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Diffstat (limited to 'contrib/llvm/lib/Target/TargetLoweringObjectFile.cpp')
| -rw-r--r-- | contrib/llvm/lib/Target/TargetLoweringObjectFile.cpp | 343 |
1 files changed, 343 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Target/TargetLoweringObjectFile.cpp b/contrib/llvm/lib/Target/TargetLoweringObjectFile.cpp new file mode 100644 index 000000000000..6bcf60fafc3e --- /dev/null +++ b/contrib/llvm/lib/Target/TargetLoweringObjectFile.cpp @@ -0,0 +1,343 @@ +//===-- llvm/Target/TargetLoweringObjectFile.cpp - Object File Info -------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements classes used to handle lowerings specific to common +// object file formats. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Target/TargetLoweringObjectFile.h" +#include "llvm/BinaryFormat/Dwarf.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/DerivedTypes.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/GlobalVariable.h" +#include "llvm/IR/Mangler.h" +#include "llvm/MC/MCContext.h" +#include "llvm/MC/MCExpr.h" +#include "llvm/MC/MCStreamer.h" +#include "llvm/MC/MCSymbol.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetMachine.h" +#include "llvm/Target/TargetOptions.h" +using namespace llvm; + +//===----------------------------------------------------------------------===// +// Generic Code +//===----------------------------------------------------------------------===// + +/// Initialize - this method must be called before any actual lowering is +/// done. This specifies the current context for codegen, and gives the +/// lowering implementations a chance to set up their default sections. +void TargetLoweringObjectFile::Initialize(MCContext &ctx, + const TargetMachine &TM) { + Ctx = &ctx; + // `Initialize` can be called more than once. + delete Mang; + Mang = new Mangler(); + InitMCObjectFileInfo(TM.getTargetTriple(), TM.isPositionIndependent(), *Ctx, + TM.getCodeModel() == CodeModel::Large); +} + +TargetLoweringObjectFile::~TargetLoweringObjectFile() { + delete Mang; +} + +static bool isNullOrUndef(const Constant *C) { + // Check that the constant isn't all zeros or undefs. + if (C->isNullValue() || isa<UndefValue>(C)) + return true; + if (!isa<ConstantAggregate>(C)) + return false; + for (auto Operand : C->operand_values()) { + if (!isNullOrUndef(cast<Constant>(Operand))) + return false; + } + return true; +} + +static bool isSuitableForBSS(const GlobalVariable *GV) { + const Constant *C = GV->getInitializer(); + + // Must have zero initializer. + if (!isNullOrUndef(C)) + return false; + + // Leave constant zeros in readonly constant sections, so they can be shared. + if (GV->isConstant()) + return false; + + // If the global has an explicit section specified, don't put it in BSS. + if (GV->hasSection()) + return false; + + // Otherwise, put it in BSS! + return true; +} + +/// IsNullTerminatedString - Return true if the specified constant (which is +/// known to have a type that is an array of 1/2/4 byte elements) ends with a +/// nul value and contains no other nuls in it. Note that this is more general +/// than ConstantDataSequential::isString because we allow 2 & 4 byte strings. +static bool IsNullTerminatedString(const Constant *C) { + // First check: is we have constant array terminated with zero + if (const ConstantDataSequential *CDS = dyn_cast<ConstantDataSequential>(C)) { + unsigned NumElts = CDS->getNumElements(); + assert(NumElts != 0 && "Can't have an empty CDS"); + + if (CDS->getElementAsInteger(NumElts-1) != 0) + return false; // Not null terminated. + + // Verify that the null doesn't occur anywhere else in the string. + for (unsigned i = 0; i != NumElts-1; ++i) + if (CDS->getElementAsInteger(i) == 0) + return false; + return true; + } + + // Another possibility: [1 x i8] zeroinitializer + if (isa<ConstantAggregateZero>(C)) + return cast<ArrayType>(C->getType())->getNumElements() == 1; + + return false; +} + +MCSymbol *TargetLoweringObjectFile::getSymbolWithGlobalValueBase( + const GlobalValue *GV, StringRef Suffix, const TargetMachine &TM) const { + assert(!Suffix.empty()); + + SmallString<60> NameStr; + NameStr += GV->getParent()->getDataLayout().getPrivateGlobalPrefix(); + TM.getNameWithPrefix(NameStr, GV, *Mang); + NameStr.append(Suffix.begin(), Suffix.end()); + return Ctx->getOrCreateSymbol(NameStr); +} + +MCSymbol *TargetLoweringObjectFile::getCFIPersonalitySymbol( + const GlobalValue *GV, const TargetMachine &TM, + MachineModuleInfo *MMI) const { + return TM.getSymbol(GV); +} + +void TargetLoweringObjectFile::emitPersonalityValue(MCStreamer &Streamer, + const DataLayout &, + const MCSymbol *Sym) const { +} + + +/// getKindForGlobal - This is a top-level target-independent classifier for +/// a global object. Given a global variable and information from the TM, this +/// function classifies the global in a target independent manner. This function +/// may be overridden by the target implementation. +SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalObject *GO, + const TargetMachine &TM){ + assert(!GO->isDeclaration() && !GO->hasAvailableExternallyLinkage() && + "Can only be used for global definitions"); + + // Functions are classified as text sections. + if (isa<Function>(GO)) + return SectionKind::getText(); + + // Global variables require more detailed analysis. + const auto *GVar = cast<GlobalVariable>(GO); + + // Handle thread-local data first. + if (GVar->isThreadLocal()) { + if (isSuitableForBSS(GVar) && !TM.Options.NoZerosInBSS) + return SectionKind::getThreadBSS(); + return SectionKind::getThreadData(); + } + + // Variables with common linkage always get classified as common. + if (GVar->hasCommonLinkage()) + return SectionKind::getCommon(); + + // Most non-mergeable zero data can be put in the BSS section unless otherwise + // specified. + if (isSuitableForBSS(GVar) && !TM.Options.NoZerosInBSS) { + if (GVar->hasLocalLinkage()) + return SectionKind::getBSSLocal(); + else if (GVar->hasExternalLinkage()) + return SectionKind::getBSSExtern(); + return SectionKind::getBSS(); + } + + // If the global is marked constant, we can put it into a mergable section, + // a mergable string section, or general .data if it contains relocations. + if (GVar->isConstant()) { + // If the initializer for the global contains something that requires a + // relocation, then we may have to drop this into a writable data section + // even though it is marked const. + const Constant *C = GVar->getInitializer(); + if (!C->needsRelocation()) { + // If the global is required to have a unique address, it can't be put + // into a mergable section: just drop it into the general read-only + // section instead. + if (!GVar->hasGlobalUnnamedAddr()) + return SectionKind::getReadOnly(); + + // If initializer is a null-terminated string, put it in a "cstring" + // section of the right width. + if (ArrayType *ATy = dyn_cast<ArrayType>(C->getType())) { + if (IntegerType *ITy = + dyn_cast<IntegerType>(ATy->getElementType())) { + if ((ITy->getBitWidth() == 8 || ITy->getBitWidth() == 16 || + ITy->getBitWidth() == 32) && + IsNullTerminatedString(C)) { + if (ITy->getBitWidth() == 8) + return SectionKind::getMergeable1ByteCString(); + if (ITy->getBitWidth() == 16) + return SectionKind::getMergeable2ByteCString(); + + assert(ITy->getBitWidth() == 32 && "Unknown width"); + return SectionKind::getMergeable4ByteCString(); + } + } + } + + // Otherwise, just drop it into a mergable constant section. If we have + // a section for this size, use it, otherwise use the arbitrary sized + // mergable section. + switch ( + GVar->getParent()->getDataLayout().getTypeAllocSize(C->getType())) { + case 4: return SectionKind::getMergeableConst4(); + case 8: return SectionKind::getMergeableConst8(); + case 16: return SectionKind::getMergeableConst16(); + case 32: return SectionKind::getMergeableConst32(); + default: + return SectionKind::getReadOnly(); + } + + } else { + // In static, ROPI and RWPI relocation models, the linker will resolve + // all addresses, so the relocation entries will actually be constants by + // the time the app starts up. However, we can't put this into a + // mergable section, because the linker doesn't take relocations into + // consideration when it tries to merge entries in the section. + Reloc::Model ReloModel = TM.getRelocationModel(); + if (ReloModel == Reloc::Static || ReloModel == Reloc::ROPI || + ReloModel == Reloc::RWPI || ReloModel == Reloc::ROPI_RWPI) + return SectionKind::getReadOnly(); + + // Otherwise, the dynamic linker needs to fix it up, put it in the + // writable data.rel section. + return SectionKind::getReadOnlyWithRel(); + } + } + + // Okay, this isn't a constant. + return SectionKind::getData(); +} + +/// This method computes the appropriate section to emit the specified global +/// variable or function definition. This should not be passed external (or +/// available externally) globals. +MCSection *TargetLoweringObjectFile::SectionForGlobal( + const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const { + // Select section name. + if (GO->hasSection()) + return getExplicitSectionGlobal(GO, Kind, TM); + + if (auto *GVar = dyn_cast<GlobalVariable>(GO)) { + auto Attrs = GVar->getAttributes(); + if ((Attrs.hasAttribute("bss-section") && Kind.isBSS()) || + (Attrs.hasAttribute("data-section") && Kind.isData()) || + (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly())) { + return getExplicitSectionGlobal(GO, Kind, TM); + } + } + + if (auto *F = dyn_cast<Function>(GO)) { + if (F->hasFnAttribute("implicit-section-name")) + return getExplicitSectionGlobal(GO, Kind, TM); + } + + // Use default section depending on the 'type' of global + return SelectSectionForGlobal(GO, Kind, TM); +} + +MCSection *TargetLoweringObjectFile::getSectionForJumpTable( + const Function &F, const TargetMachine &TM) const { + unsigned Align = 0; + return getSectionForConstant(F.getParent()->getDataLayout(), + SectionKind::getReadOnly(), /*C=*/nullptr, + Align); +} + +bool TargetLoweringObjectFile::shouldPutJumpTableInFunctionSection( + bool UsesLabelDifference, const Function &F) const { + // In PIC mode, we need to emit the jump table to the same section as the + // function body itself, otherwise the label differences won't make sense. + // FIXME: Need a better predicate for this: what about custom entries? + if (UsesLabelDifference) + return true; + + // We should also do if the section name is NULL or function is declared + // in discardable section + // FIXME: this isn't the right predicate, should be based on the MCSection + // for the function. + return F.isWeakForLinker(); +} + +/// Given a mergable constant with the specified size and relocation +/// information, return a section that it should be placed in. +MCSection *TargetLoweringObjectFile::getSectionForConstant( + const DataLayout &DL, SectionKind Kind, const Constant *C, + unsigned &Align) const { + if (Kind.isReadOnly() && ReadOnlySection != nullptr) + return ReadOnlySection; + + return DataSection; +} + +/// getTTypeGlobalReference - Return an MCExpr to use for a +/// reference to the specified global variable from exception +/// handling information. +const MCExpr *TargetLoweringObjectFile::getTTypeGlobalReference( + const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM, + MachineModuleInfo *MMI, MCStreamer &Streamer) const { + const MCSymbolRefExpr *Ref = + MCSymbolRefExpr::create(TM.getSymbol(GV), getContext()); + + return getTTypeReference(Ref, Encoding, Streamer); +} + +const MCExpr *TargetLoweringObjectFile:: +getTTypeReference(const MCSymbolRefExpr *Sym, unsigned Encoding, + MCStreamer &Streamer) const { + switch (Encoding & 0x70) { + default: + report_fatal_error("We do not support this DWARF encoding yet!"); + case dwarf::DW_EH_PE_absptr: + // Do nothing special + return Sym; + case dwarf::DW_EH_PE_pcrel: { + // Emit a label to the streamer for the current position. This gives us + // .-foo addressing. + MCSymbol *PCSym = getContext().createTempSymbol(); + Streamer.EmitLabel(PCSym); + const MCExpr *PC = MCSymbolRefExpr::create(PCSym, getContext()); + return MCBinaryExpr::createSub(Sym, PC, getContext()); + } + } +} + +const MCExpr *TargetLoweringObjectFile::getDebugThreadLocalSymbol(const MCSymbol *Sym) const { + // FIXME: It's not clear what, if any, default this should have - perhaps a + // null return could mean 'no location' & we should just do that here. + return MCSymbolRefExpr::create(Sym, *Ctx); +} + +void TargetLoweringObjectFile::getNameWithPrefix( + SmallVectorImpl<char> &OutName, const GlobalValue *GV, + const TargetMachine &TM) const { + Mang->getNameWithPrefix(OutName, GV, /*CannotUsePrivateLabel=*/false); +} |