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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/Target/Mangler.h"
     15 #include "llvm/DerivedTypes.h"
     16 #include "llvm/Function.h"
     17 #include "llvm/Target/TargetData.h"
     18 #include "llvm/MC/MCAsmInfo.h"
     19 #include "llvm/MC/MCContext.h"
     20 #include "llvm/Support/raw_ostream.h"
     21 #include "llvm/ADT/SmallString.h"
     22 #include "llvm/ADT/Twine.h"
     23 using namespace llvm;
     24 
     25 static bool isAcceptableChar(char C, bool AllowPeriod, bool AllowUTF8) {
     26   if ((C < 'a' || C > 'z') &&
     27       (C < 'A' || C > 'Z') &&
     28       (C < '0' || C > '9') &&
     29       C != '_' && C != '$' && C != '@' &&
     30       !(AllowPeriod && C == '.') &&
     31       !(AllowUTF8 && (C & 0x80)))
     32     return false;
     33   return true;
     34 }
     35 
     36 static char HexDigit(int V) {
     37   return V < 10 ? V+'0' : V+'A'-10;
     38 }
     39 
     40 static void MangleLetter(SmallVectorImpl<char> &OutName, unsigned char C) {
     41   OutName.push_back('_');
     42   OutName.push_back(HexDigit(C >> 4));
     43   OutName.push_back(HexDigit(C & 15));
     44   OutName.push_back('_');
     45 }
     46 
     47 /// NameNeedsEscaping - Return true if the identifier \arg Str needs quotes
     48 /// for this assembler.
     49 static bool NameNeedsEscaping(StringRef Str, const MCAsmInfo &MAI) {
     50   assert(!Str.empty() && "Cannot create an empty MCSymbol");
     51 
     52   // If the first character is a number and the target does not allow this, we
     53   // need quotes.
     54   if (!MAI.doesAllowNameToStartWithDigit() && Str[0] >= '0' && Str[0] <= '9')
     55     return true;
     56 
     57   // If any of the characters in the string is an unacceptable character, force
     58   // quotes.
     59   bool AllowPeriod = MAI.doesAllowPeriodsInName();
     60   bool AllowUTF8 = MAI.doesAllowUTF8();
     61   for (unsigned i = 0, e = Str.size(); i != e; ++i)
     62     if (!isAcceptableChar(Str[i], AllowPeriod, AllowUTF8))
     63       return true;
     64   return false;
     65 }
     66 
     67 /// appendMangledName - Add the specified string in mangled form if it uses
     68 /// any unusual characters.
     69 static void appendMangledName(SmallVectorImpl<char> &OutName, StringRef Str,
     70                               const MCAsmInfo &MAI) {
     71   // The first character is not allowed to be a number unless the target
     72   // explicitly allows it.
     73   if (!MAI.doesAllowNameToStartWithDigit() && Str[0] >= '0' && Str[0] <= '9') {
     74     MangleLetter(OutName, Str[0]);
     75     Str = Str.substr(1);
     76   }
     77 
     78   bool AllowPeriod = MAI.doesAllowPeriodsInName();
     79   bool AllowUTF8 = MAI.doesAllowUTF8();
     80   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
     81     if (!isAcceptableChar(Str[i], AllowPeriod, AllowUTF8))
     82       MangleLetter(OutName, Str[i]);
     83     else
     84       OutName.push_back(Str[i]);
     85   }
     86 }
     87 
     88 
     89 /// appendMangledQuotedName - On systems that support quoted symbols, we still
     90 /// have to escape some (obscure) characters like " and \n which would break the
     91 /// assembler's lexing.
     92 static void appendMangledQuotedName(SmallVectorImpl<char> &OutName,
     93                                    StringRef Str) {
     94   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
     95     if (Str[i] == '"' || Str[i] == '\n')
     96       MangleLetter(OutName, Str[i]);
     97     else
     98       OutName.push_back(Str[i]);
     99   }
    100 }
    101 
    102 
    103 /// getNameWithPrefix - Fill OutName with the name of the appropriate prefix
    104 /// and the specified name as the global variable name.  GVName must not be
    105 /// empty.
    106 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
    107                                 const Twine &GVName, ManglerPrefixTy PrefixTy) {
    108   SmallString<256> TmpData;
    109   StringRef Name = GVName.toStringRef(TmpData);
    110   assert(!Name.empty() && "getNameWithPrefix requires non-empty name");
    111 
    112   const MCAsmInfo &MAI = Context.getAsmInfo();
    113 
    114   // If the global name is not led with \1, add the appropriate prefixes.
    115   if (Name[0] == '\1') {
    116     Name = Name.substr(1);
    117   } else {
    118     if (PrefixTy == Mangler::Private) {
    119       const char *Prefix = MAI.getPrivateGlobalPrefix();
    120       OutName.append(Prefix, Prefix+strlen(Prefix));
    121     } else if (PrefixTy == Mangler::LinkerPrivate) {
    122       const char *Prefix = MAI.getLinkerPrivateGlobalPrefix();
    123       OutName.append(Prefix, Prefix+strlen(Prefix));
    124     }
    125 
    126     const char *Prefix = MAI.getGlobalPrefix();
    127     if (Prefix[0] == 0)
    128       ; // Common noop, no prefix.
    129     else if (Prefix[1] == 0)
    130       OutName.push_back(Prefix[0]);  // Common, one character prefix.
    131     else
    132       OutName.append(Prefix, Prefix+strlen(Prefix)); // Arbitrary length prefix.
    133   }
    134 
    135   // If this is a simple string that doesn't need escaping, just append it.
    136   if (!NameNeedsEscaping(Name, MAI) ||
    137       // If quotes are supported, they can be used unless the string contains
    138       // a quote or newline.
    139       (MAI.doesAllowQuotesInName() &&
    140        Name.find_first_of("\n\"") == StringRef::npos)) {
    141     OutName.append(Name.begin(), Name.end());
    142     return;
    143   }
    144 
    145   // On systems that do not allow quoted names, we need to mangle most
    146   // strange characters.
    147   if (!MAI.doesAllowQuotesInName())
    148     return appendMangledName(OutName, Name, MAI);
    149 
    150   // Okay, the system allows quoted strings.  We can quote most anything, the
    151   // only characters that need escaping are " and \n.
    152   assert(Name.find_first_of("\n\"") != StringRef::npos);
    153   return appendMangledQuotedName(OutName, Name);
    154 }
    155 
    156 /// AddFastCallStdCallSuffix - Microsoft fastcall and stdcall functions require
    157 /// a suffix on their name indicating the number of words of arguments they
    158 /// take.
    159 static void AddFastCallStdCallSuffix(SmallVectorImpl<char> &OutName,
    160                                      const Function *F, const TargetData &TD) {
    161   // Calculate arguments size total.
    162   unsigned ArgWords = 0;
    163   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
    164        AI != AE; ++AI) {
    165     Type *Ty = AI->getType();
    166     // 'Dereference' type in case of byval parameter attribute
    167     if (AI->hasByValAttr())
    168       Ty = cast<PointerType>(Ty)->getElementType();
    169     // Size should be aligned to DWORD boundary
    170     ArgWords += ((TD.getTypeAllocSize(Ty) + 3)/4)*4;
    171   }
    172 
    173   raw_svector_ostream(OutName) << '@' << ArgWords;
    174 }
    175 
    176 
    177 /// getNameWithPrefix - Fill OutName with the name of the appropriate prefix
    178 /// and the specified global variable's name.  If the global variable doesn't
    179 /// have a name, this fills in a unique name for the global.
    180 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
    181                                 const GlobalValue *GV,
    182                                 bool isImplicitlyPrivate) {
    183   ManglerPrefixTy PrefixTy = Mangler::Default;
    184   if (GV->hasPrivateLinkage() || isImplicitlyPrivate)
    185     PrefixTy = Mangler::Private;
    186   else if (GV->hasLinkerPrivateLinkage() || GV->hasLinkerPrivateWeakLinkage() ||
    187            GV->hasLinkerPrivateWeakDefAutoLinkage())
    188     PrefixTy = Mangler::LinkerPrivate;
    189 
    190   // If this global has a name, handle it simply.
    191   if (GV->hasName()) {
    192     getNameWithPrefix(OutName, GV->getName(), PrefixTy);
    193   } else {
    194     // Get the ID for the global, assigning a new one if we haven't got one
    195     // already.
    196     unsigned &ID = AnonGlobalIDs[GV];
    197     if (ID == 0) ID = NextAnonGlobalID++;
    198 
    199     // Must mangle the global into a unique ID.
    200     getNameWithPrefix(OutName, "__unnamed_" + Twine(ID), PrefixTy);
    201   }
    202 
    203   // If we are supposed to add a microsoft-style suffix for stdcall/fastcall,
    204   // add it.
    205   if (Context.getAsmInfo().hasMicrosoftFastStdCallMangling()) {
    206     if (const Function *F = dyn_cast<Function>(GV)) {
    207       CallingConv::ID CC = F->getCallingConv();
    208 
    209       // fastcall functions need to start with @.
    210       // FIXME: This logic seems unlikely to be right.
    211       if (CC == CallingConv::X86_FastCall) {
    212         if (OutName[0] == '_')
    213           OutName[0] = '@';
    214         else
    215           OutName.insert(OutName.begin(), '@');
    216       }
    217 
    218       // fastcall and stdcall functions usually need @42 at the end to specify
    219       // the argument info.
    220       FunctionType *FT = F->getFunctionType();
    221       if ((CC == CallingConv::X86_FastCall || CC == CallingConv::X86_StdCall) &&
    222           // "Pure" variadic functions do not receive @0 suffix.
    223           (!FT->isVarArg() || FT->getNumParams() == 0 ||
    224            (FT->getNumParams() == 1 && F->hasStructRetAttr())))
    225         AddFastCallStdCallSuffix(OutName, F, TD);
    226     }
    227   }
    228 }
    229 
    230 /// getSymbol - Return the MCSymbol for the specified global value.  This
    231 /// symbol is the main label that is the address of the global.
    232 MCSymbol *Mangler::getSymbol(const GlobalValue *GV) {
    233   SmallString<60> NameStr;
    234   getNameWithPrefix(NameStr, GV, false);
    235   return Context.GetOrCreateSymbol(NameStr.str());
    236 }
    237 
    238 
    239