Bug Summary

File:lib/Analysis/MemorySSA.cpp
Warning:line 1107, column 5
Value stored to 'Walker' is never read

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name MemorySSA.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-eagerly-assume -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-7/lib/clang/7.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-7~svn336939/build-llvm/lib/Analysis -I /build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis -I /build/llvm-toolchain-snapshot-7~svn336939/build-llvm/include -I /build/llvm-toolchain-snapshot-7~svn336939/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/x86_64-linux-gnu/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/x86_64-linux-gnu/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/backward -internal-isystem /usr/include/clang/7.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-7/lib/clang/7.0.0/include -internal-externc-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-7~svn336939/build-llvm/lib/Analysis -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2018-07-13-043813-3945-1 -x c++ /build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp
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
14#include "llvm/Analysis/MemorySSA.h"
15#include "llvm/ADT/DenseMap.h"
16#include "llvm/ADT/DenseMapInfo.h"
17#include "llvm/ADT/DenseSet.h"
18#include "llvm/ADT/DepthFirstIterator.h"
19#include "llvm/ADT/Hashing.h"
20#include "llvm/ADT/None.h"
21#include "llvm/ADT/Optional.h"
22#include "llvm/ADT/STLExtras.h"
23#include "llvm/ADT/SmallPtrSet.h"
24#include "llvm/ADT/SmallVector.h"
25#include "llvm/ADT/iterator.h"
26#include "llvm/ADT/iterator_range.h"
27#include "llvm/Analysis/AliasAnalysis.h"
28#include "llvm/Analysis/IteratedDominanceFrontier.h"
29#include "llvm/Analysis/MemoryLocation.h"
30#include "llvm/Config/llvm-config.h"
31#include "llvm/IR/AssemblyAnnotationWriter.h"
32#include "llvm/IR/BasicBlock.h"
33#include "llvm/IR/CallSite.h"
34#include "llvm/IR/Dominators.h"
35#include "llvm/IR/Function.h"
36#include "llvm/IR/Instruction.h"
37#include "llvm/IR/Instructions.h"
38#include "llvm/IR/IntrinsicInst.h"
39#include "llvm/IR/Intrinsics.h"
40#include "llvm/IR/LLVMContext.h"
41#include "llvm/IR/PassManager.h"
42#include "llvm/IR/Use.h"
43#include "llvm/Pass.h"
44#include "llvm/Support/AtomicOrdering.h"
45#include "llvm/Support/Casting.h"
46#include "llvm/Support/CommandLine.h"
47#include "llvm/Support/Compiler.h"
48#include "llvm/Support/Debug.h"
49#include "llvm/Support/ErrorHandling.h"
50#include "llvm/Support/FormattedStream.h"
51#include "llvm/Support/raw_ostream.h"
52#include <algorithm>
53#include <cassert>
54#include <iterator>
55#include <memory>
56#include <utility>
57
58using namespace llvm;
59
60#define DEBUG_TYPE"memoryssa" "memoryssa"
61
62INITIALIZE_PASS_BEGIN(MemorySSAWrapperPass, "memoryssa", "Memory SSA", false,static void *initializeMemorySSAWrapperPassPassOnce(PassRegistry
&Registry) {
63 true)static void *initializeMemorySSAWrapperPassPassOnce(PassRegistry
&Registry) {
64INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
65INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)initializeAAResultsWrapperPassPass(Registry);
66INITIALIZE_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))
; }
67 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))
; }
68
69INITIALIZE_PASS_BEGIN(MemorySSAPrinterLegacyPass, "print-memoryssa",static void *initializeMemorySSAPrinterLegacyPassPassOnce(PassRegistry
&Registry) {
70 "Memory SSA Printer", false, false)static void *initializeMemorySSAPrinterLegacyPassPassOnce(PassRegistry
&Registry) {
71INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry);
72INITIALIZE_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
)); }
73 "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
)); }
74
75static cl::opt<unsigned> MaxCheckLimit(
76 "memssa-check-limit", cl::Hidden, cl::init(100),
77 cl::desc("The maximum number of stores/phis MemorySSA"
78 "will consider trying to walk past (default = 100)"));
79
80static cl::opt<bool>
81 VerifyMemorySSA("verify-memoryssa", cl::init(false), cl::Hidden,
82 cl::desc("Verify MemorySSA in legacy printer pass."));
83
84namespace llvm {
85
86/// An assembly annotator class to print Memory SSA information in
87/// comments.
88class MemorySSAAnnotatedWriter : public AssemblyAnnotationWriter {
89 friend class MemorySSA;
90
91 const MemorySSA *MSSA;
92
93public:
94 MemorySSAAnnotatedWriter(const MemorySSA *M) : MSSA(M) {}
95
96 void emitBasicBlockStartAnnot(const BasicBlock *BB,
97 formatted_raw_ostream &OS) override {
98 if (MemoryAccess *MA = MSSA->getMemoryAccess(BB))
99 OS << "; " << *MA << "\n";
100 }
101
102 void emitInstructionAnnot(const Instruction *I,
103 formatted_raw_ostream &OS) override {
104 if (MemoryAccess *MA = MSSA->getMemoryAccess(I))
105 OS << "; " << *MA << "\n";
106 }
107};
108
109} // end namespace llvm
110
111namespace {
112
113/// Our current alias analysis API differentiates heavily between calls and
114/// non-calls, and functions called on one usually assert on the other.
115/// This class encapsulates the distinction to simplify other code that wants
116/// "Memory affecting instructions and related data" to use as a key.
117/// For example, this class is used as a densemap key in the use optimizer.
118class MemoryLocOrCall {
119public:
120 bool IsCall = false;
121
122 MemoryLocOrCall() = default;
123 MemoryLocOrCall(MemoryUseOrDef *MUD)
124 : MemoryLocOrCall(MUD->getMemoryInst()) {}
125 MemoryLocOrCall(const MemoryUseOrDef *MUD)
126 : MemoryLocOrCall(MUD->getMemoryInst()) {}
127
128 MemoryLocOrCall(Instruction *Inst) {
129 if (ImmutableCallSite(Inst)) {
130 IsCall = true;
131 CS = ImmutableCallSite(Inst);
132 } else {
133 IsCall = false;
134 // There is no such thing as a memorylocation for a fence inst, and it is
135 // unique in that regard.
136 if (!isa<FenceInst>(Inst))
137 Loc = MemoryLocation::get(Inst);
138 }
139 }
140
141 explicit MemoryLocOrCall(const MemoryLocation &Loc) : Loc(Loc) {}
142
143 ImmutableCallSite getCS() const {
144 assert(IsCall)(static_cast <bool> (IsCall) ? void (0) : __assert_fail
("IsCall", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 144, __extension__ __PRETTY_FUNCTION__))
;
145 return CS;
146 }
147
148 MemoryLocation getLoc() const {
149 assert(!IsCall)(static_cast <bool> (!IsCall) ? void (0) : __assert_fail
("!IsCall", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 149, __extension__ __PRETTY_FUNCTION__))
;
150 return Loc;
151 }
152
153 bool operator==(const MemoryLocOrCall &Other) const {
154 if (IsCall != Other.IsCall)
155 return false;
156
157 if (!IsCall)
158 return Loc == Other.Loc;
159
160 if (CS.getCalledValue() != Other.CS.getCalledValue())
161 return false;
162
163 return CS.arg_size() == Other.CS.arg_size() &&
164 std::equal(CS.arg_begin(), CS.arg_end(), Other.CS.arg_begin());
165 }
166
167private:
168 union {
169 ImmutableCallSite CS;
170 MemoryLocation Loc;
171 };
172};
173
174} // end anonymous namespace
175
176namespace llvm {
177
178template <> struct DenseMapInfo<MemoryLocOrCall> {
179 static inline MemoryLocOrCall getEmptyKey() {
180 return MemoryLocOrCall(DenseMapInfo<MemoryLocation>::getEmptyKey());
181 }
182
183 static inline MemoryLocOrCall getTombstoneKey() {
184 return MemoryLocOrCall(DenseMapInfo<MemoryLocation>::getTombstoneKey());
185 }
186
187 static unsigned getHashValue(const MemoryLocOrCall &MLOC) {
188 if (!MLOC.IsCall)
189 return hash_combine(
190 MLOC.IsCall,
191 DenseMapInfo<MemoryLocation>::getHashValue(MLOC.getLoc()));
192
193 hash_code hash =
194 hash_combine(MLOC.IsCall, DenseMapInfo<const Value *>::getHashValue(
195 MLOC.getCS().getCalledValue()));
196
197 for (const Value *Arg : MLOC.getCS().args())
198 hash = hash_combine(hash, DenseMapInfo<const Value *>::getHashValue(Arg));
199 return hash;
200 }
201
202 static bool isEqual(const MemoryLocOrCall &LHS, const MemoryLocOrCall &RHS) {
203 return LHS == RHS;
204 }
205};
206
207} // end namespace llvm
208
209/// This does one-way checks to see if Use could theoretically be hoisted above
210/// MayClobber. This will not check the other way around.
211///
212/// This assumes that, for the purposes of MemorySSA, Use comes directly after
213/// MayClobber, with no potentially clobbering operations in between them.
214/// (Where potentially clobbering ops are memory barriers, aliased stores, etc.)
215static bool areLoadsReorderable(const LoadInst *Use,
216 const LoadInst *MayClobber) {
217 bool VolatileUse = Use->isVolatile();
218 bool VolatileClobber = MayClobber->isVolatile();
219 // Volatile operations may never be reordered with other volatile operations.
220 if (VolatileUse && VolatileClobber)
221 return false;
222 // Otherwise, volatile doesn't matter here. From the language reference:
223 // 'optimizers may change the order of volatile operations relative to
224 // non-volatile operations.'"
225
226 // If a load is seq_cst, it cannot be moved above other loads. If its ordering
227 // is weaker, it can be moved above other loads. We just need to be sure that
228 // MayClobber isn't an acquire load, because loads can't be moved above
229 // acquire loads.
230 //
231 // Note that this explicitly *does* allow the free reordering of monotonic (or
232 // weaker) loads of the same address.
233 bool SeqCstUse = Use->getOrdering() == AtomicOrdering::SequentiallyConsistent;
234 bool MayClobberIsAcquire = isAtLeastOrStrongerThan(MayClobber->getOrdering(),
235 AtomicOrdering::Acquire);
236 return !(SeqCstUse || MayClobberIsAcquire);
237}
238
239namespace {
240
241struct ClobberAlias {
242 bool IsClobber;
243 Optional<AliasResult> AR;
244};
245
246} // end anonymous namespace
247
248// Return a pair of {IsClobber (bool), AR (AliasResult)}. It relies on AR being
249// ignored if IsClobber = false.
250static ClobberAlias instructionClobbersQuery(MemoryDef *MD,
251 const MemoryLocation &UseLoc,
252 const Instruction *UseInst,
253 AliasAnalysis &AA) {
254 Instruction *DefInst = MD->getMemoryInst();
255 assert(DefInst && "Defining instruction not actually an instruction")(static_cast <bool> (DefInst && "Defining instruction not actually an instruction"
) ? void (0) : __assert_fail ("DefInst && \"Defining instruction not actually an instruction\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 255, __extension__ __PRETTY_FUNCTION__))
;
256 ImmutableCallSite UseCS(UseInst);
257 Optional<AliasResult> AR;
258
259 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) {
260 // These intrinsics will show up as affecting memory, but they are just
261 // markers.
262 switch (II->getIntrinsicID()) {
263 case Intrinsic::lifetime_start:
264 if (UseCS)
265 return {false, NoAlias};
266 AR = AA.alias(MemoryLocation(II->getArgOperand(1)), UseLoc);
267 return {AR == MustAlias, AR};
268 case Intrinsic::lifetime_end:
269 case Intrinsic::invariant_start:
270 case Intrinsic::invariant_end:
271 case Intrinsic::assume:
272 return {false, NoAlias};
273 default:
274 break;
275 }
276 }
277
278 if (UseCS) {
279 ModRefInfo I = AA.getModRefInfo(DefInst, UseCS);
280 AR = isMustSet(I) ? MustAlias : MayAlias;
281 return {isModOrRefSet(I), AR};
282 }
283
284 if (auto *DefLoad = dyn_cast<LoadInst>(DefInst))
285 if (auto *UseLoad = dyn_cast<LoadInst>(UseInst))
286 return {!areLoadsReorderable(UseLoad, DefLoad), MayAlias};
287
288 ModRefInfo I = AA.getModRefInfo(DefInst, UseLoc);
289 AR = isMustSet(I) ? MustAlias : MayAlias;
290 return {isModSet(I), AR};
291}
292
293static ClobberAlias instructionClobbersQuery(MemoryDef *MD,
294 const MemoryUseOrDef *MU,
295 const MemoryLocOrCall &UseMLOC,
296 AliasAnalysis &AA) {
297 // FIXME: This is a temporary hack to allow a single instructionClobbersQuery
298 // to exist while MemoryLocOrCall is pushed through places.
299 if (UseMLOC.IsCall)
300 return instructionClobbersQuery(MD, MemoryLocation(), MU->getMemoryInst(),
301 AA);
302 return instructionClobbersQuery(MD, UseMLOC.getLoc(), MU->getMemoryInst(),
303 AA);
304}
305
306// Return true when MD may alias MU, return false otherwise.
307bool MemorySSAUtil::defClobbersUseOrDef(MemoryDef *MD, const MemoryUseOrDef *MU,
308 AliasAnalysis &AA) {
309 return instructionClobbersQuery(MD, MU, MemoryLocOrCall(MU), AA).IsClobber;
310}
311
312namespace {
313
314struct UpwardsMemoryQuery {
315 // True if our original query started off as a call
316 bool IsCall = false;
317 // The pointer location we started the query with. This will be empty if
318 // IsCall is true.
319 MemoryLocation StartingLoc;
320 // This is the instruction we were querying about.
321 const Instruction *Inst = nullptr;
322 // The MemoryAccess we actually got called with, used to test local domination
323 const MemoryAccess *OriginalAccess = nullptr;
324 Optional<AliasResult> AR = MayAlias;
325
326 UpwardsMemoryQuery() = default;
327
328 UpwardsMemoryQuery(const Instruction *Inst, const MemoryAccess *Access)
329 : IsCall(ImmutableCallSite(Inst)), Inst(Inst), OriginalAccess(Access) {
330 if (!IsCall)
331 StartingLoc = MemoryLocation::get(Inst);
332 }
333};
334
335} // end anonymous namespace
336
337static bool lifetimeEndsAt(MemoryDef *MD, const MemoryLocation &Loc,
338 AliasAnalysis &AA) {
339 Instruction *Inst = MD->getMemoryInst();
340 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
341 switch (II->getIntrinsicID()) {
342 case Intrinsic::lifetime_end:
343 return AA.isMustAlias(MemoryLocation(II->getArgOperand(1)), Loc);
344 default:
345 return false;
346 }
347 }
348 return false;
349}
350
351static bool isUseTriviallyOptimizableToLiveOnEntry(AliasAnalysis &AA,
352 const Instruction *I) {
353 // If the memory can't be changed, then loads of the memory can't be
354 // clobbered.
355 return isa<LoadInst>(I) && (I->getMetadata(LLVMContext::MD_invariant_load) ||
356 AA.pointsToConstantMemory(cast<LoadInst>(I)->
357 getPointerOperand()));
358}
359
360/// Verifies that `Start` is clobbered by `ClobberAt`, and that nothing
361/// inbetween `Start` and `ClobberAt` can clobbers `Start`.
362///
363/// This is meant to be as simple and self-contained as possible. Because it
364/// uses no cache, etc., it can be relatively expensive.
365///
366/// \param Start The MemoryAccess that we want to walk from.
367/// \param ClobberAt A clobber for Start.
368/// \param StartLoc The MemoryLocation for Start.
369/// \param MSSA The MemorySSA isntance that Start and ClobberAt belong to.
370/// \param Query The UpwardsMemoryQuery we used for our search.
371/// \param AA The AliasAnalysis we used for our search.
372static void LLVM_ATTRIBUTE_UNUSED__attribute__((__unused__))
373checkClobberSanity(MemoryAccess *Start, MemoryAccess *ClobberAt,
374 const MemoryLocation &StartLoc, const MemorySSA &MSSA,
375 const UpwardsMemoryQuery &Query, AliasAnalysis &AA) {
376 assert(MSSA.dominates(ClobberAt, Start) && "Clobber doesn't dominate start?")(static_cast <bool> (MSSA.dominates(ClobberAt, Start) &&
"Clobber doesn't dominate start?") ? void (0) : __assert_fail
("MSSA.dominates(ClobberAt, Start) && \"Clobber doesn't dominate start?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 376, __extension__ __PRETTY_FUNCTION__))
;
377
378 if (MSSA.isLiveOnEntryDef(Start)) {
379 assert(MSSA.isLiveOnEntryDef(ClobberAt) &&(static_cast <bool> (MSSA.isLiveOnEntryDef(ClobberAt) &&
"liveOnEntry must clobber itself") ? void (0) : __assert_fail
("MSSA.isLiveOnEntryDef(ClobberAt) && \"liveOnEntry must clobber itself\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 380, __extension__ __PRETTY_FUNCTION__))
380 "liveOnEntry must clobber itself")(static_cast <bool> (MSSA.isLiveOnEntryDef(ClobberAt) &&
"liveOnEntry must clobber itself") ? void (0) : __assert_fail
("MSSA.isLiveOnEntryDef(ClobberAt) && \"liveOnEntry must clobber itself\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 380, __extension__ __PRETTY_FUNCTION__))
;
381 return;
382 }
383
384 bool FoundClobber = false;
385 DenseSet<MemoryAccessPair> VisitedPhis;
386 SmallVector<MemoryAccessPair, 8> Worklist;
387 Worklist.emplace_back(Start, StartLoc);
388 // Walk all paths from Start to ClobberAt, while looking for clobbers. If one
389 // is found, complain.
390 while (!Worklist.empty()) {
391 MemoryAccessPair MAP = Worklist.pop_back_val();
392 // All we care about is that nothing from Start to ClobberAt clobbers Start.
393 // We learn nothing from revisiting nodes.
394 if (!VisitedPhis.insert(MAP).second)
395 continue;
396
397 for (MemoryAccess *MA : def_chain(MAP.first)) {
398 if (MA == ClobberAt) {
399 if (auto *MD = dyn_cast<MemoryDef>(MA)) {
400 // instructionClobbersQuery isn't essentially free, so don't use `|=`,
401 // since it won't let us short-circuit.
402 //
403 // Also, note that this can't be hoisted out of the `Worklist` loop,
404 // since MD may only act as a clobber for 1 of N MemoryLocations.
405 FoundClobber = FoundClobber || MSSA.isLiveOnEntryDef(MD);
406 if (!FoundClobber) {
407 ClobberAlias CA =
408 instructionClobbersQuery(MD, MAP.second, Query.Inst, AA);
409 if (CA.IsClobber) {
410 FoundClobber = true;
411 // Not used: CA.AR;
412 }
413 }
414 }
415 break;
416 }
417
418 // We should never hit liveOnEntry, unless it's the clobber.
419 assert(!MSSA.isLiveOnEntryDef(MA) && "Hit liveOnEntry before clobber?")(static_cast <bool> (!MSSA.isLiveOnEntryDef(MA) &&
"Hit liveOnEntry before clobber?") ? void (0) : __assert_fail
("!MSSA.isLiveOnEntryDef(MA) && \"Hit liveOnEntry before clobber?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 419, __extension__ __PRETTY_FUNCTION__))
;
420
421 if (auto *MD = dyn_cast<MemoryDef>(MA)) {
422 (void)MD;
423 assert(!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA)(static_cast <bool> (!instructionClobbersQuery(MD, MAP.
second, Query.Inst, AA) .IsClobber && "Found clobber before reaching ClobberAt!"
) ? void (0) : __assert_fail ("!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA) .IsClobber && \"Found clobber before reaching ClobberAt!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 425, __extension__ __PRETTY_FUNCTION__))
424 .IsClobber &&(static_cast <bool> (!instructionClobbersQuery(MD, MAP.
second, Query.Inst, AA) .IsClobber && "Found clobber before reaching ClobberAt!"
) ? void (0) : __assert_fail ("!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA) .IsClobber && \"Found clobber before reaching ClobberAt!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 425, __extension__ __PRETTY_FUNCTION__))
425 "Found clobber before reaching ClobberAt!")(static_cast <bool> (!instructionClobbersQuery(MD, MAP.
second, Query.Inst, AA) .IsClobber && "Found clobber before reaching ClobberAt!"
) ? void (0) : __assert_fail ("!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA) .IsClobber && \"Found clobber before reaching ClobberAt!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 425, __extension__ __PRETTY_FUNCTION__))
;
426 continue;
427 }
428
429 assert(isa<MemoryPhi>(MA))(static_cast <bool> (isa<MemoryPhi>(MA)) ? void (
0) : __assert_fail ("isa<MemoryPhi>(MA)", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 429, __extension__ __PRETTY_FUNCTION__))
;
430 Worklist.append(upward_defs_begin({MA, MAP.second}), upward_defs_end());
431 }
432 }
433
434 // If ClobberAt is a MemoryPhi, we can assume something above it acted as a
435 // clobber. Otherwise, `ClobberAt` should've acted as a clobber at some point.
436 assert((isa<MemoryPhi>(ClobberAt) || FoundClobber) &&(static_cast <bool> ((isa<MemoryPhi>(ClobberAt) ||
FoundClobber) && "ClobberAt never acted as a clobber"
) ? void (0) : __assert_fail ("(isa<MemoryPhi>(ClobberAt) || FoundClobber) && \"ClobberAt never acted as a clobber\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 437, __extension__ __PRETTY_FUNCTION__))
437 "ClobberAt never acted as a clobber")(static_cast <bool> ((isa<MemoryPhi>(ClobberAt) ||
FoundClobber) && "ClobberAt never acted as a clobber"
) ? void (0) : __assert_fail ("(isa<MemoryPhi>(ClobberAt) || FoundClobber) && \"ClobberAt never acted as a clobber\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 437, __extension__ __PRETTY_FUNCTION__))
;
438}
439
440namespace {
441
442/// Our algorithm for walking (and trying to optimize) clobbers, all wrapped up
443/// in one class.
444class ClobberWalker {
445 /// Save a few bytes by using unsigned instead of size_t.
446 using ListIndex = unsigned;
447
448 /// Represents a span of contiguous MemoryDefs, potentially ending in a
449 /// MemoryPhi.
450 struct DefPath {
451 MemoryLocation Loc;
452 // Note that, because we always walk in reverse, Last will always dominate
453 // First. Also note that First and Last are inclusive.
454 MemoryAccess *First;
455 MemoryAccess *Last;
456 Optional<ListIndex> Previous;
457
458 DefPath(const MemoryLocation &Loc, MemoryAccess *First, MemoryAccess *Last,
459 Optional<ListIndex> Previous)
460 : Loc(Loc), First(First), Last(Last), Previous(Previous) {}
461
462 DefPath(const MemoryLocation &Loc, MemoryAccess *Init,
463 Optional<ListIndex> Previous)
464 : DefPath(Loc, Init, Init, Previous) {}
465 };
466
467 const MemorySSA &MSSA;
468 AliasAnalysis &AA;
469 DominatorTree &DT;
470 UpwardsMemoryQuery *Query;
471
472 // Phi optimization bookkeeping
473 SmallVector<DefPath, 32> Paths;
474 DenseSet<ConstMemoryAccessPair> VisitedPhis;
475
476 /// Find the nearest def or phi that `From` can legally be optimized to.
477 const MemoryAccess *getWalkTarget(const MemoryPhi *From) const {
478 assert(From->getNumOperands() && "Phi with no operands?")(static_cast <bool> (From->getNumOperands() &&
"Phi with no operands?") ? void (0) : __assert_fail ("From->getNumOperands() && \"Phi with no operands?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 478, __extension__ __PRETTY_FUNCTION__))
;
479
480 BasicBlock *BB = From->getBlock();
481 MemoryAccess *Result = MSSA.getLiveOnEntryDef();
482 DomTreeNode *Node = DT.getNode(BB);
483 while ((Node = Node->getIDom())) {
484 auto *Defs = MSSA.getBlockDefs(Node->getBlock());
485 if (Defs)
486 return &*Defs->rbegin();
487 }
488 return Result;
489 }
490
491 /// Result of calling walkToPhiOrClobber.
492 struct UpwardsWalkResult {
493 /// The "Result" of the walk. Either a clobber, the last thing we walked, or
494 /// both. Include alias info when clobber found.
495 MemoryAccess *Result;
496 bool IsKnownClobber;
497 Optional<AliasResult> AR;
498 };
499
500 /// Walk to the next Phi or Clobber in the def chain starting at Desc.Last.
501 /// This will update Desc.Last as it walks. It will (optionally) also stop at
502 /// StopAt.
503 ///
504 /// This does not test for whether StopAt is a clobber
505 UpwardsWalkResult
506 walkToPhiOrClobber(DefPath &Desc,
507 const MemoryAccess *StopAt = nullptr) const {
508 assert(!isa<MemoryUse>(Desc.Last) && "Uses don't exist in my world")(static_cast <bool> (!isa<MemoryUse>(Desc.Last) &&
"Uses don't exist in my world") ? void (0) : __assert_fail (
"!isa<MemoryUse>(Desc.Last) && \"Uses don't exist in my world\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 508, __extension__ __PRETTY_FUNCTION__))
;
509
510 for (MemoryAccess *Current : def_chain(Desc.Last)) {
511 Desc.Last = Current;
512 if (Current == StopAt)
513 return {Current, false, MayAlias};
514
515 if (auto *MD = dyn_cast<MemoryDef>(Current)) {
516 if (MSSA.isLiveOnEntryDef(MD))
517 return {MD, true, MustAlias};
518 ClobberAlias CA =
519 instructionClobbersQuery(MD, Desc.Loc, Query->Inst, AA);
520 if (CA.IsClobber)
521 return {MD, true, CA.AR};
522 }
523 }
524
525 assert(isa<MemoryPhi>(Desc.Last) &&(static_cast <bool> (isa<MemoryPhi>(Desc.Last) &&
"Ended at a non-clobber that's not a phi?") ? void (0) : __assert_fail
("isa<MemoryPhi>(Desc.Last) && \"Ended at a non-clobber that's not a phi?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 526, __extension__ __PRETTY_FUNCTION__))
526 "Ended at a non-clobber that's not a phi?")(static_cast <bool> (isa<MemoryPhi>(Desc.Last) &&
"Ended at a non-clobber that's not a phi?") ? void (0) : __assert_fail
("isa<MemoryPhi>(Desc.Last) && \"Ended at a non-clobber that's not a phi?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 526, __extension__ __PRETTY_FUNCTION__))
;
527 return {Desc.Last, false, MayAlias};
528 }
529
530 void addSearches(MemoryPhi *Phi, SmallVectorImpl<ListIndex> &PausedSearches,
531 ListIndex PriorNode) {
532 auto UpwardDefs = make_range(upward_defs_begin({Phi, Paths[PriorNode].Loc}),
533 upward_defs_end());
534 for (const MemoryAccessPair &P : UpwardDefs) {
535 PausedSearches.push_back(Paths.size());
536 Paths.emplace_back(P.second, P.first, PriorNode);
537 }
538 }
539
540 /// Represents a search that terminated after finding a clobber. This clobber
541 /// may or may not be present in the path of defs from LastNode..SearchStart,
542 /// since it may have been retrieved from cache.
543 struct TerminatedPath {
544 MemoryAccess *Clobber;
545 ListIndex LastNode;
546 };
547
548 /// Get an access that keeps us from optimizing to the given phi.
549 ///
550 /// PausedSearches is an array of indices into the Paths array. Its incoming
551 /// value is the indices of searches that stopped at the last phi optimization
552 /// target. It's left in an unspecified state.
553 ///
554 /// If this returns None, NewPaused is a vector of searches that terminated
555 /// at StopWhere. Otherwise, NewPaused is left in an unspecified state.
556 Optional<TerminatedPath>
557 getBlockingAccess(const MemoryAccess *StopWhere,
558 SmallVectorImpl<ListIndex> &PausedSearches,
559 SmallVectorImpl<ListIndex> &NewPaused,
560 SmallVectorImpl<TerminatedPath> &Terminated) {
561 assert(!PausedSearches.empty() && "No searches to continue?")(static_cast <bool> (!PausedSearches.empty() &&
"No searches to continue?") ? void (0) : __assert_fail ("!PausedSearches.empty() && \"No searches to continue?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 561, __extension__ __PRETTY_FUNCTION__))
;
562
563 // BFS vs DFS really doesn't make a difference here, so just do a DFS with
564 // PausedSearches as our stack.
565 while (!PausedSearches.empty()) {
566 ListIndex PathIndex = PausedSearches.pop_back_val();
567 DefPath &Node = Paths[PathIndex];
568
569 // If we've already visited this path with this MemoryLocation, we don't
570 // need to do so again.
571 //
572 // NOTE: That we just drop these paths on the ground makes caching
573 // behavior sporadic. e.g. given a diamond:
574 // A
575 // B C
576 // D
577 //
578 // ...If we walk D, B, A, C, we'll only cache the result of phi
579 // optimization for A, B, and D; C will be skipped because it dies here.
580 // This arguably isn't the worst thing ever, since:
581 // - We generally query things in a top-down order, so if we got below D
582 // without needing cache entries for {C, MemLoc}, then chances are
583 // that those cache entries would end up ultimately unused.
584 // - We still cache things for A, so C only needs to walk up a bit.
585 // If this behavior becomes problematic, we can fix without a ton of extra
586 // work.
587 if (!VisitedPhis.insert({Node.Last, Node.Loc}).second)
588 continue;
589
590 UpwardsWalkResult Res = walkToPhiOrClobber(Node, /*StopAt=*/StopWhere);
591 if (Res.IsKnownClobber) {
592 assert(Res.Result != StopWhere)(static_cast <bool> (Res.Result != StopWhere) ? void (0
) : __assert_fail ("Res.Result != StopWhere", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 592, __extension__ __PRETTY_FUNCTION__))
;
593 // If this wasn't a cache hit, we hit a clobber when walking. That's a
594 // failure.
595 TerminatedPath Term{Res.Result, PathIndex};
596 if (!MSSA.dominates(Res.Result, StopWhere))
597 return Term;
598
599 // Otherwise, it's a valid thing to potentially optimize to.
600 Terminated.push_back(Term);
601 continue;
602 }
603
604 if (Res.Result == StopWhere) {
605 // We've hit our target. Save this path off for if we want to continue
606 // walking.
607 NewPaused.push_back(PathIndex);
608 continue;
609 }
610
611 assert(!MSSA.isLiveOnEntryDef(Res.Result) && "liveOnEntry is a clobber")(static_cast <bool> (!MSSA.isLiveOnEntryDef(Res.Result)
&& "liveOnEntry is a clobber") ? void (0) : __assert_fail
("!MSSA.isLiveOnEntryDef(Res.Result) && \"liveOnEntry is a clobber\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 611, __extension__ __PRETTY_FUNCTION__))
;
612 addSearches(cast<MemoryPhi>(Res.Result), PausedSearches, PathIndex);
613 }
614
615 return None;
616 }
617
618 template <typename T, typename Walker>
619 struct generic_def_path_iterator
620 : public iterator_facade_base<generic_def_path_iterator<T, Walker>,
621 std::forward_iterator_tag, T *> {
622 generic_def_path_iterator() = default;
623 generic_def_path_iterator(Walker *W, ListIndex N) : W(W), N(N) {}
624
625 T &operator*() const { return curNode(); }
626
627 generic_def_path_iterator &operator++() {
628 N = curNode().Previous;
629 return *this;
630 }
631
632 bool operator==(const generic_def_path_iterator &O) const {
633 if (N.hasValue() != O.N.hasValue())
634 return false;
635 return !N.hasValue() || *N == *O.N;
636 }
637
638 private:
639 T &curNode() const { return W->Paths[*N]; }
640
641 Walker *W = nullptr;
642 Optional<ListIndex> N = None;
643 };
644
645 using def_path_iterator = generic_def_path_iterator<DefPath, ClobberWalker>;
646 using const_def_path_iterator =
647 generic_def_path_iterator<const DefPath, const ClobberWalker>;
648
649 iterator_range<def_path_iterator> def_path(ListIndex From) {
650 return make_range(def_path_iterator(this, From), def_path_iterator());
651 }
652
653 iterator_range<const_def_path_iterator> const_def_path(ListIndex From) const {
654 return make_range(const_def_path_iterator(this, From),
655 const_def_path_iterator());
656 }
657
658 struct OptznResult {
659 /// The path that contains our result.
660 TerminatedPath PrimaryClobber;
661 /// The paths that we can legally cache back from, but that aren't
662 /// necessarily the result of the Phi optimization.
663 SmallVector<TerminatedPath, 4> OtherClobbers;
664 };
665
666 ListIndex defPathIndex(const DefPath &N) const {
667 // The assert looks nicer if we don't need to do &N
668 const DefPath *NP = &N;
669 assert(!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() &&(static_cast <bool> (!Paths.empty() && NP >=
&Paths.front() && NP <= &Paths.back() &&
"Out of bounds DefPath!") ? void (0) : __assert_fail ("!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() && \"Out of bounds DefPath!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 670, __extension__ __PRETTY_FUNCTION__))
670 "Out of bounds DefPath!")(static_cast <bool> (!Paths.empty() && NP >=
&Paths.front() && NP <= &Paths.back() &&
"Out of bounds DefPath!") ? void (0) : __assert_fail ("!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() && \"Out of bounds DefPath!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 670, __extension__ __PRETTY_FUNCTION__))
;
671 return NP - &Paths.front();
672 }
673
674 /// Try to optimize a phi as best as we can. Returns a SmallVector of Paths
675 /// that act as legal clobbers. Note that this won't return *all* clobbers.
676 ///
677 /// Phi optimization algorithm tl;dr:
678 /// - Find the earliest def/phi, A, we can optimize to
679 /// - Find if all paths from the starting memory access ultimately reach A
680 /// - If not, optimization isn't possible.
681 /// - Otherwise, walk from A to another clobber or phi, A'.
682 /// - If A' is a def, we're done.
683 /// - If A' is a phi, try to optimize it.
684 ///
685 /// A path is a series of {MemoryAccess, MemoryLocation} pairs. A path
686 /// terminates when a MemoryAccess that clobbers said MemoryLocation is found.
687 OptznResult tryOptimizePhi(MemoryPhi *Phi, MemoryAccess *Start,
688 const MemoryLocation &Loc) {
689 assert(Paths.empty() && VisitedPhis.empty() &&(static_cast <bool> (Paths.empty() && VisitedPhis
.empty() && "Reset the optimization state.") ? void (
0) : __assert_fail ("Paths.empty() && VisitedPhis.empty() && \"Reset the optimization state.\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 690, __extension__ __PRETTY_FUNCTION__))
690 "Reset the optimization state.")(static_cast <bool> (Paths.empty() && VisitedPhis
.empty() && "Reset the optimization state.") ? void (
0) : __assert_fail ("Paths.empty() && VisitedPhis.empty() && \"Reset the optimization state.\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 690, __extension__ __PRETTY_FUNCTION__))
;
691
692 Paths.emplace_back(Loc, Start, Phi, None);
693 // Stores how many "valid" optimization nodes we had prior to calling
694 // addSearches/getBlockingAccess. Necessary for caching if we had a blocker.
695 auto PriorPathsSize = Paths.size();
696
697 SmallVector<ListIndex, 16> PausedSearches;
698 SmallVector<ListIndex, 8> NewPaused;
699 SmallVector<TerminatedPath, 4> TerminatedPaths;
700
701 addSearches(Phi, PausedSearches, 0);
702
703 // Moves the TerminatedPath with the "most dominated" Clobber to the end of
704 // Paths.
705 auto MoveDominatedPathToEnd = [&](SmallVectorImpl<TerminatedPath> &Paths) {
706 assert(!Paths.empty() && "Need a path to move")(static_cast <bool> (!Paths.empty() && "Need a path to move"
) ? void (0) : __assert_fail ("!Paths.empty() && \"Need a path to move\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 706, __extension__ __PRETTY_FUNCTION__))
;
707 auto Dom = Paths.begin();
708 for (auto I = std::next(Dom), E = Paths.end(); I != E; ++I)
709 if (!MSSA.dominates(I->Clobber, Dom->Clobber))
710 Dom = I;
711 auto Last = Paths.end() - 1;
712 if (Last != Dom)
713 std::iter_swap(Last, Dom);
714 };
715
716 MemoryPhi *Current = Phi;
717 while (true) {
718 assert(!MSSA.isLiveOnEntryDef(Current) &&(static_cast <bool> (!MSSA.isLiveOnEntryDef(Current) &&
"liveOnEntry wasn't treated as a clobber?") ? void (0) : __assert_fail
("!MSSA.isLiveOnEntryDef(Current) && \"liveOnEntry wasn't treated as a clobber?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 719, __extension__ __PRETTY_FUNCTION__))
719 "liveOnEntry wasn't treated as a clobber?")(static_cast <bool> (!MSSA.isLiveOnEntryDef(Current) &&
"liveOnEntry wasn't treated as a clobber?") ? void (0) : __assert_fail
("!MSSA.isLiveOnEntryDef(Current) && \"liveOnEntry wasn't treated as a clobber?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 719, __extension__ __PRETTY_FUNCTION__))
;
720
721 const auto *Target = getWalkTarget(Current);
722 // If a TerminatedPath doesn't dominate Target, then it wasn't a legal
723 // optimization for the prior phi.
724 assert(all_of(TerminatedPaths, [&](const TerminatedPath &P) {(static_cast <bool> (all_of(TerminatedPaths, [&](const
TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target
); })) ? void (0) : __assert_fail ("all_of(TerminatedPaths, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target); })"
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 726, __extension__ __PRETTY_FUNCTION__))
725 return MSSA.dominates(P.Clobber, Target);(static_cast <bool> (all_of(TerminatedPaths, [&](const
TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target
); })) ? void (0) : __assert_fail ("all_of(TerminatedPaths, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target); })"
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 726, __extension__ __PRETTY_FUNCTION__))
726 }))(static_cast <bool> (all_of(TerminatedPaths, [&](const
TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target
); })) ? void (0) : __assert_fail ("all_of(TerminatedPaths, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, Target); })"
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 726, __extension__ __PRETTY_FUNCTION__))
;
727
728 // FIXME: This is broken, because the Blocker may be reported to be
729 // liveOnEntry, and we'll happily wait for that to disappear (read: never)
730 // For the moment, this is fine, since we do nothing with blocker info.
731 if (Optional<TerminatedPath> Blocker = getBlockingAccess(
732 Target, PausedSearches, NewPaused, TerminatedPaths)) {
733
734 // Find the node we started at. We can't search based on N->Last, since
735 // we may have gone around a loop with a different MemoryLocation.
736 auto Iter = find_if(def_path(Blocker->LastNode), [&](const DefPath &N) {
737 return defPathIndex(N) < PriorPathsSize;
738 });
739 assert(Iter != def_path_iterator())(static_cast <bool> (Iter != def_path_iterator()) ? void
(0) : __assert_fail ("Iter != def_path_iterator()", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 739, __extension__ __PRETTY_FUNCTION__))
;
740
741 DefPath &CurNode = *Iter;
742 assert(CurNode.Last == Current)(static_cast <bool> (CurNode.Last == Current) ? void (0
) : __assert_fail ("CurNode.Last == Current", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 742, __extension__ __PRETTY_FUNCTION__))
;
743
744 // Two things:
745 // A. We can't reliably cache all of NewPaused back. Consider a case
746 // where we have two paths in NewPaused; one of which can't optimize
747 // above this phi, whereas the other can. If we cache the second path
748 // back, we'll end up with suboptimal cache entries. We can handle
749 // cases like this a bit better when we either try to find all
750 // clobbers that block phi optimization, or when our cache starts
751 // supporting unfinished searches.
752 // B. We can't reliably cache TerminatedPaths back here without doing
753 // extra checks; consider a case like:
754 // T
755 // / \
756 // D C
757 // \ /
758 // S
759 // Where T is our target, C is a node with a clobber on it, D is a
760 // diamond (with a clobber *only* on the left or right node, N), and
761 // S is our start. Say we walk to D, through the node opposite N
762 // (read: ignoring the clobber), and see a cache entry in the top
763 // node of D. That cache entry gets put into TerminatedPaths. We then
764 // walk up to C (N is later in our worklist), find the clobber, and
765 // quit. If we append TerminatedPaths to OtherClobbers, we'll cache
766 // the bottom part of D to the cached clobber, ignoring the clobber
767 // in N. Again, this problem goes away if we start tracking all
768 // blockers for a given phi optimization.
769 TerminatedPath Result{CurNode.Last, defPathIndex(CurNode)};
770 return {Result, {}};
771 }
772
773 // If there's nothing left to search, then all paths led to valid clobbers
774 // that we got from our cache; pick the nearest to the start, and allow
775 // the rest to be cached back.
776 if (NewPaused.empty()) {
777 MoveDominatedPathToEnd(TerminatedPaths);
778 TerminatedPath Result = TerminatedPaths.pop_back_val();
779 return {Result, std::move(TerminatedPaths)};
780 }
781
782 MemoryAccess *DefChainEnd = nullptr;
783 SmallVector<TerminatedPath, 4> Clobbers;
784 for (ListIndex Paused : NewPaused) {
785 UpwardsWalkResult WR = walkToPhiOrClobber(Paths[Paused]);
786 if (WR.IsKnownClobber)
787 Clobbers.push_back({WR.Result, Paused});
788 else
789 // Micro-opt: If we hit the end of the chain, save it.
790 DefChainEnd = WR.Result;
791 }
792
793 if (!TerminatedPaths.empty()) {
794 // If we couldn't find the dominating phi/liveOnEntry in the above loop,
795 // do it now.
796 if (!DefChainEnd)
797 for (auto *MA : def_chain(const_cast<MemoryAccess *>(Target)))
798 DefChainEnd = MA;
799
800 // If any of the terminated paths don't dominate the phi we'll try to
801 // optimize, we need to figure out what they are and quit.
802 const BasicBlock *ChainBB = DefChainEnd->getBlock();
803 for (const TerminatedPath &TP : TerminatedPaths) {
804 // Because we know that DefChainEnd is as "high" as we can go, we
805 // don't need local dominance checks; BB dominance is sufficient.
806 if (DT.dominates(ChainBB, TP.Clobber->getBlock()))
807 Clobbers.push_back(TP);
808 }
809 }
810
811 // If we have clobbers in the def chain, find the one closest to Current
812 // and quit.
813 if (!Clobbers.empty()) {
814 MoveDominatedPathToEnd(Clobbers);
815 TerminatedPath Result = Clobbers.pop_back_val();
816 return {Result, std::move(Clobbers)};
817 }
818
819 assert(all_of(NewPaused,(static_cast <bool> (all_of(NewPaused, [&](ListIndex
I) { return Paths[I].Last == DefChainEnd; })) ? void (0) : __assert_fail
("all_of(NewPaused, [&](ListIndex I) { return Paths[I].Last == DefChainEnd; })"
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 820, __extension__ __PRETTY_FUNCTION__))
820 [&](ListIndex I) { return Paths[I].Last == DefChainEnd; }))(static_cast <bool> (all_of(NewPaused, [&](ListIndex
I) { return Paths[I].Last == DefChainEnd; })) ? void (0) : __assert_fail
("all_of(NewPaused, [&](ListIndex I) { return Paths[I].Last == DefChainEnd; })"
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 820, __extension__ __PRETTY_FUNCTION__))
;
821
822 // Because liveOnEntry is a clobber, this must be a phi.
823 auto *DefChainPhi = cast<MemoryPhi>(DefChainEnd);
824
825 PriorPathsSize = Paths.size();
826 PausedSearches.clear();
827 for (ListIndex I : NewPaused)
828 addSearches(DefChainPhi, PausedSearches, I);
829 NewPaused.clear();
830
831 Current = DefChainPhi;
832 }
833 }
834
835 void verifyOptResult(const OptznResult &R) const {
836 assert(all_of(R.OtherClobbers, [&](const TerminatedPath &P) {(static_cast <bool> (all_of(R.OtherClobbers, [&](const
TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.
PrimaryClobber.Clobber); })) ? void (0) : __assert_fail ("all_of(R.OtherClobbers, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber); })"
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 838, __extension__ __PRETTY_FUNCTION__))
837 return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber);(static_cast <bool> (all_of(R.OtherClobbers, [&](const
TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.
PrimaryClobber.Clobber); })) ? void (0) : __assert_fail ("all_of(R.OtherClobbers, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber); })"
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 838, __extension__ __PRETTY_FUNCTION__))
838 }))(static_cast <bool> (all_of(R.OtherClobbers, [&](const
TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.
PrimaryClobber.Clobber); })) ? void (0) : __assert_fail ("all_of(R.OtherClobbers, [&](const TerminatedPath &P) { return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber); })"
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 838, __extension__ __PRETTY_FUNCTION__))
;
839 }
840
841 void resetPhiOptznState() {
842 Paths.clear();
843 VisitedPhis.clear();
844 }
845
846public:
847 ClobberWalker(const MemorySSA &MSSA, AliasAnalysis &AA, DominatorTree &DT)
848 : MSSA(MSSA), AA(AA), DT(DT) {}
849
850 /// Finds the nearest clobber for the given query, optimizing phis if
851 /// possible.
852 MemoryAccess *findClobber(MemoryAccess *Start, UpwardsMemoryQuery &Q) {
853 Query = &Q;
854
855 MemoryAccess *Current = Start;
856 // This walker pretends uses don't exist. If we're handed one, silently grab
857 // its def. (This has the nice side-effect of ensuring we never cache uses)
858 if (auto *MU = dyn_cast<MemoryUse>(Start))
859 Current = MU->getDefiningAccess();
860
861 DefPath FirstDesc(Q.StartingLoc, Current, Current, None);
862 // Fast path for the overly-common case (no crazy phi optimization
863 // necessary)
864 UpwardsWalkResult WalkResult = walkToPhiOrClobber(FirstDesc);
865 MemoryAccess *Result;
866 if (WalkResult.IsKnownClobber) {
867 Result = WalkResult.Result;
868 Q.AR = WalkResult.AR;
869 } else {
870 OptznResult OptRes = tryOptimizePhi(cast<MemoryPhi>(FirstDesc.Last),
871 Current, Q.StartingLoc);
872 verifyOptResult(OptRes);
873 resetPhiOptznState();
874 Result = OptRes.PrimaryClobber.Clobber;
875 }
876
877#ifdef EXPENSIVE_CHECKS
878 checkClobberSanity(Current, Result, Q.StartingLoc, MSSA, Q, AA);
879#endif
880 return Result;
881 }
882
883 void verify(const MemorySSA *MSSA) { assert(MSSA == &this->MSSA)(static_cast <bool> (MSSA == &this->MSSA) ? void
(0) : __assert_fail ("MSSA == &this->MSSA", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 883, __extension__ __PRETTY_FUNCTION__))
; }
884};
885
886struct RenamePassData {
887 DomTreeNode *DTN;
888 DomTreeNode::const_iterator ChildIt;
889 MemoryAccess *IncomingVal;
890
891 RenamePassData(DomTreeNode *D, DomTreeNode::const_iterator It,
892 MemoryAccess *M)
893 : DTN(D), ChildIt(It), IncomingVal(M) {}
894
895 void swap(RenamePassData &RHS) {
896 std::swap(DTN, RHS.DTN);
897 std::swap(ChildIt, RHS.ChildIt);
898 std::swap(IncomingVal, RHS.IncomingVal);
899 }
900};
901
902} // end anonymous namespace
903
904namespace llvm {
905
906/// A MemorySSAWalker that does AA walks to disambiguate accesses. It no
907/// longer does caching on its own, but the name has been retained for the
908/// moment.
909class MemorySSA::CachingWalker final : public MemorySSAWalker {
910 ClobberWalker Walker;
911
912 MemoryAccess *getClobberingMemoryAccess(MemoryAccess *, UpwardsMemoryQuery &);
913
914public:
915 CachingWalker(MemorySSA *, AliasAnalysis *, DominatorTree *);
916 ~CachingWalker() override = default;
917
918 using MemorySSAWalker::getClobberingMemoryAccess;
919
920 MemoryAccess *getClobberingMemoryAccess(MemoryAccess *) override;
921 MemoryAccess *getClobberingMemoryAccess(MemoryAccess *,
922 const MemoryLocation &) override;
923 void invalidateInfo(MemoryAccess *) override;
924
925 void verify(const MemorySSA *MSSA) override {
926 MemorySSAWalker::verify(MSSA);
927 Walker.verify(MSSA);
928 }
929};
930
931} // end namespace llvm
932
933void MemorySSA::renameSuccessorPhis(BasicBlock *BB, MemoryAccess *IncomingVal,
934 bool RenameAllUses) {
935 // Pass through values to our successors
936 for (const BasicBlock *S : successors(BB)) {
937 auto It = PerBlockAccesses.find(S);
938 // Rename the phi nodes in our successor block
939 if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
940 continue;
941 AccessList *Accesses = It->second.get();
942 auto *Phi = cast<MemoryPhi>(&Accesses->front());
943 if (RenameAllUses) {
944 int PhiIndex = Phi->getBasicBlockIndex(BB);
945 assert(PhiIndex != -1 && "Incomplete phi during partial rename")(static_cast <bool> (PhiIndex != -1 && "Incomplete phi during partial rename"
) ? void (0) : __assert_fail ("PhiIndex != -1 && \"Incomplete phi during partial rename\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 945, __extension__ __PRETTY_FUNCTION__))
;
946 Phi->setIncomingValue(PhiIndex, IncomingVal);
947 } else
948 Phi->addIncoming(IncomingVal, BB);
949 }
950}
951
952/// Rename a single basic block into MemorySSA form.
953/// Uses the standard SSA renaming algorithm.
954/// \returns The new incoming value.
955MemoryAccess *MemorySSA::renameBlock(BasicBlock *BB, MemoryAccess *IncomingVal,
956 bool RenameAllUses) {
957 auto It = PerBlockAccesses.find(BB);
958 // Skip most processing if the list is empty.
959 if (It != PerBlockAccesses.end()) {
960 AccessList *Accesses = It->second.get();
961 for (MemoryAccess &L : *Accesses) {
962 if (MemoryUseOrDef *MUD = dyn_cast<MemoryUseOrDef>(&L)) {
963 if (MUD->getDefiningAccess() == nullptr || RenameAllUses)
964 MUD->setDefiningAccess(IncomingVal);
965 if (isa<MemoryDef>(&L))
966 IncomingVal = &L;
967 } else {
968 IncomingVal = &L;
969 }
970 }
971 }
972 return IncomingVal;
973}
974
975/// This is the standard SSA renaming algorithm.
976///
977/// We walk the dominator tree in preorder, renaming accesses, and then filling
978/// in phi nodes in our successors.
979void MemorySSA::renamePass(DomTreeNode *Root, MemoryAccess *IncomingVal,
980 SmallPtrSetImpl<BasicBlock *> &Visited,
981 bool SkipVisited, bool RenameAllUses) {
982 SmallVector<RenamePassData, 32> WorkStack;
983 // Skip everything if we already renamed this block and we are skipping.
984 // Note: You can't sink this into the if, because we need it to occur
985 // regardless of whether we skip blocks or not.
986 bool AlreadyVisited = !Visited.insert(Root->getBlock()).second;
987 if (SkipVisited && AlreadyVisited)
988 return;
989
990 IncomingVal = renameBlock(Root->getBlock(), IncomingVal, RenameAllUses);
991 renameSuccessorPhis(Root->getBlock(), IncomingVal, RenameAllUses);
992 WorkStack.push_back({Root, Root->begin(), IncomingVal});
993
994 while (!WorkStack.empty()) {
995 DomTreeNode *Node = WorkStack.back().DTN;
996 DomTreeNode::const_iterator ChildIt = WorkStack.back().ChildIt;
997 IncomingVal = WorkStack.back().IncomingVal;
998
999 if (ChildIt == Node->end()) {
1000 WorkStack.pop_back();
1001 } else {
1002 DomTreeNode *Child = *ChildIt;
1003 ++WorkStack.back().ChildIt;
1004 BasicBlock *BB = Child->getBlock();
1005 // Note: You can't sink this into the if, because we need it to occur
1006 // regardless of whether we skip blocks or not.
1007 AlreadyVisited = !Visited.insert(BB).second;
1008 if (SkipVisited && AlreadyVisited) {
1009 // We already visited this during our renaming, which can happen when
1010 // being asked to rename multiple blocks. Figure out the incoming val,
1011 // which is the last def.
1012 // Incoming value can only change if there is a block def, and in that
1013 // case, it's the last block def in the list.
1014 if (auto *BlockDefs = getWritableBlockDefs(BB))
1015 IncomingVal = &*BlockDefs->rbegin();
1016 } else
1017 IncomingVal = renameBlock(BB, IncomingVal, RenameAllUses);
1018 renameSuccessorPhis(BB, IncomingVal, RenameAllUses);
1019 WorkStack.push_back({Child, Child->begin(), IncomingVal});
1020 }
1021 }
1022}
1023
1024/// This handles unreachable block accesses by deleting phi nodes in
1025/// unreachable blocks, and marking all other unreachable MemoryAccess's as
1026/// being uses of the live on entry definition.
1027void MemorySSA::markUnreachableAsLiveOnEntry(BasicBlock *BB) {
1028 assert(!DT->isReachableFromEntry(BB) &&(static_cast <bool> (!DT->isReachableFromEntry(BB) &&
"Reachable block found while handling unreachable blocks") ?
void (0) : __assert_fail ("!DT->isReachableFromEntry(BB) && \"Reachable block found while handling unreachable blocks\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1029, __extension__ __PRETTY_FUNCTION__))
1029 "Reachable block found while handling unreachable blocks")(static_cast <bool> (!DT->isReachableFromEntry(BB) &&
"Reachable block found while handling unreachable blocks") ?
void (0) : __assert_fail ("!DT->isReachableFromEntry(BB) && \"Reachable block found while handling unreachable blocks\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1029, __extension__ __PRETTY_FUNCTION__))
;
1030
1031 // Make sure phi nodes in our reachable successors end up with a
1032 // LiveOnEntryDef for our incoming edge, even though our block is forward
1033 // unreachable. We could just disconnect these blocks from the CFG fully,
1034 // but we do not right now.
1035 for (const BasicBlock *S : successors(BB)) {
1036 if (!DT->isReachableFromEntry(S))
1037 continue;
1038 auto It = PerBlockAccesses.find(S);
1039 // Rename the phi nodes in our successor block
1040 if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
1041 continue;
1042 AccessList *Accesses = It->second.get();
1043 auto *Phi = cast<MemoryPhi>(&Accesses->front());
1044 Phi->addIncoming(LiveOnEntryDef.get(), BB);
1045 }
1046
1047 auto It = PerBlockAccesses.find(BB);
1048 if (It == PerBlockAccesses.end())
1049 return;
1050
1051 auto &Accesses = It->second;
1052 for (auto AI = Accesses->begin(), AE = Accesses->end(); AI != AE;) {
1053 auto Next = std::next(AI);
1054 // If we have a phi, just remove it. We are going to replace all
1055 // users with live on entry.
1056 if (auto *UseOrDef = dyn_cast<MemoryUseOrDef>(AI))
1057 UseOrDef->setDefiningAccess(LiveOnEntryDef.get());
1058 else
1059 Accesses->erase(AI);
1060 AI = Next;
1061 }
1062}
1063
1064MemorySSA::MemorySSA(Function &Func, AliasAnalysis *AA, DominatorTree *DT)
1065 : AA(AA), DT(DT), F(Func), LiveOnEntryDef(nullptr), Walker(nullptr),
1066 NextID(0) {
1067 buildMemorySSA();
1068}
1069
1070MemorySSA::~MemorySSA() {
1071 // Drop all our references
1072 for (const auto &Pair : PerBlockAccesses)
1073 for (MemoryAccess &MA : *Pair.second)
1074 MA.dropAllReferences();
1075}
1076
1077MemorySSA::AccessList *MemorySSA::getOrCreateAccessList(const BasicBlock *BB) {
1078 auto Res = PerBlockAccesses.insert(std::make_pair(BB, nullptr));
1079
1080 if (Res.second)
1081 Res.first->second = llvm::make_unique<AccessList>();
1082 return Res.first->second.get();
1083}
1084
1085MemorySSA::DefsList *MemorySSA::getOrCreateDefsList(const BasicBlock *BB) {
1086 auto Res = PerBlockDefs.insert(std::make_pair(BB, nullptr));
1087
1088 if (Res.second)
1089 Res.first->second = llvm::make_unique<DefsList>();
1090 return Res.first->second.get();
1091}
1092
1093namespace llvm {
1094
1095/// This class is a batch walker of all MemoryUse's in the program, and points
1096/// their defining access at the thing that actually clobbers them. Because it
1097/// is a batch walker that touches everything, it does not operate like the
1098/// other walkers. This walker is basically performing a top-down SSA renaming
1099/// pass, where the version stack is used as the cache. This enables it to be
1100/// significantly more time and memory efficient than using the regular walker,
1101/// which is walking bottom-up.
1102class MemorySSA::OptimizeUses {
1103public:
1104 OptimizeUses(MemorySSA *MSSA, MemorySSAWalker *Walker, AliasAnalysis *AA,
1105 DominatorTree *DT)
1106 : MSSA(MSSA), Walker(Walker), AA(AA), DT(DT) {
1107 Walker = MSSA->getWalker();
Value stored to 'Walker' is never read
1108 }
1109
1110 void optimizeUses();
1111
1112private:
1113 /// This represents where a given memorylocation is in the stack.
1114 struct MemlocStackInfo {
1115 // This essentially is keeping track of versions of the stack. Whenever
1116 // the stack changes due to pushes or pops, these versions increase.
1117 unsigned long StackEpoch;
1118 unsigned long PopEpoch;
1119 // This is the lower bound of places on the stack to check. It is equal to
1120 // the place the last stack walk ended.
1121 // Note: Correctness depends on this being initialized to 0, which densemap
1122 // does
1123 unsigned long LowerBound;
1124 const BasicBlock *LowerBoundBlock;
1125 // This is where the last walk for this memory location ended.
1126 unsigned long LastKill;
1127 bool LastKillValid;
1128 Optional<AliasResult> AR;
1129 };
1130
1131 void optimizeUsesInBlock(const BasicBlock *, unsigned long &, unsigned long &,
1132 SmallVectorImpl<MemoryAccess *> &,
1133 DenseMap<MemoryLocOrCall, MemlocStackInfo> &);
1134
1135 MemorySSA *MSSA;
1136 MemorySSAWalker *Walker;
1137 AliasAnalysis *AA;
1138 DominatorTree *DT;
1139};
1140
1141} // end namespace llvm
1142
1143/// Optimize the uses in a given block This is basically the SSA renaming
1144/// algorithm, with one caveat: We are able to use a single stack for all
1145/// MemoryUses. This is because the set of *possible* reaching MemoryDefs is
1146/// the same for every MemoryUse. The *actual* clobbering MemoryDef is just
1147/// going to be some position in that stack of possible ones.
1148///
1149/// We track the stack positions that each MemoryLocation needs
1150/// to check, and last ended at. This is because we only want to check the
1151/// things that changed since last time. The same MemoryLocation should
1152/// get clobbered by the same store (getModRefInfo does not use invariantness or
1153/// things like this, and if they start, we can modify MemoryLocOrCall to
1154/// include relevant data)
1155void MemorySSA::OptimizeUses::optimizeUsesInBlock(
1156 const BasicBlock *BB, unsigned long &StackEpoch, unsigned long &PopEpoch,
1157 SmallVectorImpl<MemoryAccess *> &VersionStack,
1158 DenseMap<MemoryLocOrCall, MemlocStackInfo> &LocStackInfo) {
1159
1160 /// If no accesses, nothing to do.
1161 MemorySSA::AccessList *Accesses = MSSA->getWritableBlockAccesses(BB);
1162 if (Accesses == nullptr)
1163 return;
1164
1165 // Pop everything that doesn't dominate the current block off the stack,
1166 // increment the PopEpoch to account for this.
1167 while (true) {
1168 assert((static_cast <bool> (!VersionStack.empty() && "Version stack should have liveOnEntry sentinel dominating everything"
) ? void (0) : __assert_fail ("!VersionStack.empty() && \"Version stack should have liveOnEntry sentinel dominating everything\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1170, __extension__ __PRETTY_FUNCTION__))
1169 !VersionStack.empty() &&(static_cast <bool> (!VersionStack.empty() && "Version stack should have liveOnEntry sentinel dominating everything"
) ? void (0) : __assert_fail ("!VersionStack.empty() && \"Version stack should have liveOnEntry sentinel dominating everything\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1170, __extension__ __PRETTY_FUNCTION__))
1170 "Version stack should have liveOnEntry sentinel dominating everything")(static_cast <bool> (!VersionStack.empty() && "Version stack should have liveOnEntry sentinel dominating everything"
) ? void (0) : __assert_fail ("!VersionStack.empty() && \"Version stack should have liveOnEntry sentinel dominating everything\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1170, __extension__ __PRETTY_FUNCTION__))
;
1171 BasicBlock *BackBlock = VersionStack.back()->getBlock();
1172 if (DT->dominates(BackBlock, BB))
1173 break;
1174 while (VersionStack.back()->getBlock() == BackBlock)
1175 VersionStack.pop_back();
1176 ++PopEpoch;
1177 }
1178
1179 for (MemoryAccess &MA : *Accesses) {
1180 auto *MU = dyn_cast<MemoryUse>(&MA);
1181 if (!MU) {
1182 VersionStack.push_back(&MA);
1183 ++StackEpoch;
1184 continue;
1185 }
1186
1187 if (isUseTriviallyOptimizableToLiveOnEntry(*AA, MU->getMemoryInst())) {
1188 MU->setDefiningAccess(MSSA->getLiveOnEntryDef(), true, None);
1189 continue;
1190 }
1191
1192 MemoryLocOrCall UseMLOC(MU);
1193 auto &LocInfo = LocStackInfo[UseMLOC];
1194 // If the pop epoch changed, it means we've removed stuff from top of
1195 // stack due to changing blocks. We may have to reset the lower bound or
1196 // last kill info.
1197 if (LocInfo.PopEpoch != PopEpoch) {
1198 LocInfo.PopEpoch = PopEpoch;
1199 LocInfo.StackEpoch = StackEpoch;
1200 // If the lower bound was in something that no longer dominates us, we
1201 // have to reset it.
1202 // We can't simply track stack size, because the stack may have had
1203 // pushes/pops in the meantime.
1204 // XXX: This is non-optimal, but only is slower cases with heavily
1205 // branching dominator trees. To get the optimal number of queries would
1206 // be to make lowerbound and lastkill a per-loc stack, and pop it until
1207 // the top of that stack dominates us. This does not seem worth it ATM.
1208 // A much cheaper optimization would be to always explore the deepest
1209 // branch of the dominator tree first. This will guarantee this resets on
1210 // the smallest set of blocks.
1211 if (LocInfo.LowerBoundBlock && LocInfo.LowerBoundBlock != BB &&
1212 !DT->dominates(LocInfo.LowerBoundBlock, BB)) {
1213 // Reset the lower bound of things to check.
1214 // TODO: Some day we should be able to reset to last kill, rather than
1215 // 0.
1216 LocInfo.LowerBound = 0;
1217 LocInfo.LowerBoundBlock = VersionStack[0]->getBlock();
1218 LocInfo.LastKillValid = false;
1219 }
1220 } else if (LocInfo.StackEpoch != StackEpoch) {
1221 // If all that has changed is the StackEpoch, we only have to check the
1222 // new things on the stack, because we've checked everything before. In
1223 // this case, the lower bound of things to check remains the same.
1224 LocInfo.PopEpoch = PopEpoch;
1225 LocInfo.StackEpoch = StackEpoch;
1226 }
1227 if (!LocInfo.LastKillValid) {
1228 LocInfo.LastKill = VersionStack.size() - 1;
1229 LocInfo.LastKillValid = true;
1230 LocInfo.AR = MayAlias;
1231 }
1232
1233 // At this point, we should have corrected last kill and LowerBound to be
1234 // in bounds.
1235 assert(LocInfo.LowerBound < VersionStack.size() &&(static_cast <bool> (LocInfo.LowerBound < VersionStack
.size() && "Lower bound out of range") ? void (0) : __assert_fail
("LocInfo.LowerBound < VersionStack.size() && \"Lower bound out of range\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1236, __extension__ __PRETTY_FUNCTION__))
1236 "Lower bound out of range")(static_cast <bool> (LocInfo.LowerBound < VersionStack
.size() && "Lower bound out of range") ? void (0) : __assert_fail
("LocInfo.LowerBound < VersionStack.size() && \"Lower bound out of range\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1236, __extension__ __PRETTY_FUNCTION__))
;
1237 assert(LocInfo.LastKill < VersionStack.size() &&(static_cast <bool> (LocInfo.LastKill < VersionStack
.size() && "Last kill info out of range") ? void (0) :
__assert_fail ("LocInfo.LastKill < VersionStack.size() && \"Last kill info out of range\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1238, __extension__ __PRETTY_FUNCTION__))
1238 "Last kill info out of range")(static_cast <bool> (LocInfo.LastKill < VersionStack
.size() && "Last kill info out of range") ? void (0) :
__assert_fail ("LocInfo.LastKill < VersionStack.size() && \"Last kill info out of range\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1238, __extension__ __PRETTY_FUNCTION__))
;
1239 // In any case, the new upper bound is the top of the stack.
1240 unsigned long UpperBound = VersionStack.size() - 1;
1241
1242 if (UpperBound - LocInfo.LowerBound > MaxCheckLimit) {
1243 LLVM_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)
1244 << *(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)
1245 << " because there are "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)
1246 << 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)
1247 << " 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)
;
1248 // Because we did not walk, LastKill is no longer valid, as this may
1249 // have been a kill.
1250 LocInfo.LastKillValid = false;
1251 continue;
1252 }
1253 bool FoundClobberResult = false;
1254 while (UpperBound > LocInfo.LowerBound) {
1255 if (isa<MemoryPhi>(VersionStack[UpperBound])) {
1256 // For phis, use the walker, see where we ended up, go there
1257 Instruction *UseInst = MU->getMemoryInst();
1258 MemoryAccess *Result = Walker->getClobberingMemoryAccess(UseInst);
1259 // We are guaranteed to find it or something is wrong
1260 while (VersionStack[UpperBound] != Result) {
1261 assert(UpperBound != 0)(static_cast <bool> (UpperBound != 0) ? void (0) : __assert_fail
("UpperBound != 0", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1261, __extension__ __PRETTY_FUNCTION__))
;
1262 --UpperBound;
1263 }
1264 FoundClobberResult = true;
1265 break;
1266 }
1267
1268 MemoryDef *MD = cast<MemoryDef>(VersionStack[UpperBound]);
1269 // If the lifetime of the pointer ends at this instruction, it's live on
1270 // entry.
1271 if (!UseMLOC.IsCall && lifetimeEndsAt(MD, UseMLOC.getLoc(), *AA)) {
1272 // Reset UpperBound to liveOnEntryDef's place in the stack
1273 UpperBound = 0;
1274 FoundClobberResult = true;
1275 LocInfo.AR = MustAlias;
1276 break;
1277 }
1278 ClobberAlias CA = instructionClobbersQuery(MD, MU, UseMLOC, *AA);
1279 if (CA.IsClobber) {
1280 FoundClobberResult = true;
1281 LocInfo.AR = CA.AR;
1282 break;
1283 }
1284 --UpperBound;
1285 }
1286
1287 // Note: Phis always have AliasResult AR set to MayAlias ATM.
1288
1289 // At the end of this loop, UpperBound is either a clobber, or lower bound
1290 // PHI walking may cause it to be < LowerBound, and in fact, < LastKill.
1291 if (FoundClobberResult || UpperBound < LocInfo.LastKill) {
1292 // We were last killed now by where we got to
1293 if (MSSA->isLiveOnEntryDef(VersionStack[UpperBound]))
1294 LocInfo.AR = None;
1295 MU->setDefiningAccess(VersionStack[UpperBound], true, LocInfo.AR);
1296 LocInfo.LastKill = UpperBound;
1297 } else {
1298 // Otherwise, we checked all the new ones, and now we know we can get to
1299 // LastKill.
1300 MU->setDefiningAccess(VersionStack[LocInfo.LastKill], true, LocInfo.AR);
1301 }
1302 LocInfo.LowerBound = VersionStack.size() - 1;
1303 LocInfo.LowerBoundBlock = BB;
1304 }
1305}
1306
1307/// Optimize uses to point to their actual clobbering definitions.
1308void MemorySSA::OptimizeUses::optimizeUses() {
1309 SmallVector<MemoryAccess *, 16> VersionStack;
1310 DenseMap<MemoryLocOrCall, MemlocStackInfo> LocStackInfo;
1311 VersionStack.push_back(MSSA->getLiveOnEntryDef());
1312
1313 unsigned long StackEpoch = 1;
1314 unsigned long PopEpoch = 1;
1315 // We perform a non-recursive top-down dominator tree walk.
1316 for (const auto *DomNode : depth_first(DT->getRootNode()))
1317 optimizeUsesInBlock(DomNode->getBlock(), StackEpoch, PopEpoch, VersionStack,
1318 LocStackInfo);
1319}
1320
1321void MemorySSA::placePHINodes(
1322 const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks) {
1323 // Determine where our MemoryPhi's should go
1324 ForwardIDFCalculator IDFs(*DT);
1325 IDFs.setDefiningBlocks(DefiningBlocks);
1326 SmallVector<BasicBlock *, 32> IDFBlocks;
1327 IDFs.calculate(IDFBlocks);
1328
1329 // Now place MemoryPhi nodes.
1330 for (auto &BB : IDFBlocks)
1331 createMemoryPhi(BB);
1332}
1333
1334void MemorySSA::buildMemorySSA() {
1335 // We create an access to represent "live on entry", for things like
1336 // arguments or users of globals, where the memory they use is defined before
1337 // the beginning of the function. We do not actually insert it into the IR.
1338 // We do not define a live on exit for the immediate uses, and thus our
1339 // semantics do *not* imply that something with no immediate uses can simply
1340 // be removed.
1341 BasicBlock &StartingPoint = F.getEntryBlock();
1342 LiveOnEntryDef.reset(new MemoryDef(F.getContext(), nullptr, nullptr,
1343 &StartingPoint, NextID++));
1344
1345 // We maintain lists of memory accesses per-block, trading memory for time. We
1346 // could just look up the memory access for every possible instruction in the
1347 // stream.
1348 SmallPtrSet<BasicBlock *, 32> DefiningBlocks;
1349 // Go through each block, figure out where defs occur, and chain together all
1350 // the accesses.
1351 for (BasicBlock &B : F) {
1352 bool InsertIntoDef = false;
1353 AccessList *Accesses = nullptr;
1354 DefsList *Defs = nullptr;
1355 for (Instruction &I : B) {
1356 MemoryUseOrDef *MUD = createNewAccess(&I);
1357 if (!MUD)
1358 continue;
1359
1360 if (!Accesses)
1361 Accesses = getOrCreateAccessList(&B);
1362 Accesses->push_back(MUD);
1363 if (isa<MemoryDef>(MUD)) {
1364 InsertIntoDef = true;
1365 if (!Defs)
1366 Defs = getOrCreateDefsList(&B);
1367 Defs->push_back(*MUD);
1368 }
1369 }
1370 if (InsertIntoDef)
1371 DefiningBlocks.insert(&B);
1372 }
1373 placePHINodes(DefiningBlocks);
1374
1375 // Now do regular SSA renaming on the MemoryDef/MemoryUse. Visited will get
1376 // filled in with all blocks.
1377 SmallPtrSet<BasicBlock *, 16> Visited;
1378 renamePass(DT->getRootNode(), LiveOnEntryDef.get(), Visited);
1379
1380 CachingWalker *Walker = getWalkerImpl();
1381
1382 OptimizeUses(this, Walker, AA, DT).optimizeUses();
1383
1384 // Mark the uses in unreachable blocks as live on entry, so that they go
1385 // somewhere.
1386 for (auto &BB : F)
1387 if (!Visited.count(&BB))
1388 markUnreachableAsLiveOnEntry(&BB);
1389}
1390
1391MemorySSAWalker *MemorySSA::getWalker() { return getWalkerImpl(); }
1392
1393MemorySSA::CachingWalker *MemorySSA::getWalkerImpl() {
1394 if (Walker)
1395 return Walker.get();
1396
1397 Walker = llvm::make_unique<CachingWalker>(this, AA, DT);
1398 return Walker.get();
1399}
1400
1401// This is a helper function used by the creation routines. It places NewAccess
1402// into the access and defs lists for a given basic block, at the given
1403// insertion point.
1404void MemorySSA::insertIntoListsForBlock(MemoryAccess *NewAccess,
1405 const BasicBlock *BB,
1406 InsertionPlace Point) {
1407 auto *Accesses = getOrCreateAccessList(BB);
1408 if (Point == Beginning) {
1409 // If it's a phi node, it goes first, otherwise, it goes after any phi
1410 // nodes.
1411 if (isa<MemoryPhi>(NewAccess)) {
1412 Accesses->push_front(NewAccess);
1413 auto *Defs = getOrCreateDefsList(BB);
1414 Defs->push_front(*NewAccess);
1415 } else {
1416 auto AI = find_if_not(
1417 *Accesses, [](const MemoryAccess &MA) { return isa<MemoryPhi>(MA); });
1418 Accesses->insert(AI, NewAccess);
1419 if (!isa<MemoryUse>(NewAccess)) {
1420 auto *Defs = getOrCreateDefsList(BB);
1421 auto DI = find_if_not(
1422 *Defs, [](const MemoryAccess &MA) { return isa<MemoryPhi>(MA); });
1423 Defs->insert(DI, *NewAccess);
1424 }
1425 }
1426 } else {
1427 Accesses->push_back(NewAccess);
1428 if (!isa<MemoryUse>(NewAccess)) {
1429 auto *Defs = getOrCreateDefsList(BB);
1430 Defs->push_back(*NewAccess);
1431 }
1432 }
1433 BlockNumberingValid.erase(BB);
1434}
1435
1436void MemorySSA::insertIntoListsBefore(MemoryAccess *What, const BasicBlock *BB,
1437 AccessList::iterator InsertPt) {
1438 auto *Accesses = getWritableBlockAccesses(BB);
1439 bool WasEnd = InsertPt == Accesses->end();
1440 Accesses->insert(AccessList::iterator(InsertPt), What);
1441 if (!isa<MemoryUse>(What)) {
1442 auto *Defs = getOrCreateDefsList(BB);
1443 // If we got asked to insert at the end, we have an easy job, just shove it
1444 // at the end. If we got asked to insert before an existing def, we also get
1445 // an iterator. If we got asked to insert before a use, we have to hunt for
1446 // the next def.
1447 if (WasEnd) {
1448 Defs->push_back(*What);
1449 } else if (isa<MemoryDef>(InsertPt)) {
1450 Defs->insert(InsertPt->getDefsIterator(), *What);
1451 } else {
1452 while (InsertPt != Accesses->end() && !isa<MemoryDef>(InsertPt))
1453 ++InsertPt;
1454 // Either we found a def, or we are inserting at the end
1455 if (InsertPt == Accesses->end())
1456 Defs->push_back(*What);
1457 else
1458 Defs->insert(InsertPt->getDefsIterator(), *What);
1459 }
1460 }
1461 BlockNumberingValid.erase(BB);
1462}
1463
1464// Move What before Where in the IR. The end result is that What will belong to
1465// the right lists and have the right Block set, but will not otherwise be
1466// correct. It will not have the right defining access, and if it is a def,
1467// things below it will not properly be updated.
1468void MemorySSA::moveTo(MemoryUseOrDef *What, BasicBlock *BB,
1469 AccessList::iterator Where) {
1470 // Keep it in the lookup tables, remove from the lists
1471 removeFromLists(What, false);
1472 What->setBlock(BB);
1473 insertIntoListsBefore(What, BB, Where);
1474}
1475
1476void MemorySSA::moveTo(MemoryAccess *What, BasicBlock *BB,
1477 InsertionPlace Point) {
1478 if (isa<MemoryPhi>(What)) {
1479 assert(Point == Beginning &&(static_cast <bool> (Point == Beginning && "Can only move a Phi at the beginning of the block"
) ? void (0) : __assert_fail ("Point == Beginning && \"Can only move a Phi at the beginning of the block\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1480, __extension__ __PRETTY_FUNCTION__))
1480 "Can only move a Phi at the beginning of the block")(static_cast <bool> (Point == Beginning && "Can only move a Phi at the beginning of the block"
) ? void (0) : __assert_fail ("Point == Beginning && \"Can only move a Phi at the beginning of the block\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1480, __extension__ __PRETTY_FUNCTION__))
;
1481 // Update lookup table entry
1482 ValueToMemoryAccess.erase(What->getBlock());
1483 bool Inserted = ValueToMemoryAccess.insert({BB, What}).second;
1484 (void)Inserted;
1485 assert(Inserted && "Cannot move a Phi to a block that already has one")(static_cast <bool> (Inserted && "Cannot move a Phi to a block that already has one"
) ? void (0) : __assert_fail ("Inserted && \"Cannot move a Phi to a block that already has one\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1485, __extension__ __PRETTY_FUNCTION__))
;
1486 }
1487
1488 removeFromLists(What, false);
1489 What->setBlock(BB);
1490 insertIntoListsForBlock(What, BB, Point);
1491}
1492
1493MemoryPhi *MemorySSA::createMemoryPhi(BasicBlock *BB) {
1494 assert(!getMemoryAccess(BB) && "MemoryPhi already exists for this BB")(static_cast <bool> (!getMemoryAccess(BB) && "MemoryPhi already exists for this BB"
) ? void (0) : __assert_fail ("!getMemoryAccess(BB) && \"MemoryPhi already exists for this BB\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1494, __extension__ __PRETTY_FUNCTION__))
;
1495 MemoryPhi *Phi = new MemoryPhi(BB->getContext(), BB, NextID++);
1496 // Phi's always are placed at the front of the block.
1497 insertIntoListsForBlock(Phi, BB, Beginning);
1498 ValueToMemoryAccess[BB] = Phi;
1499 return Phi;
1500}
1501
1502MemoryUseOrDef *MemorySSA::createDefinedAccess(Instruction *I,
1503 MemoryAccess *Definition) {
1504 assert(!isa<PHINode>(I) && "Cannot create a defined access for a PHI")(static_cast <bool> (!isa<PHINode>(I) && "Cannot create a defined access for a PHI"
) ? void (0) : __assert_fail ("!isa<PHINode>(I) && \"Cannot create a defined access for a PHI\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1504, __extension__ __PRETTY_FUNCTION__))
;
1505 MemoryUseOrDef *NewAccess = createNewAccess(I);
1506 assert((static_cast <bool> (NewAccess != nullptr && "Tried to create a memory access for a non-memory touching instruction"
) ? void (0) : __assert_fail ("NewAccess != nullptr && \"Tried to create a memory access for a non-memory touching instruction\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1508, __extension__ __PRETTY_FUNCTION__))
1507 NewAccess != nullptr &&(static_cast <bool> (NewAccess != nullptr && "Tried to create a memory access for a non-memory touching instruction"
) ? void (0) : __assert_fail ("NewAccess != nullptr && \"Tried to create a memory access for a non-memory touching instruction\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1508, __extension__ __PRETTY_FUNCTION__))
1508 "Tried to create a memory access for a non-memory touching instruction")(static_cast <bool> (NewAccess != nullptr && "Tried to create a memory access for a non-memory touching instruction"
) ? void (0) : __assert_fail ("NewAccess != nullptr && \"Tried to create a memory access for a non-memory touching instruction\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1508, __extension__ __PRETTY_FUNCTION__))
;
1509 NewAccess->setDefiningAccess(Definition);
1510 return NewAccess;
1511}
1512
1513// Return true if the instruction has ordering constraints.
1514// Note specifically that this only considers stores and loads
1515// because others are still considered ModRef by getModRefInfo.
1516static inline bool isOrdered(const Instruction *I) {
1517 if (auto *SI = dyn_cast<StoreInst>(I)) {
1518 if (!SI->isUnordered())
1519 return true;
1520 } else if (auto *LI = dyn_cast<LoadInst>(I)) {
1521 if (!LI->isUnordered())
1522 return true;
1523 }
1524 return false;
1525}
1526
1527/// Helper function to create new memory accesses
1528MemoryUseOrDef *MemorySSA::createNewAccess(Instruction *I) {
1529 // The assume intrinsic has a control dependency which we model by claiming
1530 // that it writes arbitrarily. Ignore that fake memory dependency here.
1531 // FIXME: Replace this special casing with a more accurate modelling of
1532 // assume's control dependency.
1533 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
1534 if (II->getIntrinsicID() == Intrinsic::assume)
1535 return nullptr;
1536
1537 // Find out what affect this instruction has on memory.
1538 ModRefInfo ModRef = AA->getModRefInfo(I, None);
1539 // The isOrdered check is used to ensure that volatiles end up as defs
1540 // (atomics end up as ModRef right now anyway). Until we separate the
1541 // ordering chain from the memory chain, this enables people to see at least
1542 // some relative ordering to volatiles. Note that getClobberingMemoryAccess
1543 // will still give an answer that bypasses other volatile loads. TODO:
1544 // Separate memory aliasing and ordering into two different chains so that we
1545 // can precisely represent both "what memory will this read/write/is clobbered
1546 // by" and "what instructions can I move this past".
1547 bool Def = isModSet(ModRef) || isOrdered(I);
1548 bool Use = isRefSet(ModRef);
1549
1550 // It's possible for an instruction to not modify memory at all. During
1551 // construction, we ignore them.
1552 if (!Def && !Use)
1553 return nullptr;
1554
1555 MemoryUseOrDef *MUD;
1556 if (Def)
1557 MUD = new MemoryDef(I->getContext(), nullptr, I, I->getParent(), NextID++);
1558 else
1559 MUD = new MemoryUse(I->getContext(), nullptr, I, I->getParent());
1560 ValueToMemoryAccess[I] = MUD;
1561 return MUD;
1562}
1563
1564/// Returns true if \p Replacer dominates \p Replacee .
1565bool MemorySSA::dominatesUse(const MemoryAccess *Replacer,
1566 const MemoryAccess *Replacee) const {
1567 if (isa<MemoryUseOrDef>(Replacee))
1568 return DT->dominates(Replacer->getBlock(), Replacee->getBlock());
1569 const auto *MP = cast<MemoryPhi>(Replacee);
1570 // For a phi node, the use occurs in the predecessor block of the phi node.
1571 // Since we may occur multiple times in the phi node, we have to check each
1572 // operand to ensure Replacer dominates each operand where Replacee occurs.
1573 for (const Use &Arg : MP->operands()) {
1574 if (Arg.get() != Replacee &&
1575 !DT->dominates(Replacer->getBlock(), MP->getIncomingBlock(Arg)))
1576 return false;
1577 }
1578 return true;
1579}
1580
1581/// Properly remove \p MA from all of MemorySSA's lookup tables.
1582void MemorySSA::removeFromLookups(MemoryAccess *MA) {
1583 assert(MA->use_empty() &&(static_cast <bool> (MA->use_empty() && "Trying to remove memory access that still has uses"
) ? void (0) : __assert_fail ("MA->use_empty() && \"Trying to remove memory access that still has uses\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1584, __extension__ __PRETTY_FUNCTION__))
1584 "Trying to remove memory access that still has uses")(static_cast <bool> (MA->use_empty() && "Trying to remove memory access that still has uses"
) ? void (0) : __assert_fail ("MA->use_empty() && \"Trying to remove memory access that still has uses\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1584, __extension__ __PRETTY_FUNCTION__))
;
1585 BlockNumbering.erase(MA);
1586 if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
1587 MUD->setDefiningAccess(nullptr);
1588 // Invalidate our walker's cache if necessary
1589 if (!isa<MemoryUse>(MA))
1590 Walker->invalidateInfo(MA);
1591
1592 Value *MemoryInst;
1593 if (const auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
1594 MemoryInst = MUD->getMemoryInst();
1595 else
1596 MemoryInst = MA->getBlock();
1597
1598 auto VMA = ValueToMemoryAccess.find(MemoryInst);
1599 if (VMA->second == MA)
1600 ValueToMemoryAccess.erase(VMA);
1601}
1602
1603/// Properly remove \p MA from all of MemorySSA's lists.
1604///
1605/// Because of the way the intrusive list and use lists work, it is important to
1606/// do removal in the right order.
1607/// ShouldDelete defaults to true, and will cause the memory access to also be
1608/// deleted, not just removed.
1609void MemorySSA::removeFromLists(MemoryAccess *MA, bool ShouldDelete) {
1610 BasicBlock *BB = MA->getBlock();
1611 // The access list owns the reference, so we erase it from the non-owning list
1612 // first.
1613 if (!isa<MemoryUse>(MA)) {
1614 auto DefsIt = PerBlockDefs.find(BB);
1615 std::unique_ptr<DefsList> &Defs = DefsIt->second;
1616 Defs->remove(*MA);
1617 if (Defs->empty())
1618 PerBlockDefs.erase(DefsIt);
1619 }
1620
1621 // The erase call here will delete it. If we don't want it deleted, we call
1622 // remove instead.
1623 auto AccessIt = PerBlockAccesses.find(BB);
1624 std::unique_ptr<AccessList> &Accesses = AccessIt->second;
1625 if (ShouldDelete)
1626 Accesses->erase(MA);
1627 else
1628 Accesses->remove(MA);
1629
1630 if (Accesses->empty()) {
1631 PerBlockAccesses.erase(AccessIt);
1632 BlockNumberingValid.erase(BB);
1633 }
1634}
1635
1636void MemorySSA::print(raw_ostream &OS) const {
1637 MemorySSAAnnotatedWriter Writer(this);
1638 F.print(OS, &Writer);
1639}
1640
1641#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1642LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void MemorySSA::dump() const { print(dbgs()); }
1643#endif
1644
1645void MemorySSA::verifyMemorySSA() const {
1646 verifyDefUses(F);
1647 verifyDomination(F);
1648 verifyOrdering(F);
1649 verifyDominationNumbers(F);
1650 Walker->verify(this);
1651}
1652
1653/// Verify that all of the blocks we believe to have valid domination numbers
1654/// actually have valid domination numbers.
1655void MemorySSA::verifyDominationNumbers(const Function &F) const {
1656#ifndef NDEBUG
1657 if (BlockNumberingValid.empty())
1658 return;
1659
1660 SmallPtrSet<const BasicBlock *, 16> ValidBlocks = BlockNumberingValid;
1661 for (const BasicBlock &BB : F) {
1662 if (!ValidBlocks.count(&BB))
1663 continue;
1664
1665 ValidBlocks.erase(&BB);
1666
1667 const AccessList *Accesses = getBlockAccesses(&BB);
1668 // It's correct to say an empty block has valid numbering.
1669 if (!Accesses)
1670 continue;
1671
1672 // Block numbering starts at 1.
1673 unsigned long LastNumber = 0;
1674 for (const MemoryAccess &MA : *Accesses) {
1675 auto ThisNumberIter = BlockNumbering.find(&MA);
1676 assert(ThisNumberIter != BlockNumbering.end() &&(static_cast <bool> (ThisNumberIter != BlockNumbering.end
() && "MemoryAccess has no domination number in a valid block!"
) ? void (0) : __assert_fail ("ThisNumberIter != BlockNumbering.end() && \"MemoryAccess has no domination number in a valid block!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1677, __extension__ __PRETTY_FUNCTION__))
1677 "MemoryAccess has no domination number in a valid block!")(static_cast <bool> (ThisNumberIter != BlockNumbering.end
() && "MemoryAccess has no domination number in a valid block!"
) ? void (0) : __assert_fail ("ThisNumberIter != BlockNumbering.end() && \"MemoryAccess has no domination number in a valid block!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1677, __extension__ __PRETTY_FUNCTION__))
;
1678
1679 unsigned long ThisNumber = ThisNumberIter->second;
1680 assert(ThisNumber > LastNumber &&(static_cast <bool> (ThisNumber > LastNumber &&
"Domination numbers should be strictly increasing!") ? void (
0) : __assert_fail ("ThisNumber > LastNumber && \"Domination numbers should be strictly increasing!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1681, __extension__ __PRETTY_FUNCTION__))
1681 "Domination numbers should be strictly increasing!")(static_cast <bool> (ThisNumber > LastNumber &&
"Domination numbers should be strictly increasing!") ? void (
0) : __assert_fail ("ThisNumber > LastNumber && \"Domination numbers should be strictly increasing!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1681, __extension__ __PRETTY_FUNCTION__))
;
1682 LastNumber = ThisNumber;
1683 }
1684 }
1685
1686 assert(ValidBlocks.empty() &&(static_cast <bool> (ValidBlocks.empty() && "All valid BasicBlocks should exist in F -- dangling pointers?"
) ? void (0) : __assert_fail ("ValidBlocks.empty() && \"All valid BasicBlocks should exist in F -- dangling pointers?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1687, __extension__ __PRETTY_FUNCTION__))
1687 "All valid BasicBlocks should exist in F -- dangling pointers?")(static_cast <bool> (ValidBlocks.empty() && "All valid BasicBlocks should exist in F -- dangling pointers?"
) ? void (0) : __assert_fail ("ValidBlocks.empty() && \"All valid BasicBlocks should exist in F -- dangling pointers?\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1687, __extension__ __PRETTY_FUNCTION__))
;
1688#endif
1689}
1690
1691/// Verify that the order and existence of MemoryAccesses matches the
1692/// order and existence of memory affecting instructions.
1693void MemorySSA::verifyOrdering(Function &F) const {
1694 // Walk all the blocks, comparing what the lookups think and what the access
1695 // lists think, as well as the order in the blocks vs the order in the access
1696 // lists.
1697 SmallVector<MemoryAccess *, 32> ActualAccesses;
1698 SmallVector<MemoryAccess *, 32> ActualDefs;
1699 for (BasicBlock &B : F) {
1700 const AccessList *AL = getBlockAccesses(&B);
1701 const auto *DL = getBlockDefs(&B);
1702 MemoryAccess *Phi = getMemoryAccess(&B);
1703 if (Phi) {
1704 ActualAccesses.push_back(Phi);
1705 ActualDefs.push_back(Phi);
1706 }
1707
1708 for (Instruction &I : B) {
1709 MemoryAccess *MA = getMemoryAccess(&I);
1710 assert((!MA || (AL && (isa<MemoryUse>(MA) || DL))) &&(static_cast <bool> ((!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"
) ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1713, __extension__ __PRETTY_FUNCTION__))
1711 "We have memory affecting instructions "(static_cast <bool> ((!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"
) ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1713, __extension__ __PRETTY_FUNCTION__))
1712 "in this block but they are not in the "(static_cast <bool> ((!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"
) ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1713, __extension__ __PRETTY_FUNCTION__))
1713 "access list or defs list")(static_cast <bool> ((!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"
) ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1713, __extension__ __PRETTY_FUNCTION__))
;
1714 if (MA) {
1715 ActualAccesses.push_back(MA);
1716 if (isa<MemoryDef>(MA))
1717 ActualDefs.push_back(MA);
1718 }
1719 }
1720 // Either we hit the assert, really have no accesses, or we have both
1721 // accesses and an access list.
1722 // Same with defs.
1723 if (!AL && !DL)
1724 continue;
1725 assert(AL->size() == ActualAccesses.size() &&(static_cast <bool> (AL->size() == ActualAccesses.size
() && "We don't have the same number of accesses in the block as on the "
"access list") ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1727, __extension__ __PRETTY_FUNCTION__))
1726 "We don't have the same number of accesses in the block as on the "(static_cast <bool> (AL->size() == ActualAccesses.size
() && "We don't have the same number of accesses in the block as on the "
"access list") ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1727, __extension__ __PRETTY_FUNCTION__))
1727 "access list")(static_cast <bool> (AL->size() == ActualAccesses.size
() && "We don't have the same number of accesses in the block as on the "
"access list") ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1727, __extension__ __PRETTY_FUNCTION__))
;
1728 assert((DL || ActualDefs.size() == 0) &&(static_cast <bool> ((DL || ActualDefs.size() == 0) &&
"Either we should have a defs list, or we should have no defs"
) ? void (0) : __assert_fail ("(DL || ActualDefs.size() == 0) && \"Either we should have a defs list, or we should have no defs\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1729, __extension__ __PRETTY_FUNCTION__))
1729 "Either we should have a defs list, or we should have no defs")(static_cast <bool> ((DL || ActualDefs.size() == 0) &&
"Either we should have a defs list, or we should have no defs"
) ? void (0) : __assert_fail ("(DL || ActualDefs.size() == 0) && \"Either we should have a defs list, or we should have no defs\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1729, __extension__ __PRETTY_FUNCTION__))
;
1730 assert((!DL || DL->size() == ActualDefs.size()) &&(static_cast <bool> ((!DL || DL->size() == ActualDefs
.size()) && "We don't have the same number of defs in the block as on the "
"def list") ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1732, __extension__ __PRETTY_FUNCTION__))
1731 "We don't have the same number of defs in the block as on the "(static_cast <bool> ((!DL || DL->size() == ActualDefs
.size()) && "We don't have the same number of defs in the block as on the "
"def list") ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1732, __extension__ __PRETTY_FUNCTION__))
1732 "def list")(static_cast <bool> ((!DL || DL->size() == ActualDefs
.size()) && "We don't have the same number of defs in the block as on the "
"def list") ? 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\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1732, __extension__ __PRETTY_FUNCTION__))
;
1733 auto ALI = AL->begin();
1734 auto AAI = ActualAccesses.begin();
1735 while (ALI != AL->end() && AAI != ActualAccesses.end()) {
1736 assert(&*ALI == *AAI && "Not the same accesses in the same order")(static_cast <bool> (&*ALI == *AAI && "Not the same accesses in the same order"
) ? void (0) : __assert_fail ("&*ALI == *AAI && \"Not the same accesses in the same order\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1736, __extension__ __PRETTY_FUNCTION__))
;
1737 ++ALI;
1738 ++AAI;
1739 }
1740 ActualAccesses.clear();
1741 if (DL) {
1742 auto DLI = DL->begin();
1743 auto ADI = ActualDefs.begin();
1744 while (DLI != DL->end() && ADI != ActualDefs.end()) {
1745 assert(&*DLI == *ADI && "Not the same defs in the same order")(static_cast <bool> (&*DLI == *ADI && "Not the same defs in the same order"
) ? void (0) : __assert_fail ("&*DLI == *ADI && \"Not the same defs in the same order\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1745, __extension__ __PRETTY_FUNCTION__))
;
1746 ++DLI;
1747 ++ADI;
1748 }
1749 }
1750 ActualDefs.clear();
1751 }
1752}
1753
1754/// Verify the domination properties of MemorySSA by checking that each
1755/// definition dominates all of its uses.
1756void MemorySSA::verifyDomination(Function &F) const {
1757#ifndef NDEBUG
1758 for (BasicBlock &B : F) {
1759 // Phi nodes are attached to basic blocks
1760 if (MemoryPhi *MP = getMemoryAccess(&B))
1761 for (const Use &U : MP->uses())
1762 assert(dominates(MP, U) && "Memory PHI does not dominate it's uses")(static_cast <bool> (dominates(MP, U) && "Memory PHI does not dominate it's uses"
) ? void (0) : __assert_fail ("dominates(MP, U) && \"Memory PHI does not dominate it's uses\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1762, __extension__ __PRETTY_FUNCTION__))
;
1763
1764 for (Instruction &I : B) {
1765 MemoryAccess *MD = dyn_cast_or_null<MemoryDef>(getMemoryAccess(&I));
1766 if (!MD)
1767 continue;
1768
1769 for (const Use &U : MD->uses())
1770 assert(dominates(MD, U) && "Memory Def does not dominate it's uses")(static_cast <bool> (dominates(MD, U) && "Memory Def does not dominate it's uses"
) ? void (0) : __assert_fail ("dominates(MD, U) && \"Memory Def does not dominate it's uses\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1770, __extension__ __PRETTY_FUNCTION__))
;
1771 }
1772 }
1773#endif
1774}
1775
1776/// Verify the def-use lists in MemorySSA, by verifying that \p Use
1777/// appears in the use list of \p Def.
1778void MemorySSA::verifyUseInDefs(MemoryAccess *Def, MemoryAccess *Use) const {
1779#ifndef NDEBUG
1780 // The live on entry use may cause us to get a NULL def here
1781 if (!Def)
1782 assert(isLiveOnEntryDef(Use) &&(static_cast <bool> (isLiveOnEntryDef(Use) && "Null def but use not point to live on entry def"
) ? void (0) : __assert_fail ("isLiveOnEntryDef(Use) && \"Null def but use not point to live on entry def\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1783, __extension__ __PRETTY_FUNCTION__))
1783 "Null def but use not point to live on entry def")(static_cast <bool> (isLiveOnEntryDef(Use) && "Null def but use not point to live on entry def"
) ? void (0) : __assert_fail ("isLiveOnEntryDef(Use) && \"Null def but use not point to live on entry def\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1783, __extension__ __PRETTY_FUNCTION__))
;
1784 else
1785 assert(is_contained(Def->users(), Use) &&(static_cast <bool> (is_contained(Def->users(), Use)
&& "Did not find use in def's use list") ? void (0) :
__assert_fail ("is_contained(Def->users(), Use) && \"Did not find use in def's use list\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1786, __extension__ __PRETTY_FUNCTION__))
1786 "Did not find use in def's use list")(static_cast <bool> (is_contained(Def->users(), Use)
&& "Did not find use in def's use list") ? void (0) :
__assert_fail ("is_contained(Def->users(), Use) && \"Did not find use in def's use list\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1786, __extension__ __PRETTY_FUNCTION__))
;
1787#endif
1788}
1789
1790/// Verify the immediate use information, by walking all the memory
1791/// accesses and verifying that, for each use, it appears in the
1792/// appropriate def's use list
1793void MemorySSA::verifyDefUses(Function &F) const {
1794 for (BasicBlock &B : F) {
1795 // Phi nodes are attached to basic blocks
1796 if (MemoryPhi *Phi = getMemoryAccess(&B)) {
1797 assert(Phi->getNumOperands() == static_cast<unsigned>(std::distance((static_cast <bool> (Phi->getNumOperands() == static_cast
<unsigned>(std::distance( pred_begin(&B), pred_end(
&B))) && "Incomplete MemoryPhi Node") ? void (0) :
__assert_fail ("Phi->getNumOperands() == static_cast<unsigned>(std::distance( pred_begin(&B), pred_end(&B))) && \"Incomplete MemoryPhi Node\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1799, __extension__ __PRETTY_FUNCTION__))
1798 pred_begin(&B), pred_end(&B))) &&(static_cast <bool> (Phi->getNumOperands() == static_cast
<unsigned>(std::distance( pred_begin(&B), pred_end(
&B))) && "Incomplete MemoryPhi Node") ? void (0) :
__assert_fail ("Phi->getNumOperands() == static_cast<unsigned>(std::distance( pred_begin(&B), pred_end(&B))) && \"Incomplete MemoryPhi Node\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1799, __extension__ __PRETTY_FUNCTION__))
1799 "Incomplete MemoryPhi Node")(static_cast <bool> (Phi->getNumOperands() == static_cast
<unsigned>(std::distance( pred_begin(&B), pred_end(
&B))) && "Incomplete MemoryPhi Node") ? void (0) :
__assert_fail ("Phi->getNumOperands() == static_cast<unsigned>(std::distance( pred_begin(&B), pred_end(&B))) && \"Incomplete MemoryPhi Node\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1799, __extension__ __PRETTY_FUNCTION__))
;
1800 for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I) {
1801 verifyUseInDefs(Phi->getIncomingValue(I), Phi);
1802 assert(find(predecessors(&B), Phi->getIncomingBlock(I)) !=(static_cast <bool> (find(predecessors(&B), Phi->
getIncomingBlock(I)) != pred_end(&B) && "Incoming phi block not a block predecessor"
) ? void (0) : __assert_fail ("find(predecessors(&B), Phi->getIncomingBlock(I)) != pred_end(&B) && \"Incoming phi block not a block predecessor\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1804, __extension__ __PRETTY_FUNCTION__))
1803 pred_end(&B) &&(static_cast <bool> (find(predecessors(&B), Phi->
getIncomingBlock(I)) != pred_end(&B) && "Incoming phi block not a block predecessor"
) ? void (0) : __assert_fail ("find(predecessors(&B), Phi->getIncomingBlock(I)) != pred_end(&B) && \"Incoming phi block not a block predecessor\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1804, __extension__ __PRETTY_FUNCTION__))
1804 "Incoming phi block not a block predecessor")(static_cast <bool> (find(predecessors(&B), Phi->
getIncomingBlock(I)) != pred_end(&B) && "Incoming phi block not a block predecessor"
) ? void (0) : __assert_fail ("find(predecessors(&B), Phi->getIncomingBlock(I)) != pred_end(&B) && \"Incoming phi block not a block predecessor\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1804, __extension__ __PRETTY_FUNCTION__))
;
1805 }
1806 }
1807
1808 for (Instruction &I : B) {
1809 if (MemoryUseOrDef *MA = getMemoryAccess(&I)) {
1810 verifyUseInDefs(MA->getDefiningAccess(), MA);
1811 }
1812 }
1813 }
1814}
1815
1816MemoryUseOrDef *MemorySSA::getMemoryAccess(const Instruction *I) const {
1817 return cast_or_null<MemoryUseOrDef>(ValueToMemoryAccess.lookup(I));
1818}
1819
1820MemoryPhi *MemorySSA::getMemoryAccess(const BasicBlock *BB) const {
1821 return cast_or_null<MemoryPhi>(ValueToMemoryAccess.lookup(cast<Value>(BB)));
1822}
1823
1824/// Perform a local numbering on blocks so that instruction ordering can be
1825/// determined in constant time.
1826/// TODO: We currently just number in order. If we numbered by N, we could
1827/// allow at least N-1 sequences of insertBefore or insertAfter (and at least
1828/// log2(N) sequences of mixed before and after) without needing to invalidate
1829/// the numbering.
1830void MemorySSA::renumberBlock(const BasicBlock *B) const {
1831 // The pre-increment ensures the numbers really start at 1.
1832 unsigned long CurrentNumber = 0;
1833 const AccessList *AL = getBlockAccesses(B);
1834 assert(AL != nullptr && "Asking to renumber an empty block")(static_cast <bool> (AL != nullptr && "Asking to renumber an empty block"
) ? void (0) : __assert_fail ("AL != nullptr && \"Asking to renumber an empty block\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1834, __extension__ __PRETTY_FUNCTION__))
;
1835 for (const auto &I : *AL)
1836 BlockNumbering[&I] = ++CurrentNumber;
1837 BlockNumberingValid.insert(B);
1838}
1839
1840/// Determine, for two memory accesses in the same block,
1841/// whether \p Dominator dominates \p Dominatee.
1842/// \returns True if \p Dominator dominates \p Dominatee.
1843bool MemorySSA::locallyDominates(const MemoryAccess *Dominator,
1844 const MemoryAccess *Dominatee) const {
1845 const BasicBlock *DominatorBlock = Dominator->getBlock();
1846
1847 assert((DominatorBlock == Dominatee->getBlock()) &&(static_cast <bool> ((DominatorBlock == Dominatee->getBlock
()) && "Asking for local domination when accesses are in different blocks!"
) ? void (0) : __assert_fail ("(DominatorBlock == Dominatee->getBlock()) && \"Asking for local domination when accesses are in different blocks!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1848, __extension__ __PRETTY_FUNCTION__))
1848 "Asking for local domination when accesses are in different blocks!")(static_cast <bool> ((DominatorBlock == Dominatee->getBlock
()) && "Asking for local domination when accesses are in different blocks!"
) ? void (0) : __assert_fail ("(DominatorBlock == Dominatee->getBlock()) && \"Asking for local domination when accesses are in different blocks!\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1848, __extension__ __PRETTY_FUNCTION__))
;
1849 // A node dominates itself.
1850 if (Dominatee == Dominator)
1851 return true;
1852
1853 // When Dominatee is defined on function entry, it is not dominated by another
1854 // memory access.
1855 if (isLiveOnEntryDef(Dominatee))
1856 return false;
1857
1858 // When Dominator is defined on function entry, it dominates the other memory
1859 // access.
1860 if (isLiveOnEntryDef(Dominator))
1861 return true;
1862
1863 if (!BlockNumberingValid.count(DominatorBlock))
1864 renumberBlock(DominatorBlock);
1865
1866 unsigned long DominatorNum = BlockNumbering.lookup(Dominator);
1867 // All numbers start with 1
1868 assert(DominatorNum != 0 && "Block was not numbered properly")(static_cast <bool> (DominatorNum != 0 && "Block was not numbered properly"
) ? void (0) : __assert_fail ("DominatorNum != 0 && \"Block was not numbered properly\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1868, __extension__ __PRETTY_FUNCTION__))
;
1869 unsigned long DominateeNum = BlockNumbering.lookup(Dominatee);
1870 assert(DominateeNum != 0 && "Block was not numbered properly")(static_cast <bool> (DominateeNum != 0 && "Block was not numbered properly"
) ? void (0) : __assert_fail ("DominateeNum != 0 && \"Block was not numbered properly\""
, "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1870, __extension__ __PRETTY_FUNCTION__))
;
1871 return DominatorNum < DominateeNum;
1872}
1873
1874bool MemorySSA::dominates(const MemoryAccess *Dominator,
1875 const MemoryAccess *Dominatee) const {
1876 if (Dominator == Dominatee)
1877 return true;
1878
1879 if (isLiveOnEntryDef(Dominatee))
1880 return false;
1881
1882 if (Dominator->getBlock() != Dominatee->getBlock())
1883 return DT->dominates(Dominator->getBlock(), Dominatee->getBlock());
1884 return locallyDominates(Dominator, Dominatee);
1885}
1886
1887bool MemorySSA::dominates(const MemoryAccess *Dominator,
1888 const Use &Dominatee) const {
1889 if (MemoryPhi *MP = dyn_cast<MemoryPhi>(Dominatee.getUser())) {
1890 BasicBlock *UseBB = MP->getIncomingBlock(Dominatee);
1891 // The def must dominate the incoming block of the phi.
1892 if (UseBB != Dominator->getBlock())
1893 return DT->dominates(Dominator->getBlock(), UseBB);
1894 // If the UseBB and the DefBB are the same, compare locally.
1895 return locallyDominates(Dominator, cast<MemoryAccess>(Dominatee));
1896 }
1897 // If it's not a PHI node use, the normal dominates can already handle it.
1898 return dominates(Dominator, cast<MemoryAccess>(Dominatee.getUser()));
1899}
1900
1901const static char LiveOnEntryStr[] = "liveOnEntry";
1902
1903void MemoryAccess::print(raw_ostream &OS) const {
1904 switch (getValueID()) {
1905 case MemoryPhiVal: return static_cast<const MemoryPhi *>(this)->print(OS);
1906 case MemoryDefVal: return static_cast<const MemoryDef *>(this)->print(OS);
1907 case MemoryUseVal: return static_cast<const MemoryUse *>(this)->print(OS);
1908 }
1909 llvm_unreachable("invalid value id")::llvm::llvm_unreachable_internal("invalid value id", "/build/llvm-toolchain-snapshot-7~svn336939/lib/Analysis/MemorySSA.cpp"
, 1909)
;
1910}
1911
1912void MemoryDef::print(raw_ostream &OS) const {
1913 MemoryAccess *UO = getDefiningAccess();
1914
1915 auto printID = [&OS](MemoryAccess *A) {
1916 if (A && A->getID())
1917 OS << A->getID();
1918 else
1919 OS << LiveOnEntryStr;
1920 };
1921
1922 OS << getID() << " = MemoryDef(";
1923 printID(UO);
1924 OS << ")";
1925
1926 if (isOptimized()) {
1927 OS << "->";
1928 printID(getOptimized());
1929
1930 if (Optional<AliasResult> AR = getOptimizedAccessType())
1931 OS << " " << *AR;
1932 }
1933}
1934
1935void MemoryPhi::print(raw_ostream &OS) const {
1936 bool First = true;
1937 OS << getID() << " = MemoryPhi(";
1938 for (const auto &Op : operands()) {
1939 BasicBlock *BB = getIncomingBlock(Op);
1940 MemoryAccess *MA = cast<MemoryAccess>(Op);
1941 if (!First)
1942 OS << ',';
1943 else
1944 First = false;
1945
1946 OS << '{';
1947 if (BB->hasName())
1948 OS << BB->getName();
1949 else
1950 BB->printAsOperand(OS, false);
1951 OS << ',';
1952 if (unsigned ID = MA->getID())
1953 OS << ID;
1954 else
1955 OS << LiveOnEntryStr;
1956 OS << '}';
1957 }
1958 OS << ')';
1959}
1960
1961void MemoryUse::print(raw_ostream &OS) const {
1962 MemoryAccess *UO = getDefiningAccess();
1963 OS << "MemoryUse(";
1964 if (UO && UO->getID())
1965 OS << UO->getID();
1966 else
1967 OS << LiveOnEntryStr;
1968 OS << ')';
1969
1970 if (Optional<AliasResult> AR = getOptimizedAccessType())
1971 OS << " " << *AR;
1972}
1973
1974void MemoryAccess::dump() const {
1975// Cannot completely remove virtual function even in release mode.
1976#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1977 print(dbgs());
1978 dbgs() << "\n";
1979#endif
1980}
1981
1982char MemorySSAPrinterLegacyPass::ID = 0;
1983
1984MemorySSAPrinterLegacyPass::MemorySSAPrinterLegacyPass() : FunctionPass(ID) {
1985 initializeMemorySSAPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
1986}
1987
1988void MemorySSAPrinterLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
1989 AU.setPreservesAll();
1990 AU.addRequired<MemorySSAWrapperPass>();
1991}
1992
1993bool MemorySSAPrinterLegacyPass::runOnFunction(Function &F) {
1994 auto &MSSA = getAnalysis<MemorySSAWrapperPass>().getMSSA();
1995 MSSA.print(dbgs());
1996 if (VerifyMemorySSA)
1997 MSSA.verifyMemorySSA();
1998 return false;
1999}
2000
2001AnalysisKey MemorySSAAnalysis::Key;
2002
2003MemorySSAAnalysis::Result MemorySSAAnalysis::run(Function &F,
2004 FunctionAnalysisManager &AM) {
2005 auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
2006 auto &AA = AM.getResult<AAManager>(F);
2007 return MemorySSAAnalysis::Result(llvm::make_unique<MemorySSA>(F, &AA, &DT));
2008}
2009
2010PreservedAnalyses MemorySSAPrinterPass::run(Function &F,
2011 FunctionAnalysisManager &AM) {
2012 OS << "MemorySSA for function: " << F.getName() << "\n";
2013 AM.getResult<MemorySSAAnalysis>(F).getMSSA().print(OS);
2014
2015 return PreservedAnalyses::all();
2016}
2017
2018PreservedAnalyses MemorySSAVerifierPass::run(Function &F,
2019 FunctionAnalysisManager &AM) {
2020 AM.getResult<MemorySSAAnalysis>(F).getMSSA().verifyMemorySSA();
2021
2022 return PreservedAnalyses::all();
2023}
2024
2025char MemorySSAWrapperPass::ID = 0;
2026
2027MemorySSAWrapperPass::MemorySSAWrapperPass() : FunctionPass(ID) {
2028 initializeMemorySSAWrapperPassPass(*PassRegistry::getPassRegistry());
2029}
2030
2031void MemorySSAWrapperPass::releaseMemory() { MSSA.reset(); }
2032
2033void MemorySSAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
2034 AU.setPreservesAll();
2035 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
2036 AU.addRequiredTransitive<AAResultsWrapperPass>();
2037}
2038
2039bool MemorySSAWrapperPass::runOnFunction(Function &F) {
2040 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
2041 auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
2042 MSSA.reset(new MemorySSA(F, &AA, &DT));
2043 return false;
2044}
2045
2046void MemorySSAWrapperPass::verifyAnalysis() const { MSSA->verifyMemorySSA(); }
2047
2048void MemorySSAWrapperPass::print(raw_ostream &OS, const Module *M) const {
2049 MSSA->print(OS);
2050}
2051
2052MemorySSAWalker::MemorySSAWalker(MemorySSA *M) : MSSA(M) {}
2053
2054MemorySSA::CachingWalker::CachingWalker(MemorySSA *M, AliasAnalysis *A,
2055 DominatorTree *D)
2056 : MemorySSAWalker(M), Walker(*M, *A, *D) {}
2057
2058void MemorySSA::CachingWalker::invalidateInfo(MemoryAccess *MA) {
2059 if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
2060 MUD->resetOptimized();
2061}
2062
2063/// Walk the use-def chains starting at \p MA and find
2064/// the MemoryAccess that actually clobbers Loc.
2065///
2066/// \returns our clobbering memory access
2067MemoryAccess *MemorySSA::CachingWalker::getClobberingMemoryAccess(
2068 MemoryAccess *StartingAccess, UpwardsMemoryQuery &Q) {
2069 return Walker.findClobber(StartingAccess, Q);
2070}
2071
2072MemoryAccess *MemorySSA::CachingWalker::getClobberingMemoryAccess(
2073 MemoryAccess *StartingAccess, const MemoryLocation &Loc) {
2074 if (isa<MemoryPhi>(StartingAccess))
2075 return StartingAccess;
2076
2077 auto *StartingUseOrDef = cast<MemoryUseOrDef>(StartingAccess);
2078 if (MSSA->isLiveOnEntryDef(StartingUseOrDef))
2079 return StartingUseOrDef;
2080
2081 Instruction *I = StartingUseOrDef->getMemoryInst();
2082
2083 // Conservatively, fences are always clobbers, so don't perform the walk if we
2084 // hit a fence.
2085 if (!ImmutableCallSite(I) && I->isFenceLike())
2086 return StartingUseOrDef;
2087
2088 UpwardsMemoryQuery Q;
2089 Q.OriginalAccess = StartingUseOrDef;
2090 Q.StartingLoc = Loc;
2091 Q.Inst = I;
2092 Q.IsCall = false;
2093
2094 // Unlike the other function, do not walk to the def of a def, because we are
2095 // handed something we already believe is the clobbering access.
2096 MemoryAccess *DefiningAccess = isa<MemoryUse>(StartingUseOrDef)
2097 ? StartingUseOrDef->getDefiningAccess()
2098 : StartingUseOrDef;
2099
2100 MemoryAccess *Clobber = getClobberingMemoryAccess(DefiningAccess, Q);
2101 LLVM_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)
;
2102 LLVM_DEBUG(dbgs() << *StartingUseOrDef << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << *StartingUseOrDef << "\n"
; } } while (false)
;
2103 LLVM_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)
;
2104 LLVM_DEBUG(dbgs() << *Clobber << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << *Clobber << "\n"; } } while
(false)
;
2105 return Clobber;
2106}
2107
2108MemoryAccess *
2109MemorySSA::CachingWalker::getClobberingMemoryAccess(MemoryAccess *MA) {
2110 auto *StartingAccess = dyn_cast<MemoryUseOrDef>(MA);
2111 // If this is a MemoryPhi, we can't do anything.
2112 if (!StartingAccess)
2113 return MA;
2114
2115 // If this is an already optimized use or def, return the optimized result.
2116 // Note: Currently, we store the optimized def result in a separate field,
2117 // since we can't use the defining access.
2118 if (StartingAccess->isOptimized())
2119 return StartingAccess->getOptimized();
2120
2121 const Instruction *I = StartingAccess->getMemoryInst();
2122 UpwardsMemoryQuery Q(I, StartingAccess);
2123 // We can't sanely do anything with a fence, since they conservatively clobber
2124 // all memory, and have no locations to get pointers from to try to
2125 // disambiguate.
2126 if (!Q.IsCall && I->isFenceLike())
2127 return StartingAccess;
2128
2129 if (isUseTriviallyOptimizableToLiveOnEntry(*MSSA->AA, I)) {
2130 MemoryAccess *LiveOnEntry = MSSA->getLiveOnEntryDef();
2131 StartingAccess->setOptimized(LiveOnEntry);
2132 StartingAccess->setOptimizedAccessType(None);
2133 return LiveOnEntry;
2134 }
2135
2136 // Start with the thing we already think clobbers this location
2137 MemoryAccess *DefiningAccess = StartingAccess->getDefiningAccess();
2138
2139 // At this point, DefiningAccess may be the live on entry def.
2140 // If it is, we will not get a better result.
2141 if (MSSA->isLiveOnEntryDef(DefiningAccess)) {
2142 StartingAccess->setOptimized(DefiningAccess);
2143 StartingAccess->setOptimizedAccessType(None);
2144 return DefiningAccess;
2145 }
2146
2147 MemoryAccess *Result = getClobberingMemoryAccess(DefiningAccess, Q);
2148 LLVM_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)
;
2149 LLVM_DEBUG(dbgs() << *DefiningAccess << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << *DefiningAccess << "\n"
; } } while (false)
;
2150 LLVM_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)
;
2151 LLVM_DEBUG(dbgs() << *Result << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("memoryssa")) { dbgs() << *Result << "\n"; } } while
(false)
;
2152
2153 StartingAccess->setOptimized(Result);
2154 if (MSSA->isLiveOnEntryDef(Result))
2155 StartingAccess->setOptimizedAccessType(None);
2156 else if (Q.AR == MustAlias)
2157 StartingAccess->setOptimizedAccessType(MustAlias);
2158
2159 return Result;
2160}
2161
2162MemoryAccess *
2163DoNothingMemorySSAWalker::getClobberingMemoryAccess(MemoryAccess *MA) {
2164 if (auto *Use = dyn_cast<MemoryUseOrDef>(MA))
2165 return Use->getDefiningAccess();
2166 return MA;
2167}
2168
2169MemoryAccess *DoNothingMemorySSAWalker::getClobberingMemoryAccess(
2170 MemoryAccess *StartingAccess, const MemoryLocation &) {
2171 if (auto *Use = dyn_cast<MemoryUseOrDef>(StartingAccess))
2172 return Use->getDefiningAccess();
2173 return StartingAccess;
2174}
2175
2176void MemoryPhi::deleteMe(DerivedUser *Self) {
2177 delete static_cast<MemoryPhi *>(Self);
2178}
2179
2180void MemoryDef::deleteMe(DerivedUser *Self) {
2181 delete static_cast<MemoryDef *>(Self);
2182}
2183
2184void MemoryUse::deleteMe(DerivedUser *Self) {
2185 delete static_cast<MemoryUse *>(Self);
2186}