1 //===- MemoryLocation.cpp - Memory location descriptions -------------------==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "llvm/Analysis/MemoryLocation.h"
10 #include "llvm/Analysis/TargetLibraryInfo.h"
11 #include "llvm/IR/BasicBlock.h"
12 #include "llvm/IR/DataLayout.h"
13 #include "llvm/IR/Instructions.h"
14 #include "llvm/IR/IntrinsicInst.h"
15 #include "llvm/IR/IntrinsicsARM.h"
16 #include "llvm/IR/LLVMContext.h"
17 #include "llvm/IR/Module.h"
18 #include "llvm/IR/Type.h"
19 using namespace llvm;
20 
21 void LocationSize::print(raw_ostream &OS) const {
22   OS << "LocationSize::";
23   if (*this == beforeOrAfterPointer())
24     OS << "beforeOrAfterPointer";
25   else if (*this == afterPointer())
26     OS << "afterPointer";
27   else if (*this == mapEmpty())
28     OS << "mapEmpty";
29   else if (*this == mapTombstone())
30     OS << "mapTombstone";
31   else if (isPrecise())
32     OS << "precise(" << getValue() << ')';
33   else
34     OS << "upperBound(" << getValue() << ')';
35 }
36 
37 MemoryLocation MemoryLocation::get(const LoadInst *LI) {
38   const auto &DL = LI->getModule()->getDataLayout();
39 
40   return MemoryLocation(
41       LI->getPointerOperand(),
42       LocationSize::precise(DL.getTypeStoreSize(LI->getType())),
43       LI->getAAMetadata());
44 }
45 
46 MemoryLocation MemoryLocation::get(const StoreInst *SI) {
47   const auto &DL = SI->getModule()->getDataLayout();
48 
49   return MemoryLocation(SI->getPointerOperand(),
50                         LocationSize::precise(DL.getTypeStoreSize(
51                             SI->getValueOperand()->getType())),
52                         SI->getAAMetadata());
53 }
54 
55 MemoryLocation MemoryLocation::get(const VAArgInst *VI) {
56   return MemoryLocation(VI->getPointerOperand(),
57                         LocationSize::afterPointer(), VI->getAAMetadata());
58 }
59 
60 MemoryLocation MemoryLocation::get(const AtomicCmpXchgInst *CXI) {
61   const auto &DL = CXI->getModule()->getDataLayout();
62 
63   return MemoryLocation(CXI->getPointerOperand(),
64                         LocationSize::precise(DL.getTypeStoreSize(
65                             CXI->getCompareOperand()->getType())),
66                         CXI->getAAMetadata());
67 }
68 
69 MemoryLocation MemoryLocation::get(const AtomicRMWInst *RMWI) {
70   const auto &DL = RMWI->getModule()->getDataLayout();
71 
72   return MemoryLocation(RMWI->getPointerOperand(),
73                         LocationSize::precise(DL.getTypeStoreSize(
74                             RMWI->getValOperand()->getType())),
75                         RMWI->getAAMetadata());
76 }
77 
78 Optional<MemoryLocation> MemoryLocation::getOrNone(const Instruction *Inst) {
79   switch (Inst->getOpcode()) {
80   case Instruction::Load:
81     return get(cast<LoadInst>(Inst));
82   case Instruction::Store:
83     return get(cast<StoreInst>(Inst));
84   case Instruction::VAArg:
85     return get(cast<VAArgInst>(Inst));
86   case Instruction::AtomicCmpXchg:
87     return get(cast<AtomicCmpXchgInst>(Inst));
88   case Instruction::AtomicRMW:
89     return get(cast<AtomicRMWInst>(Inst));
90   default:
91     return None;
92   }
93 }
94 
95 MemoryLocation MemoryLocation::getForSource(const MemTransferInst *MTI) {
96   return getForSource(cast<AnyMemTransferInst>(MTI));
97 }
98 
99 MemoryLocation MemoryLocation::getForSource(const AtomicMemTransferInst *MTI) {
100   return getForSource(cast<AnyMemTransferInst>(MTI));
101 }
102 
103 MemoryLocation MemoryLocation::getForSource(const AnyMemTransferInst *MTI) {
104   auto Size = LocationSize::afterPointer();
105   if (ConstantInt *C = dyn_cast<ConstantInt>(MTI->getLength()))
106     Size = LocationSize::precise(C->getValue().getZExtValue());
107 
108   // memcpy/memmove can have AA tags. For memcpy, they apply
109   // to both the source and the destination.
110   return MemoryLocation(MTI->getRawSource(), Size, MTI->getAAMetadata());
111 }
112 
113 MemoryLocation MemoryLocation::getForDest(const MemIntrinsic *MI) {
114   return getForDest(cast<AnyMemIntrinsic>(MI));
115 }
116 
117 MemoryLocation MemoryLocation::getForDest(const AtomicMemIntrinsic *MI) {
118   return getForDest(cast<AnyMemIntrinsic>(MI));
119 }
120 
121 MemoryLocation MemoryLocation::getForDest(const AnyMemIntrinsic *MI) {
122   auto Size = LocationSize::afterPointer();
123   if (ConstantInt *C = dyn_cast<ConstantInt>(MI->getLength()))
124     Size = LocationSize::precise(C->getValue().getZExtValue());
125 
126   // memcpy/memmove can have AA tags. For memcpy, they apply
127   // to both the source and the destination.
128   return MemoryLocation(MI->getRawDest(), Size, MI->getAAMetadata());
129 }
130 
131 Optional<MemoryLocation>
132 MemoryLocation::getForDest(const CallBase *CB, const TargetLibraryInfo &TLI) {
133   if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CB)) {
134     if (auto *MemInst = dyn_cast<AnyMemIntrinsic>(CB))
135       return getForDest(MemInst);
136 
137     switch (II->getIntrinsicID()) {
138     default:
139       return None;
140     case Intrinsic::init_trampoline:
141       return MemoryLocation::getForArgument(CB, 0, TLI);
142     case Intrinsic::masked_store:
143       return MemoryLocation::getForArgument(CB, 1, TLI);
144     }
145   }
146 
147   LibFunc LF;
148   if (TLI.getLibFunc(*CB, LF) && TLI.has(LF)) {
149     switch (LF) {
150     case LibFunc_strncpy:
151     case LibFunc_strcpy:
152     case LibFunc_strcat:
153     case LibFunc_strncat:
154       return getForArgument(CB, 0, &TLI);
155     default:
156       break;
157     }
158   }
159 
160   return None;
161 }
162 
163 MemoryLocation MemoryLocation::getForArgument(const CallBase *Call,
164                                               unsigned ArgIdx,
165                                               const TargetLibraryInfo *TLI) {
166   AAMDNodes AATags = Call->getAAMetadata();
167   const Value *Arg = Call->getArgOperand(ArgIdx);
168 
169   // We may be able to produce an exact size for known intrinsics.
170   if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Call)) {
171     const DataLayout &DL = II->getModule()->getDataLayout();
172 
173     switch (II->getIntrinsicID()) {
174     default:
175       break;
176     case Intrinsic::memset:
177     case Intrinsic::memcpy:
178     case Intrinsic::memcpy_inline:
179     case Intrinsic::memmove:
180       assert((ArgIdx == 0 || ArgIdx == 1) &&
181              "Invalid argument index for memory intrinsic");
182       if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2)))
183         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
184                               AATags);
185       return MemoryLocation::getAfter(Arg, AATags);
186 
187     case Intrinsic::lifetime_start:
188     case Intrinsic::lifetime_end:
189     case Intrinsic::invariant_start:
190       assert(ArgIdx == 1 && "Invalid argument index");
191       return MemoryLocation(
192           Arg,
193           LocationSize::precise(
194               cast<ConstantInt>(II->getArgOperand(0))->getZExtValue()),
195           AATags);
196 
197     case Intrinsic::masked_load:
198       assert(ArgIdx == 0 && "Invalid argument index");
199       return MemoryLocation(
200           Arg,
201           LocationSize::upperBound(DL.getTypeStoreSize(II->getType())),
202           AATags);
203 
204     case Intrinsic::masked_store:
205       assert(ArgIdx == 1 && "Invalid argument index");
206       return MemoryLocation(
207           Arg,
208           LocationSize::upperBound(
209               DL.getTypeStoreSize(II->getArgOperand(0)->getType())),
210           AATags);
211 
212     case Intrinsic::invariant_end:
213       // The first argument to an invariant.end is a "descriptor" type (e.g. a
214       // pointer to a empty struct) which is never actually dereferenced.
215       if (ArgIdx == 0)
216         return MemoryLocation(Arg, LocationSize::precise(0), AATags);
217       assert(ArgIdx == 2 && "Invalid argument index");
218       return MemoryLocation(
219           Arg,
220           LocationSize::precise(
221               cast<ConstantInt>(II->getArgOperand(1))->getZExtValue()),
222           AATags);
223 
224     case Intrinsic::arm_neon_vld1:
225       assert(ArgIdx == 0 && "Invalid argument index");
226       // LLVM's vld1 and vst1 intrinsics currently only support a single
227       // vector register.
228       return MemoryLocation(
229           Arg, LocationSize::precise(DL.getTypeStoreSize(II->getType())),
230           AATags);
231 
232     case Intrinsic::arm_neon_vst1:
233       assert(ArgIdx == 0 && "Invalid argument index");
234       return MemoryLocation(Arg,
235                             LocationSize::precise(DL.getTypeStoreSize(
236                                 II->getArgOperand(1)->getType())),
237                             AATags);
238     }
239   }
240 
241   // We can bound the aliasing properties of memset_pattern16 just as we can
242   // for memcpy/memset.  This is particularly important because the
243   // LoopIdiomRecognizer likes to turn loops into calls to memset_pattern16
244   // whenever possible.
245   LibFunc F;
246   if (TLI && TLI->getLibFunc(*Call, F) && TLI->has(F)) {
247     switch (F) {
248     case LibFunc_strcpy:
249     case LibFunc_strcat:
250     case LibFunc_strncat:
251       assert((ArgIdx == 0 || ArgIdx == 1) && "Invalid argument index for str function");
252       return MemoryLocation::getAfter(Arg, AATags);
253 
254     case LibFunc_memset_chk: {
255       assert(ArgIdx == 0 && "Invalid argument index for memset_chk");
256       LocationSize Size = LocationSize::afterPointer();
257       if (const auto *Len = dyn_cast<ConstantInt>(Call->getArgOperand(2))) {
258         // memset_chk writes at most Len bytes. It may write less, if Len
259         // exceeds the specified max size and aborts.
260         Size = LocationSize::upperBound(Len->getZExtValue());
261       }
262       return MemoryLocation(Arg, Size, AATags);
263     }
264     case LibFunc_strncpy: {
265       assert((ArgIdx == 0 || ArgIdx == 1) &&
266              "Invalid argument index for strncpy");
267       LocationSize Size = LocationSize::afterPointer();
268       if (const auto *Len = dyn_cast<ConstantInt>(Call->getArgOperand(2))) {
269         // strncpy is guaranteed to write Len bytes, but only reads up to Len
270         // bytes.
271         Size = ArgIdx == 0 ? LocationSize::precise(Len->getZExtValue())
272                            : LocationSize::upperBound(Len->getZExtValue());
273       }
274       return MemoryLocation(Arg, Size, AATags);
275     }
276     case LibFunc_memset_pattern16:
277       assert((ArgIdx == 0 || ArgIdx == 1) &&
278              "Invalid argument index for memset_pattern16");
279       if (ArgIdx == 1)
280         return MemoryLocation(Arg, LocationSize::precise(16), AATags);
281       if (const ConstantInt *LenCI =
282               dyn_cast<ConstantInt>(Call->getArgOperand(2)))
283         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
284                               AATags);
285       return MemoryLocation::getAfter(Arg, AATags);
286     case LibFunc_bcmp:
287     case LibFunc_memcmp:
288       assert((ArgIdx == 0 || ArgIdx == 1) &&
289              "Invalid argument index for memcmp/bcmp");
290       if (const ConstantInt *LenCI =
291               dyn_cast<ConstantInt>(Call->getArgOperand(2)))
292         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
293                               AATags);
294       return MemoryLocation::getAfter(Arg, AATags);
295     case LibFunc_memchr:
296       assert((ArgIdx == 0) && "Invalid argument index for memchr");
297       if (const ConstantInt *LenCI =
298               dyn_cast<ConstantInt>(Call->getArgOperand(2)))
299         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
300                               AATags);
301       return MemoryLocation::getAfter(Arg, AATags);
302     case LibFunc_memccpy:
303       assert((ArgIdx == 0 || ArgIdx == 1) &&
304              "Invalid argument index for memccpy");
305       // We only know an upper bound on the number of bytes read/written.
306       if (const ConstantInt *LenCI =
307               dyn_cast<ConstantInt>(Call->getArgOperand(3)))
308         return MemoryLocation(
309             Arg, LocationSize::upperBound(LenCI->getZExtValue()), AATags);
310       return MemoryLocation::getAfter(Arg, AATags);
311     default:
312       break;
313     };
314   }
315   // FIXME: Handle memset_pattern4 and memset_pattern8 also.
316 
317   return MemoryLocation::getBeforeOrAfter(Call->getArgOperand(ArgIdx), AATags);
318 }
319