1//===-- MipsTargetObjectFile.cpp - Mips 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 "MipsTargetObjectFile.h" 11#include "MipsSubtarget.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" 20using namespace llvm; 21 22static cl::opt<unsigned> 23SSThreshold("mips-ssection-threshold", cl::Hidden, 24 cl::desc("Small data and bss section threshold size (default=8)"), 25 cl::init(8)); 26 27void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){ 28 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 29 InitializeELF(TM.Options.UseInitArray); 30 31 SmallDataSection = 32 getContext().getELFSection(".sdata", ELF::SHT_PROGBITS, 33 ELF::SHF_WRITE |ELF::SHF_ALLOC, 34 SectionKind::getDataRel()); 35 36 SmallBSSSection = 37 getContext().getELFSection(".sbss", ELF::SHT_NOBITS, 38 ELF::SHF_WRITE |ELF::SHF_ALLOC, 39 SectionKind::getBSS()); 40 41} 42 43// A address must be loaded from a small section if its size is less than the 44// small section size threshold. Data in this section must be addressed using 45// gp_rel operator. 46static bool IsInSmallSection(uint64_t Size) { 47 return Size > 0 && Size <= SSThreshold; 48} 49 50bool MipsTargetObjectFile::IsGlobalInSmallSection(const GlobalValue *GV, 51 const TargetMachine &TM) const { 52 if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage()) 53 return false; 54 55 return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM)); 56} 57 58/// IsGlobalInSmallSection - Return true if this global address should be 59/// placed into small data/bss section. 60bool MipsTargetObjectFile:: 61IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM, 62 SectionKind Kind) const { 63 64 const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>(); 65 66 // Return if small section is not available. 67 if (!Subtarget.useSmallSection()) 68 return false; 69 70 // Only global variables, not functions. 71 const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV); 72 if (!GVA) 73 return false; 74 75 // We can only do this for datarel or BSS objects for now. 76 if (!Kind.isBSS() && !Kind.isDataRel()) 77 return false; 78 79 // If this is a internal constant string, there is a special 80 // section for it, but not in small data/bss. 81 if (Kind.isMergeable1ByteCString()) 82 return false; 83 84 Type *Ty = GV->getType()->getElementType(); 85 return IsInSmallSection(TM.getTargetData()->getTypeAllocSize(Ty)); 86} 87 88 89 90const MCSection *MipsTargetObjectFile:: 91SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind, 92 Mangler *Mang, const TargetMachine &TM) const { 93 // TODO: Could also support "weak" symbols as well with ".gnu.linkonce.s.*" 94 // sections? 95 96 // Handle Small Section classification here. 97 if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind)) 98 return SmallBSSSection; 99 if (Kind.isDataNoRel() && IsGlobalInSmallSection(GV, TM, Kind)) 100 return SmallDataSection; 101 102 // Otherwise, we work the same as ELF. 103 return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM); 104} 105