1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
|
//===-- MipsTargetObjectFile.cpp - Mips Object Files ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "MipsTargetObjectFile.h"
#include "MipsSubtarget.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ELF.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
static cl::opt<unsigned>
SSThreshold("mips-ssection-threshold", cl::Hidden,
cl::desc("Small data and bss section threshold size (default=8)"),
cl::init(8));
static cl::opt<bool>
LocalSData("mlocal-sdata", cl::Hidden,
cl::desc("MIPS: Use gp_rel for object-local data."),
cl::init(true));
static cl::opt<bool>
ExternSData("mextern-sdata", cl::Hidden,
cl::desc("MIPS: Use gp_rel for data that is not defined by the "
"current object."),
cl::init(true));
void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){
TargetLoweringObjectFileELF::Initialize(Ctx, TM);
InitializeELF(TM.Options.UseInitArray);
SmallDataSection =
getContext().getELFSection(".sdata", ELF::SHT_PROGBITS,
ELF::SHF_WRITE |ELF::SHF_ALLOC,
SectionKind::getDataRel());
SmallBSSSection =
getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
ELF::SHF_WRITE |ELF::SHF_ALLOC,
SectionKind::getBSS());
this->TM = &TM;
}
// A address must be loaded from a small section if its size is less than the
// small section size threshold. Data in this section must be addressed using
// gp_rel operator.
static bool IsInSmallSection(uint64_t Size) {
// gcc has traditionally not treated zero-sized objects as small data, so this
// is effectively part of the ABI.
return Size > 0 && Size <= SSThreshold;
}
/// Return true if this global address should be placed into small data/bss
/// section.
bool MipsTargetObjectFile::
IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM) const {
// We first check the case where global is a declaration, because finding
// section kind using getKindForGlobal() is only allowed for global
// definitions.
if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
return IsGlobalInSmallSectionImpl(GV, TM);
return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM));
}
/// Return true if this global address should be placed into small data/bss
/// section.
bool MipsTargetObjectFile::
IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
SectionKind Kind) const {
return (IsGlobalInSmallSectionImpl(GV, TM) &&
(Kind.isDataRel() || Kind.isBSS() || Kind.isCommon()));
}
/// Return true if this global address should be placed into small data/bss
/// section. This method does all the work, except for checking the section
/// kind.
bool MipsTargetObjectFile::
IsGlobalInSmallSectionImpl(const GlobalValue *GV,
const TargetMachine &TM) const {
const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>();
// Return if small section is not available.
if (!Subtarget.useSmallSection())
return false;
// Only global variables, not functions.
const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
if (!GVA)
return false;
// Enforce -mlocal-sdata.
if (!LocalSData && GV->hasLocalLinkage())
return false;
// Enforce -mextern-sdata.
if (!ExternSData && ((GV->hasExternalLinkage() && GV->isDeclaration()) ||
GV->hasCommonLinkage()))
return false;
Type *Ty = GV->getType()->getElementType();
return IsInSmallSection(TM.getDataLayout()->getTypeAllocSize(Ty));
}
const MCSection *MipsTargetObjectFile::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
// TODO: Could also support "weak" symbols as well with ".gnu.linkonce.s.*"
// sections?
// Handle Small Section classification here.
if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind))
return SmallBSSSection;
if (Kind.isDataRel() && IsGlobalInSmallSection(GV, TM, Kind))
return SmallDataSection;
// Otherwise, we work the same as ELF.
return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM);
}
/// Return true if this constant should be placed into small data section.
bool MipsTargetObjectFile::
IsConstantInSmallSection(const Constant *CN, const TargetMachine &TM) const {
return (
TM.getSubtarget<MipsSubtarget>().useSmallSection() && LocalSData &&
IsInSmallSection(TM.getDataLayout()->getTypeAllocSize(CN->getType())));
}
const MCSection *MipsTargetObjectFile::
getSectionForConstant(SectionKind Kind, const Constant *C) const {
if (IsConstantInSmallSection(C, *TM))
return SmallDataSection;
// Otherwise, we work the same as ELF.
return TargetLoweringObjectFileELF::getSectionForConstant(Kind, C);
}
|
