HexagonTargetObjectFile.cpp revision 288943 
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/IR/DataLayout.h"
18#include "llvm/IR/DerivedTypes.h"
19#include "llvm/IR/Function.h"
20#include "llvm/IR/GlobalVariable.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/Support/CommandLine.h"
23#include "llvm/Support/ELF.h"
24
25using namespace llvm;
26
27static cl::opt<int> SmallDataThreshold("hexagon-small-data-threshold",
28                                cl::init(8), cl::Hidden,
29                cl::desc("The maximum size of an object in the sdata section"));
30
31void HexagonTargetObjectFile::Initialize(MCContext &Ctx,
32                                         const TargetMachine &TM) {
33  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
34  InitializeELF(TM.Options.UseInitArray);
35
36  SmallDataSection = getContext().getELFSection(
37      ".sdata", ELF::SHT_PROGBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
38  SmallBSSSection = getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
39                                               ELF::SHF_WRITE | ELF::SHF_ALLOC);
40}
41
42// sdata/sbss support taken largely from the MIPS Backend.
43static bool IsInSmallSection(uint64_t Size) {
44  return Size > 0 && Size <= (uint64_t)SmallDataThreshold;
45}
46
47bool HexagonTargetObjectFile::IsSmallDataEnabled () const {
48  return SmallDataThreshold > 0;
49}
50
51/// IsGlobalInSmallSection - Return true if this global value should be
52/// placed into small data/bss section.
53bool HexagonTargetObjectFile::IsGlobalInSmallSection(const GlobalValue *GV,
54                                                const TargetMachine &TM) const {
55  // If the primary definition of this global value is outside the current
56  // translation unit or the global value is available for inspection but not
57  // emission, then do nothing.
58  if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
59    return false;
60
61  // Otherwise, Check if GV should be in sdata/sbss, when normally it would end
62  // up in getKindForGlobal(GV, TM).
63  return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM));
64}
65
66/// IsGlobalInSmallSection - Return true if this global value should be
67/// placed into small data/bss section.
68bool HexagonTargetObjectFile::
69IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
70                       SectionKind Kind) const {
71  // Only global variables, not functions.
72  const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
73  if (!GVA)
74    return false;
75
76  if (Kind.isBSS() || Kind.isDataNoRel() || Kind.isCommon()) {
77    Type *Ty = GV->getType()->getElementType();
78    return IsInSmallSection(TM.getDataLayout()->getTypeAllocSize(Ty));
79  }
80
81  return false;
82}
83
84MCSection *
85HexagonTargetObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
86                                                SectionKind Kind, Mangler &Mang,
87                                                const TargetMachine &TM) const {
88
89  // Handle Small Section classification here.
90  if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind))
91    return SmallBSSSection;
92  if (Kind.isDataNoRel() && IsGlobalInSmallSection(GV, TM, Kind))
93    return SmallDataSection;
94
95  // Otherwise, we work the same as ELF.
96  return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM);
97}
98