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| //
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "LanaiTargetObjectFile.h"
#include "LanaiSubtarget.h"
#include "LanaiTargetMachine.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
static cl::opt<unsigned> SSThreshold(
"lanai-ssection-threshold", cl::Hidden,
cl::desc("Small data and bss section threshold size (default=0)"),
cl::init(0));
void LanaiTargetObjectFile::Initialize(MCContext &Ctx,
const TargetMachine &TM) {
TargetLoweringObjectFileELF::Initialize(Ctx, TM);
InitializeELF(TM.Options.UseInitArray);
SmallDataSection = getContext().getELFSection(
".sdata", ELF::SHT_PROGBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
SmallBSSSection = getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
ELF::SHF_WRITE | ELF::SHF_ALLOC);
}
// A address must be loaded from a small section if its size is less than the
// small section size threshold. Data in this section must be addressed using
// gp_rel operator.
static bool isInSmallSection(uint64_t Size) {
// gcc has traditionally not treated zero-sized objects as small data, so this
// is effectively part of the ABI.
return Size > 0 && Size <= SSThreshold;
}
// Return true if this global address should be placed into small data/bss
// section.
bool LanaiTargetObjectFile::isGlobalInSmallSection(
const GlobalObject *GO, const TargetMachine &TM) const {
if (GO == nullptr) return TM.getCodeModel() == CodeModel::Small;
// We first check the case where global is a declaration, because finding
// section kind using getKindForGlobal() is only allowed for global
// definitions.
if (GO->isDeclaration() || GO->hasAvailableExternallyLinkage())
return isGlobalInSmallSectionImpl(GO, TM);
return isGlobalInSmallSection(GO, TM, getKindForGlobal(GO, TM));
}
// Return true if this global address should be placed into small data/bss
// section.
bool LanaiTargetObjectFile::isGlobalInSmallSection(const GlobalObject *GO,
const TargetMachine &TM,
SectionKind Kind) const {
return isGlobalInSmallSectionImpl(GO, TM);
}
// Return true if this global address should be placed into small data/bss
// section. This method does all the work, except for checking the section
// kind.
bool LanaiTargetObjectFile::isGlobalInSmallSectionImpl(
const GlobalObject *GO, const TargetMachine &TM) const {
const auto *GVA = dyn_cast<GlobalVariable>(GO);
// If not a GlobalVariable, only consider the code model.
if (!GVA) return TM.getCodeModel() == CodeModel::Small;
// Global values placed in sections starting with .ldata do not fit in
// 21-bits, so always use large memory access for them. FIXME: This is a
// workaround for a tool limitation.
if (GVA->getSection().startswith(".ldata"))
return false;
if (TM.getCodeModel() == CodeModel::Small)
return true;
if (GVA->hasLocalLinkage())
return false;
if (((GVA->hasExternalLinkage() && GVA->isDeclaration()) ||
GVA->hasCommonLinkage()))
return false;
Type *Ty = GVA->getValueType();
return isInSmallSection(
GVA->getParent()->getDataLayout().getTypeAllocSize(Ty));
}
MCSection *LanaiTargetObjectFile::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
// Handle Small Section classification here.
if (Kind.isBSS() && isGlobalInSmallSection(GO, TM, Kind))
return SmallBSSSection;
if (Kind.isData() && isGlobalInSmallSection(GO, TM, Kind))
return SmallDataSection;
// Otherwise, we work the same as ELF.
return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
}
/// Return true if this constant should be placed into small data section.
bool LanaiTargetObjectFile::isConstantInSmallSection(const DataLayout &DL,
const Constant *CN) const {
return isInSmallSection(DL.getTypeAllocSize(CN->getType()));
}
MCSection *LanaiTargetObjectFile::getSectionForConstant(const DataLayout &DL,
SectionKind Kind,
const Constant *C,
unsigned &Align) const {
if (isConstantInSmallSection(DL, C))
return SmallDataSection;
// Otherwise, we work the same as ELF.
return TargetLoweringObjectFileELF::getSectionForConstant(DL, Kind, C, Align);
}
|