TargetOptions.h

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//===-- llvm/Target/TargetOptions.h - Target Options ------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines command line option flags that are shared across various
// targets.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TARGET_TARGETOPTIONS_H
#define LLVM_TARGET_TARGETOPTIONS_H

#include "llvm/MC/MCTargetOptions.h"

namespace llvm {
  class MachineFunction;
  class Module;

  namespace FloatABI {
    enum ABIType {
      Default, // Target-specific (either soft or hard depending on triple, etc).
      Soft,    // Soft float.
      Hard     // Hard float.
    };
  }

  namespace FPOpFusion {
    enum FPOpFusionMode {
      Fast,     // Enable fusion of FP ops wherever it's profitable.
      Standard, // Only allow fusion of 'blessed' ops (currently just fmuladd).
      Strict    // Never fuse FP-ops.
    };
  }

  namespace JumpTable {
    enum JumpTableType {
      Single,          // Use a single table for all indirect jumptable calls.
      Arity,           // Use one table per number of function parameters.
      Simplified,      // Use one table per function type, with types projected
                       // into 4 types: pointer to non-function, struct,
                       // primitive, and function pointer.
      Full             // Use one table per unique function type
    };
  }

  namespace ThreadModel {
    enum Model {
      POSIX,  // POSIX Threads
      Single  // Single Threaded Environment
    };
  }

  namespace FPDenormal {
    enum DenormalMode {
      IEEE,           // IEEE 754 denormal numbers
      PreserveSign,   // the sign of a flushed-to-zero number is preserved in
                      // the sign of 0
      PositiveZero    // denormals are flushed to positive zero
    };
  }

  enum class EABI {
    Unknown,
    Default, // Default means not specified
    EABI4,   // Target-specific (either 4, 5 or gnu depending on triple).
    EABI5,
    GNU
  };

  /// Identify a debugger for "tuning" the debug info.
  ///
  /// The "debugger tuning" concept allows us to present a more intuitive
  /// interface that unpacks into different sets of defaults for the various
  /// individual feature-flag settings, that suit the preferences of the
  /// various debuggers.  However, it's worth remembering that debuggers are
  /// not the only consumers of debug info, and some variations in DWARF might
  /// better be treated as target/platform issues. Fundamentally,
  /// o if the feature is useful (or not) to a particular debugger, regardless
  ///   of the target, that's a tuning decision;
  /// o if the feature is useful (or not) on a particular platform, regardless
  ///   of the debugger, that's a target decision.
  /// It's not impossible to see both factors in some specific case.
  ///
  /// The "tuning" should be used to set defaults for individual feature flags
  /// in DwarfDebug; if a given feature has a more specific command-line option,
  /// that option should take precedence over the tuning.
  enum class DebuggerKind {
    Default,  // No specific tuning requested.
    GDB,      // Tune debug info for gdb.
    LLDB,     // Tune debug info for lldb.
    SCE       // Tune debug info for SCE targets (e.g. PS4).
  };

  /// Enable abort calls when global instruction selection fails to lower/select
  /// an instruction.
  enum class GlobalISelAbortMode {
    Disable,        // Disable the abort.
    Enable,         // Enable the abort.
    DisableWithDiag // Disable the abort but emit a diagnostic on failure.
  };

  class TargetOptions {
  public:
    TargetOptions()
        : PrintMachineCode(false), UnsafeFPMath(false), NoInfsFPMath(false),
          NoNaNsFPMath(false), NoTrappingFPMath(false),
          NoSignedZerosFPMath(false),
          HonorSignDependentRoundingFPMathOption(false), NoZerosInBSS(false),
          GuaranteedTailCallOpt(false), StackSymbolOrdering(true),
          EnableFastISel(false), EnableGlobalISel(false), UseInitArray(false),
          DisableIntegratedAS(false), RelaxELFRelocations(false),
          FunctionSections(false), DataSections(false),
          UniqueSectionNames(true), TrapUnreachable(false),
          NoTrapAfterNoreturn(false), EmulatedTLS(false),
          ExplicitEmulatedTLS(false), EnableIPRA(false),
          EmitStackSizeSection(false), EnableMachineOutliner(false),
          SupportsDefaultOutlining(false), EmitAddrsig(false) {}

    /// PrintMachineCode - This flag is enabled when the -print-machineinstrs
    /// option is specified on the command line, and should enable debugging
    /// output from the code generator.
    unsigned PrintMachineCode : 1;

    /// DisableFramePointerElim - This returns true if frame pointer elimination
    /// optimization should be disabled for the given machine function.
    bool DisableFramePointerElim(const MachineFunction &MF) const;

    /// UnsafeFPMath - This flag is enabled when the
    /// -enable-unsafe-fp-math flag is specified on the command line.  When
    /// this flag is off (the default), the code generator is not allowed to
    /// produce results that are "less precise" than IEEE allows.  This includes
    /// use of X86 instructions like FSIN and FCOS instead of libcalls.
    unsigned UnsafeFPMath : 1;

    /// NoInfsFPMath - This flag is enabled when the
    /// -enable-no-infs-fp-math flag is specified on the command line. When
    /// this flag is off (the default), the code generator is not allowed to
    /// assume the FP arithmetic arguments and results are never +-Infs.
    unsigned NoInfsFPMath : 1;

    /// NoNaNsFPMath - This flag is enabled when the
    /// -enable-no-nans-fp-math flag is specified on the command line. When
    /// this flag is off (the default), the code generator is not allowed to
    /// assume the FP arithmetic arguments and results are never NaNs.
    unsigned NoNaNsFPMath : 1;

    /// NoTrappingFPMath - This flag is enabled when the
    /// -enable-no-trapping-fp-math is specified on the command line. This
    /// specifies that there are no trap handlers to handle exceptions.
    unsigned NoTrappingFPMath : 1;

    /// NoSignedZerosFPMath - This flag is enabled when the
    /// -enable-no-signed-zeros-fp-math is specified on the command line. This
    /// specifies that optimizations are allowed to treat the sign of a zero
    /// argument or result as insignificant.
    unsigned NoSignedZerosFPMath : 1;

    /// HonorSignDependentRoundingFPMath - This returns true when the
    /// -enable-sign-dependent-rounding-fp-math is specified.  If this returns
    /// false (the default), the code generator is allowed to assume that the
    /// rounding behavior is the default (round-to-zero for all floating point
    /// to integer conversions, and round-to-nearest for all other arithmetic
    /// truncations).  If this is enabled (set to true), the code generator must
    /// assume that the rounding mode may dynamically change.
    unsigned HonorSignDependentRoundingFPMathOption : 1;
    bool HonorSignDependentRoundingFPMath() const;

    /// NoZerosInBSS - By default some codegens place zero-initialized data to
    /// .bss section. This flag disables such behaviour (necessary, e.g. for
    /// crt*.o compiling).
    unsigned NoZerosInBSS : 1;

    /// GuaranteedTailCallOpt - This flag is enabled when -tailcallopt is
    /// specified on the commandline. When the flag is on, participating targets
    /// will perform tail call optimization on all calls which use the fastcc
    /// calling convention and which satisfy certain target-independent
    /// criteria (being at the end of a function, having the same return type
    /// as their parent function, etc.), using an alternate ABI if necessary.
    unsigned GuaranteedTailCallOpt : 1;

    /// StackAlignmentOverride - Override default stack alignment for target.
    unsigned StackAlignmentOverride = 0;

    /// StackSymbolOrdering - When true, this will allow CodeGen to order
    /// the local stack symbols (for code size, code locality, or any other
    /// heuristics). When false, the local symbols are left in whatever order
    /// they were generated. Default is true.
    unsigned StackSymbolOrdering : 1;

    /// EnableFastISel - This flag enables fast-path instruction selection
    /// which trades away generated code quality in favor of reducing
    /// compile time.
    unsigned EnableFastISel : 1;

    /// EnableGlobalISel - This flag enables global instruction selection.
    unsigned EnableGlobalISel : 1;

    /// EnableGlobalISelAbort - Control abort behaviour when global instruction
    /// selection fails to lower/select an instruction.
    GlobalISelAbortMode GlobalISelAbort = GlobalISelAbortMode::Enable;

    /// UseInitArray - Use .init_array instead of .ctors for static
    /// constructors.
    unsigned UseInitArray : 1;

    /// Disable the integrated assembler.
    unsigned DisableIntegratedAS : 1;

    /// Compress DWARF debug sections.
    DebugCompressionType CompressDebugSections = DebugCompressionType::None;

    unsigned RelaxELFRelocations : 1;

    /// Emit functions into separate sections.
    unsigned FunctionSections : 1;

    /// Emit data into separate sections.
    unsigned DataSections : 1;

    unsigned UniqueSectionNames : 1;

    /// Emit target-specific trap instruction for 'unreachable' IR instructions.
    unsigned TrapUnreachable : 1;

    /// Do not emit a trap instruction for 'unreachable' IR instructions behind
    /// noreturn calls, even if TrapUnreachable is true.
    unsigned NoTrapAfterNoreturn : 1;

    /// EmulatedTLS - This flag enables emulated TLS model, using emutls
    /// function in the runtime library..
    unsigned EmulatedTLS : 1;

    /// Whether -emulated-tls or -no-emulated-tls is set.
    unsigned ExplicitEmulatedTLS : 1;

    /// This flag enables InterProcedural Register Allocation (IPRA).
    unsigned EnableIPRA : 1;

    /// Emit section containing metadata on function stack sizes.
    unsigned EmitStackSizeSection : 1;

    /// Enables the MachineOutliner pass.
    unsigned EnableMachineOutliner : 1;

    /// Set if the target supports default outlining behaviour.
    unsigned SupportsDefaultOutlining : 1;

    /// Emit address-significance table.
    unsigned EmitAddrsig : 1;

    /// FloatABIType - This setting is set by -float-abi=xxx option is specfied
    /// on the command line. This setting may either be Default, Soft, or Hard.
    /// Default selects the target's default behavior. Soft selects the ABI for
    /// software floating point, but does not indicate that FP hardware may not
    /// be used. Such a combination is unfortunately popular (e.g.
    /// arm-apple-darwin). Hard presumes that the normal FP ABI is used.
    FloatABI::ABIType FloatABIType = FloatABI::Default;

    /// AllowFPOpFusion - This flag is set by the -fuse-fp-ops=xxx option.
    /// This controls the creation of fused FP ops that store intermediate
    /// results in higher precision than IEEE allows (E.g. FMAs).
    ///
    /// Fast mode - allows formation of fused FP ops whenever they're
    /// profitable.
    /// Standard mode - allow fusion only for 'blessed' FP ops. At present the
    /// only blessed op is the fmuladd intrinsic. In the future more blessed ops
    /// may be added.
    /// Strict mode - allow fusion only if/when it can be proven that the excess
    /// precision won't effect the result.
    ///
    /// Note: This option only controls formation of fused ops by the
    /// optimizers.  Fused operations that are explicitly specified (e.g. FMA
    /// via the llvm.fma.* intrinsic) will always be honored, regardless of
    /// the value of this option.
    FPOpFusion::FPOpFusionMode AllowFPOpFusion = FPOpFusion::Standard;

    /// ThreadModel - This flag specifies the type of threading model to assume
    /// for things like atomics
    ThreadModel::Model ThreadModel = ThreadModel::POSIX;

    /// EABIVersion - This flag specifies the EABI version
    EABI EABIVersion = EABI::Default;

    /// Which debugger to tune for.
    DebuggerKind DebuggerTuning = DebuggerKind::Default;

    /// FPDenormalMode - This flags specificies which denormal numbers the code
    /// is permitted to require.
    FPDenormal::DenormalMode FPDenormalMode = FPDenormal::IEEE;

    /// What exception model to use
    ExceptionHandling ExceptionModel = ExceptionHandling::None;

    /// Machine level options.
    MCTargetOptions MCOptions;
  };

} // End llvm namespace

#endif