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Owen Anderson78e02f72007-07-06 23:14:35 +00001//===- MemoryDependenceAnalysis.cpp - Mem Deps Implementation --*- C++ -*-===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file was developed by the Owen Anderson and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements an analysis that determines, for a given memory
11// operation, what preceding memory operations it depends on. It builds on
12// alias analysis information, and tries to provide a lazy, caching interface to
13// a common kind of alias information query.
14//
15//===----------------------------------------------------------------------===//
16
17#include "llvm/Analysis/MemoryDependenceAnalysis.h"
Owen Anderson7a616a12007-07-10 17:25:03 +000018#include "llvm/Constants.h"
Owen Anderson78e02f72007-07-06 23:14:35 +000019#include "llvm/Instructions.h"
20#include "llvm/Function.h"
21#include "llvm/Analysis/AliasAnalysis.h"
Owen Anderson4beedbd2007-07-24 21:52:37 +000022#include "llvm/Support/CFG.h"
Owen Anderson78e02f72007-07-06 23:14:35 +000023#include "llvm/Target/TargetData.h"
24
25using namespace llvm;
26
27char MemoryDependenceAnalysis::ID = 0;
28
Owen Anderson0cd32032007-07-25 19:57:03 +000029Instruction* MemoryDependenceAnalysis::NonLocal = (Instruction*)-2;
30Instruction* MemoryDependenceAnalysis::None = (Instruction*)-3;
Owen Anderson78e02f72007-07-06 23:14:35 +000031
32// Register this pass...
Owen Anderson776ee1f2007-07-10 20:21:08 +000033static RegisterPass<MemoryDependenceAnalysis> X("memdep",
34 "Memory Dependence Analysis");
Owen Anderson78e02f72007-07-06 23:14:35 +000035
36/// getAnalysisUsage - Does not modify anything. It uses Alias Analysis.
37///
38void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
39 AU.setPreservesAll();
40 AU.addRequiredTransitive<AliasAnalysis>();
41 AU.addRequiredTransitive<TargetData>();
42}
43
Owen Anderson5f323202007-07-10 17:59:22 +000044// Find the dependency of a CallSite
Owen Andersonfaac5182007-07-16 21:52:50 +000045Instruction* MemoryDependenceAnalysis::getCallSiteDependency(CallSite C, Instruction* start,
46 bool local) {
Owen Anderson5f323202007-07-10 17:59:22 +000047 assert(local && "Non-local memory dependence analysis not yet implemented");
48
49 AliasAnalysis& AA = getAnalysis<AliasAnalysis>();
50 TargetData& TD = getAnalysis<TargetData>();
51 BasicBlock::iterator blockBegin = C.getInstruction()->getParent()->begin();
52 BasicBlock::iterator QI = C.getInstruction();
53
54 while (QI != blockBegin) {
55 --QI;
56
57 // If this inst is a memory op, get the pointer it accessed
58 Value* pointer = 0;
59 uint64_t pointerSize = 0;
60 if (StoreInst* S = dyn_cast<StoreInst>(QI)) {
61 pointer = S->getPointerOperand();
62 pointerSize = TD.getTypeSize(S->getOperand(0)->getType());
63 } else if (LoadInst* L = dyn_cast<LoadInst>(QI)) {
64 pointer = L->getPointerOperand();
65 pointerSize = TD.getTypeSize(L->getType());
66 } else if (AllocationInst* AI = dyn_cast<AllocationInst>(QI)) {
67 pointer = AI;
68 if (ConstantInt* C = dyn_cast<ConstantInt>(AI->getArraySize()))
Owen Anderson8e850482007-07-10 20:48:38 +000069 pointerSize = C->getZExtValue() * TD.getTypeSize(AI->getAllocatedType());
Owen Anderson5f323202007-07-10 17:59:22 +000070 else
71 pointerSize = ~0UL;
Owen Anderson06b6e822007-07-10 18:43:15 +000072 } else if (VAArgInst* V = dyn_cast<VAArgInst>(QI)) {
73 pointer = V->getOperand(0);
74 pointerSize = TD.getTypeSize(V->getType());
Owen Anderson5f323202007-07-10 17:59:22 +000075 } else if (FreeInst* F = dyn_cast<FreeInst>(QI)) {
76 pointer = F->getPointerOperand();
77
78 // FreeInsts erase the entire structure
79 pointerSize = ~0UL;
80 } else if (CallSite::get(QI).getInstruction() != 0) {
81 if (AA.getModRefInfo(C, CallSite::get(QI)) != AliasAnalysis::NoModRef) {
82 depGraphLocal.insert(std::make_pair(C.getInstruction(), std::make_pair(QI, true)));
83 reverseDep.insert(std::make_pair(QI, C.getInstruction()));
84 return QI;
85 } else {
86 continue;
87 }
Owen Anderson202da142007-07-10 20:39:07 +000088 } else
89 continue;
Owen Anderson5f323202007-07-10 17:59:22 +000090
91 if (AA.getModRefInfo(C, pointer, pointerSize) != AliasAnalysis::NoModRef) {
92 depGraphLocal.insert(std::make_pair(C.getInstruction(), std::make_pair(QI, true)));
93 reverseDep.insert(std::make_pair(QI, C.getInstruction()));
94 return QI;
95 }
96 }
97
98 // No dependence found
99 depGraphLocal.insert(std::make_pair(C.getInstruction(), std::make_pair(NonLocal, true)));
100 reverseDep.insert(std::make_pair(NonLocal, C.getInstruction()));
101 return NonLocal;
102}
103
Owen Anderson0cd32032007-07-25 19:57:03 +0000104bool MemoryDependenceAnalysis::nonLocalHelper(Instruction* query,
105 BasicBlock* block,
Owen Anderson3dfcf332007-07-25 21:26:36 +0000106 DenseMap<BasicBlock*, Value*>& resp,
107 SmallPtrSet<BasicBlock*, 4>& visited) {
Owen Anderson0cd32032007-07-25 19:57:03 +0000108 if (resp.count(block))
109 return resp[block] != None;
Owen Anderson4beedbd2007-07-24 21:52:37 +0000110
Owen Anderson0cd32032007-07-25 19:57:03 +0000111 Instruction* localDep = getDependency(query, 0, block);
Owen Anderson4beedbd2007-07-24 21:52:37 +0000112 if (localDep != NonLocal) {
Owen Anderson0cd32032007-07-25 19:57:03 +0000113 resp.insert(std::make_pair(block, localDep));
114 return true;
Owen Anderson4beedbd2007-07-24 21:52:37 +0000115 }
116
Owen Anderson3dfcf332007-07-25 21:26:36 +0000117 visited.insert(block);
118
Owen Anderson0cd32032007-07-25 19:57:03 +0000119 bool inserted = false;
Owen Anderson4beedbd2007-07-24 21:52:37 +0000120 for (pred_iterator PI = pred_begin(block), PE = pred_end(block);
Owen Anderson0cd32032007-07-25 19:57:03 +0000121 PI != PE; ++PI)
Owen Anderson3dfcf332007-07-25 21:26:36 +0000122 if (!visited.count(*PI))
123 inserted |= nonLocalHelper(query, *PI, resp, visited);
124
125 visited.erase(block);
Owen Anderson4beedbd2007-07-24 21:52:37 +0000126
Owen Anderson0cd32032007-07-25 19:57:03 +0000127 if (!inserted)
128 resp.insert(std::make_pair(block, None));
Owen Anderson4beedbd2007-07-24 21:52:37 +0000129
Owen Anderson0cd32032007-07-25 19:57:03 +0000130 return inserted;
Owen Anderson4beedbd2007-07-24 21:52:37 +0000131}
132
Owen Anderson0cd32032007-07-25 19:57:03 +0000133bool MemoryDependenceAnalysis::getNonLocalDependency(Instruction* query,
134 DenseMap<BasicBlock*, Value*>& resp) {
Owen Anderson4beedbd2007-07-24 21:52:37 +0000135 Instruction* localDep = getDependency(query);
136 if (localDep != NonLocal) {
Owen Anderson0cd32032007-07-25 19:57:03 +0000137 resp.insert(std::make_pair(query->getParent(), localDep));
138 return true;
Owen Anderson4beedbd2007-07-24 21:52:37 +0000139 }
140
Owen Anderson0cd32032007-07-25 19:57:03 +0000141 bool inserted = false;
Owen Anderson3dfcf332007-07-25 21:26:36 +0000142 SmallPtrSet<BasicBlock*, 4> visited;
143 visited.insert(query->getParent());
Owen Anderson0cd32032007-07-25 19:57:03 +0000144
Owen Anderson4beedbd2007-07-24 21:52:37 +0000145 BasicBlock* parent = query->getParent();
146 for (pred_iterator PI = pred_begin(parent), PE = pred_end(parent);
147 PI != PE; ++PI) {
Owen Anderson3dfcf332007-07-25 21:26:36 +0000148 if (!visited.count(*PI))
149 inserted |= nonLocalHelper(query, *PI, resp, visited);
Owen Anderson4beedbd2007-07-24 21:52:37 +0000150 }
151
Owen Anderson0cd32032007-07-25 19:57:03 +0000152 if (!inserted)
153 resp.insert(std::make_pair(query->getParent(), None));
Owen Anderson4beedbd2007-07-24 21:52:37 +0000154
Owen Anderson0cd32032007-07-25 19:57:03 +0000155 return inserted;
Owen Anderson4beedbd2007-07-24 21:52:37 +0000156}
157
Owen Anderson78e02f72007-07-06 23:14:35 +0000158/// getDependency - Return the instruction on which a memory operation
Owen Anderson6b278fc2007-07-10 17:08:11 +0000159/// depends. The local paramter indicates if the query should only
160/// evaluate dependencies within the same basic block.
Owen Anderson78e02f72007-07-06 23:14:35 +0000161Instruction* MemoryDependenceAnalysis::getDependency(Instruction* query,
Owen Andersonfaac5182007-07-16 21:52:50 +0000162 Instruction* start,
Owen Anderson4beedbd2007-07-24 21:52:37 +0000163 BasicBlock* block) {
Owen Anderson78e02f72007-07-06 23:14:35 +0000164 // Start looking for dependencies with the queried inst
165 BasicBlock::iterator QI = query;
166
167 // Check for a cached result
168 std::pair<Instruction*, bool> cachedResult = depGraphLocal[query];
169 // If we have a _confirmed_ cached entry, return it
170 if (cachedResult.second)
171 return cachedResult.first;
Owen Anderson0cd32032007-07-25 19:57:03 +0000172 else if (cachedResult.first && cachedResult.first != NonLocal)
Owen Anderson78e02f72007-07-06 23:14:35 +0000173 // If we have an unconfirmed cached entry, we can start our search from there
174 QI = cachedResult.first;
175
Owen Andersonfaac5182007-07-16 21:52:50 +0000176 if (start)
177 QI = start;
Owen Anderson0cd32032007-07-25 19:57:03 +0000178 else if (!start && block)
179 QI = block->end();
Owen Andersonfaac5182007-07-16 21:52:50 +0000180
Owen Anderson78e02f72007-07-06 23:14:35 +0000181 AliasAnalysis& AA = getAnalysis<AliasAnalysis>();
Owen Anderson6b278fc2007-07-10 17:08:11 +0000182 TargetData& TD = getAnalysis<TargetData>();
Owen Anderson78e02f72007-07-06 23:14:35 +0000183
184 // Get the pointer value for which dependence will be determined
185 Value* dependee = 0;
Owen Anderson6b278fc2007-07-10 17:08:11 +0000186 uint64_t dependeeSize = 0;
Owen Andersone314eb32007-07-10 18:11:42 +0000187 bool queryIsVolatile = false;
Owen Andersonfaac5182007-07-16 21:52:50 +0000188 if (StoreInst* S = dyn_cast<StoreInst>(query)) {
Owen Anderson78e02f72007-07-06 23:14:35 +0000189 dependee = S->getPointerOperand();
Owen Anderson7a616a12007-07-10 17:25:03 +0000190 dependeeSize = TD.getTypeSize(S->getOperand(0)->getType());
Owen Andersone314eb32007-07-10 18:11:42 +0000191 queryIsVolatile = S->isVolatile();
Owen Andersonfaac5182007-07-16 21:52:50 +0000192 } else if (LoadInst* L = dyn_cast<LoadInst>(query)) {
Owen Anderson78e02f72007-07-06 23:14:35 +0000193 dependee = L->getPointerOperand();
Owen Anderson7a616a12007-07-10 17:25:03 +0000194 dependeeSize = TD.getTypeSize(L->getType());
Owen Andersone314eb32007-07-10 18:11:42 +0000195 queryIsVolatile = L->isVolatile();
Owen Andersonfaac5182007-07-16 21:52:50 +0000196 } else if (VAArgInst* V = dyn_cast<VAArgInst>(query)) {
Owen Anderson06b6e822007-07-10 18:43:15 +0000197 dependee = V->getOperand(0);
198 dependeeSize = TD.getTypeSize(V->getType());
Owen Andersonfaac5182007-07-16 21:52:50 +0000199 } else if (FreeInst* F = dyn_cast<FreeInst>(query)) {
Owen Anderson78e02f72007-07-06 23:14:35 +0000200 dependee = F->getPointerOperand();
Owen Anderson6b278fc2007-07-10 17:08:11 +0000201
202 // FreeInsts erase the entire structure, not just a field
203 dependeeSize = ~0UL;
Owen Andersonfaac5182007-07-16 21:52:50 +0000204 } else if (CallSite::get(query).getInstruction() != 0)
205 return getCallSiteDependency(CallSite::get(query), start);
Owen Anderson5f323202007-07-10 17:59:22 +0000206 else if (isa<AllocationInst>(query))
Owen Anderson78e02f72007-07-06 23:14:35 +0000207 return None;
Owen Anderson7a616a12007-07-10 17:25:03 +0000208 else
Owen Anderson6b278fc2007-07-10 17:08:11 +0000209 return None;
Owen Anderson78e02f72007-07-06 23:14:35 +0000210
Owen Anderson4beedbd2007-07-24 21:52:37 +0000211 BasicBlock::iterator blockBegin = block ? block->begin()
212 : query->getParent()->begin();
Owen Anderson78e02f72007-07-06 23:14:35 +0000213
214 while (QI != blockBegin) {
Owen Anderson6b278fc2007-07-10 17:08:11 +0000215 --QI;
216
Owen Anderson78e02f72007-07-06 23:14:35 +0000217 // If this inst is a memory op, get the pointer it accessed
218 Value* pointer = 0;
Owen Anderson6b278fc2007-07-10 17:08:11 +0000219 uint64_t pointerSize = 0;
220 if (StoreInst* S = dyn_cast<StoreInst>(QI)) {
Owen Andersone314eb32007-07-10 18:11:42 +0000221 // All volatile loads/stores depend on each other
222 if (queryIsVolatile && S->isVolatile()) {
Owen Anderson0cd32032007-07-25 19:57:03 +0000223 if (!start || block) {
Owen Andersonfaac5182007-07-16 21:52:50 +0000224 depGraphLocal.insert(std::make_pair(query, std::make_pair(S, true)));
225 reverseDep.insert(std::make_pair(S, query));
226 }
227
Owen Andersone314eb32007-07-10 18:11:42 +0000228 return S;
229 }
230
Owen Anderson78e02f72007-07-06 23:14:35 +0000231 pointer = S->getPointerOperand();
Owen Anderson7a616a12007-07-10 17:25:03 +0000232 pointerSize = TD.getTypeSize(S->getOperand(0)->getType());
Owen Anderson6b278fc2007-07-10 17:08:11 +0000233 } else if (LoadInst* L = dyn_cast<LoadInst>(QI)) {
Owen Andersone314eb32007-07-10 18:11:42 +0000234 // All volatile loads/stores depend on each other
235 if (queryIsVolatile && L->isVolatile()) {
Owen Anderson0cd32032007-07-25 19:57:03 +0000236 if (!start || block) {
Owen Andersonfaac5182007-07-16 21:52:50 +0000237 depGraphLocal.insert(std::make_pair(query, std::make_pair(L, true)));
238 reverseDep.insert(std::make_pair(L, query));
239 }
240
Owen Andersone314eb32007-07-10 18:11:42 +0000241 return L;
242 }
243
Owen Anderson78e02f72007-07-06 23:14:35 +0000244 pointer = L->getPointerOperand();
Owen Anderson7a616a12007-07-10 17:25:03 +0000245 pointerSize = TD.getTypeSize(L->getType());
Owen Anderson6b278fc2007-07-10 17:08:11 +0000246 } else if (AllocationInst* AI = dyn_cast<AllocationInst>(QI)) {
247 pointer = AI;
Owen Anderson7a616a12007-07-10 17:25:03 +0000248 if (ConstantInt* C = dyn_cast<ConstantInt>(AI->getArraySize()))
Owen Anderson8e850482007-07-10 20:48:38 +0000249 pointerSize = C->getZExtValue() * TD.getTypeSize(AI->getAllocatedType());
Owen Anderson6b278fc2007-07-10 17:08:11 +0000250 else
251 pointerSize = ~0UL;
Owen Anderson06b6e822007-07-10 18:43:15 +0000252 } else if (VAArgInst* V = dyn_cast<VAArgInst>(QI)) {
253 pointer = V->getOperand(0);
254 pointerSize = TD.getTypeSize(V->getType());
Owen Anderson6b278fc2007-07-10 17:08:11 +0000255 } else if (FreeInst* F = dyn_cast<FreeInst>(QI)) {
Owen Anderson78e02f72007-07-06 23:14:35 +0000256 pointer = F->getPointerOperand();
Owen Anderson6b278fc2007-07-10 17:08:11 +0000257
258 // FreeInsts erase the entire structure
259 pointerSize = ~0UL;
Owen Anderson5f323202007-07-10 17:59:22 +0000260 } else if (CallSite::get(QI).getInstruction() != 0) {
Owen Anderson78e02f72007-07-06 23:14:35 +0000261 // Call insts need special handling. Check is they can modify our pointer
Owen Anderson5f323202007-07-10 17:59:22 +0000262 if (AA.getModRefInfo(CallSite::get(QI), dependee, dependeeSize) !=
263 AliasAnalysis::NoModRef) {
Owen Anderson0cd32032007-07-25 19:57:03 +0000264 if (!start || block) {
Owen Andersonfaac5182007-07-16 21:52:50 +0000265 depGraphLocal.insert(std::make_pair(query, std::make_pair(QI, true)));
266 reverseDep.insert(std::make_pair(QI, query));
267 }
268
Owen Anderson5f323202007-07-10 17:59:22 +0000269 return QI;
Owen Anderson7a616a12007-07-10 17:25:03 +0000270 } else {
271 continue;
272 }
Owen Anderson78e02f72007-07-06 23:14:35 +0000273 }
274
275 // If we found a pointer, check if it could be the same as our pointer
276 if (pointer) {
Owen Anderson6b278fc2007-07-10 17:08:11 +0000277 AliasAnalysis::AliasResult R = AA.alias(pointer, pointerSize,
278 dependee, dependeeSize);
Owen Anderson78e02f72007-07-06 23:14:35 +0000279
280 if (R != AliasAnalysis::NoAlias) {
Owen Anderson0cd32032007-07-25 19:57:03 +0000281 if (!start || block) {
Owen Andersonfaac5182007-07-16 21:52:50 +0000282 depGraphLocal.insert(std::make_pair(query, std::make_pair(QI, true)));
283 reverseDep.insert(std::make_pair(QI, query));
284 }
285
Owen Anderson78e02f72007-07-06 23:14:35 +0000286 return QI;
287 }
288 }
Owen Anderson78e02f72007-07-06 23:14:35 +0000289 }
290
291 // If we found nothing, return the non-local flag
Owen Anderson0cd32032007-07-25 19:57:03 +0000292 if (!start || block) {
Owen Andersonfaac5182007-07-16 21:52:50 +0000293 depGraphLocal.insert(std::make_pair(query,
294 std::make_pair(NonLocal, true)));
295 reverseDep.insert(std::make_pair(NonLocal, query));
296 }
Owen Anderson78e02f72007-07-06 23:14:35 +0000297
298 return NonLocal;
299}
300
301/// removeInstruction - Remove an instruction from the dependence analysis,
302/// updating the dependence of instructions that previously depended on it.
303void MemoryDependenceAnalysis::removeInstruction(Instruction* rem) {
304 // Figure out the new dep for things that currently depend on rem
305 Instruction* newDep = NonLocal;
Owen Anderson521a2022007-07-20 06:16:07 +0000306 if (depGraphLocal[rem].first != NonLocal &&
307 depGraphLocal[rem].second) {
Owen Anderson78e02f72007-07-06 23:14:35 +0000308 // If we have dep info for rem, set them to it
309 BasicBlock::iterator RI = depGraphLocal[rem].first;
310 RI++;
311 newDep = RI;
312 } else if (depGraphLocal[rem].first == NonLocal &&
313 depGraphLocal[rem].second ) {
314 // If we have a confirmed non-local flag, use it
315 newDep = NonLocal;
316 } else {
317 // Otherwise, use the immediate successor of rem
318 // NOTE: This is because, when getDependence is called, it will first check
319 // the immediate predecessor of what is in the cache.
320 BasicBlock::iterator RI = rem;
321 RI++;
322 newDep = RI;
323 }
324
325 std::multimap<Instruction*, Instruction*>::iterator I = reverseDep.find(rem);
326 while (I->first == rem) {
327 // Insert the new dependencies
328 // Mark it as unconfirmed as long as it is not the non-local flag
329 depGraphLocal[I->second] = std::make_pair(newDep, !newDep);
330 reverseDep.erase(I);
331 I = reverseDep.find(rem);
332 }
Owen Anderson1cb960a2007-07-12 00:06:21 +0000333
334 getAnalysis<AliasAnalysis>().deleteValue(rem);
Owen Anderson78e02f72007-07-06 23:14:35 +0000335}