HexagonTargetObjectFile.cpp revision 234285 
1//===-- HexagonTargetObjectFile.cpp - Hexagon asm properties --------------===//
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// This file contains the declarations of the HexagonTargetAsmInfo properties.
11//
12//===----------------------------------------------------------------------===//
13
14#include "HexagonTargetObjectFile.h"
15#include "HexagonSubtarget.h"
16#include "HexagonTargetMachine.h"
17#include "llvm/Function.h"
18#include "llvm/GlobalVariable.h"
19#include "llvm/Target/TargetData.h"
20#include "llvm/DerivedTypes.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/Support/ELF.h"
23#include "llvm/Support/CommandLine.h"
24
25using namespace llvm;
26
27static cl::opt<int> SmallDataThreshold("hexagon-small-data-threshold",
28                                cl::init(8), cl::Hidden);
29
30void HexagonTargetObjectFile::Initialize(MCContext &Ctx,
31                                         const TargetMachine &TM) {
32  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
33
34
35  SmallDataSection =
36    getContext().getELFSection(".sdata", ELF::SHT_PROGBITS,
37                               ELF::SHF_WRITE | ELF::SHF_ALLOC,
38                               SectionKind::getDataRel());
39  SmallBSSSection =
40    getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
41                               ELF::SHF_WRITE | ELF::SHF_ALLOC,
42                               SectionKind::getBSS());
43}
44
45// sdata/sbss support taken largely from the MIPS Backend.
46static bool IsInSmallSection(uint64_t Size) {
47  return Size > 0 && Size <= (uint64_t)SmallDataThreshold;
48}
49/// IsGlobalInSmallSection - Return true if this global value should be
50/// placed into small data/bss section.
51bool HexagonTargetObjectFile::IsGlobalInSmallSection(const GlobalValue *GV,
52                                                const TargetMachine &TM) const {
53  // If the primary definition of this global value is outside the current
54  // translation unit or the global value is available for inspection but not
55  // emission, then do nothing.
56  if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
57    return false;
58
59  // Otherwise, Check if GV should be in sdata/sbss, when normally it would end
60  // up in getKindForGlobal(GV, TM).
61  return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM));
62}
63
64/// IsGlobalInSmallSection - Return true if this global value should be
65/// placed into small data/bss section.
66bool HexagonTargetObjectFile::
67IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
68                       SectionKind Kind) const {
69  // Only global variables, not functions.
70  const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
71  if (!GVA)
72    return false;
73
74  if (Kind.isBSS() || Kind.isDataNoRel() || Kind.isCommon()) {
75    Type *Ty = GV->getType()->getElementType();
76    return IsInSmallSection(TM.getTargetData()->getTypeAllocSize(Ty));
77  }
78
79  return false;
80}
81
82const MCSection *HexagonTargetObjectFile::
83SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
84                       Mangler *Mang, const TargetMachine &TM) const {
85
86  // Handle Small Section classification here.
87  if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind))
88    return SmallBSSSection;
89  if (Kind.isDataNoRel() && IsGlobalInSmallSection(GV, TM, Kind))
90    return SmallDataSection;
91
92  // Otherwise, we work the same as ELF.
93  return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM);
94}
95