSA.getBlockDefs(Node->getBlock());
532 if (Defs)
533 return &*Defs->rbegin();
534 }
535 return Result;
536 }
537
538 /// Result of calling walkToPhiOrClobber.
539 struct UpwardsWalkResult {
540 /// The "Result" of the walk. Either a clobber, the last thing we walked, or
541 /// both.
542 MemoryAccess *Result;
543 bool IsKnownClobber;
544 bool FromCache;
545 };
546
547 /// Walk to the next Phi or Clobber in the def chain starting at Desc.Last.
548 /// This will update Desc.Last as it walks. It will (optionally) also stop at
549 /// StopAt.
550 ///
551 /// This does not test for whether StopAt is a clobber
552 UpwardsWalkResult
553 walkToPhiOrClobber(DefPath &Desc,
554 const MemoryAccess *StopAt = nullptr) const {
555 assert(!isa<MemoryUse>(Desc.Last) && "Uses don't exist in my world")((!isa<MemoryUse>(Desc.Last) && "Uses don't exist in my world"
) ? static_cast<void> (0) : __assert_fail ("!isa<MemoryUse>(Desc.Last) && \"Uses don't exist in my world\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 555, __PRETTY_FUNCTION__));
556
557 for (MemoryAccess *Current : def_chain(Desc.Last)) {
558 Desc.Last = Current;
559 if (Current == StopAt)
560 return {Current, false, false};
561
562 if (auto *MD = dyn_cast<MemoryDef>(Current))
563 if (MSSA.isLiveOnEntryDef(MD) ||
564 instructionClobbersQuery(MD, Desc.Loc, Query->Inst, AA))
565 return {MD, true, false};
566
567 // Cache checks must be done last, because if Current is a clobber, the
568 // cache will contain the clobber for Current.
569 if (MemoryAccess *MA = lookupCache(Current, Desc.Loc))
570 return {MA, true, true};
571 }
572
573 assert(isa<MemoryPhi>(Desc.Last) &&((isa<MemoryPhi>(Desc.Last) && "Ended at a non-clobber that's not a phi?"
) ? static_cast<void> (0) : __assert_fail ("isa<MemoryPhi>(Desc.Last) && \"Ended at a non-clobber that's not a phi?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 574, __PRETTY_FUNCTION__))
574 "Ended at a non-clobber that's not a phi?")((isa<MemoryPhi>(Desc.Last) && "Ended at a non-clobber that's not a phi?"
) ? static_cast<void> (0) : __assert_fail ("isa<MemoryPhi>(Desc.Last) && \"Ended at a non-clobber that's not a phi?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 574, __PRETTY_FUNCTION__));
575 return {Desc.Last, false, false};
576 }
577
578 void addSearches(MemoryPhi *Phi, SmallVectorImpl<ListIndex> &PausedSearches,
579 ListIndex PriorNode) {
580 auto UpwardDefs = make_range(upward_defs_begin({Phi, Paths[PriorNode].Loc}),
581 upward_defs_end());
582 for (const MemoryAccessPair &P : UpwardDefs) {
583 PausedSearches.push_back(Paths.size());
584 Paths.emplace_back(P.second, P.first, PriorNode);
585 }
586 }
587
588 /// Represents a search that terminated after finding a clobber. This clobber
589 /// may or may not be present in the path of defs from LastNode..SearchStart,
590 /// since it may have been retrieved from cache.
591 struct TerminatedPath {
592 MemoryAccess *Clobber;
593 ListIndex LastNode;
594 };
595
596 /// Get an access that keeps us from optimizing to the given phi.
597 ///
598 /// PausedSearches is an array of indices into the Paths array. Its incoming
599 /// value is the indices of searches that stopped at the last phi optimization
600 /// target. It's left in an unspecified state.
601 ///
602 /// If this returns None, NewPaused is a vector of searches that terminated
603 /// at StopWhere. Otherwise, NewPaused is left in an unspecified state.
604 Optional<TerminatedPath>
605 getBlockingAccess(const MemoryAccess *StopWhere,
606 SmallVectorImpl<ListIndex> &PausedSearches,
607 SmallVectorImpl<ListIndex> &NewPaused,
608 SmallVectorImpl<TerminatedPath> &Terminated) {
609 assert(!PausedSearches.empty() && "No searches to continue?")((!PausedSearches.empty() && "No searches to continue?"
) ? static_cast<void> (0) : __assert_fail ("!PausedSearches.empty() && \"No searches to continue?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 609, __PRETTY_FUNCTION__));
610
611 // BFS vs DFS really doesn't make a difference here, so just do a DFS with
612 // PausedSearches as our stack.
613 while (!PausedSearches.empty()) {
614 ListIndex PathIndex = PausedSearches.pop_back_val();
615 DefPath &Node = Paths[PathIndex];
616
617 // If we've already visited this path with this MemoryLocation, we don't
618 // need to do so again.
619 //
620 // NOTE: That we just drop these paths on the ground makes caching
621 // behavior sporadic. e.g. given a diamond:
622 // A
623 // B C
624 // D
625 //
626 // ...If we walk D, B, A, C, we'll only cache the result of phi
627 // optimization for A, B, and D; C will be skipped because it dies here.
628 // This arguably isn't the worst thing ever, since:
629 // - We generally query things in a top-down order, so if we got below D
630 // without needing cache entries for {C, MemLoc}, then chances are
631 // that those cache entries would end up ultimately unused.
632 // - We still cache things for A, so C only needs to walk up a bit.
633 // If this behavior becomes problematic, we can fix without a ton of extra
634 // work.
635 if (!VisitedPhis.insert({Node.Last, Node.Loc}).second)
636 continue;
637
638 UpwardsWalkResult Res = walkToPhiOrClobber(Node, /*StopAt=*/StopWhere);
639 if (Res.IsKnownClobber) {
640 assert(Res.Result != StopWhere || Res.FromCache)((Res.Result != StopWhere || Res.FromCache) ? static_cast<
void> (0) : __assert_fail ("Res.Result != StopWhere || Res.FromCache"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 640, __PRETTY_FUNCTION__));
641 // If this wasn't a cache hit, we hit a clobber when walking. That's a
642 // failure.
643 TerminatedPath Term{Res.Result, PathIndex};
644 if (!Res.FromCache || !MSSA.dominates(Res.Result, StopWhere))
645 return Term;
646
647 // Otherwise, it's a valid thing to potentially optimize to.
648 Terminated.push_back(Term);
649 continue;
650 }
651
652 if (Res.Result == StopWhere) {
653 // We've hit our target. Save this path off for if we want to continue
654 // walking.
655 NewPaused.push_back(PathIndex);
656 continue;
657 }
658
659 assert(!MSSA.isLiveOnEntryDef(Res.Result) && "liveOnEntry is a clobber")((!MSSA.isLiveOnEntryDef(Res.Result) && "liveOnEntry is a clobber"
) ? static_cast<void> (0) : __assert_fail ("!MSSA.isLiveOnEntryDef(Res.Result) && \"liveOnEntry is a clobber\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 659, __PRETTY_FUNCTION__));
660 addSearches(cast<MemoryPhi>(Res.Result), PausedSearches, PathIndex);
661 }
662
663 return None;
664 }
665
666 template <typename T, typename Walker>
667 struct generic_def_path_iterator
668 : public iterator_facade_base<generic_def_path_iterator<T, Walker>,
669 std::forward_iterator_tag, T *> {
670 generic_def_path_iterator() : W(nullptr), N(None) {}
671 generic_def_path_iterator(Walker *W, ListIndex N) : W(W), N(N) {}
672
673 T &operator*() const { return curNode(); }
674
675 generic_def_path_iterator &operator++() {
676 N = curNode().Previous;
677 return *this;
678 }
679
680 bool operator==(const generic_def_path_iterator &O) const {
681 if (N.hasValue() != O.N.hasValue())
682 return false;
683 return !N.hasValue() || *N == *O.N;
684 }
685
686 private:
687 T &curNode() const { return W->Paths[*N]; }
688
689 Walker *W;
690 Optional<ListIndex> N;
691 };
692
693 using def_path_iterator = generic_def_path_iterator<DefPath, ClobberWalker>;
694 using const_def_path_iterator =
695 generic_def_path_iterator<const DefPath, const ClobberWalker>;
696
697 iterator_range<def_path_iterator> def_path(ListIndex From) {
698 return make_range(def_path_iterator(this, From), def_path_iterator());
699 }
700
701 iterator_range<const_def_path_iterator> const_def_path(ListIndex From) const {
702 return make_range(const_def_path_iterator(this, From),
703 const_def_path_iterator());
704 }
705
706 struct OptznResult {
707 /// The path that contains our result.
708 TerminatedPath PrimaryClobber;
709 /// The paths that we can legally cache back from, but that aren't
710 /// necessarily the result of the Phi optimization.
711 SmallVector<TerminatedPath, 4> OtherClobbers;
712 };
713
714 ListIndex defPathIndex(const DefPath &N) const {
715 // The assert looks nicer if we don't need to do &N
716 const DefPath *NP = &N;
717 assert(!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() &&((!Paths.empty() && NP >= &Paths.front() &&
NP <= &Paths.back() && "Out of bounds DefPath!"
) ? static_cast<void> (0) : __assert_fail ("!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() && \"Out of bounds DefPath!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 718, __PRETTY_FUNCTION__))
718 "Out of bounds DefPath!")((!Paths.empty() && NP >= &Paths.front() &&
NP <= &Paths.back() && "Out of bounds DefPath!"
) ? static_cast<void> (0) : __assert_fail ("!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() && \"Out of bounds DefPath!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 718, __PRETTY_FUNCTION__));
719 return NP - &Paths.front();
720 }
721
722 /// Try to optimize a phi as best as we can. Returns a SmallVector of Paths
723 /// that act as legal clobbers. Note that this won't return *all* clobbers.
724 ///
725 /// Phi optimization algorithm tl;dr:
726 /// - Find the earliest def/phi, A, we can optimize to
727 /// - Find if all paths from the starting memory access ultimately reach A
728 /// - If not, optimization isn't possible.
729 /// - Otherwise, walk from A to another clobber or phi, A'.
730 /// - If A' is a def, we're done.
731 /// - If A' is a phi, try to optimize it.
732 ///
733 /// A path is a series of {MemoryAccess, MemoryLocation} pairs. A path
734 /// terminates when a MemoryAccess that clobbers said MemoryLocation is found.
735 OptznResult tryOptimizePhi(MemoryPhi *Phi, MemoryAccess *Start,
736 const MemoryLocation &Loc) {
737 assert(Paths.empty() && VisitedPhis.empty() &&((Paths.empty() && VisitedPhis.empty() && "Reset the optimization state."
) ? static_cast<void> (0) : __assert_fail ("Paths.empty() && VisitedPhis.empty() && \"Reset the optimization state.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 738, __PRETTY_FUNCTION__))
738 "Reset the optimization state.")((Paths.empty() && VisitedPhis.empty() && "Reset the optimization state."
) ? static_cast<void> (0) : __assert_fail ("Paths.empty() && VisitedPhis.empty() && \"Reset the optimization state.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 738, __PRETTY_FUNCTION__));
739
740 Paths.emplace_back(Loc, Start, Phi, None);
741 // Stores how many "valid" optimization nodes we had prior to calling
742 // addSearches/getBlockingAccess. Necessary for caching if we had a blocker.
743 auto PriorPathsSize = Paths.size();
744
745 SmallVector<ListIndex, 16> PausedSearches;
746 SmallVector<ListIndex, 8> NewPaused;
747 SmallVector<TerminatedPath, 4> TerminatedPaths;
748
749 addSearches(Phi, PausedSearches, 0);
750
751 // Moves the TerminatedPath with the "most dominated" Clobber to the end of
752 // Paths.
753 auto MoveDominatedPathToEnd = [&](SmallVectorImpl<TerminatedPath> &Paths) {
754 assert(!Paths.empty() && "Need a path to move")((!Paths.empty() && "Need a path to move") ? static_cast
<void> (0) : __assert_fail ("!Paths.empty() && \"Need a path to move\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 754, __PRETTY_FUNCTION__));
755 auto Dom = Paths.begin();
756 for (auto I = std::next(Dom), E = Paths.end(); I != E; ++I)
757 if (!MSSA.dominates(I->Clobber, Dom->Clobber))
758 Dom = I;
759 auto Last = Paths.end() - 1;
760 if (Last != Dom)
761 std::iter_swap(Last, Dom);
762 };
763
764 MemoryPhi *Current = Phi;
765 while (1) {
1
Loop condition is true. Entering loop body
→
766 assert(!MSSA.isLiveOnEntryDef(Current) &&((!MSSA.isLiveOnEntryDef(Current) && "liveOnEntry wasn't treated as a clobber?"
) ? static_cast<void> (0) : __assert_fail ("!MSSA.isLiveOnEntryDef(Current) && \"liveOnEntry wasn't treated as a clobber?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 767, __PRETTY_FUNCTION__))
767 "liveOnEntry wasn't treated as a clobber?")((!MSSA.isLiveOnEntryDef(Current) && "liveOnEntry wasn't treated as a clobber?"
) ? static_cast<void> (0) : __assert_fail ("!MSSA.isLiveOnEntryDef(Current) && \"liveOnEntry wasn't treated as a clobber?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 767, __PRETTY_FUNCTION__));
768
769 const auto *Target = getWalkTarget(Current);
770 // If a TerminatedPath doesn't dominate Target, then it wasn't a legal
771 // optimization for the prior phi.
772 assert(all_of(TerminatedPaths, [&](const TerminatedPath &P) {((all_of(TerminatedPaths, [&](const TerminatedPath &P
) { return MSSA.dominates(P.Clobber, Target); })) ? static_cast
<void> (0) : __assert_fail ("all_of(TerminatedPaths, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target); })"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 774, __PRETTY_FUNCTION__))
773 return MSSA.dominates(P.Clobber, Target);((all_of(TerminatedPaths, [&](const TerminatedPath &P
) { return MSSA.dominates(P.Clobber, Target); })) ? static_cast
<void> (0) : __assert_fail ("all_of(TerminatedPaths, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target); })"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 774, __PRETTY_FUNCTION__))
774 }))((all_of(TerminatedPaths, [&](const TerminatedPath &P
) { return MSSA.dominates(P.Clobber, Target); })) ? static_cast
<void> (0) : __assert_fail ("all_of(TerminatedPaths, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target); })"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 774, __PRETTY_FUNCTION__));
775
776 // FIXME: This is broken, because the Blocker may be reported to be
777 // liveOnEntry, and we'll happily wait for that to disappear (read: never)
778 // For the moment, this is fine, since we do nothing with blocker info.
779 if (Optional<TerminatedPath> Blocker = getBlockingAccess(
2
←
Taking false branch
→
780 Target, PausedSearches, NewPaused, TerminatedPaths)) {
781 // Cache our work on the blocking node, since we know that's correct.
782 cacheDefPath(Paths[Blocker->LastNode], Blocker->Clobber);
783
784 // Find the node we started at. We can't search based on N->Last, since
785 // we may have gone around a loop with a different MemoryLocation.
786 auto Iter = find_if(def_path(Blocker->LastNode), [&](const DefPath &N) {
787 return defPathIndex(N) < PriorPathsSize;
788 });
789 assert(Iter != def_path_iterator())((Iter != def_path_iterator()) ? static_cast<void> (0) :
__assert_fail ("Iter != def_path_iterator()", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 789, __PRETTY_FUNCTION__));
790
791 DefPath &CurNode = *Iter;
792 assert(CurNode.Last == Current)((CurNode.Last == Current) ? static_cast<void> (0) : __assert_fail
("CurNode.Last == Current", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 792, __PRETTY_FUNCTION__));
793
794 // Two things:
795 // A. We can't reliably cache all of NewPaused back. Consider a case
796 // where we have two paths in NewPaused; one of which can't optimize
797 // above this phi, whereas the other can. If we cache the second path
798 // back, we'll end up with suboptimal cache entries. We can handle
799 // cases like this a bit better when we either try to find all
800 // clobbers that block phi optimization, or when our cache starts
801 // supporting unfinished searches.
802 // B. We can't reliably cache TerminatedPaths back here without doing
803 // extra checks; consider a case like:
804 // T
805 // / \
806 // D C
807 // \ /
808 // S
809 // Where T is our target, C is a node with a clobber on it, D is a
810 // diamond (with a clobber *only* on the left or right node, N), and
811 // S is our start. Say we walk to D, through the node opposite N
812 // (read: ignoring the clobber), and see a cache entry in the top
813 // node of D. That cache entry gets put into TerminatedPaths. We then
814 // walk up to C (N is later in our worklist), find the clobber, and
815 // quit. If we append TerminatedPaths to OtherClobbers, we'll cache
816 // the bottom part of D to the cached clobber, ignoring the clobber
817 // in N. Again, this problem goes away if we start tracking all
818 // blockers for a given phi optimization.
819 TerminatedPath Result{CurNode.Last, defPathIndex(CurNode)};
820 return {Result, {}};
821 }
822
823 // If there's nothing left to search, then all paths led to valid clobbers
824 // that we got from our cache; pick the nearest to the start, and allow
825 // the rest to be cached back.
826 if (NewPaused.empty()) {
3
←
Taking false branch
→
827 MoveDominatedPathToEnd(TerminatedPaths);
828 TerminatedPath Result = TerminatedPaths.pop_back_val();
829 return {Result, std::move(TerminatedPaths)};
830 }
831
832 MemoryAccess *DefChainEnd = nullptr;
4
←
'DefChainEnd' initialized to a null pointer value
→
833 SmallVector<TerminatedPath, 4> Clobbers;
834 for (ListIndex Paused : NewPaused) {
5
←
Assuming '__begin' is equal to '__end'
→
835 UpwardsWalkResult WR = walkToPhiOrClobber(Paths[Paused]);
836 if (WR.IsKnownClobber)
837 Clobbers.push_back({WR.Result, Paused});
838 else
839 // Micro-opt: If we hit the end of the chain, save it.
840 DefChainEnd = WR.Result;
841 }
842
843 if (!TerminatedPaths.empty()) {
6
←
Taking true branch
→
844 // If we couldn't find the dominating phi/liveOnEntry in the above loop,
845 // do it now.
846 if (!DefChainEnd)
7
←
Taking true branch
→
847 for (auto *MA : def_chain(const_cast<MemoryAccess *>(Target)))
848 DefChainEnd = MA;
849
850 // If any of the terminated paths don't dominate the phi we'll try to
851 // optimize, we need to figure out what they are and quit.
852 const BasicBlock *ChainBB = DefChainEnd->getBlock();
8
←
Called C++ object pointer is null
853 for (const TerminatedPath &TP : TerminatedPaths) {
854 // Because we know that DefChainEnd is as "high" as we can go, we
855 // don't need local dominance checks; BB dominance is sufficient.
856 if (DT.dominates(ChainBB, TP.Clobber->getBlock()))
857 Clobbers.push_back(TP);
858 }
859 }
860
861 // If we have clobbers in the def chain, find the one closest to Current
862 // and quit.
863 if (!Clobbers.empty()) {
864 MoveDominatedPathToEnd(Clobbers);
865 TerminatedPath Result = Clobbers.pop_back_val();
866 return {Result, std::move(Clobbers)};
867 }
868
869 assert(all_of(NewPaused,((all_of(NewPaused, [&](ListIndex I) { return Paths[I].Last
== DefChainEnd; })) ? static_cast<void> (0) : __assert_fail
("all_of(NewPaused, [&](ListIndex I) { return Paths[I].Last == DefChainEnd; })"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 870, __PRETTY_FUNCTION__))
870 [&](ListIndex I) { return Paths[I].Last == DefChainEnd; }))((all_of(NewPaused, [&](ListIndex I) { return Paths[I].Last
== DefChainEnd; })) ? static_cast<void> (0) : __assert_fail
("all_of(NewPaused, [&](ListIndex I) { return Paths[I].Last == DefChainEnd; })"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 870, __PRETTY_FUNCTION__));
871
872 // Because liveOnEntry is a clobber, this must be a phi.
873 auto *DefChainPhi = cast<MemoryPhi>(DefChainEnd);
874
875 PriorPathsSize = Paths.size();
876 PausedSearches.clear();
877 for (ListIndex I : NewPaused)
878 addSearches(DefChainPhi, PausedSearches, I);
879 NewPaused.clear();
880
881 Current = DefChainPhi;
882 }
883 }
884
885 /// Caches everything in an OptznResult.
886 void cacheOptResult(const OptznResult &R) {
887 if (R.OtherClobbers.empty()) {
888 // If we're not going to be caching OtherClobbers, don't bother with
889 // marking visited/etc.
890 for (const DefPath &N : const_def_path(R.PrimaryClobber.LastNode))
891 cacheDefPath(N, R.PrimaryClobber.Clobber);
892 return;
893 }
894
895 // PrimaryClobber is our answer. If we can cache anything back, we need to
896 // stop caching when we visit PrimaryClobber.
897 SmallBitVector Visited(Paths.size());
898 for (const DefPath &N : const_def_path(R.PrimaryClobber.LastNode)) {
899 Visited[defPathIndex(N)] = true;
900 cacheDefPath(N, R.PrimaryClobber.Clobber);
901 }
902
903 for (const TerminatedPath &P : R.OtherClobbers) {
904 for (const DefPath &N : const_def_path(P.LastNode)) {
905 ListIndex NIndex = defPathIndex(N);
906 if (Visited[NIndex])
907 break;
908 Visited[NIndex] = true;
909 cacheDefPath(N, P.Clobber);
910 }
911 }
912 }
913
914 void verifyOptResult(const OptznResult &R) const {
915 assert(all_of(R.OtherClobbers, [&](const TerminatedPath &P) {((all_of(R.OtherClobbers, [&](const TerminatedPath &P
) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber
); })) ? static_cast<void> (0) : __assert_fail ("all_of(R.OtherClobbers, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber); })"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 917, __PRETTY_FUNCTION__))
916 return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber);((all_of(R.OtherClobbers, [&](const TerminatedPath &P
) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber
); })) ? static_cast<void> (0) : __assert_fail ("all_of(R.OtherClobbers, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber); })"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 917, __PRETTY_FUNCTION__))
917 }))((all_of(R.OtherClobbers, [&](const TerminatedPath &P
) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber
); })) ? static_cast<void> (0) : __assert_fail ("all_of(R.OtherClobbers, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber); })"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 917, __PRETTY_FUNCTION__));
918 }
919
920 void resetPhiOptznState() {
921 Paths.clear();
922 VisitedPhis.clear();
923 }
924
925public:
926 ClobberWalker(const MemorySSA &MSSA, AliasAnalysis &AA, DominatorTree &DT,
927 WalkerCache &WC)
928 : MSSA(MSSA), AA(AA), DT(DT), WC(WC), UseCache(true) {}
929
930 void reset() {}
931
932 /// Finds the nearest clobber for the given query, optimizing phis if
933 /// possible.
934 MemoryAccess *findClobber(MemoryAccess *Start, UpwardsMemoryQuery &Q,
935 bool UseWalkerCache = true) {
936 setUseCache(UseWalkerCache);
937 Query = &Q;
938
939 MemoryAccess *Current = Start;
940 // This walker pretends uses don't exist. If we're handed one, silently grab
941 // its def. (This has the nice side-effect of ensuring we never cache uses)
942 if (auto *MU = dyn_cast<MemoryUse>(Start))
943 Current = MU->getDefiningAccess();
944
945 DefPath FirstDesc(Q.StartingLoc, Current, Current, None);
946 // Fast path for the overly-common case (no crazy phi optimization
947 // necessary)
948 UpwardsWalkResult WalkResult = walkToPhiOrClobber(FirstDesc);
949 MemoryAccess *Result;
950 if (WalkResult.IsKnownClobber) {
951 cacheDefPath(FirstDesc, WalkResult.Result);
952 Result = WalkResult.Result;
953 } else {
954 OptznResult OptRes = tryOptimizePhi(cast<MemoryPhi>(FirstDesc.Last),
955 Current, Q.StartingLoc);
956 verifyOptResult(OptRes);
957 cacheOptResult(OptRes);
958 resetPhiOptznState();
959 Result = OptRes.PrimaryClobber.Clobber;
960 }
961
962#ifdef EXPENSIVE_CHECKS
963 checkClobberSanity(Current, Result, Q.StartingLoc, MSSA, Q, AA);
964#endif
965 return Result;
966 }
967
968 void verify(const MemorySSA *MSSA) { assert(MSSA == &this->MSSA)((MSSA == &this->MSSA) ? static_cast<void> (0) :
__assert_fail ("MSSA == &this->MSSA", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 968, __PRETTY_FUNCTION__)); }
969};
970
971struct RenamePassData {
972 DomTreeNode *DTN;
973 DomTreeNode::const_iterator ChildIt;
974 MemoryAccess *IncomingVal;
975
976 RenamePassData(DomTreeNode *D, DomTreeNode::const_iterator It,
977 MemoryAccess *M)
978 : DTN(D), ChildIt(It), IncomingVal(M) {}
979 void swap(RenamePassData &RHS) {
980 std::swap(DTN, RHS.DTN);
981 std::swap(ChildIt, RHS.ChildIt);
982 std::swap(IncomingVal, RHS.IncomingVal);
983 }
984};
985} // anonymous namespace
986
987namespace llvm {
988/// \brief A MemorySSAWalker that does AA walks and caching of lookups to
989/// disambiguate accesses.
990///
991/// FIXME: The current implementation of this can take quadratic space in rare
992/// cases. This can be fixed, but it is something to note until it is fixed.
993///
994/// In order to trigger this behavior, you need to store to N distinct locations
995/// (that AA can prove don't alias), perform M stores to other memory
996/// locations that AA can prove don't alias any of the initial N locations, and
997/// then load from all of the N locations. In this case, we insert M cache
998/// entries for each of the N loads.
999///
1000/// For example:
1001/// define i32 @foo() {
1002/// %a = alloca i32, align 4
1003/// %b = alloca i32, align 4
1004/// store i32 0, i32* %a, align 4
1005/// store i32 0, i32* %b, align 4
1006///
1007/// ; Insert M stores to other memory that doesn't alias %a or %b here
1008///
1009/// %c = load i32, i32* %a, align 4 ; Caches M entries in
1010/// ; CachedUpwardsClobberingAccess for the
1011/// ; MemoryLocation %a
1012/// %d = load i32, i32* %b, align 4 ; Caches M entries in
1013/// ; CachedUpwardsClobberingAccess for the
1014/// ; MemoryLocation %b
1015///
1016/// ; For completeness' sake, loading %a or %b again would not cache *another*
1017/// ; M entries.
1018/// %r = add i32 %c, %d
1019/// ret i32 %r
1020/// }
1021class MemorySSA::CachingWalker final : public MemorySSAWalker {
1022 WalkerCache Cache;
1023 ClobberWalker Walker;
1024 bool AutoResetWalker;
1025
1026 MemoryAccess *getClobberingMemoryAccess(MemoryAccess *, UpwardsMemoryQuery &);
1027 void verifyRemoved(MemoryAccess *);
1028
1029public:
1030 CachingWalker(MemorySSA *, AliasAnalysis *, DominatorTree *);
1031 ~CachingWalker() override;
1032
1033 using MemorySSAWalker::getClobberingMemoryAccess;
1034 MemoryAccess *getClobberingMemoryAccess(MemoryAccess *) override;
1035 MemoryAccess *getClobberingMemoryAccess(MemoryAccess *,
1036 const MemoryLocation &) override;
1037 void invalidateInfo(MemoryAccess *) override;
1038
1039 /// Whether we call resetClobberWalker() after each time we *actually* walk to
1040 /// answer a clobber query.
1041 void setAutoResetWalker(bool AutoReset) { AutoResetWalker = AutoReset; }
1042
1043 /// Drop the walker's persistent data structures.
1044 void resetClobberWalker() { Walker.reset(); }
1045
1046 void verify(const MemorySSA *MSSA) override {
1047 MemorySSAWalker::verify(MSSA);
1048 Walker.verify(MSSA);
1049 }
1050};
1051
1052void MemorySSA::renameSuccessorPhis(BasicBlock *BB, MemoryAccess *IncomingVal,
1053 bool RenameAllUses) {
1054 // Pass through values to our successors
1055 for (const BasicBlock *S : successors(BB)) {
1056 auto It = PerBlockAccesses.find(S);
1057 // Rename the phi nodes in our successor block
1058 if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
1059 continue;
1060 AccessList *Accesses = It->second.get();
1061 auto *Phi = cast<MemoryPhi>(&Accesses->front());
1062 if (RenameAllUses) {
1063 int PhiIndex = Phi->getBasicBlockIndex(BB);
1064 assert(PhiIndex != -1 && "Incomplete phi during partial rename")((PhiIndex != -1 && "Incomplete phi during partial rename"
) ? static_cast<void> (0) : __assert_fail ("PhiIndex != -1 && \"Incomplete phi during partial rename\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1064, __PRETTY_FUNCTION__));
1065 Phi->setIncomingValue(PhiIndex, IncomingVal);
1066 } else
1067 Phi->addIncoming(IncomingVal, BB);
1068 }
1069}
1070
1071/// \brief Rename a single basic block into MemorySSA form.
1072/// Uses the standard SSA renaming algorithm.
1073/// \returns The new incoming value.
1074MemoryAccess *MemorySSA::renameBlock(BasicBlock *BB, MemoryAccess *IncomingVal,
1075 bool RenameAllUses) {
1076 auto It = PerBlockAccesses.find(BB);
1077 // Skip most processing if the list is empty.
1078 if (It != PerBlockAccesses.end()) {
1079 AccessList *Accesses = It->second.get();
1080 for (MemoryAccess &L : *Accesses) {
1081 if (MemoryUseOrDef *MUD = dyn_cast<MemoryUseOrDef>(&L)) {
1082 if (MUD->getDefiningAccess() == nullptr || RenameAllUses)
1083 MUD->setDefiningAccess(IncomingVal);
1084 if (isa<MemoryDef>(&L))
1085 IncomingVal = &L;
1086 } else {
1087 IncomingVal = &L;
1088 }
1089 }
1090 }
1091 return IncomingVal;
1092}
1093
1094/// \brief This is the standard SSA renaming algorithm.
1095///
1096/// We walk the dominator tree in preorder, renaming accesses, and then filling
1097/// in phi nodes in our successors.
1098void MemorySSA::renamePass(DomTreeNode *Root, MemoryAccess *IncomingVal,
1099 SmallPtrSetImpl<BasicBlock *> &Visited,
1100 bool SkipVisited, bool RenameAllUses) {
1101 SmallVector<RenamePassData, 32> WorkStack;
1102 // Skip everything if we already renamed this block and we are skipping.
1103 // Note: You can't sink this into the if, because we need it to occur
1104 // regardless of whether we skip blocks or not.
1105 bool AlreadyVisited = !Visited.insert(Root->getBlock()).second;
1106 if (SkipVisited && AlreadyVisited)
1107 return;
1108
1109 IncomingVal = renameBlock(Root->getBlock(), IncomingVal, RenameAllUses);
1110 renameSuccessorPhis(Root->getBlock(), IncomingVal, RenameAllUses);
1111 WorkStack.push_back({Root, Root->begin(), IncomingVal});
1112
1113 while (!WorkStack.empty()) {
1114 DomTreeNode *Node = WorkStack.back().DTN;
1115 DomTreeNode::const_iterator ChildIt = WorkStack.back().ChildIt;
1116 IncomingVal = WorkStack.back().IncomingVal;
1117
1118 if (ChildIt == Node->end()) {
1119 WorkStack.pop_back();
1120 } else {
1121 DomTreeNode *Child = *ChildIt;
1122 ++WorkStack.back().ChildIt;
1123 BasicBlock *BB = Child->getBlock();
1124 // Note: You can't sink this into the if, because we need it to occur
1125 // regardless of whether we skip blocks or not.
1126 AlreadyVisited = !Visited.insert(BB).second;
1127 if (SkipVisited && AlreadyVisited) {
1128 // We already visited this during our renaming, which can happen when
1129 // being asked to rename multiple blocks. Figure out the incoming val,
1130 // which is the last def.
1131 // Incoming value can only change if there is a block def, and in that
1132 // case, it's the last block def in the list.
1133 if (auto *BlockDefs = getWritableBlockDefs(BB))
1134 IncomingVal = &*BlockDefs->rbegin();
1135 } else
1136 IncomingVal = renameBlock(BB, IncomingVal, RenameAllUses);
1137 renameSuccessorPhis(BB, IncomingVal, RenameAllUses);
1138 WorkStack.push_back({Child, Child->begin(), IncomingVal});
1139 }
1140 }
1141}
1142
1143/// \brief Compute dominator levels, used by the phi insertion algorithm above.
1144void MemorySSA::computeDomLevels(DenseMap<DomTreeNode *, unsigned> &DomLevels) {
1145 for (auto DFI = df_begin(DT->getRootNode()), DFE = df_end(DT->getRootNode());
1146 DFI != DFE; ++DFI)
1147 DomLevels[*DFI] = DFI.getPathLength() - 1;
1148}
1149
1150/// \brief This handles unreachable block accesses by deleting phi nodes in
1151/// unreachable blocks, and marking all other unreachable MemoryAccess's as
1152/// being uses of the live on entry definition.
1153void MemorySSA::markUnreachableAsLiveOnEntry(BasicBlock *BB) {
1154 assert(!DT->isReachableFromEntry(BB) &&((!DT->isReachableFromEntry(BB) && "Reachable block found while handling unreachable blocks"
) ? static_cast<void> (0) : __assert_fail ("!DT->isReachableFromEntry(BB) && \"Reachable block found while handling unreachable blocks\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1155, __PRETTY_FUNCTION__))
1155 "Reachable block found while handling unreachable blocks")((!DT->isReachableFromEntry(BB) && "Reachable block found while handling unreachable blocks"
) ? static_cast<void> (0) : __assert_fail ("!DT->isReachableFromEntry(BB) && \"Reachable block found while handling unreachable blocks\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1155, __PRETTY_FUNCTION__));
1156
1157 // Make sure phi nodes in our reachable successors end up with a
1158 // LiveOnEntryDef for our incoming edge, even though our block is forward
1159 // unreachable. We could just disconnect these blocks from the CFG fully,
1160 // but we do not right now.
1161 for (const BasicBlock *S : successors(BB)) {
1162 if (!DT->isReachableFromEntry(S))
1163 continue;
1164 auto It = PerBlockAccesses.find(S);
1165 // Rename the phi nodes in our successor block
1166 if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
1167 continue;
1168 AccessList *Accesses = It->second.get();
1169 auto *Phi = cast<MemoryPhi>(&Accesses->front());
1170 Phi->addIncoming(LiveOnEntryDef.get(), BB);
1171 }
1172
1173 auto It = PerBlockAccesses.find(BB);
1174 if (It == PerBlockAccesses.end())
1175 return;
1176
1177 auto &Accesses = It->second;
1178 for (auto AI = Accesses->begin(), AE = Accesses->end(); AI != AE;) {
1179 auto Next = std::next(AI);
1180 // If we have a phi, just remove it. We are going to replace all
1181 // users with live on entry.
1182 if (auto *UseOrDef = dyn_cast<MemoryUseOrDef>(AI))
1183 UseOrDef->setDefiningAccess(LiveOnEntryDef.get());
1184 else
1185 Accesses->erase(AI);
1186 AI = Next;
1187 }
1188}
1189
1190MemorySSA::MemorySSA(Function &Func, AliasAnalysis *AA, DominatorTree *DT)
1191 : AA(AA), DT(DT), F(Func), LiveOnEntryDef(nullptr), Walker(nullptr),
1192 NextID(INVALID_MEMORYACCESS_ID) {
1193 buildMemorySSA();
1194}
1195
1196MemorySSA::~MemorySSA() {
1197 // Drop all our references
1198 for (const auto &Pair : PerBlockAccesses)
1199 for (MemoryAccess &MA : *Pair.second)
1200 MA.dropAllReferences();
1201}
1202
1203MemorySSA::AccessList *MemorySSA::getOrCreateAccessList(const BasicBlock *BB) {
1204 auto Res = PerBlockAccesses.insert(std::make_pair(BB, nullptr));
1205
1206 if (Res.second)
1207 Res.first->second = make_unique<AccessList>();
1208 return Res.first->second.get();
1209}
1210MemorySSA::DefsList *MemorySSA::getOrCreateDefsList(const BasicBlock *BB) {
1211 auto Res = PerBlockDefs.insert(std::make_pair(BB, nullptr));
1212
1213 if (Res.second)
1214 Res.first->second = make_unique<DefsList>();
1215 return Res.first->second.get();
1216}
1217
1218/// This class is a batch walker of all MemoryUse's in the program, and points
1219/// their defining access at the thing that actually clobbers them. Because it
1220/// is a batch walker that touches everything, it does not operate like the
1221/// other walkers. This walker is basically performing a top-down SSA renaming
1222/// pass, where the version stack is used as the cache. This enables it to be
1223/// significantly more time and memory efficient than using the regular walker,
1224/// which is walking bottom-up.
1225class MemorySSA::OptimizeUses {
1226public:
1227 OptimizeUses(MemorySSA *MSSA, MemorySSAWalker *Walker, AliasAnalysis *AA,
1228 DominatorTree *DT)
1229 : MSSA(MSSA), Walker(Walker), AA(AA), DT(DT) {
1230 Walker = MSSA->getWalker();
1231 }
1232
1233 void optimizeUses();
1234
1235private:
1236 /// This represents where a given memorylocation is in the stack.
1237 struct MemlocStackInfo {
1238 // This essentially is keeping track of versions of the stack. Whenever
1239 // the stack changes due to pushes or pops, these versions increase.
1240 unsigned long StackEpoch;
1241 unsigned long PopEpoch;
1242 // This is the lower bound of places on the stack to check. It is equal to
1243 // the place the last stack walk ended.
1244 // Note: Correctness depends on this being initialized to 0, which densemap
1245 // does
1246 unsigned long LowerBound;
1247 const BasicBlock *LowerBoundBlock;
1248 // This is where the last walk for this memory location ended.
1249 unsigned long LastKill;
1250 bool LastKillValid;
1251 };
1252 void optimizeUsesInBlock(const BasicBlock *, unsigned long &, unsigned long &,
1253 SmallVectorImpl<MemoryAccess *> &,
1254 DenseMap<MemoryLocOrCall, MemlocStackInfo> &);
1255 MemorySSA *MSSA;
1256 MemorySSAWalker *Walker;
1257 AliasAnalysis *AA;
1258 DominatorTree *DT;
1259};
1260
1261/// Optimize the uses in a given block This is basically the SSA renaming
1262/// algorithm, with one caveat: We are able to use a single stack for all
1263/// MemoryUses. This is because the set of *possible* reaching MemoryDefs is
1264/// the same for every MemoryUse. The *actual* clobbering MemoryDef is just
1265/// going to be some position in that stack of possible ones.
1266///
1267/// We track the stack positions that each MemoryLocation needs
1268/// to check, and last ended at. This is because we only want to check the
1269/// things that changed since last time. The same MemoryLocation should
1270/// get clobbered by the same store (getModRefInfo does not use invariantness or
1271/// things like this, and if they start, we can modify MemoryLocOrCall to
1272/// include relevant data)
1273void MemorySSA::OptimizeUses::optimizeUsesInBlock(
1274 const BasicBlock *BB, unsigned long &StackEpoch, unsigned long &PopEpoch,
1275 SmallVectorImpl<MemoryAccess *> &VersionStack,
1276 DenseMap<MemoryLocOrCall, MemlocStackInfo> &LocStackInfo) {
1277
1278 /// If no accesses, nothing to do.
1279 MemorySSA::AccessList *Accesses = MSSA->getWritableBlockAccesses(BB);
1280 if (Accesses == nullptr)
1281 return;
1282
1283 // Pop everything that doesn't dominate the current block off the stack,
1284 // increment the PopEpoch to account for this.
1285 while (true) {
1286 assert(((!VersionStack.empty() && "Version stack should have liveOnEntry sentinel dominating everything"
) ? static_cast<void> (0) : __assert_fail ("!VersionStack.empty() && \"Version stack should have liveOnEntry sentinel dominating everything\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1288, __PRETTY_FUNCTION__))
1287 !VersionStack.empty() &&((!VersionStack.empty() && "Version stack should have liveOnEntry sentinel dominating everything"
) ? static_cast<void> (0) : __assert_fail ("!VersionStack.empty() && \"Version stack should have liveOnEntry sentinel dominating everything\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1288, __PRETTY_FUNCTION__))
1288 "Version stack should have liveOnEntry sentinel dominating everything")((!VersionStack.empty() && "Version stack should have liveOnEntry sentinel dominating everything"
) ? static_cast<void> (0) : __assert_fail ("!VersionStack.empty() && \"Version stack should have liveOnEntry sentinel dominating everything\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1288, __PRETTY_FUNCTION__));
1289 BasicBlock *BackBlock = VersionStack.back()->getBlock();
1290 if (DT->dominates(BackBlock, BB))
1291 break;
1292 while (VersionStack.back()->getBlock() == BackBlock)
1293 VersionStack.pop_back();
1294 ++PopEpoch;
1295 }
1296
1297 for (MemoryAccess &MA : *Accesses) {
1298 auto *MU = dyn_cast<MemoryUse>(&MA);
1299 if (!MU) {
1300 VersionStack.push_back(&MA);
1301 ++StackEpoch;
1302 continue;
1303 }
1304
1305 if (isUseTriviallyOptimizableToLiveOnEntry(*AA, MU->getMemoryInst())) {
1306 MU->setDefiningAccess(MSSA->getLiveOnEntryDef(), true);
1307 continue;
1308 }
1309
1310 MemoryLocOrCall UseMLOC(MU);
1311 auto &LocInfo = LocStackInfo[UseMLOC];
1312 // If the pop epoch changed, it means we've removed stuff from top of
1313 // stack due to changing blocks. We may have to reset the lower bound or
1314 // last kill info.
1315 if (LocInfo.PopEpoch != PopEpoch) {
1316 LocInfo.PopEpoch = PopEpoch;
1317 LocInfo.StackEpoch = StackEpoch;
1318 // If the lower bound was in something that no longer dominates us, we
1319 // have to reset it.
1320 // We can't simply track stack size, because the stack may have had
1321 // pushes/pops in the meantime.
1322 // XXX: This is non-optimal, but only is slower cases with heavily
1323 // branching dominator trees. To get the optimal number of queries would
1324 // be to make lowerbound and lastkill a per-loc stack, and pop it until
1325 // the top of that stack dominates us. This does not seem worth it ATM.
1326 // A much cheaper optimization would be to always explore the deepest
1327 // branch of the dominator tree first. This will guarantee this resets on
1328 // the smallest set of blocks.
1329 if (LocInfo.LowerBoundBlock && LocInfo.LowerBoundBlock != BB &&
1330 !DT->dominates(LocInfo.LowerBoundBlock, BB)) {
1331 // Reset the lower bound of things to check.
1332 // TODO: Some day we should be able to reset to last kill, rather than
1333 // 0.
1334 LocInfo.LowerBound = 0;
1335 LocInfo.LowerBoundBlock = VersionStack[0]->getBlock();
1336 LocInfo.LastKillValid = false;
1337 }
1338 } else if (LocInfo.StackEpoch != StackEpoch) {
1339 // If all that has changed is the StackEpoch, we only have to check the
1340 // new things on the stack, because we've checked everything before. In
1341 // this case, the lower bound of things to check remains the same.
1342 LocInfo.PopEpoch = PopEpoch;
1343 LocInfo.StackEpoch = StackEpoch;
1344 }
1345 if (!LocInfo.LastKillValid) {
1346 LocInfo.LastKill = VersionStack.size() - 1;
1347 LocInfo.LastKillValid = true;
1348 }
1349
1350 // At this point, we should have corrected last kill and LowerBound to be
1351 // in bounds.
1352 assert(LocInfo.LowerBound < VersionStack.size() &&((LocInfo.LowerBound < VersionStack.size() && "Lower bound out of range"
) ? static_cast<void> (0) : __assert_fail ("LocInfo.LowerBound < VersionStack.size() && \"Lower bound out of range\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1353, __PRETTY_FUNCTION__))
1353 "Lower bound out of range")((LocInfo.LowerBound < VersionStack.size() && "Lower bound out of range"
) ? static_cast<void> (0) : __assert_fail ("LocInfo.LowerBound < VersionStack.size() && \"Lower bound out of range\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1353, __PRETTY_FUNCTION__));
1354 assert(LocInfo.LastKill < VersionStack.size() &&((LocInfo.LastKill < VersionStack.size() && "Last kill info out of range"
) ? static_cast<void> (0) : __assert_fail ("LocInfo.LastKill < VersionStack.size() && \"Last kill info out of range\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1355, __PRETTY_FUNCTION__))
1355 "Last kill info out of range")((LocInfo.LastKill < VersionStack.size() && "Last kill info out of range"
) ? static_cast<void> (0) : __assert_fail ("LocInfo.LastKill < VersionStack.size() && \"Last kill info out of range\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1355, __PRETTY_FUNCTION__));
1356 // In any case, the new upper bound is the top of the stack.
1357 unsigned long UpperBound = VersionStack.size() - 1;
1358
1359 if (UpperBound - LocInfo.LowerBound > MaxCheckLimit) {
1360 DEBUG(dbgs() << "MemorySSA skipping optimization of " << *MU << " ("do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << "MemorySSA skipping optimization of "
<< *MU << " (" << *(MU->getMemoryInst()
) << ")" << " because there are " << UpperBound
- LocInfo.LowerBound << " stores to disambiguate\n"; }
} while (false)
1361 << *(MU->getMemoryInst()) << ")"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << "MemorySSA skipping optimization of "
<< *MU << " (" << *(MU->getMemoryInst()
) << ")" << " because there are " << UpperBound
- LocInfo.LowerBound << " stores to disambiguate\n"; }
} while (false)
1362 << " because there are " << UpperBound - LocInfo.LowerBounddo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << "MemorySSA skipping optimization of "
<< *MU << " (" << *(MU->getMemoryInst()
) << ")" << " because there are " << UpperBound
- LocInfo.LowerBound << " stores to disambiguate\n"; }
} while (false)
1363 << " stores to disambiguate\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << "MemorySSA skipping optimization of "
<< *MU << " (" << *(MU->getMemoryInst()
) << ")" << " because there are " << UpperBound
- LocInfo.LowerBound << " stores to disambiguate\n"; }
} while (false);
1364 // Because we did not walk, LastKill is no longer valid, as this may
1365 // have been a kill.
1366 LocInfo.LastKillValid = false;
1367 continue;
1368 }
1369 bool FoundClobberResult = false;
1370 while (UpperBound > LocInfo.LowerBound) {
1371 if (isa<MemoryPhi>(VersionStack[UpperBound])) {
1372 // For phis, use the walker, see where we ended up, go there
1373 Instruction *UseInst = MU->getMemoryInst();
1374 MemoryAccess *Result = Walker->getClobberingMemoryAccess(UseInst);
1375 // We are guaranteed to find it or something is wrong
1376 while (VersionStack[UpperBound] != Result) {
1377 assert(UpperBound != 0)((UpperBound != 0) ? static_cast<void> (0) : __assert_fail
("UpperBound != 0", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1377, __PRETTY_FUNCTION__));
1378 --UpperBound;
1379 }
1380 FoundClobberResult = true;
1381 break;
1382 }
1383
1384 MemoryDef *MD = cast<MemoryDef>(VersionStack[UpperBound]);
1385 // If the lifetime of the pointer ends at this instruction, it's live on
1386 // entry.
1387 if (!UseMLOC.IsCall && lifetimeEndsAt(MD, UseMLOC.getLoc(), *AA)) {
1388 // Reset UpperBound to liveOnEntryDef's place in the stack
1389 UpperBound = 0;
1390 FoundClobberResult = true;
1391 break;
1392 }
1393 if (instructionClobbersQuery(MD, MU, UseMLOC, *AA)) {
1394 FoundClobberResult = true;
1395 break;
1396 }
1397 --UpperBound;
1398 }
1399 // At the end of this loop, UpperBound is either a clobber, or lower bound
1400 // PHI walking may cause it to be < LowerBound, and in fact, < LastKill.
1401 if (FoundClobberResult || UpperBound < LocInfo.LastKill) {
1402 MU->setDefiningAccess(VersionStack[UpperBound], true);
1403 // We were last killed now by where we got to
1404 LocInfo.LastKill = UpperBound;
1405 } else {
1406 // Otherwise, we checked all the new ones, and now we know we can get to
1407 // LastKill.
1408 MU->setDefiningAccess(VersionStack[LocInfo.LastKill], true);
1409 }
1410 LocInfo.LowerBound = VersionStack.size() - 1;
1411 LocInfo.LowerBoundBlock = BB;
1412 }
1413}
1414
1415/// Optimize uses to point to their actual clobbering definitions.
1416void MemorySSA::OptimizeUses::optimizeUses() {
1417 SmallVector<MemoryAccess *, 16> VersionStack;
1418 DenseMap<MemoryLocOrCall, MemlocStackInfo> LocStackInfo;
1419 VersionStack.push_back(MSSA->getLiveOnEntryDef());
1420
1421 unsigned long StackEpoch = 1;
1422 unsigned long PopEpoch = 1;
1423 // We perform a non-recursive top-down dominator tree walk.
1424 for (const auto *DomNode : depth_first(DT->getRootNode()))
1425 optimizeUsesInBlock(DomNode->getBlock(), StackEpoch, PopEpoch, VersionStack,
1426 LocStackInfo);
1427}
1428
1429void MemorySSA::placePHINodes(
1430 const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks,
1431 const DenseMap<const BasicBlock *, unsigned int> &BBNumbers) {
1432 // Determine where our MemoryPhi's should go
1433 ForwardIDFCalculator IDFs(*DT);
1434 IDFs.setDefiningBlocks(DefiningBlocks);
1435 SmallVector<BasicBlock *, 32> IDFBlocks;
1436 IDFs.calculate(IDFBlocks);
1437
1438 std::sort(IDFBlocks.begin(), IDFBlocks.end(),
1439 [&BBNumbers](const BasicBlock *A, const BasicBlock *B) {
1440 return BBNumbers.lookup(A) < BBNumbers.lookup(B);
1441 });
1442
1443 // Now place MemoryPhi nodes.
1444 for (auto &BB : IDFBlocks)
1445 createMemoryPhi(BB);
1446}
1447
1448void MemorySSA::buildMemorySSA() {
1449 // We create an access to represent "live on entry", for things like
1450 // arguments or users of globals, where the memory they use is defined before
1451 // the beginning of the function. We do not actually insert it into the IR.
1452 // We do not define a live on exit for the immediate uses, and thus our
1453 // semantics do *not* imply that something with no immediate uses can simply
1454 // be removed.
1455 BasicBlock &StartingPoint = F.getEntryBlock();
1456 LiveOnEntryDef = make_unique<MemoryDef>(F.getContext(), nullptr, nullptr,
1457 &StartingPoint, NextID++);
1458 DenseMap<const BasicBlock *, unsigned int> BBNumbers;
1459 unsigned NextBBNum = 0;
1460
1461 // We maintain lists of memory accesses per-block, trading memory for time. We
1462 // could just look up the memory access for every possible instruction in the
1463 // stream.
1464 SmallPtrSet<BasicBlock *, 32> DefiningBlocks;
1465 SmallPtrSet<BasicBlock *, 32> DefUseBlocks;
1466 // Go through each block, figure out where defs occur, and chain together all
1467 // the accesses.
1468 for (BasicBlock &B : F) {
1469 BBNumbers[&B] = NextBBNum++;
1470 bool InsertIntoDef = false;
1471 AccessList *Accesses = nullptr;
1472 DefsList *Defs = nullptr;
1473 for (Instruction &I : B) {
1474 MemoryUseOrDef *MUD = createNewAccess(&I);
1475 if (!MUD)
1476 continue;
1477
1478 if (!Accesses)
1479 Accesses = getOrCreateAccessList(&B);
1480 Accesses->push_back(MUD);
1481 if (isa<MemoryDef>(MUD)) {
1482 InsertIntoDef = true;
1483 if (!Defs)
1484 Defs = getOrCreateDefsList(&B);
1485 Defs->push_back(*MUD);
1486 }
1487 }
1488 if (InsertIntoDef)
1489 DefiningBlocks.insert(&B);
1490 if (Accesses)
1491 DefUseBlocks.insert(&B);
1492 }
1493 placePHINodes(DefiningBlocks, BBNumbers);
1494
1495 // Now do regular SSA renaming on the MemoryDef/MemoryUse. Visited will get
1496 // filled in with all blocks.
1497 SmallPtrSet<BasicBlock *, 16> Visited;
1498 renamePass(DT->getRootNode(), LiveOnEntryDef.get(), Visited);
1499
1500 CachingWalker *Walker = getWalkerImpl();
1501
1502 // We're doing a batch of updates; don't drop useful caches between them.
1503 Walker->setAutoResetWalker(false);
1504 OptimizeUses(this, Walker, AA, DT).optimizeUses();
1505 Walker->setAutoResetWalker(true);
1506 Walker->resetClobberWalker();
1507
1508 // Mark the uses in unreachable blocks as live on entry, so that they go
1509 // somewhere.
1510 for (auto &BB : F)
1511 if (!Visited.count(&BB))
1512 markUnreachableAsLiveOnEntry(&BB);
1513}
1514
1515MemorySSAWalker *MemorySSA::getWalker() { return getWalkerImpl(); }
1516
1517MemorySSA::CachingWalker *MemorySSA::getWalkerImpl() {
1518 if (Walker)
1519 return Walker.get();
1520
1521 Walker = make_unique<CachingWalker>(this, AA, DT);
1522 return Walker.get();
1523}
1524
1525// This is a helper function used by the creation routines. It places NewAccess
1526// into the access and defs lists for a given basic block, at the given
1527// insertion point.
1528void MemorySSA::insertIntoListsForBlock(MemoryAccess *NewAccess,
1529 const BasicBlock *BB,
1530 InsertionPlace Point) {
1531 auto *Accesses = getOrCreateAccessList(BB);
1532 if (Point == Beginning) {
1533 // If it's a phi node, it goes first, otherwise, it goes after any phi
1534 // nodes.
1535 if (isa<MemoryPhi>(NewAccess)) {
1536 Accesses->push_front(NewAccess);
1537 auto *Defs = getOrCreateDefsList(BB);
1538 Defs->push_front(*NewAccess);
1539 } else {
1540 auto AI = find_if_not(
1541 *Accesses, [](const MemoryAccess &MA) { return isa<MemoryPhi>(MA); });
1542 Accesses->insert(AI, NewAccess);
1543 if (!isa<MemoryUse>(NewAccess)) {
1544 auto *Defs = getOrCreateDefsList(BB);
1545 auto DI = find_if_not(
1546 *Defs, [](const MemoryAccess &MA) { return isa<MemoryPhi>(MA); });
1547 Defs->insert(DI, *NewAccess);
1548 }
1549 }
1550 } else {
1551 Accesses->push_back(NewAccess);
1552 if (!isa<MemoryUse>(NewAccess)) {
1553 auto *Defs = getOrCreateDefsList(BB);
1554 Defs->push_back(*NewAccess);
1555 }
1556 }
1557 BlockNumberingValid.erase(BB);
1558}
1559
1560void MemorySSA::insertIntoListsBefore(MemoryAccess *What, const BasicBlock *BB,
1561 AccessList::iterator InsertPt) {
1562 auto *Accesses = getWritableBlockAccesses(BB);
1563 bool WasEnd = InsertPt == Accesses->end();
1564 Accesses->insert(AccessList::iterator(InsertPt), What);
1565 if (!isa<MemoryUse>(What)) {
1566 auto *Defs = getOrCreateDefsList(BB);
1567 // If we got asked to insert at the end, we have an easy job, just shove it
1568 // at the end. If we got asked to insert before an existing def, we also get
1569 // an terator. If we got asked to insert before a use, we have to hunt for
1570 // the next def.
1571 if (WasEnd) {
1572 Defs->push_back(*What);
1573 } else if (isa<MemoryDef>(InsertPt)) {
1574 Defs->insert(InsertPt->getDefsIterator(), *What);
1575 } else {
1576 while (InsertPt != Accesses->end() && !isa<MemoryDef>(InsertPt))
1577 ++InsertPt;
1578 // Either we found a def, or we are inserting at the end
1579 if (InsertPt == Accesses->end())
1580 Defs->push_back(*What);
1581 else
1582 Defs->insert(InsertPt->getDefsIterator(), *What);
1583 }
1584 }
1585 BlockNumberingValid.erase(BB);
1586}
1587
1588// Move What before Where in the IR. The end result is taht What will belong to
1589// the right lists and have the right Block set, but will not otherwise be
1590// correct. It will not have the right defining access, and if it is a def,
1591// things below it will not properly be updated.
1592void MemorySSA::moveTo(MemoryUseOrDef *What, BasicBlock *BB,
1593 AccessList::iterator Where) {
1594 // Keep it in the lookup tables, remove from the lists
1595 removeFromLists(What, false);
1596 What->setBlock(BB);
1597 insertIntoListsBefore(What, BB, Where);
1598}
1599
1600void MemorySSA::moveTo(MemoryUseOrDef *What, BasicBlock *BB,
1601 InsertionPlace Point) {
1602 removeFromLists(What, false);
1603 What->setBlock(BB);
1604 insertIntoListsForBlock(What, BB, Point);
1605}
1606
1607MemoryPhi *MemorySSA::createMemoryPhi(BasicBlock *BB) {
1608 assert(!getMemoryAccess(BB) && "MemoryPhi already exists for this BB")((!getMemoryAccess(BB) && "MemoryPhi already exists for this BB"
) ? static_cast<void> (0) : __assert_fail ("!getMemoryAccess(BB) && \"MemoryPhi already exists for this BB\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1608, __PRETTY_FUNCTION__));
1609 MemoryPhi *Phi = new MemoryPhi(BB->getContext(), BB, NextID++);
1610 // Phi's always are placed at the front of the block.
1611 insertIntoListsForBlock(Phi, BB, Beginning);
1612 ValueToMemoryAccess[BB] = Phi;
1613 return Phi;
1614}
1615
1616MemoryUseOrDef *MemorySSA::createDefinedAccess(Instruction *I,
1617 MemoryAccess *Definition) {
1618 assert(!isa<PHINode>(I) && "Cannot create a defined access for a PHI")((!isa<PHINode>(I) && "Cannot create a defined access for a PHI"
) ? static_cast<void> (0) : __assert_fail ("!isa<PHINode>(I) && \"Cannot create a defined access for a PHI\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1618, __PRETTY_FUNCTION__));
1619 MemoryUseOrDef *NewAccess = createNewAccess(I);
1620 assert(((NewAccess != nullptr && "Tried to create a memory access for a non-memory touching instruction"
) ? static_cast<void> (0) : __assert_fail ("NewAccess != nullptr && \"Tried to create a memory access for a non-memory touching instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1622, __PRETTY_FUNCTION__))
1621 NewAccess != nullptr &&((NewAccess != nullptr && "Tried to create a memory access for a non-memory touching instruction"
) ? static_cast<void> (0) : __assert_fail ("NewAccess != nullptr && \"Tried to create a memory access for a non-memory touching instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1622, __PRETTY_FUNCTION__))
1622 "Tried to create a memory access for a non-memory touching instruction")((NewAccess != nullptr && "Tried to create a memory access for a non-memory touching instruction"
) ? static_cast<void> (0) : __assert_fail ("NewAccess != nullptr && \"Tried to create a memory access for a non-memory touching instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1622, __PRETTY_FUNCTION__));
1623 NewAccess->setDefiningAccess(Definition);
1624 return NewAccess;
1625}
1626
1627/// \brief Helper function to create new memory accesses
1628MemoryUseOrDef *MemorySSA::createNewAccess(Instruction *I) {
1629 // The assume intrinsic has a control dependency which we model by claiming
1630 // that it writes arbitrarily. Ignore that fake memory dependency here.
1631 // FIXME: Replace this special casing with a more accurate modelling of
1632 // assume's control dependency.
1633 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
1634 if (II->getIntrinsicID() == Intrinsic::assume)
1635 return nullptr;
1636
1637 // Find out what affect this instruction has on memory.
1638 ModRefInfo ModRef = AA->getModRefInfo(I);
1639 bool Def = bool(ModRef & MRI_Mod);
1640 bool Use = bool(ModRef & MRI_Ref);
1641
1642 // It's possible for an instruction to not modify memory at all. During
1643 // construction, we ignore them.
1644 if (!Def && !Use)
1645 return nullptr;
1646
1647 assert((Def || Use) &&(((Def || Use) && "Trying to create a memory access with a non-memory instruction"
) ? static_cast<void> (0) : __assert_fail ("(Def || Use) && \"Trying to create a memory access with a non-memory instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1648, __PRETTY_FUNCTION__))
1648 "Trying to create a memory access with a non-memory instruction")(((Def || Use) && "Trying to create a memory access with a non-memory instruction"
) ? static_cast<void> (0) : __assert_fail ("(Def || Use) && \"Trying to create a memory access with a non-memory instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1648, __PRETTY_FUNCTION__));
1649
1650 MemoryUseOrDef *MUD;
1651 if (Def)
1652 MUD = new MemoryDef(I->getContext(), nullptr, I, I->getParent(), NextID++);
1653 else
1654 MUD = new MemoryUse(I->getContext(), nullptr, I, I->getParent());
1655 ValueToMemoryAccess[I] = MUD;
1656 return MUD;
1657}
1658
1659/// \brief Returns true if \p Replacer dominates \p Replacee .
1660bool MemorySSA::dominatesUse(const MemoryAccess *Replacer,
1661 const MemoryAccess *Replacee) const {
1662 if (isa<MemoryUseOrDef>(Replacee))
1663 return DT->dominates(Replacer->getBlock(), Replacee->getBlock());
1664 const auto *MP = cast<MemoryPhi>(Replacee);
1665 // For a phi node, the use occurs in the predecessor block of the phi node.
1666 // Since we may occur multiple times in the phi node, we have to check each
1667 // operand to ensure Replacer dominates each operand where Replacee occurs.
1668 for (const Use &Arg : MP->operands()) {
1669 if (Arg.get() != Replacee &&
1670 !DT->dominates(Replacer->getBlock(), MP->getIncomingBlock(Arg)))
1671 return false;
1672 }
1673 return true;
1674}
1675
1676/// \brief Properly remove \p MA from all of MemorySSA's lookup tables.
1677void MemorySSA::removeFromLookups(MemoryAccess *MA) {
1678 assert(MA->use_empty() &&((MA->use_empty() && "Trying to remove memory access that still has uses"
) ? static_cast<void> (0) : __assert_fail ("MA->use_empty() && \"Trying to remove memory access that still has uses\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1679, __PRETTY_FUNCTION__))
1679 "Trying to remove memory access that still has uses")((MA->use_empty() && "Trying to remove memory access that still has uses"
) ? static_cast<void> (0) : __assert_fail ("MA->use_empty() && \"Trying to remove memory access that still has uses\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1679, __PRETTY_FUNCTION__));
1680 BlockNumbering.erase(MA);
1681 if (MemoryUseOrDef *MUD = dyn_cast<MemoryUseOrDef>(MA))
1682 MUD->setDefiningAccess(nullptr);
1683 // Invalidate our walker's cache if necessary
1684 if (!isa<MemoryUse>(MA))
1685 Walker->invalidateInfo(MA);
1686 // The call below to erase will destroy MA, so we can't change the order we
1687 // are doing things here
1688 Value *MemoryInst;
1689 if (MemoryUseOrDef *MUD = dyn_cast<MemoryUseOrDef>(MA)) {
1690 MemoryInst = MUD->getMemoryInst();
1691 } else {
1692 MemoryInst = MA->getBlock();
1693 }
1694 auto VMA = ValueToMemoryAccess.find(MemoryInst);
1695 if (VMA->second == MA)
1696 ValueToMemoryAccess.erase(VMA);
1697}
1698
1699/// \brief Properly remove \p MA from all of MemorySSA's lists.
1700///
1701/// Because of the way the intrusive list and use lists work, it is important to
1702/// do removal in the right order.
1703/// ShouldDelete defaults to true, and will cause the memory access to also be
1704/// deleted, not just removed.
1705void MemorySSA::removeFromLists(MemoryAccess *MA, bool ShouldDelete) {
1706 // The access list owns the reference, so we erase it from the non-owning list
1707 // first.
1708 if (!isa<MemoryUse>(MA)) {
1709 auto DefsIt = PerBlockDefs.find(MA->getBlock());
1710 std::unique_ptr<DefsList> &Defs = DefsIt->second;
1711 Defs->remove(*MA);
1712 if (Defs->empty())
1713 PerBlockDefs.erase(DefsIt);
1714 }
1715
1716 // The erase call here will delete it. If we don't want it deleted, we call
1717 // remove instead.
1718 auto AccessIt = PerBlockAccesses.find(MA->getBlock());
1719 std::unique_ptr<AccessList> &Accesses = AccessIt->second;
1720 if (ShouldDelete)
1721 Accesses->erase(MA);
1722 else
1723 Accesses->remove(MA);
1724
1725 if (Accesses->empty())
1726 PerBlockAccesses.erase(AccessIt);
1727}
1728
1729void MemorySSA::print(raw_ostream &OS) const {
1730 MemorySSAAnnotatedWriter Writer(this);
1731 F.print(OS, &Writer);
1732}
1733
1734#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1735LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void MemorySSA::dump() const { print(dbgs()); }
1736#endif
1737
1738void MemorySSA::verifyMemorySSA() const {
1739 verifyDefUses(F);
1740 verifyDomination(F);
1741 verifyOrdering(F);
1742 Walker->verify(this);
1743}
1744
1745/// \brief Verify that the order and existence of MemoryAccesses matches the
1746/// order and existence of memory affecting instructions.
1747void MemorySSA::verifyOrdering(Function &F) const {
1748 // Walk all the blocks, comparing what the lookups think and what the access
1749 // lists think, as well as the order in the blocks vs the order in the access
1750 // lists.
1751 SmallVector<MemoryAccess *, 32> ActualAccesses;
1752 SmallVector<MemoryAccess *, 32> ActualDefs;
1753 for (BasicBlock &B : F) {
1754 const AccessList *AL = getBlockAccesses(&B);
1755 const auto *DL = getBlockDefs(&B);
1756 MemoryAccess *Phi = getMemoryAccess(&B);
1757 if (Phi) {
1758 ActualAccesses.push_back(Phi);
1759 ActualDefs.push_back(Phi);
1760 }
1761
1762 for (Instruction &I : B) {
1763 MemoryAccess *MA = getMemoryAccess(&I);
1764 assert((!MA || (AL && (isa<MemoryUse>(MA) || DL))) &&(((!MA || (AL && (isa<MemoryUse>(MA) || DL))) &&
"We have memory affecting instructions " "in this block but they are not in the "
"access list or defs list") ? static_cast<void> (0) : __assert_fail
("(!MA || (AL && (isa<MemoryUse>(MA) || DL))) && \"We have memory affecting instructions \" \"in this block but they are not in the \" \"access list or defs list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1767, __PRETTY_FUNCTION__))
1765 "We have memory affecting instructions "(((!MA || (AL && (isa<MemoryUse>(MA) || DL))) &&
"We have memory affecting instructions " "in this block but they are not in the "
"access list or defs list") ? static_cast<void> (0) : __assert_fail
("(!MA || (AL && (isa<MemoryUse>(MA) || DL))) && \"We have memory affecting instructions \" \"in this block but they are not in the \" \"access list or defs list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1767, __PRETTY_FUNCTION__))
1766 "in this block but they are not in the "(((!MA || (AL && (isa<MemoryUse>(MA) || DL))) &&
"We have memory affecting instructions " "in this block but they are not in the "
"access list or defs list") ? static_cast<void> (0) : __assert_fail
("(!MA || (AL && (isa<MemoryUse>(MA) || DL))) && \"We have memory affecting instructions \" \"in this block but they are not in the \" \"access list or defs list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1767, __PRETTY_FUNCTION__))
1767 "access list or defs list")(((!MA || (AL && (isa<MemoryUse>(MA) || DL))) &&
"We have memory affecting instructions " "in this block but they are not in the "
"access list or defs list") ? static_cast<void> (0) : __assert_fail
("(!MA || (AL && (isa<MemoryUse>(MA) || DL))) && \"We have memory affecting instructions \" \"in this block but they are not in the \" \"access list or defs list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1767, __PRETTY_FUNCTION__));
1768 if (MA) {
1769 ActualAccesses.push_back(MA);
1770 if (isa<MemoryDef>(MA))
1771 ActualDefs.push_back(MA);
1772 }
1773 }
1774 // Either we hit the assert, really have no accesses, or we have both
1775 // accesses and an access list.
1776 // Same with defs.
1777 if (!AL && !DL)
1778 continue;
1779 assert(AL->size() == ActualAccesses.size() &&((AL->size() == ActualAccesses.size() && "We don't have the same number of accesses in the block as on the "
"access list") ? static_cast<void> (0) : __assert_fail
("AL->size() == ActualAccesses.size() && \"We don't have the same number of accesses in the block as on the \" \"access list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1781, __PRETTY_FUNCTION__))
1780 "We don't have the same number of accesses in the block as on the "((AL->size() == ActualAccesses.size() && "We don't have the same number of accesses in the block as on the "
"access list") ? static_cast<void> (0) : __assert_fail
("AL->size() == ActualAccesses.size() && \"We don't have the same number of accesses in the block as on the \" \"access list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1781, __PRETTY_FUNCTION__))
1781 "access list")((AL->size() == ActualAccesses.size() && "We don't have the same number of accesses in the block as on the "
"access list") ? static_cast<void> (0) : __assert_fail
("AL->size() == ActualAccesses.size() && \"We don't have the same number of accesses in the block as on the \" \"access list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1781, __PRETTY_FUNCTION__));
1782 assert((DL || ActualDefs.size() == 0) &&(((DL || ActualDefs.size() == 0) && "Either we should have a defs list, or we should have no defs"
) ? static_cast<void> (0) : __assert_fail ("(DL || ActualDefs.size() == 0) && \"Either we should have a defs list, or we should have no defs\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1783, __PRETTY_FUNCTION__))
1783 "Either we should have a defs list, or we should have no defs")(((DL || ActualDefs.size() == 0) && "Either we should have a defs list, or we should have no defs"
) ? static_cast<void> (0) : __assert_fail ("(DL || ActualDefs.size() == 0) && \"Either we should have a defs list, or we should have no defs\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1783, __PRETTY_FUNCTION__));
1784 assert((!DL || DL->size() == ActualDefs.size()) &&(((!DL || DL->size() == ActualDefs.size()) && "We don't have the same number of defs in the block as on the "
"def list") ? static_cast<void> (0) : __assert_fail ("(!DL || DL->size() == ActualDefs.size()) && \"We don't have the same number of defs in the block as on the \" \"def list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1786, __PRETTY_FUNCTION__))
1785 "We don't have the same number of defs in the block as on the "(((!DL || DL->size() == ActualDefs.size()) && "We don't have the same number of defs in the block as on the "
"def list") ? static_cast<void> (0) : __assert_fail ("(!DL || DL->size() == ActualDefs.size()) && \"We don't have the same number of defs in the block as on the \" \"def list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1786, __PRETTY_FUNCTION__))
1786 "def list")(((!DL || DL->size() == ActualDefs.size()) && "We don't have the same number of defs in the block as on the "
"def list") ? static_cast<void> (0) : __assert_fail ("(!DL || DL->size() == ActualDefs.size()) && \"We don't have the same number of defs in the block as on the \" \"def list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1786, __PRETTY_FUNCTION__));
1787 auto ALI = AL->begin();
1788 auto AAI = ActualAccesses.begin();
1789 while (ALI != AL->end() && AAI != ActualAccesses.end()) {
1790 assert(&*ALI == *AAI && "Not the same accesses in the same order")((&*ALI == *AAI && "Not the same accesses in the same order"
) ? static_cast<void> (0) : __assert_fail ("&*ALI == *AAI && \"Not the same accesses in the same order\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1790, __PRETTY_FUNCTION__));
1791 ++ALI;
1792 ++AAI;
1793 }
1794 ActualAccesses.clear();
1795 if (DL) {
1796 auto DLI = DL->begin();
1797 auto ADI = ActualDefs.begin();
1798 while (DLI != DL->end() && ADI != ActualDefs.end()) {
1799 assert(&*DLI == *ADI && "Not the same defs in the same order")((&*DLI == *ADI && "Not the same defs in the same order"
) ? static_cast<void> (0) : __assert_fail ("&*DLI == *ADI && \"Not the same defs in the same order\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1799, __PRETTY_FUNCTION__));
1800 ++DLI;
1801 ++ADI;
1802 }
1803 }
1804 ActualDefs.clear();
1805 }
1806}
1807
1808/// \brief Verify the domination properties of MemorySSA by checking that each
1809/// definition dominates all of its uses.
1810void MemorySSA::verifyDomination(Function &F) const {
1811#ifndef NDEBUG
1812 for (BasicBlock &B : F) {
1813 // Phi nodes are attached to basic blocks
1814 if (MemoryPhi *MP = getMemoryAccess(&B))
1815 for (const Use &U : MP->uses())
1816 assert(dominates(MP, U) && "Memory PHI does not dominate it's uses")((dominates(MP, U) && "Memory PHI does not dominate it's uses"
) ? static_cast<void> (0) : __assert_fail ("dominates(MP, U) && \"Memory PHI does not dominate it's uses\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1816, __PRETTY_FUNCTION__));
1817
1818 for (Instruction &I : B) {
1819 MemoryAccess *MD = dyn_cast_or_null<MemoryDef>(getMemoryAccess(&I));
1820 if (!MD)
1821 continue;
1822
1823 for (const Use &U : MD->uses())
1824 assert(dominates(MD, U) && "Memory Def does not dominate it's uses")((dominates(MD, U) && "Memory Def does not dominate it's uses"
) ? static_cast<void> (0) : __assert_fail ("dominates(MD, U) && \"Memory Def does not dominate it's uses\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1824, __PRETTY_FUNCTION__));
1825 }
1826 }
1827#endif
1828}
1829
1830/// \brief Verify the def-use lists in MemorySSA, by verifying that \p Use
1831/// appears in the use list of \p Def.
1832
1833void MemorySSA::verifyUseInDefs(MemoryAccess *Def, MemoryAccess *Use) const {
1834#ifndef NDEBUG
1835 // The live on entry use may cause us to get a NULL def here
1836 if (!Def)
1837 assert(isLiveOnEntryDef(Use) &&((isLiveOnEntryDef(Use) && "Null def but use not point to live on entry def"
) ? static_cast<void> (0) : __assert_fail ("isLiveOnEntryDef(Use) && \"Null def but use not point to live on entry def\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1838, __PRETTY_FUNCTION__))
1838 "Null def but use not point to live on entry def")((isLiveOnEntryDef(Use) && "Null def but use not point to live on entry def"
) ? static_cast<void> (0) : __assert_fail ("isLiveOnEntryDef(Use) && \"Null def but use not point to live on entry def\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1838, __PRETTY_FUNCTION__));
1839 else
1840 assert(is_contained(Def->users(), Use) &&((is_contained(Def->users(), Use) && "Did not find use in def's use list"
) ? static_cast<void> (0) : __assert_fail ("is_contained(Def->users(), Use) && \"Did not find use in def's use list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1841, __PRETTY_FUNCTION__))
1841 "Did not find use in def's use list")((is_contained(Def->users(), Use) && "Did not find use in def's use list"
) ? static_cast<void> (0) : __assert_fail ("is_contained(Def->users(), Use) && \"Did not find use in def's use list\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1841, __PRETTY_FUNCTION__));
1842#endif
1843}
1844
1845/// \brief Verify the immediate use information, by walking all the memory
1846/// accesses and verifying that, for each use, it appears in the
1847/// appropriate def's use list
1848void MemorySSA::verifyDefUses(Function &F) const {
1849 for (BasicBlock &B : F) {
1850 // Phi nodes are attached to basic blocks
1851 if (MemoryPhi *Phi = getMemoryAccess(&B)) {
1852 assert(Phi->getNumOperands() == static_cast<unsigned>(std::distance(((Phi->getNumOperands() == static_cast<unsigned>(std
::distance( pred_begin(&B), pred_end(&B))) &&
"Incomplete MemoryPhi Node") ? static_cast<void> (0) :
__assert_fail ("Phi->getNumOperands() == static_cast<unsigned>(std::distance( pred_begin(&B), pred_end(&B))) && \"Incomplete MemoryPhi Node\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1854, __PRETTY_FUNCTION__))
1853 pred_begin(&B), pred_end(&B))) &&((Phi->getNumOperands() == static_cast<unsigned>(std
::distance( pred_begin(&B), pred_end(&B))) &&
"Incomplete MemoryPhi Node") ? static_cast<void> (0) :
__assert_fail ("Phi->getNumOperands() == static_cast<unsigned>(std::distance( pred_begin(&B), pred_end(&B))) && \"Incomplete MemoryPhi Node\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1854, __PRETTY_FUNCTION__))
1854 "Incomplete MemoryPhi Node")((Phi->getNumOperands() == static_cast<unsigned>(std
::distance( pred_begin(&B), pred_end(&B))) &&
"Incomplete MemoryPhi Node") ? static_cast<void> (0) :
__assert_fail ("Phi->getNumOperands() == static_cast<unsigned>(std::distance( pred_begin(&B), pred_end(&B))) && \"Incomplete MemoryPhi Node\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1854, __PRETTY_FUNCTION__));
1855 for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I)
1856 verifyUseInDefs(Phi->getIncomingValue(I), Phi);
1857 }
1858
1859 for (Instruction &I : B) {
1860 if (MemoryUseOrDef *MA = getMemoryAccess(&I)) {
1861 verifyUseInDefs(MA->getDefiningAccess(), MA);
1862 }
1863 }
1864 }
1865}
1866
1867MemoryUseOrDef *MemorySSA::getMemoryAccess(const Instruction *I) const {
1868 return cast_or_null<MemoryUseOrDef>(ValueToMemoryAccess.lookup(I));
1869}
1870
1871MemoryPhi *MemorySSA::getMemoryAccess(const BasicBlock *BB) const {
1872 return cast_or_null<MemoryPhi>(ValueToMemoryAccess.lookup(cast<Value>(BB)));
1873}
1874
1875/// Perform a local numbering on blocks so that instruction ordering can be
1876/// determined in constant time.
1877/// TODO: We currently just number in order. If we numbered by N, we could
1878/// allow at least N-1 sequences of insertBefore or insertAfter (and at least
1879/// log2(N) sequences of mixed before and after) without needing to invalidate
1880/// the numbering.
1881void MemorySSA::renumberBlock(const BasicBlock *B) const {
1882 // The pre-increment ensures the numbers really start at 1.
1883 unsigned long CurrentNumber = 0;
1884 const AccessList *AL = getBlockAccesses(B);
1885 assert(AL != nullptr && "Asking to renumber an empty block")((AL != nullptr && "Asking to renumber an empty block"
) ? static_cast<void> (0) : __assert_fail ("AL != nullptr && \"Asking to renumber an empty block\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1885, __PRETTY_FUNCTION__));
1886 for (const auto &I : *AL)
1887 BlockNumbering[&I] = ++CurrentNumber;
1888 BlockNumberingValid.insert(B);
1889}
1890
1891/// \brief Determine, for two memory accesses in the same block,
1892/// whether \p Dominator dominates \p Dominatee.
1893/// \returns True if \p Dominator dominates \p Dominatee.
1894bool MemorySSA::locallyDominates(const MemoryAccess *Dominator,
1895 const MemoryAccess *Dominatee) const {
1896
1897 const BasicBlock *DominatorBlock = Dominator->getBlock();
1898
1899 assert((DominatorBlock == Dominatee->getBlock()) &&(((DominatorBlock == Dominatee->getBlock()) && "Asking for local domination when accesses are in different blocks!"
) ? static_cast<void> (0) : __assert_fail ("(DominatorBlock == Dominatee->getBlock()) && \"Asking for local domination when accesses are in different blocks!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1900, __PRETTY_FUNCTION__))
1900 "Asking for local domination when accesses are in different blocks!")(((DominatorBlock == Dominatee->getBlock()) && "Asking for local domination when accesses are in different blocks!"
) ? static_cast<void> (0) : __assert_fail ("(DominatorBlock == Dominatee->getBlock()) && \"Asking for local domination when accesses are in different blocks!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1900, __PRETTY_FUNCTION__));
1901 // A node dominates itself.
1902 if (Dominatee == Dominator)
1903 return true;
1904
1905 // When Dominatee is defined on function entry, it is not dominated by another
1906 // memory access.
1907 if (isLiveOnEntryDef(Dominatee))
1908 return false;
1909
1910 // When Dominator is defined on function entry, it dominates the other memory
1911 // access.
1912 if (isLiveOnEntryDef(Dominator))
1913 return true;
1914
1915 if (!BlockNumberingValid.count(DominatorBlock))
1916 renumberBlock(DominatorBlock);
1917
1918 unsigned long DominatorNum = BlockNumbering.lookup(Dominator);
1919 // All numbers start with 1
1920 assert(DominatorNum != 0 && "Block was not numbered properly")((DominatorNum != 0 && "Block was not numbered properly"
) ? static_cast<void> (0) : __assert_fail ("DominatorNum != 0 && \"Block was not numbered properly\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1920, __PRETTY_FUNCTION__));
1921 unsigned long DominateeNum = BlockNumbering.lookup(Dominatee);
1922 assert(DominateeNum != 0 && "Block was not numbered properly")((DominateeNum != 0 && "Block was not numbered properly"
) ? static_cast<void> (0) : __assert_fail ("DominateeNum != 0 && \"Block was not numbered properly\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 1922, __PRETTY_FUNCTION__));
1923 return DominatorNum < DominateeNum;
1924}
1925
1926bool MemorySSA::dominates(const MemoryAccess *Dominator,
1927 const MemoryAccess *Dominatee) const {
1928 if (Dominator == Dominatee)
1929 return true;
1930
1931 if (isLiveOnEntryDef(Dominatee))
1932 return false;
1933
1934 if (Dominator->getBlock() != Dominatee->getBlock())
1935 return DT->dominates(Dominator->getBlock(), Dominatee->getBlock());
1936 return locallyDominates(Dominator, Dominatee);
1937}
1938
1939bool MemorySSA::dominates(const MemoryAccess *Dominator,
1940 const Use &Dominatee) const {
1941 if (MemoryPhi *MP = dyn_cast<MemoryPhi>(Dominatee.getUser())) {
1942 BasicBlock *UseBB = MP->getIncomingBlock(Dominatee);
1943 // The def must dominate the incoming block of the phi.
1944 if (UseBB != Dominator->getBlock())
1945 return DT->dominates(Dominator->getBlock(), UseBB);
1946 // If the UseBB and the DefBB are the same, compare locally.
1947 return locallyDominates(Dominator, cast<MemoryAccess>(Dominatee));
1948 }
1949 // If it's not a PHI node use, the normal dominates can already handle it.
1950 return dominates(Dominator, cast<MemoryAccess>(Dominatee.getUser()));
1951}
1952
1953const static char LiveOnEntryStr[] = "liveOnEntry";
1954
1955void MemoryDef::print(raw_ostream &OS) const {
1956 MemoryAccess *UO = getDefiningAccess();
1957
1958 OS << getID() << " = MemoryDef(";
1959 if (UO && UO->getID())
1960 OS << UO->getID();
1961 else
1962 OS << LiveOnEntryStr;
1963 OS << ')';
1964}
1965
1966void MemoryPhi::print(raw_ostream &OS) const {
1967 bool First = true;
1968 OS << getID() << " = MemoryPhi(";
1969 for (const auto &Op : operands()) {
1970 BasicBlock *BB = getIncomingBlock(Op);
1971 MemoryAccess *MA = cast<MemoryAccess>(Op);
1972 if (!First)
1973 OS << ',';
1974 else
1975 First = false;
1976
1977 OS << '{';
1978 if (BB->hasName())
1979 OS << BB->getName();
1980 else
1981 BB->printAsOperand(OS, false);
1982 OS << ',';
1983 if (unsigned ID = MA->getID())
1984 OS << ID;
1985 else
1986 OS << LiveOnEntryStr;
1987 OS << '}';
1988 }
1989 OS << ')';
1990}
1991
1992MemoryAccess::~MemoryAccess() {}
1993
1994void MemoryUse::print(raw_ostream &OS) const {
1995 MemoryAccess *UO = getDefiningAccess();
1996 OS << "MemoryUse(";
1997 if (UO && UO->getID())
1998 OS << UO->getID();
1999 else
2000 OS << LiveOnEntryStr;
2001 OS << ')';
2002}
2003
2004void MemoryAccess::dump() const {
2005// Cannot completely remove virtual function even in release mode.
2006#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
2007 print(dbgs());
2008 dbgs() << "\n";
2009#endif
2010}
2011
2012char MemorySSAPrinterLegacyPass::ID = 0;
2013
2014MemorySSAPrinterLegacyPass::MemorySSAPrinterLegacyPass() : FunctionPass(ID) {
2015 initializeMemorySSAPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
2016}
2017
2018void MemorySSAPrinterLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
2019 AU.setPreservesAll();
2020 AU.addRequired<MemorySSAWrapperPass>();
2021 AU.addPreserved<MemorySSAWrapperPass>();
2022}
2023
2024bool MemorySSAPrinterLegacyPass::runOnFunction(Function &F) {
2025 auto &MSSA = getAnalysis<MemorySSAWrapperPass>().getMSSA();
2026 MSSA.print(dbgs());
2027 if (VerifyMemorySSA)
2028 MSSA.verifyMemorySSA();
2029 return false;
2030}
2031
2032AnalysisKey MemorySSAAnalysis::Key;
2033
2034MemorySSAAnalysis::Result MemorySSAAnalysis::run(Function &F,
2035 FunctionAnalysisManager &AM) {
2036 auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
2037 auto &AA = AM.getResult<AAManager>(F);
2038 return MemorySSAAnalysis::Result(make_unique<MemorySSA>(F, &AA, &DT));
2039}
2040
2041PreservedAnalyses MemorySSAPrinterPass::run(Function &F,
2042 FunctionAnalysisManager &AM) {
2043 OS << "MemorySSA for function: " << F.getName() << "\n";
2044 AM.getResult<MemorySSAAnalysis>(F).getMSSA().print(OS);
2045
2046 return PreservedAnalyses::all();
2047}
2048
2049PreservedAnalyses MemorySSAVerifierPass::run(Function &F,
2050 FunctionAnalysisManager &AM) {
2051 AM.getResult<MemorySSAAnalysis>(F).getMSSA().verifyMemorySSA();
2052
2053 return PreservedAnalyses::all();
2054}
2055
2056char MemorySSAWrapperPass::ID = 0;
2057
2058MemorySSAWrapperPass::MemorySSAWrapperPass() : FunctionPass(ID) {
2059 initializeMemorySSAWrapperPassPass(*PassRegistry::getPassRegistry());
2060}
2061
2062void MemorySSAWrapperPass::releaseMemory() { MSSA.reset(); }
2063
2064void MemorySSAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
2065 AU.setPreservesAll();
2066 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
2067 AU.addRequiredTransitive<AAResultsWrapperPass>();
2068}
2069
2070bool MemorySSAWrapperPass::runOnFunction(Function &F) {
2071 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
2072 auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
2073 MSSA.reset(new MemorySSA(F, &AA, &DT));
2074 return false;
2075}
2076
2077void MemorySSAWrapperPass::verifyAnalysis() const { MSSA->verifyMemorySSA(); }
2078
2079void MemorySSAWrapperPass::print(raw_ostream &OS, const Module *M) const {
2080 MSSA->print(OS);
2081}
2082
2083MemorySSAWalker::MemorySSAWalker(MemorySSA *M) : MSSA(M) {}
2084
2085MemorySSA::CachingWalker::CachingWalker(MemorySSA *M, AliasAnalysis *A,
2086 DominatorTree *D)
2087 : MemorySSAWalker(M), Walker(*M, *A, *D, Cache), AutoResetWalker(true) {}
2088
2089MemorySSA::CachingWalker::~CachingWalker() {}
2090
2091void MemorySSA::CachingWalker::invalidateInfo(MemoryAccess *MA) {
2092 // TODO: We can do much better cache invalidation with differently stored
2093 // caches. For now, for MemoryUses, we simply remove them
2094 // from the cache, and kill the entire call/non-call cache for everything
2095 // else. The problem is for phis or defs, currently we'd need to follow use
2096 // chains down and invalidate anything below us in the chain that currently
2097 // terminates at this access.
2098
2099 // See if this is a MemoryUse, if so, just remove the cached info. MemoryUse
2100 // is by definition never a barrier, so nothing in the cache could point to
2101 // this use. In that case, we only need invalidate the info for the use
2102 // itself.
2103
2104 if (MemoryUse *MU = dyn_cast<MemoryUse>(MA)) {
2105 UpwardsMemoryQuery Q(MU->getMemoryInst(), MU);
2106 Cache.remove(MU, Q.StartingLoc, Q.IsCall);
2107 MU->resetOptimized();
2108 } else {
2109 // If it is not a use, the best we can do right now is destroy the cache.
2110 Cache.clear();
2111 }
2112
2113#ifdef EXPENSIVE_CHECKS
2114 verifyRemoved(MA);
2115#endif
2116}
2117
2118/// \brief Walk the use-def chains starting at \p MA and find
2119/// the MemoryAccess that actually clobbers Loc.
2120///
2121/// \returns our clobbering memory access
2122MemoryAccess *MemorySSA::CachingWalker::getClobberingMemoryAccess(
2123 MemoryAccess *StartingAccess, UpwardsMemoryQuery &Q) {
2124 MemoryAccess *New = Walker.findClobber(StartingAccess, Q);
2125#ifdef EXPENSIVE_CHECKS
2126 MemoryAccess *NewNoCache =
2127 Walker.findClobber(StartingAccess, Q, /*UseWalkerCache=*/false);
2128 assert(NewNoCache == New && "Cache made us hand back a different result?")((NewNoCache == New && "Cache made us hand back a different result?"
) ? static_cast<void> (0) : __assert_fail ("NewNoCache == New && \"Cache made us hand back a different result?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 2128, __PRETTY_FUNCTION__));
2129#endif
2130 if (AutoResetWalker)
2131 resetClobberWalker();
2132 return New;
2133}
2134
2135MemoryAccess *MemorySSA::CachingWalker::getClobberingMemoryAccess(
2136 MemoryAccess *StartingAccess, const MemoryLocation &Loc) {
2137 if (isa<MemoryPhi>(StartingAccess))
2138 return StartingAccess;
2139
2140 auto *StartingUseOrDef = cast<MemoryUseOrDef>(StartingAccess);
2141 if (MSSA->isLiveOnEntryDef(StartingUseOrDef))
2142 return StartingUseOrDef;
2143
2144 Instruction *I = StartingUseOrDef->getMemoryInst();
2145
2146 // Conservatively, fences are always clobbers, so don't perform the walk if we
2147 // hit a fence.
2148 if (!ImmutableCallSite(I) && I->isFenceLike())
2149 return StartingUseOrDef;
2150
2151 UpwardsMemoryQuery Q;
2152 Q.OriginalAccess = StartingUseOrDef;
2153 Q.StartingLoc = Loc;
2154 Q.Inst = I;
2155 Q.IsCall = false;
2156
2157 if (auto *CacheResult = Cache.lookup(StartingUseOrDef, Loc, Q.IsCall))
2158 return CacheResult;
2159
2160 // Unlike the other function, do not walk to the def of a def, because we are
2161 // handed something we already believe is the clobbering access.
2162 MemoryAccess *DefiningAccess = isa<MemoryUse>(StartingUseOrDef)
2163 ? StartingUseOrDef->getDefiningAccess()
2164 : StartingUseOrDef;
2165
2166 MemoryAccess *Clobber = getClobberingMemoryAccess(DefiningAccess, Q);
2167 DEBUG(dbgs() << "Starting Memory SSA clobber for " << *I << " is ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << "Starting Memory SSA clobber for "
<< *I << " is "; } } while (false);
2168 DEBUG(dbgs() << *StartingUseOrDef << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << *StartingUseOrDef << "\n"
; } } while (false);
2169 DEBUG(dbgs() << "Final Memory SSA clobber for " << *I << " is ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << "Final Memory SSA clobber for "
<< *I << " is "; } } while (false);
2170 DEBUG(dbgs() << *Clobber << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << *Clobber << "\n"; } } while
(false);
2171 return Clobber;
2172}
2173
2174MemoryAccess *
2175MemorySSA::CachingWalker::getClobberingMemoryAccess(MemoryAccess *MA) {
2176 auto *StartingAccess = dyn_cast<MemoryUseOrDef>(MA);
2177 // If this is a MemoryPhi, we can't do anything.
2178 if (!StartingAccess)
2179 return MA;
2180
2181 // If this is an already optimized use or def, return the optimized result.
2182 // Note: Currently, we do not store the optimized def result because we'd need
2183 // a separate field, since we can't use it as the defining access.
2184 if (auto *MUD = dyn_cast<MemoryUseOrDef>(StartingAccess))
2185 if (MUD->isOptimized())
2186 return MUD->getOptimized();
2187
2188 const Instruction *I = StartingAccess->getMemoryInst();
2189 UpwardsMemoryQuery Q(I, StartingAccess);
2190 // We can't sanely do anything with a fences, they conservatively
2191 // clobber all memory, and have no locations to get pointers from to
2192 // try to disambiguate.
2193 if (!Q.IsCall && I->isFenceLike())
2194 return StartingAccess;
2195
2196 if (auto *CacheResult = Cache.lookup(StartingAccess, Q.StartingLoc, Q.IsCall))
2197 return CacheResult;
2198
2199 if (isUseTriviallyOptimizableToLiveOnEntry(*MSSA->AA, I)) {
2200 MemoryAccess *LiveOnEntry = MSSA->getLiveOnEntryDef();
2201 Cache.insert(StartingAccess, LiveOnEntry, Q.StartingLoc, Q.IsCall);
2202 if (auto *MUD = dyn_cast<MemoryUseOrDef>(StartingAccess))
2203 MUD->setOptimized(LiveOnEntry);
2204 return LiveOnEntry;
2205 }
2206
2207 // Start with the thing we already think clobbers this location
2208 MemoryAccess *DefiningAccess = StartingAccess->getDefiningAccess();
2209
2210 // At this point, DefiningAccess may be the live on entry def.
2211 // If it is, we will not get a better result.
2212 if (MSSA->isLiveOnEntryDef(DefiningAccess))
2213 return DefiningAccess;
2214
2215 MemoryAccess *Result = getClobberingMemoryAccess(DefiningAccess, Q);
2216 DEBUG(dbgs() << "Starting Memory SSA clobber for " << *I << " is ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << "Starting Memory SSA clobber for "
<< *I << " is "; } } while (false);
2217 DEBUG(dbgs() << *DefiningAccess << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << *DefiningAccess << "\n"
; } } while (false);
2218 DEBUG(dbgs() << "Final Memory SSA clobber for " << *I << " is ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << "Final Memory SSA clobber for "
<< *I << " is "; } } while (false);
2219 DEBUG(dbgs() << *Result << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << *Result << "\n"; } } while
(false);
2220 if (auto *MUD = dyn_cast<MemoryUseOrDef>(StartingAccess))
2221 MUD->setOptimized(Result);
2222
2223 return Result;
2224}
2225
2226// Verify that MA doesn't exist in any of the caches.
2227void MemorySSA::CachingWalker::verifyRemoved(MemoryAccess *MA) {
2228 assert(!Cache.contains(MA) && "Found removed MemoryAccess in cache.")((!Cache.contains(MA) && "Found removed MemoryAccess in cache."
) ? static_cast<void> (0) : __assert_fail ("!Cache.contains(MA) && \"Found removed MemoryAccess in cache.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn299523/lib/Transforms/Utils/MemorySSA.cpp"
, 2228, __PRETTY_FUNCTION__));
2229}
2230
2231MemoryAccess *
2232DoNothingMemorySSAWalker::getClobberingMemoryAccess(MemoryAccess *MA) {
2233 if (auto *Use = dyn_cast<MemoryUseOrDef>(MA))
2234 return Use->getDefiningAccess();
2235 return MA;
2236}
2237
2238MemoryAccess *DoNothingMemorySSAWalker::getClobberingMemoryAccess(
2239 MemoryAccess *StartingAccess, const MemoryLocation &) {
2240 if (auto *Use = dyn_cast<MemoryUseOrDef>(StartingAccess))
2241 return Use->getDefiningAccess();
2242 return StartingAccess;
2243}
2244} // namespace llvm