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   assert(MTI->getRawSource() == MTI->getArgOperand(1));
105   return getForArgument(MTI, 1, nullptr);
106 }
107 
108 MemoryLocation MemoryLocation::getForDest(const MemIntrinsic *MI) {
109   return getForDest(cast<AnyMemIntrinsic>(MI));
110 }
111 
112 MemoryLocation MemoryLocation::getForDest(const AtomicMemIntrinsic *MI) {
113   return getForDest(cast<AnyMemIntrinsic>(MI));
114 }
115 
116 MemoryLocation MemoryLocation::getForDest(const AnyMemIntrinsic *MI) {
117   assert(MI->getRawDest() == MI->getArgOperand(0));
118   return getForArgument(MI, 0, nullptr);
119 }
120 
121 Optional<MemoryLocation>
122 MemoryLocation::getForDest(const CallBase *CB, const TargetLibraryInfo &TLI) {
123   if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CB)) {
124     if (auto *MemInst = dyn_cast<AnyMemIntrinsic>(CB))
125       return getForDest(MemInst);
126 
127     switch (II->getIntrinsicID()) {
128     default:
129       return None;
130     case Intrinsic::init_trampoline:
131       return MemoryLocation::getForArgument(CB, 0, TLI);
132     case Intrinsic::masked_store:
133       return MemoryLocation::getForArgument(CB, 1, TLI);
134     }
135   }
136 
137   LibFunc LF;
138   if (TLI.getLibFunc(*CB, LF) && TLI.has(LF)) {
139     switch (LF) {
140     case LibFunc_memset_pattern4:
141     case LibFunc_memset_pattern8:
142     case LibFunc_memset_pattern16:
143     case LibFunc_strncpy:
144     case LibFunc_strcpy:
145     case LibFunc_strcat:
146     case LibFunc_strncat:
147       return getForArgument(CB, 0, &TLI);
148     default:
149       break;
150     }
151   }
152 
153   return None;
154 }
155 
156 MemoryLocation MemoryLocation::getForArgument(const CallBase *Call,
157                                               unsigned ArgIdx,
158                                               const TargetLibraryInfo *TLI) {
159   AAMDNodes AATags = Call->getAAMetadata();
160   const Value *Arg = Call->getArgOperand(ArgIdx);
161 
162   // We may be able to produce an exact size for known intrinsics.
163   if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Call)) {
164     const DataLayout &DL = II->getModule()->getDataLayout();
165 
166     switch (II->getIntrinsicID()) {
167     default:
168       break;
169     case Intrinsic::memset:
170     case Intrinsic::memcpy:
171     case Intrinsic::memcpy_inline:
172     case Intrinsic::memmove:
173     case Intrinsic::memcpy_element_unordered_atomic:
174     case Intrinsic::memmove_element_unordered_atomic:
175     case Intrinsic::memset_element_unordered_atomic:
176       assert((ArgIdx == 0 || ArgIdx == 1) &&
177              "Invalid argument index for memory intrinsic");
178       if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2)))
179         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
180                               AATags);
181       return MemoryLocation::getAfter(Arg, AATags);
182 
183     case Intrinsic::lifetime_start:
184     case Intrinsic::lifetime_end:
185     case Intrinsic::invariant_start:
186       assert(ArgIdx == 1 && "Invalid argument index");
187       return MemoryLocation(
188           Arg,
189           LocationSize::precise(
190               cast<ConstantInt>(II->getArgOperand(0))->getZExtValue()),
191           AATags);
192 
193     case Intrinsic::masked_load:
194       assert(ArgIdx == 0 && "Invalid argument index");
195       return MemoryLocation(
196           Arg,
197           LocationSize::upperBound(DL.getTypeStoreSize(II->getType())),
198           AATags);
199 
200     case Intrinsic::masked_store:
201       assert(ArgIdx == 1 && "Invalid argument index");
202       return MemoryLocation(
203           Arg,
204           LocationSize::upperBound(
205               DL.getTypeStoreSize(II->getArgOperand(0)->getType())),
206           AATags);
207 
208     case Intrinsic::invariant_end:
209       // The first argument to an invariant.end is a "descriptor" type (e.g. a
210       // pointer to a empty struct) which is never actually dereferenced.
211       if (ArgIdx == 0)
212         return MemoryLocation(Arg, LocationSize::precise(0), AATags);
213       assert(ArgIdx == 2 && "Invalid argument index");
214       return MemoryLocation(
215           Arg,
216           LocationSize::precise(
217               cast<ConstantInt>(II->getArgOperand(1))->getZExtValue()),
218           AATags);
219 
220     case Intrinsic::arm_neon_vld1:
221       assert(ArgIdx == 0 && "Invalid argument index");
222       // LLVM's vld1 and vst1 intrinsics currently only support a single
223       // vector register.
224       return MemoryLocation(
225           Arg, LocationSize::precise(DL.getTypeStoreSize(II->getType())),
226           AATags);
227 
228     case Intrinsic::arm_neon_vst1:
229       assert(ArgIdx == 0 && "Invalid argument index");
230       return MemoryLocation(Arg,
231                             LocationSize::precise(DL.getTypeStoreSize(
232                                 II->getArgOperand(1)->getType())),
233                             AATags);
234     }
235 
236     assert(
237         !isa<AnyMemTransferInst>(II) &&
238         "all memory transfer intrinsics should be handled by the switch above");
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     case LibFunc_memset_pattern4:
278     case LibFunc_memset_pattern8:
279       assert((ArgIdx == 0 || ArgIdx == 1) &&
280              "Invalid argument index for memset_pattern16");
281       if (ArgIdx == 1) {
282         unsigned Size = 16;
283         if (F == LibFunc_memset_pattern4)
284           Size = 4;
285         else if (F == LibFunc_memset_pattern8)
286           Size = 8;
287         return MemoryLocation(Arg, LocationSize::precise(Size), AATags);
288       }
289       if (const ConstantInt *LenCI =
290               dyn_cast<ConstantInt>(Call->getArgOperand(2)))
291         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
292                               AATags);
293       return MemoryLocation::getAfter(Arg, AATags);
294     case LibFunc_bcmp:
295     case LibFunc_memcmp:
296       assert((ArgIdx == 0 || ArgIdx == 1) &&
297              "Invalid argument index for memcmp/bcmp");
298       if (const ConstantInt *LenCI =
299               dyn_cast<ConstantInt>(Call->getArgOperand(2)))
300         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
301                               AATags);
302       return MemoryLocation::getAfter(Arg, AATags);
303     case LibFunc_memchr:
304       assert((ArgIdx == 0) && "Invalid argument index for memchr");
305       if (const ConstantInt *LenCI =
306               dyn_cast<ConstantInt>(Call->getArgOperand(2)))
307         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
308                               AATags);
309       return MemoryLocation::getAfter(Arg, AATags);
310     case LibFunc_memccpy:
311       assert((ArgIdx == 0 || ArgIdx == 1) &&
312              "Invalid argument index for memccpy");
313       // We only know an upper bound on the number of bytes read/written.
314       if (const ConstantInt *LenCI =
315               dyn_cast<ConstantInt>(Call->getArgOperand(3)))
316         return MemoryLocation(
317             Arg, LocationSize::upperBound(LenCI->getZExtValue()), AATags);
318       return MemoryLocation::getAfter(Arg, AATags);
319     default:
320       break;
321     };
322   }
323 
324   return MemoryLocation::getBeforeOrAfter(Call->getArgOperand(ArgIdx), AATags);
325 }
326