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