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"
20 using namespace llvm;
21
22 static cl::opt<unsigned>
23 SSThreshold("mips-ssection-threshold", cl::Hidden,
24 cl::desc("Small data and bss section threshold size (default=8)"),
25 cl::init(8));
26
Initialize(MCContext & Ctx,const TargetMachine & TM)27 void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){
28 TargetLoweringObjectFileELF::Initialize(Ctx, TM);
29
30 SmallDataSection =
31 getContext().getELFSection(".sdata", ELF::SHT_PROGBITS,
32 ELF::SHF_WRITE |ELF::SHF_ALLOC,
33 SectionKind::getDataRel());
34
35 SmallBSSSection =
36 getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
37 ELF::SHF_WRITE |ELF::SHF_ALLOC,
38 SectionKind::getBSS());
39
40 }
41
42 // A address must be loaded from a small section if its size is less than the
43 // small section size threshold. Data in this section must be addressed using
44 // gp_rel operator.
IsInSmallSection(uint64_t Size)45 static bool IsInSmallSection(uint64_t Size) {
46 return Size > 0 && Size <= SSThreshold;
47 }
48
IsGlobalInSmallSection(const GlobalValue * GV,const TargetMachine & TM) const49 bool MipsTargetObjectFile::IsGlobalInSmallSection(const GlobalValue *GV,
50 const TargetMachine &TM) const {
51 if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
52 return false;
53
54 return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM));
55 }
56
57 /// IsGlobalInSmallSection - Return true if this global address should be
58 /// placed into small data/bss section.
59 bool MipsTargetObjectFile::
IsGlobalInSmallSection(const GlobalValue * GV,const TargetMachine & TM,SectionKind Kind) const60 IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
61 SectionKind Kind) const {
62
63 // Only use small section for non linux targets.
64 const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>();
65 if (Subtarget.isLinux())
66 return false;
67
68 // Only global variables, not functions.
69 const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
70 if (!GVA)
71 return false;
72
73 // We can only do this for datarel or BSS objects for now.
74 if (!Kind.isBSS() && !Kind.isDataRel())
75 return false;
76
77 // If this is a internal constant string, there is a special
78 // section for it, but not in small data/bss.
79 if (Kind.isMergeable1ByteCString())
80 return false;
81
82 Type *Ty = GV->getType()->getElementType();
83 return IsInSmallSection(TM.getTargetData()->getTypeAllocSize(Ty));
84 }
85
86
87
88 const MCSection *MipsTargetObjectFile::
SelectSectionForGlobal(const GlobalValue * GV,SectionKind Kind,Mangler * Mang,const TargetMachine & TM) const89 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
90 Mangler *Mang, const TargetMachine &TM) const {
91 // TODO: Could also support "weak" symbols as well with ".gnu.linkonce.s.*"
92 // sections?
93
94 // Handle Small Section classification here.
95 if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind))
96 return SmallBSSSection;
97 if (Kind.isDataNoRel() && IsGlobalInSmallSection(GV, TM, Kind))
98 return SmallDataSection;
99
100 // Otherwise, we work the same as ELF.
101 return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM);
102 }
103