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      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   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 }
     91