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