LLVM 17.0.0git
RISCVTargetObjectFile.cpp
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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"
12#include "llvm/MC/MCContext.h"
14
15using 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
89 M.getModuleFlagsMetadata(ModuleFlags);
90
91 for (const auto &MFE : ModuleFlags) {
92 StringRef Key = MFE.Key->getString();
93 if (Key == "SmallDataLimit") {
94 SSThreshold = mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
95 break;
96 }
97 }
98}
99
100/// Return true if this constant should be placed into small data section.
102 const DataLayout &DL, const Constant *CN) const {
103 return isInSmallSection(DL.getTypeAllocSize(CN->getType()));
104}
105
107 const DataLayout &DL, SectionKind Kind, const Constant *C,
108 Align &Alignment) const {
110 return SmallDataSection;
111
112 // Otherwise, we work the same as ELF.
114 Alignment);
115}
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
uint64_t Size
const char LLVMTargetMachineRef TM
This is an important base class in LLVM.
Definition: Constant.h:41
A parsed version of the target data layout string in and methods for querying it.
Definition: DataLayout.h:114
TypeSize getTypeAllocSize(Type *Ty) const
Returns the offset in bytes between successive objects of the specified type, including alignment pad...
Definition: DataLayout.h:507
StringRef getSection() const
Get the custom section of this global if it has one.
Definition: GlobalObject.h:117
bool hasSection() const
Check if this global has a custom object file section.
Definition: GlobalObject.h:109
bool hasExternalLinkage() const
Definition: GlobalValue.h:506
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:275
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:652
bool hasCommonLinkage() const
Definition: GlobalValue.h:527
Type * getValueType() const
Definition: GlobalValue.h:292
Context object for machine code objects.
Definition: MCContext.h:76
MCSectionELF * getELFSection(const Twine &Section, unsigned Type, unsigned Flags)
Definition: MCContext.h:563
MCContext & getContext() const
Instances of this class represent a uniqued identifier for a section in the current translation unit.
Definition: MCSection.h:39
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
const DataLayout & getDataLayout() const
Get the data layout for the module's target platform.
Definition: Module.cpp:398
bool isGlobalInSmallSection(const GlobalObject *GO, const TargetMachine &TM) const
Return true if this global address should be placed into small data/bss section.
MCSection * SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
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 isInSmallSection(uint64_t Size) const
void Initialize(MCContext &Ctx, const TargetMachine &TM) override
This method must be called before any actual lowering is done.
bool isConstantInSmallSection(const DataLayout &DL, const Constant *CN) const
Return true if this constant should be placed into small data section.
SectionKind - This is a simple POD value that classifies the properties of a section.
Definition: SectionKind.h:22
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1200
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
void Initialize(MCContext &Ctx, const TargetMachine &TM) override
This method must be called before any actual lowering is done.
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.
void getModuleMetadata(Module &M) override
Get the module-level metadata that the platform cares about.
MCSection * SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
Primary interface to the complete machine description for the target machine.
Definition: TargetMachine.h:78
The instances of the Type class are immutable: once they are created, they are never changed.
Definition: Type.h:45
bool isSized(SmallPtrSetImpl< Type * > *Visited=nullptr) const
Return true if it makes sense to take the size of this type.
Definition: Type.h:295
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:255
@ C
The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
@ SHF_ALLOC
Definition: ELF.h:1083
@ SHF_WRITE
Definition: ELF.h:1080
@ SHT_PROGBITS
Definition: ELF.h:995
@ SHT_NOBITS
Definition: ELF.h:1002
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39