lib/IR/Mangler.cpp

   1 //===-- Mangler.cpp - Self-contained c/asm llvm name mangler --------------===//
   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 // Unified name mangler for assembly backends.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/IR/Mangler.h"
  14 #include "llvm/ADT/SmallString.h"
  15 #include "llvm/ADT/Triple.h"
  16 #include "llvm/ADT/Twine.h"
  17 #include "llvm/IR/DataLayout.h"
  18 #include "llvm/IR/DerivedTypes.h"
  19 #include "llvm/IR/Function.h"
  20 #include "llvm/IR/Module.h"
  21 #include "llvm/Support/raw_ostream.h"
  22 using namespace llvm;
  23
  24 namespace {
  25 enum ManglerPrefixTy {
  26   Default,      ///< Emit default string before each symbol.
  27   Private,      ///< Emit "private" prefix before each symbol.
  28   LinkerPrivate ///< Emit "linker private" prefix before each symbol.
  29 };
  30 }
  31
  32 static void getNameWithPrefixImpl(raw_ostream &OS, const Twine &GVName,
  33                                   ManglerPrefixTy PrefixTy,
  34                                   const DataLayout &DL, char Prefix) {
  35   SmallString<256> TmpData;
  36   StringRef Name = GVName.toStringRef(TmpData);
  37   assert(!Name.empty() && "getNameWithPrefix requires non-empty name");
  38
  39   // No need to do anything special if the global has the special "do not
  40   // mangle" flag in the name.
  41   if (Name[0] == '\1') {
  42     OS << Name.substr(1);
  43     return;
  44   }
  45
  46   if (DL.doNotMangleLeadingQuestionMark() && Name[0] == '?')
  47     Prefix = '\0';
  48
  49   if (PrefixTy == Private)
  50     OS << DL.getPrivateGlobalPrefix();
  51   else if (PrefixTy == LinkerPrivate)
  52     OS << DL.getLinkerPrivateGlobalPrefix();
  53
  54   if (Prefix != '\0')
  55     OS << Prefix;
  56
  57   // If this is a simple string that doesn't need escaping, just append it.
  58   OS << Name;
  59 }
  60
  61 static void getNameWithPrefixImpl(raw_ostream &OS, const Twine &GVName,
  62                                   const DataLayout &DL,
  63                                   ManglerPrefixTy PrefixTy) {
  64   char Prefix = DL.getGlobalPrefix();
  65   return getNameWithPrefixImpl(OS, GVName, PrefixTy, DL, Prefix);
  66 }
  67
  68 void Mangler::getNameWithPrefix(raw_ostream &OS, const Twine &GVName,
  69                                 const DataLayout &DL) {
  70   return getNameWithPrefixImpl(OS, GVName, DL, Default);
  71 }
  72
  73 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
  74                                 const Twine &GVName, const DataLayout &DL) {
  75   raw_svector_ostream OS(OutName);
  76   char Prefix = DL.getGlobalPrefix();
  77   return getNameWithPrefixImpl(OS, GVName, Default, DL, Prefix);
  78 }
  79
  80 static bool hasByteCountSuffix(CallingConv::ID CC) {
  81   switch (CC) {
  82   case CallingConv::X86_FastCall:
  83   case CallingConv::X86_StdCall:
  84   case CallingConv::X86_VectorCall:
  85     return true;
  86   default:
  87     return false;
  88   }
  89 }
  90
  91 /// Microsoft fastcall and stdcall functions require a suffix on their name
  92 /// indicating the number of words of arguments they take.
  93 static void addByteCountSuffix(raw_ostream &OS, const Function *F,
  94                                const DataLayout &DL) {
  95   // Calculate arguments size total.
  96   unsigned ArgWords = 0;
  97   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
  98        AI != AE; ++AI) {
  99     Type *Ty = AI->getType();
 100     // 'Dereference' type in case of byval or inalloca parameter attribute.
 101     if (AI->hasByValOrInAllocaAttr())
 102       Ty = cast<PointerType>(Ty)->getElementType();
 103     // Size should be aligned to pointer size.
 104     unsigned PtrSize = DL.getPointerSize();
 105     ArgWords += alignTo(DL.getTypeAllocSize(Ty), PtrSize);
 106   }
 107
 108   OS << '@' << ArgWords;
 109 }
 110
 111 void Mangler::getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV,
 112                                 bool CannotUsePrivateLabel) const {
 113   ManglerPrefixTy PrefixTy = Default;
 114   if (GV->hasPrivateLinkage()) {
 115     if (CannotUsePrivateLabel)
 116       PrefixTy = LinkerPrivate;
 117     else
 118       PrefixTy = Private;
 119   }
 120
 121   const DataLayout &DL = GV->getParent()->getDataLayout();
 122   if (!GV->hasName()) {
 123     // Get the ID for the global, assigning a new one if we haven't got one
 124     // already.
 125     unsigned &ID = AnonGlobalIDs[GV];
 126     if (ID == 0)
 127       ID = AnonGlobalIDs.size();
 128
 129     // Must mangle the global into a unique ID.
 130     getNameWithPrefixImpl(OS, "__unnamed_" + Twine(ID), DL, PrefixTy);
 131     return;
 132   }
 133
 134   StringRef Name = GV->getName();
 135   char Prefix = DL.getGlobalPrefix();
 136
 137   // Mangle functions with Microsoft calling conventions specially.  Only do
 138   // this mangling for x86_64 vectorcall and 32-bit x86.
 139   const Function *MSFunc = dyn_cast<Function>(GV);
 140
 141   // Don't add byte count suffixes when '\01' or '?' are in the first
 142   // character.
 143   if (Name.startswith("\01") ||
 144       (DL.doNotMangleLeadingQuestionMark() && Name.startswith("?")))
 145     MSFunc = nullptr;
 146
 147   CallingConv::ID CC =
 148       MSFunc ? MSFunc->getCallingConv() : (unsigned)CallingConv::C;
 149   if (!DL.hasMicrosoftFastStdCallMangling() &&
 150       CC != CallingConv::X86_VectorCall)
 151     MSFunc = nullptr;
 152   if (MSFunc) {
 153     if (CC == CallingConv::X86_FastCall)
 154       Prefix = '@'; // fastcall functions have an @ prefix instead of _.
 155     else if (CC == CallingConv::X86_VectorCall)
 156       Prefix = '\0'; // vectorcall functions have no prefix.
 157   }
 158
 159   getNameWithPrefixImpl(OS, Name, PrefixTy, DL, Prefix);
 160
 161   if (!MSFunc)
 162     return;
 163
 164   // If we are supposed to add a microsoft-style suffix for stdcall, fastcall,
 165   // or vectorcall, add it.  These functions have a suffix of @N where N is the
 166   // cumulative byte size of all of the parameters to the function in decimal.
 167   if (CC == CallingConv::X86_VectorCall)
 168     OS << '@'; // vectorcall functions use a double @ suffix.
 169   FunctionType *FT = MSFunc->getFunctionType();
 170   if (hasByteCountSuffix(CC) &&
 171       // "Pure" variadic functions do not receive @0 suffix.
 172       (!FT->isVarArg() || FT->getNumParams() == 0 ||
 173        (FT->getNumParams() == 1 && MSFunc->hasStructRetAttr())))
 174     addByteCountSuffix(OS, MSFunc, DL);
 175 }
 176
 177 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
 178                                 const GlobalValue *GV,
 179                                 bool CannotUsePrivateLabel) const {
 180   raw_svector_ostream OS(OutName);
 181   getNameWithPrefix(OS, GV, CannotUsePrivateLabel);
 182 }
 183
 184 void llvm::emitLinkerFlagsForGlobalCOFF(raw_ostream &OS, const GlobalValue *GV,
 185                                         const Triple &TT, Mangler &Mangler) {
 186   if (!GV->hasDLLExportStorageClass() || GV->isDeclaration())
 187     return;
 188
 189   if (TT.isWindowsMSVCEnvironment())
 190     OS << " /EXPORT:";
 191   else
 192     OS << " -export:";
 193
 194   if (TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment()) {
 195     std::string Flag;
 196     raw_string_ostream FlagOS(Flag);
 197     Mangler.getNameWithPrefix(FlagOS, GV, false);
 198     FlagOS.flush();
 199     if (Flag[0] == GV->getParent()->getDataLayout().getGlobalPrefix())
 200       OS << Flag.substr(1);
 201     else
 202       OS << Flag;
 203   } else {
 204     Mangler.getNameWithPrefix(OS, GV, false);
 205   }
 206
 207   if (!GV->getValueType()->isFunctionTy()) {
 208     if (TT.isWindowsMSVCEnvironment())
 209       OS << ",DATA";
 210     else
 211       OS << ",data";
 212   }
 213 }
 214
 215 void llvm::emitLinkerFlagsForUsedCOFF(raw_ostream &OS, const GlobalValue *GV,
 216                                       const Triple &T, Mangler &M) {
 217   if (!T.isWindowsMSVCEnvironment())
 218     return;
 219
 220   OS << " /INCLUDE:";
 221   M.getNameWithPrefix(OS, GV, false);
 222 }
 223