| //===-- HexagonTargetObjectFile.cpp ---------------------------------------===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file contains the declarations of the HexagonTargetAsmInfo properties. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "hexagon-sdata" |
| |
| #include "HexagonTargetObjectFile.h" |
| #include "llvm/ADT/SmallString.h" |
| #include "llvm/ADT/StringRef.h" |
| #include "llvm/ADT/Twine.h" |
| #include "llvm/BinaryFormat/ELF.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/GlobalObject.h" |
| #include "llvm/IR/GlobalValue.h" |
| #include "llvm/IR/GlobalVariable.h" |
| #include "llvm/IR/Type.h" |
| #include "llvm/MC/MCContext.h" |
| #include "llvm/MC/SectionKind.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetMachine.h" |
| |
| using namespace llvm; |
| |
| static cl::opt<unsigned> SmallDataThreshold("hexagon-small-data-threshold", |
| cl::init(8), cl::Hidden, |
| cl::desc("The maximum size of an object in the sdata section")); |
| |
| static cl::opt<bool> NoSmallDataSorting("mno-sort-sda", cl::init(false), |
| cl::Hidden, cl::desc("Disable small data sections sorting")); |
| |
| static cl::opt<bool> StaticsInSData("hexagon-statics-in-small-data", |
| cl::init(false), cl::Hidden, cl::ZeroOrMore, |
| cl::desc("Allow static variables in .sdata")); |
| |
| static cl::opt<bool> TraceGVPlacement("trace-gv-placement", |
| cl::Hidden, cl::init(false), |
| cl::desc("Trace global value placement")); |
| |
| static cl::opt<bool> |
| EmitJtInText("hexagon-emit-jt-text", cl::Hidden, cl::init(false), |
| cl::desc("Emit hexagon jump tables in function section")); |
| |
| static cl::opt<bool> |
| EmitLutInText("hexagon-emit-lut-text", cl::Hidden, cl::init(false), |
| cl::desc("Emit hexagon lookup tables in function section")); |
| |
| // TraceGVPlacement controls messages for all builds. For builds with assertions |
| // (debug or release), messages are also controlled by the usual debug flags |
| // (e.g. -debug and -debug-only=globallayout) |
| #define TRACE_TO(s, X) s << X |
| #ifdef NDEBUG |
| #define TRACE(X) \ |
| do { \ |
| if (TraceGVPlacement) { \ |
| TRACE_TO(errs(), X); \ |
| } \ |
| } while (false) |
| #else |
| #define TRACE(X) \ |
| do { \ |
| if (TraceGVPlacement) { \ |
| TRACE_TO(errs(), X); \ |
| } else { \ |
| LLVM_DEBUG(TRACE_TO(dbgs(), X)); \ |
| } \ |
| } while (false) |
| #endif |
| |
| // Returns true if the section name is such that the symbol will be put |
| // in a small data section. |
| // For instance, global variables with section attributes such as ".sdata" |
| // ".sdata.*", ".sbss", and ".sbss.*" will go into small data. |
| static bool isSmallDataSection(StringRef Sec) { |
| // sectionName is either ".sdata" or ".sbss". Looking for an exact match |
| // obviates the need for checks for section names such as ".sdatafoo". |
| if (Sec.equals(".sdata") || Sec.equals(".sbss") || Sec.equals(".scommon")) |
| return true; |
| // If either ".sdata." or ".sbss." is a substring of the section name |
| // then put the symbol in small data. |
| return Sec.find(".sdata.") != StringRef::npos || |
| Sec.find(".sbss.") != StringRef::npos || |
| Sec.find(".scommon.") != StringRef::npos; |
| } |
| |
| static const char *getSectionSuffixForSize(unsigned Size) { |
| switch (Size) { |
| default: |
| return ""; |
| case 1: |
| return ".1"; |
| case 2: |
| return ".2"; |
| case 4: |
| return ".4"; |
| case 8: |
| return ".8"; |
| } |
| } |
| |
| void HexagonTargetObjectFile::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 | |
| ELF::SHF_HEX_GPREL); |
| SmallBSSSection = |
| getContext().getELFSection(".sbss", ELF::SHT_NOBITS, |
| ELF::SHF_WRITE | ELF::SHF_ALLOC | |
| ELF::SHF_HEX_GPREL); |
| } |
| |
| MCSection *HexagonTargetObjectFile::SelectSectionForGlobal( |
| const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const { |
| TRACE("[SelectSectionForGlobal] GO(" << GO->getName() << ") "); |
| TRACE("input section(" << GO->getSection() << ") "); |
| |
| TRACE((GO->hasPrivateLinkage() ? "private_linkage " : "") |
| << (GO->hasLocalLinkage() ? "local_linkage " : "") |
| << (GO->hasInternalLinkage() ? "internal " : "") |
| << (GO->hasExternalLinkage() ? "external " : "") |
| << (GO->hasCommonLinkage() ? "common_linkage " : "") |
| << (GO->hasCommonLinkage() ? "common " : "" ) |
| << (Kind.isCommon() ? "kind_common " : "" ) |
| << (Kind.isBSS() ? "kind_bss " : "" ) |
| << (Kind.isBSSLocal() ? "kind_bss_local " : "" )); |
| |
| // If the lookup table is used by more than one function, do not place |
| // it in text section. |
| if (EmitLutInText && GO->getName().startswith("switch.table")) { |
| if (const Function *Fn = getLutUsedFunction(GO)) |
| return selectSectionForLookupTable(GO, TM, Fn); |
| } |
| |
| if (isGlobalInSmallSection(GO, TM)) |
| return selectSmallSectionForGlobal(GO, Kind, TM); |
| |
| if (Kind.isCommon()) { |
| // This is purely for LTO+Linker Script because commons don't really have a |
| // section. However, the BitcodeSectionWriter pass will query for the |
| // sections of commons (and the linker expects us to know their section) so |
| // we'll return one here. |
| return BSSSection; |
| } |
| |
| TRACE("default_ELF_section\n"); |
| // Otherwise, we work the same as ELF. |
| return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM); |
| } |
| |
| MCSection *HexagonTargetObjectFile::getExplicitSectionGlobal( |
| const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const { |
| TRACE("[getExplicitSectionGlobal] GO(" << GO->getName() << ") from(" |
| << GO->getSection() << ") "); |
| TRACE((GO->hasPrivateLinkage() ? "private_linkage " : "") |
| << (GO->hasLocalLinkage() ? "local_linkage " : "") |
| << (GO->hasInternalLinkage() ? "internal " : "") |
| << (GO->hasExternalLinkage() ? "external " : "") |
| << (GO->hasCommonLinkage() ? "common_linkage " : "") |
| << (GO->hasCommonLinkage() ? "common " : "" ) |
| << (Kind.isCommon() ? "kind_common " : "" ) |
| << (Kind.isBSS() ? "kind_bss " : "" ) |
| << (Kind.isBSSLocal() ? "kind_bss_local " : "" )); |
| |
| if (GO->hasSection()) { |
| StringRef Section = GO->getSection(); |
| if (Section.find(".access.text.group") != StringRef::npos) |
| return getContext().getELFSection(GO->getSection(), ELF::SHT_PROGBITS, |
| ELF::SHF_ALLOC | ELF::SHF_EXECINSTR); |
| if (Section.find(".access.data.group") != StringRef::npos) |
| return getContext().getELFSection(GO->getSection(), ELF::SHT_PROGBITS, |
| ELF::SHF_WRITE | ELF::SHF_ALLOC); |
| } |
| |
| if (isGlobalInSmallSection(GO, TM)) |
| return selectSmallSectionForGlobal(GO, Kind, TM); |
| |
| // Otherwise, we work the same as ELF. |
| TRACE("default_ELF_section\n"); |
| return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, Kind, TM); |
| } |
| |
| /// Return true if this global value should be placed into small data/bss |
| /// section. |
| bool HexagonTargetObjectFile::isGlobalInSmallSection(const GlobalObject *GO, |
| const TargetMachine &TM) const { |
| bool HaveSData = isSmallDataEnabled(TM); |
| if (!HaveSData) |
| LLVM_DEBUG(dbgs() << "Small-data allocation is disabled, but symbols " |
| "may have explicit section assignments...\n"); |
| // Only global variables, not functions. |
| LLVM_DEBUG(dbgs() << "Checking if value is in small-data, -G" |
| << SmallDataThreshold << ": \"" << GO->getName() << "\": "); |
| const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO); |
| if (!GVar) { |
| LLVM_DEBUG(dbgs() << "no, not a global variable\n"); |
| return false; |
| } |
| |
| // Globals with external linkage that have an original section set must be |
| // emitted to that section, regardless of whether we would put them into |
| // small data or not. This is how we can support mixing -G0/-G8 in LTO. |
| if (GVar->hasSection()) { |
| bool IsSmall = isSmallDataSection(GVar->getSection()); |
| LLVM_DEBUG(dbgs() << (IsSmall ? "yes" : "no") |
| << ", has section: " << GVar->getSection() << '\n'); |
| return IsSmall; |
| } |
| |
| // If sdata is disabled, stop the checks here. |
| if (!HaveSData) { |
| LLVM_DEBUG(dbgs() << "no, small-data allocation is disabled\n"); |
| return false; |
| } |
| |
| if (GVar->isConstant()) { |
| LLVM_DEBUG(dbgs() << "no, is a constant\n"); |
| return false; |
| } |
| |
| bool IsLocal = GVar->hasLocalLinkage(); |
| if (!StaticsInSData && IsLocal) { |
| LLVM_DEBUG(dbgs() << "no, is static\n"); |
| return false; |
| } |
| |
| Type *GType = GVar->getValueType(); |
| if (isa<ArrayType>(GType)) { |
| LLVM_DEBUG(dbgs() << "no, is an array\n"); |
| return false; |
| } |
| |
| // If the type is a struct with no body provided, treat is conservatively. |
| // There cannot be actual definitions of object of such a type in this CU |
| // (only references), so assuming that they are not in sdata is safe. If |
| // these objects end up in the sdata, the references will still be valid. |
| if (StructType *ST = dyn_cast<StructType>(GType)) { |
| if (ST->isOpaque()) { |
| LLVM_DEBUG(dbgs() << "no, has opaque type\n"); |
| return false; |
| } |
| } |
| |
| unsigned Size = GVar->getParent()->getDataLayout().getTypeAllocSize(GType); |
| if (Size == 0) { |
| LLVM_DEBUG(dbgs() << "no, has size 0\n"); |
| return false; |
| } |
| if (Size > SmallDataThreshold) { |
| LLVM_DEBUG(dbgs() << "no, size exceeds sdata threshold: " << Size << '\n'); |
| return false; |
| } |
| |
| LLVM_DEBUG(dbgs() << "yes\n"); |
| return true; |
| } |
| |
| bool HexagonTargetObjectFile::isSmallDataEnabled(const TargetMachine &TM) |
| const { |
| return SmallDataThreshold > 0 && !TM.isPositionIndependent(); |
| } |
| |
| unsigned HexagonTargetObjectFile::getSmallDataSize() const { |
| return SmallDataThreshold; |
| } |
| |
| bool HexagonTargetObjectFile::shouldPutJumpTableInFunctionSection( |
| bool UsesLabelDifference, const Function &F) const { |
| return EmitJtInText; |
| } |
| |
| /// Descends any type down to "elementary" components, |
| /// discovering the smallest addressable one. |
| /// If zero is returned, declaration will not be modified. |
| unsigned HexagonTargetObjectFile::getSmallestAddressableSize(const Type *Ty, |
| const GlobalValue *GV, const TargetMachine &TM) const { |
| // Assign the smallest element access size to the highest |
| // value which assembler can handle. |
| unsigned SmallestElement = 8; |
| |
| if (!Ty) |
| return 0; |
| switch (Ty->getTypeID()) { |
| case Type::StructTyID: { |
| const StructType *STy = cast<const StructType>(Ty); |
| for (auto &E : STy->elements()) { |
| unsigned AtomicSize = getSmallestAddressableSize(E, GV, TM); |
| if (AtomicSize < SmallestElement) |
| SmallestElement = AtomicSize; |
| } |
| return (STy->getNumElements() == 0) ? 0 : SmallestElement; |
| } |
| case Type::ArrayTyID: { |
| const ArrayType *ATy = cast<const ArrayType>(Ty); |
| return getSmallestAddressableSize(ATy->getElementType(), GV, TM); |
| } |
| case Type::VectorTyID: { |
| const VectorType *PTy = cast<const VectorType>(Ty); |
| return getSmallestAddressableSize(PTy->getElementType(), GV, TM); |
| } |
| case Type::PointerTyID: |
| case Type::HalfTyID: |
| case Type::FloatTyID: |
| case Type::DoubleTyID: |
| case Type::IntegerTyID: { |
| const DataLayout &DL = GV->getParent()->getDataLayout(); |
| // It is unfortunate that DL's function take non-const Type*. |
| return DL.getTypeAllocSize(const_cast<Type*>(Ty)); |
| } |
| case Type::FunctionTyID: |
| case Type::VoidTyID: |
| case Type::X86_FP80TyID: |
| case Type::FP128TyID: |
| case Type::PPC_FP128TyID: |
| case Type::LabelTyID: |
| case Type::MetadataTyID: |
| case Type::X86_MMXTyID: |
| case Type::TokenTyID: |
| return 0; |
| } |
| |
| return 0; |
| } |
| |
| MCSection *HexagonTargetObjectFile::selectSmallSectionForGlobal( |
| const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const { |
| const Type *GTy = GO->getValueType(); |
| unsigned Size = getSmallestAddressableSize(GTy, GO, TM); |
| |
| // If we have -ffunction-section or -fdata-section then we should emit the |
| // global value to a unique section specifically for it... even for sdata. |
| bool EmitUniquedSection = TM.getDataSections(); |
| |
| TRACE("Small data. Size(" << Size << ")"); |
| // Handle Small Section classification here. |
| if (Kind.isBSS() || Kind.isBSSLocal()) { |
| // If -mno-sort-sda is not set, find out smallest accessible entity in |
| // declaration and add it to the section name string. |
| // Note. It does not track the actual usage of the value, only its de- |
| // claration. Also, compiler adds explicit pad fields to some struct |
| // declarations - they are currently counted towards smallest addres- |
| // sable entity. |
| if (NoSmallDataSorting) { |
| TRACE(" default sbss\n"); |
| return SmallBSSSection; |
| } |
| |
| StringRef Prefix(".sbss"); |
| SmallString<128> Name(Prefix); |
| Name.append(getSectionSuffixForSize(Size)); |
| |
| if (EmitUniquedSection) { |
| Name.append("."); |
| Name.append(GO->getName()); |
| } |
| TRACE(" unique sbss(" << Name << ")\n"); |
| return getContext().getELFSection(Name.str(), ELF::SHT_NOBITS, |
| ELF::SHF_WRITE | ELF::SHF_ALLOC | ELF::SHF_HEX_GPREL); |
| } |
| |
| if (Kind.isCommon()) { |
| // This is purely for LTO+Linker Script because commons don't really have a |
| // section. However, the BitcodeSectionWriter pass will query for the |
| // sections of commons (and the linker expects us to know their section) so |
| // we'll return one here. |
| if (NoSmallDataSorting) |
| return BSSSection; |
| |
| Twine Name = Twine(".scommon") + getSectionSuffixForSize(Size); |
| TRACE(" small COMMON (" << Name << ")\n"); |
| |
| return getContext().getELFSection(Name.str(), ELF::SHT_NOBITS, |
| ELF::SHF_WRITE | ELF::SHF_ALLOC | |
| ELF::SHF_HEX_GPREL); |
| } |
| |
| // We could have changed sdata object to a constant... in this |
| // case the Kind could be wrong for it. |
| if (Kind.isMergeableConst()) { |
| TRACE(" const_object_as_data "); |
| const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO); |
| if (GVar->hasSection() && isSmallDataSection(GVar->getSection())) |
| Kind = SectionKind::getData(); |
| } |
| |
| if (Kind.isData()) { |
| if (NoSmallDataSorting) { |
| TRACE(" default sdata\n"); |
| return SmallDataSection; |
| } |
| |
| StringRef Prefix(".sdata"); |
| SmallString<128> Name(Prefix); |
| Name.append(getSectionSuffixForSize(Size)); |
| |
| if (EmitUniquedSection) { |
| Name.append("."); |
| Name.append(GO->getName()); |
| } |
| TRACE(" unique sdata(" << Name << ")\n"); |
| return getContext().getELFSection(Name.str(), ELF::SHT_PROGBITS, |
| ELF::SHF_WRITE | ELF::SHF_ALLOC | ELF::SHF_HEX_GPREL); |
| } |
| |
| TRACE("default ELF section\n"); |
| // Otherwise, we work the same as ELF. |
| return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM); |
| } |
| |
| // Return the function that uses the lookup table. If there are more |
| // than one live function that uses this look table, bail out and place |
| // the lookup table in default section. |
| const Function * |
| HexagonTargetObjectFile::getLutUsedFunction(const GlobalObject *GO) const { |
| const Function *ReturnFn = nullptr; |
| for (auto U : GO->users()) { |
| // validate each instance of user to be a live function. |
| auto *I = dyn_cast<Instruction>(U); |
| if (!I) |
| continue; |
| auto *Bb = I->getParent(); |
| if (!Bb) |
| continue; |
| auto *UserFn = Bb->getParent(); |
| if (!ReturnFn) |
| ReturnFn = UserFn; |
| else if (ReturnFn != UserFn) |
| return nullptr; |
| } |
| return ReturnFn; |
| } |
| |
| MCSection *HexagonTargetObjectFile::selectSectionForLookupTable( |
| const GlobalObject *GO, const TargetMachine &TM, const Function *Fn) const { |
| |
| SectionKind Kind = SectionKind::getText(); |
| // If the function has explicit section, place the lookup table in this |
| // explicit section. |
| if (Fn->hasSection()) |
| return getExplicitSectionGlobal(Fn, Kind, TM); |
| |
| const auto *FuncObj = dyn_cast<GlobalObject>(Fn); |
| return SelectSectionForGlobal(FuncObj, Kind, TM); |
| } |
