llvm/lib/Transforms/Utils/MemoryOpRemark.cpp

   1 //===-- MemoryOpRemark.cpp - Auto-init remark analysis---------------------===//
   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 // Implementation of the analysis for the "auto-init" remark.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Transforms/Utils/MemoryOpRemark.h"
  14 #include "llvm/ADT/SmallString.h"
  15 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
  16 #include "llvm/Analysis/ValueTracking.h"
  17 #include "llvm/IR/DebugInfo.h"
  18 #include "llvm/IR/Instructions.h"
  19 #include "llvm/IR/IntrinsicInst.h"
  20 #include <optional>
  21
  22 using namespace llvm;
  23 using namespace llvm::ore;
  24
  25 MemoryOpRemark::~MemoryOpRemark() = default;
  26
  27 bool MemoryOpRemark::canHandle(const Instruction *I, const TargetLibraryInfo &TLI) {
  28   if (isa<StoreInst>(I))
  29     return true;
  30
  31   if (auto *II = dyn_cast<IntrinsicInst>(I)) {
  32     switch (II->getIntrinsicID()) {
  33     case Intrinsic::memcpy_inline:
  34     case Intrinsic::memcpy:
  35     case Intrinsic::memmove:
  36     case Intrinsic::memset:
  37     case Intrinsic::memcpy_element_unordered_atomic:
  38     case Intrinsic::memmove_element_unordered_atomic:
  39     case Intrinsic::memset_element_unordered_atomic:
  40       return true;
  41     default:
  42       return false;
  43     }
  44   }
  45
  46   if (auto *CI = dyn_cast<CallInst>(I)) {
  47     auto *CF = CI->getCalledFunction();
  48     if (!CF)
  49       return false;
  50
  51     if (!CF->hasName())
  52       return false;
  53
  54     LibFunc LF;
  55     bool KnownLibCall = TLI.getLibFunc(*CF, LF) && TLI.has(LF);
  56     if (!KnownLibCall)
  57       return false;
  58
  59     switch (LF) {
  60     case LibFunc_memcpy_chk:
  61     case LibFunc_mempcpy_chk:
  62     case LibFunc_memset_chk:
  63     case LibFunc_memmove_chk:
  64     case LibFunc_memcpy:
  65     case LibFunc_mempcpy:
  66     case LibFunc_memset:
  67     case LibFunc_memmove:
  68     case LibFunc_bzero:
  69     case LibFunc_bcopy:
  70       return true;
  71     default:
  72       return false;
  73     }
  74   }
  75
  76   return false;
  77 }
  78
  79 void MemoryOpRemark::visit(const Instruction *I) {
  80   // For some of them, we can provide more information:
  81
  82   // For stores:
  83   // * size
  84   // * volatile / atomic
  85   if (auto *SI = dyn_cast<StoreInst>(I)) {
  86     visitStore(*SI);
  87     return;
  88   }
  89
  90   // For intrinsics:
  91   // * user-friendly name
  92   // * size
  93   if (auto *II = dyn_cast<IntrinsicInst>(I)) {
  94     visitIntrinsicCall(*II);
  95     return;
  96   }
  97
  98   // For calls:
  99   // * known/unknown function (e.g. the compiler knows bzero, but it doesn't
 100   //                                know my_bzero)
 101   // * memory operation size
 102   if (auto *CI = dyn_cast<CallInst>(I)) {
 103     visitCall(*CI);
 104     return;
 105   }
 106
 107   visitUnknown(*I);
 108 }
 109
 110 std::string MemoryOpRemark::explainSource(StringRef Type) const {
 111   return (Type + ".").str();
 112 }
 113
 114 StringRef MemoryOpRemark::remarkName(RemarkKind RK) const {
 115   switch (RK) {
 116   case RK_Store:
 117     return "MemoryOpStore";
 118   case RK_Unknown:
 119     return "MemoryOpUnknown";
 120   case RK_IntrinsicCall:
 121     return "MemoryOpIntrinsicCall";
 122   case RK_Call:
 123     return "MemoryOpCall";
 124   }
 125   llvm_unreachable("missing RemarkKind case");
 126 }
 127
 128 static void inlineVolatileOrAtomicWithExtraArgs(bool *Inline, bool Volatile,
 129                                                 bool Atomic,
 130                                                 DiagnosticInfoIROptimization &R) {
 131   if (Inline && *Inline)
 132     R << " Inlined: " << NV("StoreInlined", true) << ".";
 133   if (Volatile)
 134     R << " Volatile: " << NV("StoreVolatile", true) << ".";
 135   if (Atomic)
 136     R << " Atomic: " << NV("StoreAtomic", true) << ".";
 137   // Emit the false cases under ExtraArgs. This won't show them in the remark
 138   // message but will end up in the serialized remarks.
 139   if ((Inline && !*Inline) || !Volatile || !Atomic)
 140     R << setExtraArgs();
 141   if (Inline && !*Inline)
 142     R << " Inlined: " << NV("StoreInlined", false) << ".";
 143   if (!Volatile)
 144     R << " Volatile: " << NV("StoreVolatile", false) << ".";
 145   if (!Atomic)
 146     R << " Atomic: " << NV("StoreAtomic", false) << ".";
 147 }
 148
 149 static std::optional<uint64_t>
 150 getSizeInBytes(std::optional<uint64_t> SizeInBits) {
 151   if (!SizeInBits || *SizeInBits % 8 != 0)
 152     return std::nullopt;
 153   return *SizeInBits / 8;
 154 }
 155
 156 template<typename ...Ts>
 157 std::unique_ptr<DiagnosticInfoIROptimization>
 158 MemoryOpRemark::makeRemark(Ts... Args) {
 159   switch (diagnosticKind()) {
 160   case DK_OptimizationRemarkAnalysis:
 161     return std::make_unique<OptimizationRemarkAnalysis>(Args...);
 162   case DK_OptimizationRemarkMissed:
 163     return std::make_unique<OptimizationRemarkMissed>(Args...);
 164   default:
 165     llvm_unreachable("unexpected DiagnosticKind");
 166   }
 167 }
 168
 169 void MemoryOpRemark::visitStore(const StoreInst &SI) {
 170   bool Volatile = SI.isVolatile();
 171   bool Atomic = SI.isAtomic();
 172   int64_t Size = DL.getTypeStoreSize(SI.getOperand(0)->getType());
 173
 174   auto R = makeRemark(RemarkPass.data(), remarkName(RK_Store), &SI);
 175   *R << explainSource("Store") << "\nStore size: " << NV("StoreSize", Size)
 176      << " bytes.";
 177   visitPtr(SI.getOperand(1), /*IsRead=*/false, *R);
 178   inlineVolatileOrAtomicWithExtraArgs(nullptr, Volatile, Atomic, *R);
 179   ORE.emit(*R);
 180 }
 181
 182 void MemoryOpRemark::visitUnknown(const Instruction &I) {
 183   auto R = makeRemark(RemarkPass.data(), remarkName(RK_Unknown), &I);
 184   *R << explainSource("Initialization");
 185   ORE.emit(*R);
 186 }
 187
 188 void MemoryOpRemark::visitIntrinsicCall(const IntrinsicInst &II) {
 189   SmallString<32> CallTo;
 190   bool Atomic = false;
 191   bool Inline = false;
 192   switch (II.getIntrinsicID()) {
 193   case Intrinsic::memcpy_inline:
 194     CallTo = "memcpy";
 195     Inline = true;
 196     break;
 197   case Intrinsic::memcpy:
 198     CallTo = "memcpy";
 199     break;
 200   case Intrinsic::memmove:
 201     CallTo = "memmove";
 202     break;
 203   case Intrinsic::memset:
 204     CallTo = "memset";
 205     break;
 206   case Intrinsic::memcpy_element_unordered_atomic:
 207     CallTo = "memcpy";
 208     Atomic = true;
 209     break;
 210   case Intrinsic::memmove_element_unordered_atomic:
 211     CallTo = "memmove";
 212     Atomic = true;
 213     break;
 214   case Intrinsic::memset_element_unordered_atomic:
 215     CallTo = "memset";
 216     Atomic = true;
 217     break;
 218   default:
 219     return visitUnknown(II);
 220   }
 221
 222   auto R = makeRemark(RemarkPass.data(), remarkName(RK_IntrinsicCall), &II);
 223   visitCallee(CallTo.str(), /*KnownLibCall=*/true, *R);
 224   visitSizeOperand(II.getOperand(2), *R);
 225
 226   auto *CIVolatile = dyn_cast<ConstantInt>(II.getOperand(3));
 227   // No such thing as a memory intrinsic that is both atomic and volatile.
 228   bool Volatile = !Atomic && CIVolatile && CIVolatile->getZExtValue();
 229   switch (II.getIntrinsicID()) {
 230   case Intrinsic::memcpy_inline:
 231   case Intrinsic::memcpy:
 232   case Intrinsic::memmove:
 233   case Intrinsic::memcpy_element_unordered_atomic:
 234     visitPtr(II.getOperand(1), /*IsRead=*/true, *R);
 235     visitPtr(II.getOperand(0), /*IsRead=*/false, *R);
 236     break;
 237   case Intrinsic::memset:
 238   case Intrinsic::memset_element_unordered_atomic:
 239     visitPtr(II.getOperand(0), /*IsRead=*/false, *R);
 240     break;
 241   }
 242   inlineVolatileOrAtomicWithExtraArgs(&Inline, Volatile, Atomic, *R);
 243   ORE.emit(*R);
 244 }
 245
 246 void MemoryOpRemark::visitCall(const CallInst &CI) {
 247   Function *F = CI.getCalledFunction();
 248   if (!F)
 249     return visitUnknown(CI);
 250
 251   LibFunc LF;
 252   bool KnownLibCall = TLI.getLibFunc(*F, LF) && TLI.has(LF);
 253   auto R = makeRemark(RemarkPass.data(), remarkName(RK_Call), &CI);
 254   visitCallee(F, KnownLibCall, *R);
 255   visitKnownLibCall(CI, LF, *R);
 256   ORE.emit(*R);
 257 }
 258
 259 template <typename FTy>
 260 void MemoryOpRemark::visitCallee(FTy F, bool KnownLibCall,
 261                                  DiagnosticInfoIROptimization &R) {
 262   R << "Call to ";
 263   if (!KnownLibCall)
 264     R << NV("UnknownLibCall", "unknown") << " function ";
 265   R << NV("Callee", F) << explainSource("");
 266 }
 267
 268 void MemoryOpRemark::visitKnownLibCall(const CallInst &CI, LibFunc LF,
 269                                        DiagnosticInfoIROptimization &R) {
 270   switch (LF) {
 271   default:
 272     return;
 273   case LibFunc_memset_chk:
 274   case LibFunc_memset:
 275     visitSizeOperand(CI.getOperand(2), R);
 276     visitPtr(CI.getOperand(0), /*IsRead=*/false, R);
 277     break;
 278   case LibFunc_bzero:
 279     visitSizeOperand(CI.getOperand(1), R);
 280     visitPtr(CI.getOperand(0), /*IsRead=*/false, R);
 281     break;
 282   case LibFunc_memcpy_chk:
 283   case LibFunc_mempcpy_chk:
 284   case LibFunc_memmove_chk:
 285   case LibFunc_memcpy:
 286   case LibFunc_mempcpy:
 287   case LibFunc_memmove:
 288   case LibFunc_bcopy:
 289     visitSizeOperand(CI.getOperand(2), R);
 290     visitPtr(CI.getOperand(1), /*IsRead=*/true, R);
 291     visitPtr(CI.getOperand(0), /*IsRead=*/false, R);
 292     break;
 293   }
 294 }
 295
 296 void MemoryOpRemark::visitSizeOperand(Value *V, DiagnosticInfoIROptimization &R) {
 297   if (auto *Len = dyn_cast<ConstantInt>(V)) {
 298     uint64_t Size = Len->getZExtValue();
 299     R << " Memory operation size: " << NV("StoreSize", Size) << " bytes.";
 300   }
 301 }
 302
 303 static std::optional<StringRef> nameOrNone(const Value *V) {
 304   if (V->hasName())
 305     return V->getName();
 306   return std::nullopt;
 307 }
 308
 309 void MemoryOpRemark::visitVariable(const Value *V,
 310                                    SmallVectorImpl<VariableInfo> &Result) {
 311   if (auto *GV = dyn_cast<GlobalVariable>(V)) {
 312     auto *Ty = GV->getValueType();
 313     uint64_t Size = DL.getTypeSizeInBits(Ty).getFixedValue();
 314     VariableInfo Var{nameOrNone(GV), Size};
 315     if (!Var.isEmpty())
 316       Result.push_back(std::move(Var));
 317     return;
 318   }
 319
 320   // If we find some information in the debug info, take that.
 321   bool FoundDI = false;
 322   // Try to get an llvm.dbg.declare, which has a DILocalVariable giving us the
 323   // real debug info name and size of the variable.
 324   for (const DbgVariableIntrinsic *DVI :
 325        FindDbgDeclareUses(const_cast<Value *>(V))) {
 326     if (DILocalVariable *DILV = DVI->getVariable()) {
 327       std::optional<uint64_t> DISize = getSizeInBytes(DILV->getSizeInBits());
 328       VariableInfo Var{DILV->getName(), DISize};
 329       if (!Var.isEmpty()) {
 330         Result.push_back(std::move(Var));
 331         FoundDI = true;
 332       }
 333     }
 334   }
 335   if (FoundDI) {
 336     assert(!Result.empty());
 337     return;
 338   }
 339
 340   const auto *AI = dyn_cast<AllocaInst>(V);
 341   if (!AI)
 342     return;
 343
 344   // If not, get it from the alloca.
 345   std::optional<TypeSize> TySize = AI->getAllocationSize(DL);
 346   std::optional<uint64_t> Size =
 347       TySize ? std::optional(TySize->getFixedValue()) : std::nullopt;
 348   VariableInfo Var{nameOrNone(AI), Size};
 349   if (!Var.isEmpty())
 350     Result.push_back(std::move(Var));
 351 }
 352
 353 void MemoryOpRemark::visitPtr(Value *Ptr, bool IsRead, DiagnosticInfoIROptimization &R) {
 354   // Find if Ptr is a known variable we can give more information on.
 355   SmallVector<Value *, 2> Objects;
 356   getUnderlyingObjectsForCodeGen(Ptr, Objects);
 357   SmallVector<VariableInfo, 2> VIs;
 358   for (const Value *V : Objects)
 359     visitVariable(V, VIs);
 360
 361   if (VIs.empty()) {
 362     bool CanBeNull;
 363     bool CanBeFreed;
 364     uint64_t Size = Ptr->getPointerDereferenceableBytes(DL, CanBeNull, CanBeFreed);
 365     if (!Size)
 366       return;
 367     VIs.push_back({std::nullopt, Size});
 368   }
 369
 370   R << (IsRead ? "\n Read Variables: " : "\n Written Variables: ");
 371   for (unsigned i = 0; i < VIs.size(); ++i) {
 372     const VariableInfo &VI = VIs[i];
 373     assert(!VI.isEmpty() && "No extra content to display.");
 374     if (i != 0)
 375       R << ", ";
 376     if (VI.Name)
 377       R << NV(IsRead ? "RVarName" : "WVarName", *VI.Name);
 378     else
 379       R << NV(IsRead ? "RVarName" : "WVarName", "<unknown>");
 380     if (VI.Size)
 381       R << " (" << NV(IsRead ? "RVarSize" : "WVarSize", *VI.Size) << " bytes)";
 382   }
 383   R << ".";
 384 }
 385
 386 bool AutoInitRemark::canHandle(const Instruction *I) {
 387   if (!I->hasMetadata(LLVMContext::MD_annotation))
 388     return false;
 389   return any_of(I->getMetadata(LLVMContext::MD_annotation)->operands(),
 390                 [](const MDOperand &Op) {
 391                   return isa<MDString>(Op.get()) &&
 392                          cast<MDString>(Op.get())->getString() == "auto-init";
 393                 });
 394 }
 395
 396 std::string AutoInitRemark::explainSource(StringRef Type) const {
 397   return (Type + " inserted by -ftrivial-auto-var-init.").str();
 398 }
 399
 400 StringRef AutoInitRemark::remarkName(RemarkKind RK) const {
 401   switch (RK) {
 402   case RK_Store:
 403     return "AutoInitStore";
 404   case RK_Unknown:
 405     return "AutoInitUnknownInstruction";
 406   case RK_IntrinsicCall:
 407     return "AutoInitIntrinsicCall";
 408   case RK_Call:
 409     return "AutoInitCall";
 410   }
 411   llvm_unreachable("missing RemarkKind case");
 412 }