LLVM  12.0.0git
RISCVTargetObjectFile.cpp
Go to the documentation of this file.
1 //===-- RISCVTargetObjectFile.cpp - RISCV Object Info -----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
10 #include "RISCVTargetMachine.h"
11 #include "llvm/BinaryFormat/ELF.h"
12 #include "llvm/MC/MCContext.h"
13 #include "llvm/MC/MCSectionELF.h"
14 
15 using namespace llvm;
16 
18  const TargetMachine &TM) {
20 
21  SmallDataSection = getContext().getELFSection(
23  SmallBSSSection = getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
25 }
26 
27 // A address must be loaded from a small section if its size is less than the
28 // small section size threshold. Data in this section could be addressed by
29 // using gp_rel operator.
31  // gcc has traditionally not treated zero-sized objects as small data, so this
32  // is effectively part of the ABI.
33  return Size > 0 && Size <= SSThreshold;
34 }
35 
36 // Return true if this global address should be placed into small data/bss
37 // section.
39  const GlobalObject *GO, const TargetMachine &TM) const {
40  // Only global variables, not functions.
41  const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GO);
42  if (!GVA)
43  return false;
44 
45  // If the variable has an explicit section, it is placed in that section.
46  if (GVA->hasSection()) {
47  StringRef Section = GVA->getSection();
48 
49  // Explicitly placing any variable in the small data section overrides
50  // the global -G value.
51  if (Section == ".sdata" || Section == ".sbss")
52  return true;
53 
54  // Otherwise reject putting the variable to small section if it has an
55  // explicit section name.
56  return false;
57  }
58 
59  if (((GVA->hasExternalLinkage() && GVA->isDeclaration()) ||
60  GVA->hasCommonLinkage()))
61  return false;
62 
63  Type *Ty = GVA->getValueType();
64  // It is possible that the type of the global is unsized, i.e. a declaration
65  // of a extern struct. In this case don't presume it is in the small data
66  // section. This happens e.g. when building the FreeBSD kernel.
67  if (!Ty->isSized())
68  return false;
69 
70  return isInSmallSection(
72 }
73 
75  const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
76  // Handle Small Section classification here.
77  if (Kind.isBSS() && isGlobalInSmallSection(GO, TM))
78  return SmallBSSSection;
79  if (Kind.isData() && isGlobalInSmallSection(GO, TM))
80  return SmallDataSection;
81 
82  // Otherwise, we work the same as ELF.
84 }
85 
88  M.getModuleFlagsMetadata(ModuleFlags);
89 
90  for (const auto &MFE : ModuleFlags) {
91  StringRef Key = MFE.Key->getString();
92  if (Key == "SmallDataLimit") {
93  SSThreshold = mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
94  break;
95  }
96  }
97 }
98 
99 /// Return true if this constant should be placed into small data section.
101  const DataLayout &DL, const Constant *CN) const {
102  return isInSmallSection(DL.getTypeAllocSize(CN->getType()));
103 }
104 
106  const DataLayout &DL, SectionKind Kind, const Constant *C,
107  Align &Alignment) const {
108  if (isConstantInSmallSection(DL, C))
109  return SmallDataSection;
110 
111  // Otherwise, we work the same as ELF.
113  Alignment);
114 }
uint64_t CallInst * C
StringRef getSection() const
Get the custom section of this global if it has one.
Definition: GlobalObject.h:115
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:111
LLVM_NODISCARD std::enable_if_t< !is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type > dyn_cast(const Y &Val)
Definition: Casting.h:334
This class represents lattice values for constants.
Definition: AllocatorList.h:23
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:67
bool isSized(SmallPtrSetImpl< Type *> *Visited=nullptr) const
Return true if it makes sense to take the size of this type.
Definition: Type.h:268
MCContext & getContext() const
bool isGlobalInSmallSection(const GlobalObject *GO, const TargetMachine &TM) const
Return true if this global address should be placed into small data/bss section.
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:397
bool hasCommonLinkage() const
Definition: GlobalValue.h:449
MCSection * SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
Context object for machine code objects.
Definition: MCContext.h:67
bool hasExternalLinkage() const
Definition: GlobalValue.h:431
Key
PAL metadata keys.
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
void getModuleMetadata(Module &M) override
Get the module-level metadata that the platform cares about.
MCSection * getSectionForConstant(const DataLayout &DL, SectionKind Kind, const Constant *C, Align &Alignment) const override
Given a constant with the SectionKind, return a section that it should be placed in.
bool isConstantInSmallSection(const DataLayout &DL, const Constant *CN) const
Return true if this constant should be placed into small data section.
MCSection * SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
void getModuleFlagsMetadata(SmallVectorImpl< ModuleFlagEntry > &Flags) const
Returns the module flags in the provided vector.
Definition: Module.cpp:303
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
This is an important base class in LLVM.
Definition: Constant.h:41
TypeSize getTypeAllocSize(Type *Ty) const
Returns the offset in bytes between successive objects of the specified type, including alignment pad...
Definition: DataLayout.h:490
SectionKind - This is a simple POD value that classifies the properties of a section.
Definition: SectionKind.h:22
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39
bool isBSS() const
Definition: SectionKind.h:159
bool hasSection() const
Check if this global has a custom object file section.
Definition: GlobalObject.h:107
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:883
MCSection * getSectionForConstant(const DataLayout &DL, SectionKind Kind, const Constant *C, Align &Alignment) const override
Given a constant with the SectionKind, return a section that it should be placed in.
Type * getValueType() const
Definition: GlobalValue.h:273
uint32_t Size
Definition: Profile.cpp:46
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:227
MCSectionELF * getELFSection(const Twine &Section, unsigned Type, unsigned Flags)
Definition: MCContext.h:469
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:572
bool isData() const
Definition: SectionKind.h:165
Primary interface to the complete machine description for the target machine.
Definition: TargetMachine.h:65
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:57
bool isInSmallSection(uint64_t Size) const
void Initialize(MCContext &Ctx, const TargetMachine &TM) override
This method must be called before any actual lowering is done.
void Initialize(MCContext &Ctx, const TargetMachine &TM) override
This method must be called before any actual lowering is done.
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL