TargetMachine.h

Go to the documentation of this file.

//===-- llvm/Target/TargetMachine.h - Target Information --------*- C++ -*-===//
//
// 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 defines the TargetMachine class.
///
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_TARGET_TARGETMACHINE_H
#define LLVM_TARGET_TARGETMACHINE_H
 
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/PGOOptions.h"
#include "llvm/Target/CGPassBuilderOption.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/TargetParser/Triple.h"
#include <optional>
#include <string>
#include <utility>
 
namespace llvm {
 
LLVM_ABI extern llvm::cl::opt<bool> NoKernelInfoEndLTO;
 
class AAManager;
class CSEConfigBase;
using ModulePassManager = PassManager<Module>;
 
class Function;
class GlobalValue;
class MachineInstr;
class MachineModuleInfoWrapperPass;
struct MachineSchedContext;
class Mangler;
class MCAsmInfo;
class MCContext;
class MCInstrInfo;
class MCRegisterInfo;
class MCStreamer;
class MCSubtargetInfo;
class MCSymbol;
class raw_pwrite_stream;
class PassBuilder;
class PassInstrumentationCallbacks;
struct PerFunctionMIParsingState;
class ScheduleDAGInstrs;
class SMDiagnostic;
class SMRange;
class Target;
class TargetIRAnalysis;
class TargetTransformInfo;
class TargetLoweringObjectFile;
class TargetPassConfig;
class TargetSubtargetInfo;
 
// The old pass manager infrastructure is hidden in a legacy namespace now.
namespace legacy {
class PassManagerBase;
} // namespace legacy
using legacy::PassManagerBase;
 
struct MachineFunctionInfo;
namespace yaml {
struct MachineFunctionInfo;
} // namespace yaml
 
//===----------------------------------------------------------------------===//
///
/// Primary interface to the complete machine description for the target
/// machine.  All target-specific information should be accessible through this
/// interface.
///
class LLVM_ABI TargetMachine {
protected: // Can only create subclasses.
  TargetMachine(const Target &T, StringRef DataLayoutString,
                const Triple &TargetTriple, StringRef CPU, StringRef FS,
                const TargetOptions &Options);
 
  /// The Target that this machine was created for.
  const Target &TheTarget;
 
  /// DataLayout for the target: keep ABI type size and alignment.
  ///
  /// The DataLayout is created based on the string representation provided
  /// during construction. It is kept here only to avoid reparsing the string
  /// but should not really be used during compilation, because it has an
  /// internal cache that is context specific.
  const DataLayout DL;
 
  /// Triple string, CPU name, and target feature strings the TargetMachine
  /// instance is created with.
  Triple TargetTriple;
  std::string TargetCPU;
  std::string TargetFS;
 
  Reloc::Model RM = Reloc::Static;
  CodeModel::Model CMModel = CodeModel::Small;
  uint64_t LargeDataThreshold = 0;
  CodeGenOptLevel OptLevel = CodeGenOptLevel::Default;
 
  /// Contains target specific asm information.
  std::unique_ptr<const MCAsmInfo> AsmInfo;
  std::unique_ptr<const MCRegisterInfo> MRI;
  std::unique_ptr<const MCInstrInfo> MII;
  std::unique_ptr<const MCSubtargetInfo> STI;
 
  /// MC subtarget keyed by target features and target CPU.
  StringMap<std::unique_ptr<const MCSubtargetInfo>> MCSubtargetMap;
 
  /// Bit N is set if the target can lower exceptions using model N.
  unsigned SupportedExceptionModels = 0;
 
  unsigned RequireStructuredCFG : 1;
  unsigned O0WantsFastISel : 1;
  unsigned EnableTiedFastRegAlloc : 1;
 
  /// Set if the target supports default outlining behaviour.
  unsigned SupportsDefaultOutlining : 1;
 
  /// Set if the target supports the debug entry values by default.
  unsigned SupportsDebugEntryValues : 1;
 
  // PGO related tunables.
  std::optional<PGOOptions> PGOOption;
 
public:
  TargetOptions Options;
 
  TargetMachine(const TargetMachine &) = delete;
  void operator=(const TargetMachine &) = delete;
  virtual ~TargetMachine();
 
  const Target &getTarget() const { return TheTarget; }
 
  const Triple &getTargetTriple() const { return TargetTriple; }
  StringRef getTargetCPU() const { return TargetCPU; }
  StringRef getTargetFeatureString() const { return TargetFS; }
  void setTargetFeatureString(StringRef FS) { TargetFS = std::string(FS); }
 
  /// Returns the effective target ABI name: the "target-abi" module flag if
  /// present, otherwise the -target-abi option. This is a pure query; call
  /// verifyOptionsConsistency once per module to diagnose a conflict.
  StringRef getTargetABIName(const Module &M) const;
 
  /// Diagnoses command-line codegen options that conflict with the
  /// corresponding module flags (e.g. -target-abi vs the "target-abi" module
  /// flag). Intended to be called once per module.
  void verifyOptionsConsistency(const Module &M) const;
 
  /// Virtual method implemented by subclasses that returns a reference to that
  /// target's TargetSubtargetInfo-derived member variable.
  virtual const TargetSubtargetInfo *getSubtargetImpl(const Function &) const {
    return nullptr;
  }
  virtual TargetLoweringObjectFile *getObjFileLowering() const {
    return nullptr;
  }
 
  /// Create the target's instance of MachineFunctionInfo
  virtual MachineFunctionInfo *
  createMachineFunctionInfo(BumpPtrAllocator &Allocator, const Function &F,
                            const TargetSubtargetInfo *STI) const {
    return nullptr;
  }
 
  /// Create an instance of ScheduleDAGInstrs to be run within the standard
  /// MachineScheduler pass for this function and target at the current
  /// optimization level.
  ///
  /// This can also be used to plug a new MachineSchedStrategy into an instance
  /// of the standard ScheduleDAGMI:
  ///   return new ScheduleDAGMI(C, std::make_unique<MyStrategy>(C),
  ///   /*RemoveKillFlags=*/false)
  ///
  /// Return NULL to select the default (generic) machine scheduler.
  virtual ScheduleDAGInstrs *
  createMachineScheduler(MachineSchedContext *C) const {
    return nullptr;
  }
 
  /// Similar to createMachineScheduler but used when postRA machine scheduling
  /// is enabled.
  virtual ScheduleDAGInstrs *
  createPostMachineScheduler(MachineSchedContext *C) const {
    return nullptr;
  }
 
  /// GlobalISel CSEConfig for the new PM. Return NULL for the standard one.
  virtual CSEConfigBase *createCSEConfig() const { return nullptr; }
 
  /// Allocate and return a default initialized instance of the YAML
  /// representation for the MachineFunctionInfo.
  virtual yaml::MachineFunctionInfo *createDefaultFuncInfoYAML() const {
    return nullptr;
  }
 
  /// Allocate and initialize an instance of the YAML representation of the
  /// MachineFunctionInfo.
  virtual yaml::MachineFunctionInfo *
  convertFuncInfoToYAML(const MachineFunction &MF) const {
    return nullptr;
  }
 
  /// Parse out the target's MachineFunctionInfo from the YAML reprsentation.
  virtual bool parseMachineFunctionInfo(const yaml::MachineFunctionInfo &,
                                        PerFunctionMIParsingState &PFS,
                                        SMDiagnostic &Error,
                                        SMRange &SourceRange) const {
    return false;
  }
 
  /// This method returns a pointer to the specified type of
  /// TargetSubtargetInfo.  In debug builds, it verifies that the object being
  /// returned is of the correct type.
  template <typename STC> const STC &getSubtarget(const Function &F) const {
    return *static_cast<const STC*>(getSubtargetImpl(F));
  }
 
  /// Create a DataLayout.
  const DataLayout createDataLayout() const { return DL; }
 
  /// Test if a DataLayout if compatible with the CodeGen for this target.
  ///
  /// The LLVM Module owns a DataLayout that is used for the target independent
  /// optimizations and code generation. This hook provides a target specific
  /// check on the validity of this DataLayout.
  bool isCompatibleDataLayout(const DataLayout &Candidate) const {
    return DL == Candidate;
  }
 
  /// Get the pointer size for this target.
  ///
  /// This is the only time the DataLayout in the TargetMachine is used.
  unsigned getPointerSize(unsigned AS) const {
    return DL.getPointerSize(AS);
  }
 
  unsigned getPointerSizeInBits(unsigned AS) const {
    return DL.getPointerSizeInBits(AS);
  }
 
  unsigned getProgramPointerSize() const {
    return DL.getPointerSize(DL.getProgramAddressSpace());
  }
 
  unsigned getAllocaPointerSize() const {
    return DL.getPointerSize(DL.getAllocaAddrSpace());
  }
 
  /// Return target specific asm information.
  const MCAsmInfo &getMCAsmInfo() const { return *AsmInfo; }
 
  const MCRegisterInfo &getMCRegisterInfo() const { return *MRI; }
  const MCInstrInfo *getMCInstrInfo() const { return MII.get(); }
  const MCSubtargetInfo &getMCSubtargetInfo() const { return *STI; }
 
  /// Get the MCSubtargetInfo for the given target CPU and target features.
  /// For use in contexts where a feature-specific MC subtarget is needed,
  /// but no MachineFunctionis available, such as for module-level inline
  /// assembly.
  const MCSubtargetInfo &getMCSubtargetInfo(StringRef CPU, StringRef FS);
 
  bool requiresStructuredCFG() const { return RequireStructuredCFG; }
  void setRequiresStructuredCFG(bool Value) { RequireStructuredCFG = Value; }
 
  /// Return true if this target can lower exceptions using \p Model. Used to
  /// guard scheduling of the exception-handling preparation passes.
  bool supportsExceptionModel(ExceptionHandling Model) const {
    assert(Model != ExceptionHandling::None && "none is trivially supported");
    return SupportedExceptionModels & (1u << static_cast<unsigned>(Model));
  }
 
  /// Override whether this target can lower exceptions using \p Model. The
  /// default is derived from the object format and architecture.
  void setSupportsExceptionModel(ExceptionHandling Model, bool Value = true) {
    unsigned Bit = 1u << static_cast<unsigned>(Model);
    SupportedExceptionModels = Value ? SupportedExceptionModels | Bit
                                     : SupportedExceptionModels & ~Bit;
  }
 
  bool supportsDefaultOutlining() const { return SupportsDefaultOutlining; }
  void setSupportsDefaultOutlining(bool Enable) {
    SupportsDefaultOutlining = Enable;
  }
 
  /// NOTE: There are targets that still do not support the debug entry values
  /// production.
  bool shouldEmitDebugEntryValues() const;
 
  /// Whether the fast register allocator lowers tied operands itself instead
  /// of running TwoAddressInstructionPass. AMDGPU anchors passes on
  /// TwoAddressInstructionPassID and cannot enable it.
  bool enableTiedFastRegAlloc() const { return EnableTiedFastRegAlloc; }
  void setEnableTiedFastRegAlloc(bool Value) { EnableTiedFastRegAlloc = Value; }
 
  /// Returns the code generation relocation model. The choices are static, PIC,
  /// and dynamic-no-pic, and target default.
  Reloc::Model getRelocationModel() const;
 
  /// Returns the code model. The choices are small, kernel, medium, large, and
  /// target default.
  CodeModel::Model getCodeModel() const { return CMModel; }
 
  /// Returns the maximum code size possible under the code model.
  uint64_t getMaxCodeSize() const;
 
  /// Set the code model.
  void setCodeModel(CodeModel::Model CM) { CMModel = CM; }
 
  void setLargeDataThreshold(uint64_t LDT) { LargeDataThreshold = LDT; }
  bool isLargeGlobalValue(const GlobalValue *GV) const;
  bool isLargeDataSize(uint64_t Size) const;
 
  bool isPositionIndependent() const;
 
  bool shouldAssumeDSOLocal(const GlobalValue *GV) const;
 
  /// Returns true if this target uses emulated TLS.
  bool useEmulatedTLS() const;
 
  /// Returns true if this target uses TLS Descriptors.
  bool useTLSDESC() const;
 
  /// Returns the TLS model which should be used for the given global variable.
  TLSModel::Model getTLSModel(const GlobalValue *GV) const;
 
  /// Returns the optimization level: None, Less, Default, or Aggressive.
  CodeGenOptLevel getOptLevel() const { return OptLevel; }
 
  /// Overrides the optimization level.
  void setOptLevel(CodeGenOptLevel Level) { OptLevel = Level; }
 
  void setFastISel(bool Enable) { Options.EnableFastISel = Enable; }
  bool getO0WantsFastISel() { return O0WantsFastISel; }
  void setO0WantsFastISel(bool Enable) { O0WantsFastISel = Enable; }
  void setGlobalISel(bool Enable) { Options.EnableGlobalISel = Enable; }
  void setGlobalISelAbort(GlobalISelAbortMode Mode) {
    Options.GlobalISelAbort = Mode;
  }
  void setMachineOutliner(bool Enable) {
    Options.EnableMachineOutliner = Enable;
  }
  void setSupportsDebugEntryValues(bool Enable) {
    SupportsDebugEntryValues = Enable;
  }
  void setEnableDefaultMachineVerifier(bool Enable) {
    Options.EnableDefaultMachineVerifier = Enable;
  }
 
  void setCFIFixup(bool Enable) { Options.EnableCFIFixup = Enable; }
 
  bool getUniqueSectionNames() const { return Options.UniqueSectionNames; }
 
  /// Return true if unique basic block section names must be generated.
  bool getUniqueBasicBlockSectionNames() const {
    return Options.UniqueBasicBlockSectionNames;
  }
 
  bool getSeparateNamedSections() const {
    return Options.SeparateNamedSections;
  }
 
  /// Return true if data objects should be emitted into their own section,
  /// corresponds to -fdata-sections.
  bool getDataSections() const {
    return Options.DataSections;
  }
 
  /// Return true if functions should be emitted into their own section,
  /// corresponding to -ffunction-sections.
  bool getFunctionSections() const {
    return Options.FunctionSections;
  }
 
  bool getEnableStaticDataPartitioning() const {
    return Options.EnableStaticDataPartitioning;
  }
 
  /// Return true if visibility attribute should not be emitted in XCOFF,
  /// corresponding to -mignore-xcoff-visibility.
  bool getIgnoreXCOFFVisibility() const {
    return Options.IgnoreXCOFFVisibility;
  }
 
  /// Return true if XCOFF traceback table should be emitted,
  /// corresponding to -xcoff-traceback-table.
  bool getXCOFFTracebackTable() const { return Options.XCOFFTracebackTable; }
 
  /// If basic blocks should be emitted into their own section,
  /// corresponding to -fbasic-block-sections.
  llvm::BasicBlockSection getBBSectionsType() const {
    return Options.BBSections;
  }
 
  /// Get the list of functions and basic block ids that need unique sections.
  const MemoryBuffer *getBBSectionsFuncListBuf() const {
    return Options.BBSectionsFuncListBuf.get();
  }
 
  /// Returns true if a cast between SrcAS and DestAS is a noop.
  virtual bool isNoopAddrSpaceCast(const DataLayout &DL, unsigned SrcAS,
                                   unsigned DestAS) const {
    return false;
  }
 
  void setPGOOption(std::optional<PGOOptions> PGOOpt) { PGOOption = PGOOpt; }
  const std::optional<PGOOptions> &getPGOOption() const { return PGOOption; }
 
  /// If the specified generic pointer could be assumed as a pointer to a
  /// specific address space, return that address space.
  ///
  /// Under offloading programming, the offloading target may be passed with
  /// values only prepared on the host side and could assume certain
  /// properties.
  virtual unsigned getAssumedAddrSpace(const Value *V) const { return -1; }
 
  /// If the specified predicate checks whether a generic pointer falls within
  /// a specified address space, return that generic pointer and the address
  /// space being queried.
  ///
  /// Such predicates could be specified in @llvm.assume intrinsics for the
  /// optimizer to assume that the given generic pointer always falls within
  /// the address space based on that predicate.
  virtual std::pair<const Value *, unsigned>
  getPredicatedAddrSpace(const Value *V) const {
    return std::make_pair(nullptr, -1);
  }
 
  /// Get a \c TargetIRAnalysis appropriate for the target.
  ///
  /// This is used to construct the new pass manager's target IR analysis pass,
  /// set up appropriately for this target machine. Even the old pass manager
  /// uses this to answer queries about the IR.
  TargetIRAnalysis getTargetIRAnalysis() const;
 
  /// Return a TargetTransformInfo for a given function.
  ///
  /// The returned TargetTransformInfo is specialized to the subtarget
  /// corresponding to \p F.
  virtual TargetTransformInfo getTargetTransformInfo(const Function &F) const;
 
  /// Allow the target to modify the pass pipeline.
  // TODO: Populate all pass names by using <Target>PassRegistry.def.
  virtual void registerPassBuilderCallbacks(PassBuilder &) {}
 
  /// Allow the target to register early alias analyses (AA before BasicAA) with
  /// the AAManager for use with the new pass manager. Only affects the
  /// "default" AAManager.
  virtual void registerEarlyDefaultAliasAnalyses(AAManager &) {}
 
  /// Allow the target to register alias analyses with the AAManager for use
  /// with the new pass manager. Only affects the "default" AAManager.
  virtual void registerDefaultAliasAnalyses(AAManager &) {}
 
  /// Add passes to the specified pass manager to get the specified file
  /// emitted.  Typically this will involve several steps of code generation.
  /// This method should return true if emission of this file type is not
  /// supported, or false on success.
  /// \p MMIWP is an optional parameter that, if set to non-nullptr,
  /// will be used to set the MachineModuloInfo for this PM.
  virtual bool
  addPassesToEmitFile(PassManagerBase &, raw_pwrite_stream &,
                      raw_pwrite_stream *, CodeGenFileType,
                      bool /*DisableVerify*/ = true,
                      MachineModuleInfoWrapperPass *MMIWP = nullptr) {
    return true;
  }
 
  /// Add passes to the specified pass manager to get machine code emitted with
  /// the MCJIT. This method returns true if machine code is not supported. It
  /// fills the MCContext Ctx pointer which can be used to build custom
  /// MCStreamer.
  ///
  virtual bool addPassesToEmitMC(PassManagerBase &, MCContext *&,
                                 raw_pwrite_stream &,
                                 bool /*DisableVerify*/ = true) {
    return true;
  }
 
  /// True if subtarget inserts the final scheduling pass on its own.
  ///
  /// Branch relaxation, which must happen after block placement, can
  /// on some targets (e.g. SystemZ) expose additional post-RA
  /// scheduling opportunities.
  virtual bool targetSchedulesPostRAScheduling() const { return false; };
 
  void getNameWithPrefix(SmallVectorImpl<char> &Name, const GlobalValue *GV,
                         Mangler &Mang, bool MayAlwaysUsePrivate = false) const;
  MCSymbol *getSymbol(const GlobalValue *GV) const;
 
  /// getAddressSpaceForPseudoSourceKind - Given the kind of memory
  /// (e.g. stack) the target returns the corresponding address space.
  virtual unsigned getAddressSpaceForPseudoSourceKind(unsigned Kind) const {
    return 0;
  }
 
  /// Entry point for module splitting. Targets can implement custom module
  /// splitting logic, mainly used by LTO for --lto-partitions.
  ///
  /// On success, this guarantees that between 1 and \p NumParts modules were
  /// created and passed to \p ModuleCallBack.
  ///
  /// \returns `true` if the module was split, `false` otherwise. When  `false`
  /// is returned, it is assumed that \p ModuleCallback has never been called
  /// and \p M has not been modified.
  virtual bool splitModule(
      Module &M, unsigned NumParts,
      function_ref<void(std::unique_ptr<Module> MPart)> ModuleCallback) {
    return false;
  }
 
  /// Create a pass configuration object to be used by addPassToEmitX methods
  /// for generating a pipeline of CodeGen passes.
  virtual TargetPassConfig *createPassConfig(PassManagerBase &PM) {
    return nullptr;
  }
 
  virtual Error
  buildCodeGenPipeline(ModulePassManager &MPM, ModuleAnalysisManager &MAM,
                       raw_pwrite_stream &Out, raw_pwrite_stream *DwoOut,
                       CodeGenFileType FileType, const CGPassBuilderOption &Opt,
                       MCContext &Ctx, PassInstrumentationCallbacks *PIC) {
    return make_error<StringError>("buildCodeGenPipeline is not overridden",
                                   inconvertibleErrorCode());
  }
 
  /// Returns true if frontends should default to using the NewPM for this
  /// specific target.
  virtual bool shouldDefaultToNewPM() const { return false; }
 
  /// Returns true if the target is expected to pass all machine verifier
  /// checks. This is a stopgap measure to fix targets one by one. We will
  /// remove this at some point and always enable the verifier when
  /// EXPENSIVE_CHECKS is enabled.
  virtual bool isMachineVerifierClean() const { return true; }
 
  /// Adds an AsmPrinter pass to the pipeline that prints assembly or
  /// machine code from the MI representation.
  virtual bool addAsmPrinter(PassManagerBase &PM, raw_pwrite_stream &Out,
                             raw_pwrite_stream *DwoOut,
                             CodeGenFileType FileType, MCContext &Context) {
    return false;
  }
 
  virtual Expected<std::unique_ptr<MCStreamer>>
  createMCStreamer(raw_pwrite_stream &Out, raw_pwrite_stream *DwoOut,
                   CodeGenFileType FileType, MCContext &Ctx);
 
  /// True if the target uses physical regs (as nearly all targets do). False
  /// for stack machines such as WebAssembly and other virtual-register
  /// machines. If true, all vregs must be allocated before PEI. If false, then
  /// callee-save register spilling and scavenging are not needed or used. If
  /// false, implicitly defined registers will still be assumed to be physical
  /// registers, except that variadic defs will be allocated vregs.
  virtual bool usesPhysRegsForValues() const { return true; }
 
  /// True if the target wants to use interprocedural register allocation by
  /// default. The -enable-ipra flag can be used to override this.
  virtual bool useIPRA() const { return false; }
 
  /// The default variant to use in unqualified `asm` instructions.
  /// If this returns 0, `asm "$(foo$|bar$)"` will evaluate to `asm "foo"`.
  virtual int unqualifiedInlineAsmVariant() const { return 0; }
 
  // MachineRegisterInfo callback function
  virtual void registerMachineRegisterInfoCallback(MachineFunction &MF) const {}
 
  /// Remove all Linker Optimization Hints (LOH) associated with instructions in
  /// \p MIs and \return the number of hints removed. This is useful in
  /// transformations that cause these hints to be illegal, like in the machine
  /// outliner.
  virtual size_t clearLinkerOptimizationHints(
      const SmallPtrSetImpl<MachineInstr *> &MIs) const {
    return 0;
  }
 
  /// Returns whether the backend can lower the llvm.cond.loop intrinsic. If
  /// this function returns false, the intrinsic will be supported generically
  /// but without loop detection support.
  virtual bool canLowerCondLoop() const { return false; }
};
 
} // end namespace llvm
 
#endif // LLVM_TARGET_TARGETMACHINE_H