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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/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/MC/MCAsmInfo.h"
     21 #include "llvm/MC/MCContext.h"
     22 #include "llvm/Target/TargetMachine.h"
     23 #include "llvm/Support/raw_ostream.h"
     24 using namespace llvm;
     25 
     26 static bool isAcceptableChar(char C, bool AllowPeriod, bool AllowUTF8) {
     27   if ((C < 'a' || C > 'z') &&
     28       (C < 'A' || C > 'Z') &&
     29       (C < '0' || C > '9') &&
     30       C != '_' && C != '$' && C != '@' &&
     31       !(AllowPeriod && C == '.') &&
     32       !(AllowUTF8 && (C & 0x80)))
     33     return false;
     34   return true;
     35 }
     36 
     37 static char HexDigit(int V) {
     38   return V < 10 ? V+'0' : V+'A'-10;
     39 }
     40 
     41 static void MangleLetter(SmallVectorImpl<char> &OutName, unsigned char C) {
     42   OutName.push_back('_');
     43   OutName.push_back(HexDigit(C >> 4));
     44   OutName.push_back(HexDigit(C & 15));
     45   OutName.push_back('_');
     46 }
     47 
     48 /// NameNeedsEscaping - Return true if the identifier \p Str needs quotes
     49 /// for this assembler.
     50 static bool NameNeedsEscaping(StringRef Str, const MCAsmInfo *MAI) {
     51   assert(!Str.empty() && "Cannot create an empty MCSymbol");
     52 
     53   // If the first character is a number and the target does not allow this, we
     54   // need quotes.
     55   if (!MAI->doesAllowNameToStartWithDigit() && Str[0] >= '0' && Str[0] <= '9')
     56     return true;
     57 
     58   // If any of the characters in the string is an unacceptable character, force
     59   // quotes.
     60   bool AllowPeriod = MAI->doesAllowPeriodsInName();
     61   bool AllowUTF8 = MAI->doesAllowUTF8();
     62   for (unsigned i = 0, e = Str.size(); i != e; ++i)
     63     if (!isAcceptableChar(Str[i], AllowPeriod, AllowUTF8))
     64       return true;
     65   return false;
     66 }
     67 
     68 /// appendMangledName - Add the specified string in mangled form if it uses
     69 /// any unusual characters.
     70 static void appendMangledName(SmallVectorImpl<char> &OutName, StringRef Str,
     71                               const MCAsmInfo *MAI) {
     72   // The first character is not allowed to be a number unless the target
     73   // explicitly allows it.
     74   if (!MAI->doesAllowNameToStartWithDigit() && Str[0] >= '0' && Str[0] <= '9') {
     75     MangleLetter(OutName, Str[0]);
     76     Str = Str.substr(1);
     77   }
     78 
     79   bool AllowPeriod = MAI->doesAllowPeriodsInName();
     80   bool AllowUTF8 = MAI->doesAllowUTF8();
     81   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
     82     if (!isAcceptableChar(Str[i], AllowPeriod, AllowUTF8))
     83       MangleLetter(OutName, Str[i]);
     84     else
     85       OutName.push_back(Str[i]);
     86   }
     87 }
     88 
     89 
     90 /// appendMangledQuotedName - On systems that support quoted symbols, we still
     91 /// have to escape some (obscure) characters like " and \n which would break the
     92 /// assembler's lexing.
     93 static void appendMangledQuotedName(SmallVectorImpl<char> &OutName,
     94                                    StringRef Str) {
     95   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
     96     if (Str[i] == '"' || Str[i] == '\n')
     97       MangleLetter(OutName, Str[i]);
     98     else
     99       OutName.push_back(Str[i]);
    100   }
    101 }
    102 
    103 
    104 /// getNameWithPrefix - Fill OutName with the name of the appropriate prefix
    105 /// and the specified name as the global variable name.  GVName must not be
    106 /// empty.
    107 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
    108                                 const Twine &GVName, ManglerPrefixTy PrefixTy,
    109                                 bool UseGlobalPrefix) {
    110   SmallString<256> TmpData;
    111   StringRef Name = GVName.toStringRef(TmpData);
    112   assert(!Name.empty() && "getNameWithPrefix requires non-empty name");
    113 
    114   const MCAsmInfo *MAI = Context.getAsmInfo();
    115 
    116   // If the global name is not led with \1, add the appropriate prefixes.
    117   if (Name[0] == '\1') {
    118     Name = Name.substr(1);
    119   } else {
    120     if (PrefixTy == Mangler::Private) {
    121       const char *Prefix = MAI->getPrivateGlobalPrefix();
    122       OutName.append(Prefix, Prefix+strlen(Prefix));
    123     } else if (PrefixTy == Mangler::LinkerPrivate) {
    124       const char *Prefix = MAI->getLinkerPrivateGlobalPrefix();
    125       OutName.append(Prefix, Prefix+strlen(Prefix));
    126     }
    127 
    128     if (UseGlobalPrefix) {
    129       const char *Prefix = MAI->getGlobalPrefix();
    130       if (Prefix[0] == 0)
    131         ; // Common noop, no prefix.
    132       else if (Prefix[1] == 0)
    133         OutName.push_back(Prefix[0]);  // Common, one character prefix.
    134       else
    135         // Arbitrary length prefix.
    136         OutName.append(Prefix, Prefix+strlen(Prefix));
    137     }
    138   }
    139 
    140   // If this is a simple string that doesn't need escaping, just append it.
    141   if (!NameNeedsEscaping(Name, MAI) ||
    142       // If quotes are supported, they can be used unless the string contains
    143       // a quote or newline.
    144       (MAI->doesAllowQuotesInName() &&
    145        Name.find_first_of("\n\"") == StringRef::npos)) {
    146     OutName.append(Name.begin(), Name.end());
    147     return;
    148   }
    149 
    150   // On systems that do not allow quoted names, we need to mangle most
    151   // strange characters.
    152   if (!MAI->doesAllowQuotesInName())
    153     return appendMangledName(OutName, Name, MAI);
    154 
    155   // Okay, the system allows quoted strings.  We can quote most anything, the
    156   // only characters that need escaping are " and \n.
    157   assert(Name.find_first_of("\n\"") != StringRef::npos);
    158   return appendMangledQuotedName(OutName, Name);
    159 }
    160 
    161 /// AddFastCallStdCallSuffix - Microsoft fastcall and stdcall functions require
    162 /// a suffix on their name indicating the number of words of arguments they
    163 /// take.
    164 static void AddFastCallStdCallSuffix(SmallVectorImpl<char> &OutName,
    165                                      const Function *F, const DataLayout &TD) {
    166   // Calculate arguments size total.
    167   unsigned ArgWords = 0;
    168   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
    169        AI != AE; ++AI) {
    170     Type *Ty = AI->getType();
    171     // 'Dereference' type in case of byval parameter attribute
    172     if (AI->hasByValAttr())
    173       Ty = cast<PointerType>(Ty)->getElementType();
    174     // Size should be aligned to DWORD boundary
    175     ArgWords += ((TD.getTypeAllocSize(Ty) + 3)/4)*4;
    176   }
    177 
    178   raw_svector_ostream(OutName) << '@' << ArgWords;
    179 }
    180 
    181 
    182 /// getNameWithPrefix - Fill OutName with the name of the appropriate prefix
    183 /// and the specified global variable's name.  If the global variable doesn't
    184 /// have a name, this fills in a unique name for the global.
    185 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
    186                                 const GlobalValue *GV, bool isImplicitlyPrivate,
    187                                 bool UseGlobalPrefix) {
    188   ManglerPrefixTy PrefixTy = Mangler::Default;
    189   if (GV->hasPrivateLinkage() || isImplicitlyPrivate)
    190     PrefixTy = Mangler::Private;
    191   else if (GV->hasLinkerPrivateLinkage() || GV->hasLinkerPrivateWeakLinkage())
    192     PrefixTy = Mangler::LinkerPrivate;
    193 
    194   // If this global has a name, handle it simply.
    195   if (GV->hasName()) {
    196     StringRef Name = GV->getName();
    197     getNameWithPrefix(OutName, Name, PrefixTy, UseGlobalPrefix);
    198     // No need to do anything else if the global has the special "do not mangle"
    199     // flag in the name.
    200     if (Name[0] == 1)
    201       return;
    202   } else {
    203     // Get the ID for the global, assigning a new one if we haven't got one
    204     // already.
    205     unsigned &ID = AnonGlobalIDs[GV];
    206     if (ID == 0) ID = NextAnonGlobalID++;
    207 
    208     // Must mangle the global into a unique ID.
    209     getNameWithPrefix(OutName, "__unnamed_" + Twine(ID), PrefixTy,
    210                       UseGlobalPrefix);
    211   }
    212 
    213   // If we are supposed to add a microsoft-style suffix for stdcall/fastcall,
    214   // add it.
    215   if (Context.getAsmInfo()->hasMicrosoftFastStdCallMangling()) {
    216     if (const Function *F = dyn_cast<Function>(GV)) {
    217       CallingConv::ID CC = F->getCallingConv();
    218 
    219       // fastcall functions need to start with @.
    220       // FIXME: This logic seems unlikely to be right.
    221       if (CC == CallingConv::X86_FastCall) {
    222         if (OutName[0] == '_')
    223           OutName[0] = '@';
    224         else
    225           OutName.insert(OutName.begin(), '@');
    226       }
    227 
    228       // fastcall and stdcall functions usually need @42 at the end to specify
    229       // the argument info.
    230       FunctionType *FT = F->getFunctionType();
    231       if ((CC == CallingConv::X86_FastCall || CC == CallingConv::X86_StdCall) &&
    232           // "Pure" variadic functions do not receive @0 suffix.
    233           (!FT->isVarArg() || FT->getNumParams() == 0 ||
    234            (FT->getNumParams() == 1 && F->hasStructRetAttr())))
    235         AddFastCallStdCallSuffix(OutName, F, *TM->getDataLayout());
    236     }
    237   }
    238 }
    239 
    240 /// getSymbol - Return the MCSymbol for the specified global value.  This
    241 /// symbol is the main label that is the address of the global.
    242 MCSymbol *Mangler::getSymbol(const GlobalValue *GV) {
    243   SmallString<60> NameStr;
    244   getNameWithPrefix(NameStr, GV, false);
    245   return Context.GetOrCreateSymbol(NameStr.str());
    246 }
    247 
    248 
    249