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/IR/DataLayout.h" 13#include "llvm/IR/DerivedTypes.h" 14#include "llvm/IR/GlobalVariable.h" 15#include "llvm/MC/MCContext.h" 16#include "llvm/MC/MCSectionELF.h" 17#include "llvm/Support/CommandLine.h" 18#include "llvm/Support/ELF.h" 19#include "llvm/Target/TargetMachine.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 // Register info information 42 const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>(); 43 if (Subtarget.isABI_N64() || Subtarget.isABI_N32()) 44 ReginfoSection = 45 getContext().getELFSection(".MIPS.options", 46 ELF::SHT_MIPS_OPTIONS, 47 ELF::SHF_ALLOC |ELF::SHF_MIPS_NOSTRIP, 48 SectionKind::getMetadata()); 49 else 50 ReginfoSection = 51 getContext().getELFSection(".reginfo", 52 ELF::SHT_MIPS_REGINFO, 53 ELF::SHF_ALLOC, 54 SectionKind::getMetadata()); 55} 56 57// A address must be loaded from a small section if its size is less than the 58// small section size threshold. Data in this section must be addressed using 59// gp_rel operator. 60static bool IsInSmallSection(uint64_t Size) { 61 return Size > 0 && Size <= SSThreshold; 62} 63 64bool MipsTargetObjectFile::IsGlobalInSmallSection(const GlobalValue *GV, 65 const TargetMachine &TM) const { 66 if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage()) 67 return false; 68 69 return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM)); 70} 71 72/// IsGlobalInSmallSection - Return true if this global address should be 73/// placed into small data/bss section. 74bool MipsTargetObjectFile:: 75IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM, 76 SectionKind Kind) const { 77 78 const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>(); 79 80 // Return if small section is not available. 81 if (!Subtarget.useSmallSection()) 82 return false; 83 84 // Only global variables, not functions. 85 const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV); 86 if (!GVA) 87 return false; 88 89 // We can only do this for datarel or BSS objects for now. 90 if (!Kind.isBSS() && !Kind.isDataRel()) 91 return false; 92 93 // If this is a internal constant string, there is a special 94 // section for it, but not in small data/bss. 95 if (Kind.isMergeable1ByteCString()) 96 return false; 97 98 Type *Ty = GV->getType()->getElementType(); 99 return IsInSmallSection(TM.getDataLayout()->getTypeAllocSize(Ty)); 100} 101 102 103 104const MCSection *MipsTargetObjectFile:: 105SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind, 106 Mangler *Mang, const TargetMachine &TM) const { 107 // TODO: Could also support "weak" symbols as well with ".gnu.linkonce.s.*" 108 // sections? 109 110 // Handle Small Section classification here. 111 if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind)) 112 return SmallBSSSection; 113 if (Kind.isDataNoRel() && IsGlobalInSmallSection(GV, TM, Kind)) 114 return SmallDataSection; 115 116 // Otherwise, we work the same as ELF. 117 return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM); 118} 119