src/llvm/lib/MC/MCWinEH.cpp

   1 //===- lib/MC/MCWinEH.cpp - Windows EH implementation ---------------------===//
   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 #include "llvm/ADT/StringRef.h"
  11 #include "llvm/MC/MCContext.h"
  12 #include "llvm/MC/MCObjectFileInfo.h"
  13 #include "llvm/MC/MCSectionCOFF.h"
  14 #include "llvm/MC/MCSymbol.h"
  15 #include "llvm/MC/MCWinEH.h"
  16 #include "llvm/Support/COFF.h"
  17
  18 namespace llvm {
  19 namespace WinEH {
  20
  21 /// We can't have one section for all .pdata or .xdata because the Microsoft
  22 /// linker seems to want all code relocations to refer to the same object file
  23 /// section. If the code described is comdat, create a new comdat section
  24 /// associated with that comdat. If the code described is not in the main .text
  25 /// section, make a new section for it. Otherwise use the main unwind info
  26 /// section.
  27 static const MCSection *getUnwindInfoSection(
  28     StringRef SecName, const MCSectionCOFF *UnwindSec, const MCSymbol *Function,
  29     MCContext &Context) {
  30   if (Function && Function->isInSection()) {
  31     // If Function is in a COMDAT, get or create an unwind info section in that
  32     // COMDAT group.
  33     const MCSectionCOFF *FunctionSection =
  34         cast<MCSectionCOFF>(&Function->getSection());
  35     if (FunctionSection->getCharacteristics() & COFF::IMAGE_SCN_LNK_COMDAT) {
  36       return Context.getAssociativeCOFFSection(
  37           UnwindSec, FunctionSection->getCOMDATSymbol());
  38     }
  39
  40     // If Function is in a section other than .text, create a new .pdata section.
  41     // Otherwise use the plain .pdata section.
  42     if (const auto *Section = dyn_cast<MCSectionCOFF>(FunctionSection)) {
  43       StringRef CodeSecName = Section->getSectionName();
  44       if (CodeSecName == ".text")
  45         return UnwindSec;
  46
  47       if (CodeSecName.startswith(".text$"))
  48         CodeSecName = CodeSecName.substr(6);
  49
  50       return Context.getCOFFSection(
  51           (SecName + Twine('$') + CodeSecName).str(),
  52           COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
  53           SectionKind::getDataRel());
  54     }
  55   }
  56
  57   return UnwindSec;
  58
  59 }
  60
  61 const MCSection *UnwindEmitter::getPDataSection(const MCSymbol *Function,
  62                                                 MCContext &Context) {
  63   const MCSectionCOFF *PData =
  64       cast<MCSectionCOFF>(Context.getObjectFileInfo()->getPDataSection());
  65   return getUnwindInfoSection(".pdata", PData, Function, Context);
  66 }
  67
  68 const MCSection *UnwindEmitter::getXDataSection(const MCSymbol *Function,
  69                                                 MCContext &Context) {
  70   const MCSectionCOFF *XData =
  71       cast<MCSectionCOFF>(Context.getObjectFileInfo()->getXDataSection());
  72   return getUnwindInfoSection(".xdata", XData, Function, Context);
  73 }
  74
  75 }
  76 }
  77