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      1 //===-- Mangler.cpp - Self-contained c/asm llvm name mangler --------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // Unified name mangler for assembly backends.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "llvm/IR/Mangler.h"
     15 #include "llvm/ADT/SmallString.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 (PrefixTy == Private)
     47     OS << DL.getPrivateGlobalPrefix();
     48   else if (PrefixTy == LinkerPrivate)
     49     OS << DL.getLinkerPrivateGlobalPrefix();
     50 
     51   if (Prefix != '\0')
     52     OS << Prefix;
     53 
     54   // If this is a simple string that doesn't need escaping, just append it.
     55   OS << Name;
     56 }
     57 
     58 static void getNameWithPrefixImpl(raw_ostream &OS, const Twine &GVName,
     59                                   const DataLayout &DL,
     60                                   ManglerPrefixTy PrefixTy) {
     61   char Prefix = DL.getGlobalPrefix();
     62   return getNameWithPrefixImpl(OS, GVName, PrefixTy, DL, Prefix);
     63 }
     64 
     65 void Mangler::getNameWithPrefix(raw_ostream &OS, const Twine &GVName,
     66                                 const DataLayout &DL) {
     67   return getNameWithPrefixImpl(OS, GVName, DL, Default);
     68 }
     69 
     70 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
     71                                 const Twine &GVName, const DataLayout &DL) {
     72   raw_svector_ostream OS(OutName);
     73   char Prefix = DL.getGlobalPrefix();
     74   return getNameWithPrefixImpl(OS, GVName, Default, DL, Prefix);
     75 }
     76 
     77 static bool hasByteCountSuffix(CallingConv::ID CC) {
     78   switch (CC) {
     79   case CallingConv::X86_FastCall:
     80   case CallingConv::X86_StdCall:
     81   case CallingConv::X86_VectorCall:
     82     return true;
     83   default:
     84     return false;
     85   }
     86 }
     87 
     88 /// Microsoft fastcall and stdcall functions require a suffix on their name
     89 /// indicating the number of words of arguments they take.
     90 static void addByteCountSuffix(raw_ostream &OS, const Function *F,
     91                                const DataLayout &DL) {
     92   // Calculate arguments size total.
     93   unsigned ArgWords = 0;
     94   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
     95        AI != AE; ++AI) {
     96     Type *Ty = AI->getType();
     97     // 'Dereference' type in case of byval or inalloca parameter attribute.
     98     if (AI->hasByValOrInAllocaAttr())
     99       Ty = cast<PointerType>(Ty)->getElementType();
    100     // Size should be aligned to pointer size.
    101     unsigned PtrSize = DL.getPointerSize();
    102     ArgWords += alignTo(DL.getTypeAllocSize(Ty), PtrSize);
    103   }
    104 
    105   OS << '@' << ArgWords;
    106 }
    107 
    108 void Mangler::getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV,
    109                                 bool CannotUsePrivateLabel) const {
    110   ManglerPrefixTy PrefixTy = Default;
    111   if (GV->hasPrivateLinkage()) {
    112     if (CannotUsePrivateLabel)
    113       PrefixTy = LinkerPrivate;
    114     else
    115       PrefixTy = Private;
    116   }
    117 
    118   const DataLayout &DL = GV->getParent()->getDataLayout();
    119   if (!GV->hasName()) {
    120     // Get the ID for the global, assigning a new one if we haven't got one
    121     // already.
    122     unsigned &ID = AnonGlobalIDs[GV];
    123     if (ID == 0)
    124       ID = NextAnonGlobalID++;
    125 
    126     // Must mangle the global into a unique ID.
    127     getNameWithPrefixImpl(OS, "__unnamed_" + Twine(ID), DL, PrefixTy);
    128     return;
    129   }
    130 
    131   StringRef Name = GV->getName();
    132   char Prefix = DL.getGlobalPrefix();
    133 
    134   // Mangle functions with Microsoft calling conventions specially.  Only do
    135   // this mangling for x86_64 vectorcall and 32-bit x86.
    136   const Function *MSFunc = dyn_cast<Function>(GV);
    137   if (Name.startswith("\01"))
    138     MSFunc = nullptr; // Don't mangle when \01 is present.
    139   CallingConv::ID CC =
    140       MSFunc ? MSFunc->getCallingConv() : (unsigned)CallingConv::C;
    141   if (!DL.hasMicrosoftFastStdCallMangling() &&
    142       CC != CallingConv::X86_VectorCall)
    143     MSFunc = nullptr;
    144   if (MSFunc) {
    145     if (CC == CallingConv::X86_FastCall)
    146       Prefix = '@'; // fastcall functions have an @ prefix instead of _.
    147     else if (CC == CallingConv::X86_VectorCall)
    148       Prefix = '\0'; // vectorcall functions have no prefix.
    149   }
    150 
    151   getNameWithPrefixImpl(OS, Name, PrefixTy, DL, Prefix);
    152 
    153   if (!MSFunc)
    154     return;
    155 
    156   // If we are supposed to add a microsoft-style suffix for stdcall, fastcall,
    157   // or vectorcall, add it.  These functions have a suffix of @N where N is the
    158   // cumulative byte size of all of the parameters to the function in decimal.
    159   if (CC == CallingConv::X86_VectorCall)
    160     OS << '@'; // vectorcall functions use a double @ suffix.
    161   FunctionType *FT = MSFunc->getFunctionType();
    162   if (hasByteCountSuffix(CC) &&
    163       // "Pure" variadic functions do not receive @0 suffix.
    164       (!FT->isVarArg() || FT->getNumParams() == 0 ||
    165        (FT->getNumParams() == 1 && MSFunc->hasStructRetAttr())))
    166     addByteCountSuffix(OS, MSFunc, DL);
    167 }
    168 
    169 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
    170                                 const GlobalValue *GV,
    171                                 bool CannotUsePrivateLabel) const {
    172   raw_svector_ostream OS(OutName);
    173   getNameWithPrefix(OS, GV, CannotUsePrivateLabel);
    174 }
    175