lib/Target/MBlaze/MBlazeTargetObjectFile.cpp

   1 //===-- MBlazeTargetObjectFile.cpp - MBlaze object files ------------------===//
   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 "MBlazeTargetObjectFile.h"
  11 #include "MBlazeSubtarget.h"
  12 #include "llvm/DerivedTypes.h"
  13 #include "llvm/GlobalVariable.h"
  14 #include "llvm/MC/MCContext.h"
  15 #include "llvm/MC/MCSectionELF.h"
  16 #include "llvm/Target/TargetData.h"
  17 #include "llvm/Target/TargetMachine.h"
  18 #include "llvm/Support/CommandLine.h"
  19 #include "llvm/Support/ELF.h"
  20 using namespace llvm;
  21
  22 void MBlazeTargetObjectFile::
  23 Initialize(MCContext &Ctx, const TargetMachine &TM) {
  24   TargetLoweringObjectFileELF::Initialize(Ctx, TM);
  25
  26   SmallDataSection =
  27     getContext().getELFSection(".sdata", ELF::SHT_PROGBITS,
  28                                ELF::SHF_WRITE |ELF::SHF_ALLOC,
  29                                SectionKind::getDataRel());
  30
  31   SmallBSSSection =
  32     getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
  33                                ELF::SHF_WRITE |ELF::SHF_ALLOC,
  34                                SectionKind::getBSS());
  35
  36 }
  37
  38 // A address must be loaded from a small section if its size is less than the
  39 // small section size threshold. Data in this section must be addressed using
  40 // gp_rel operator.
  41 static bool IsInSmallSection(uint64_t Size) {
  42   return Size > 0 && Size <= 8;
  43 }
  44
  45 bool MBlazeTargetObjectFile::
  46 IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM) const {
  47   if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
  48     return false;
  49
  50   return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM));
  51 }
  52
  53 /// IsGlobalInSmallSection - Return true if this global address should be
  54 /// placed into small data/bss section.
  55 bool MBlazeTargetObjectFile::
  56 IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
  57                        SectionKind Kind) const {
  58   // Only global variables, not functions.
  59   const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
  60   if (!GVA)
  61     return false;
  62
  63   // We can only do this for datarel or BSS objects for now.
  64   if (!Kind.isBSS() && !Kind.isDataRel())
  65     return false;
  66
  67   // If this is a internal constant string, there is a special
  68   // section for it, but not in small data/bss.
  69   if (Kind.isMergeable1ByteCString())
  70     return false;
  71
  72   const Type *Ty = GV->getType()->getElementType();
  73   return IsInSmallSection(TM.getTargetData()->getTypeAllocSize(Ty));
  74 }
  75
  76 const MCSection *MBlazeTargetObjectFile::
  77 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
  78                        Mangler *Mang, const TargetMachine &TM) const {
  79   // TODO: Could also support "weak" symbols as well with ".gnu.linkonce.s.*"
  80   // sections?
  81
  82   // Handle Small Section classification here.
  83   if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind))
  84     return SmallBSSSection;
  85   if (Kind.isDataNoRel() && IsGlobalInSmallSection(GV, TM, Kind))
  86     return SmallDataSection;
  87
  88   // Otherwise, we work the same as ELF.
  89   return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM);
  90 }