llvm/lib/Target/AMDGPU/SIModeRegisterDefaults.h

//===-- SIModeRegisterDefaults.h --------------------------------*- 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_TARGET_AMDGPU_SIMODEREGISTERDEFAULTS_H
#define LLVM_LIB_TARGET_AMDGPU_SIMODEREGISTERDEFAULTS_H

#include "Utils/AMDGPUBaseInfo.h"
#include "llvm/ADT/FloatingPointMode.h"

namespace llvm {

class GCNSubtarget;

// Track defaults for fields in the MODE register.
struct SIModeRegisterDefaults {
  /// Floating point opcodes that support exception flag gathering quiet and
  /// propagate signaling NaN inputs per IEEE 754-2008. Min_dx10 and max_dx10
  /// become IEEE 754- 2008 compliant due to signaling NaN propagation and
  /// quieting.
  bool IEEE : 1;

  /// Used by the vector ALU to force DX10-style treatment of NaNs: when set,
  /// clamp NaN to zero; otherwise, pass NaN through.
  bool DX10Clamp : 1;

  /// If this is set, neither input or output denormals are flushed for most f32
  /// instructions.
  DenormalMode FP32Denormals;

  /// If this is set, neither input or output denormals are flushed for both f64
  /// and f16/v2f16 instructions.
  DenormalMode FP64FP16Denormals;

  SIModeRegisterDefaults() :
    IEEE(true),
    DX10Clamp(true),
    FP32Denormals(DenormalMode::getIEEE()),
    FP64FP16Denormals(DenormalMode::getIEEE()) {}

  SIModeRegisterDefaults(const Function &F, const GCNSubtarget &ST);

  static SIModeRegisterDefaults getDefaultForCallingConv(CallingConv::ID CC) {
    SIModeRegisterDefaults Mode;
    Mode.IEEE = !AMDGPU::isShader(CC);
    return Mode;
  }

  bool operator==(const SIModeRegisterDefaults Other) const {
    return IEEE == Other.IEEE && DX10Clamp == Other.DX10Clamp &&
           FP32Denormals == Other.FP32Denormals &&
           FP64FP16Denormals == Other.FP64FP16Denormals;
  }

  /// Get the denormal handling described by this mode.
  DenormalFPEnv getDenormalFPEnv() const {
    return DenormalFPEnv(FP64FP16Denormals, FP32Denormals);
  }

  /// Get the encoding value for the FP_DENORM bits of the mode register for the
  /// FP32 denormal mode.
  uint32_t fpDenormModeSPValue() const {
    if (FP32Denormals == DenormalMode::getPreserveSign())
      return FP_DENORM_FLUSH_IN_FLUSH_OUT;
    if (FP32Denormals.Output == DenormalMode::PreserveSign)
      return FP_DENORM_FLUSH_OUT;
    if (FP32Denormals.Input == DenormalMode::PreserveSign)
      return FP_DENORM_FLUSH_IN;
    return FP_DENORM_FLUSH_NONE;
  }

  /// Get the encoding value for the FP_DENORM bits of the mode register for the
  /// FP64/FP16 denormal mode.
  uint32_t fpDenormModeDPValue() const {
    if (FP64FP16Denormals == DenormalMode::getPreserveSign())
      return FP_DENORM_FLUSH_IN_FLUSH_OUT;
    if (FP64FP16Denormals.Output == DenormalMode::PreserveSign)
      return FP_DENORM_FLUSH_OUT;
    if (FP64FP16Denormals.Input == DenormalMode::PreserveSign)
      return FP_DENORM_FLUSH_IN;
    return FP_DENORM_FLUSH_NONE;
  }

  // FIXME: Inlining should be OK for dx10-clamp, since the caller's mode should
  // be able to override.
  bool isInlineCompatible(SIModeRegisterDefaults CalleeMode) const {
    return DX10Clamp == CalleeMode.DX10Clamp && IEEE == CalleeMode.IEEE;
  }
};

namespace AMDGPU {

/// Return values used for llvm.get.rounding
///
/// When both the F32 and F64/F16 modes are the same, returns the standard
/// values. If they differ, returns an extended mode starting at 8.
enum AMDGPUFltRounds : int8_t {
  // Inherit everything from RoundingMode
  TowardZero = static_cast<int8_t>(RoundingMode::TowardZero),
  NearestTiesToEven = static_cast<int8_t>(RoundingMode::NearestTiesToEven),
  TowardPositive = static_cast<int8_t>(RoundingMode::TowardPositive),
  TowardNegative = static_cast<int8_t>(RoundingMode::TowardNegative),
  NearestTiesToAwayUnsupported =
      static_cast<int8_t>(RoundingMode::NearestTiesToAway),

  Dynamic = static_cast<int8_t>(RoundingMode::Dynamic),

  // Permute the mismatched rounding mode cases.  If the modes are the same, use
  // the standard values, otherwise, these values are sorted such that higher
  // hardware encoded values have higher enum values.
  NearestTiesToEvenF32_NearestTiesToEvenF64 = NearestTiesToEven,
  NearestTiesToEvenF32_TowardPositiveF64 = 8,
  NearestTiesToEvenF32_TowardNegativeF64 = 9,
  NearestTiesToEvenF32_TowardZeroF64 = 10,

  TowardPositiveF32_NearestTiesToEvenF64 = 11,
  TowardPositiveF32_TowardPositiveF64 = TowardPositive,
  TowardPositiveF32_TowardNegativeF64 = 12,
  TowardPositiveF32_TowardZeroF64 = 13,

  TowardNegativeF32_NearestTiesToEvenF64 = 14,
  TowardNegativeF32_TowardPositiveF64 = 15,
  TowardNegativeF32_TowardNegativeF64 = TowardNegative,
  TowardNegativeF32_TowardZeroF64 = 16,

  TowardZeroF32_NearestTiesToEvenF64 = 17,
  TowardZeroF32_TowardPositiveF64 = 18,
  TowardZeroF32_TowardNegativeF64 = 19,
  TowardZeroF32_TowardZeroF64 = TowardZero,

  Invalid = static_cast<int8_t>(RoundingMode::Invalid)
};

/// Offset of nonstandard values for llvm.get.rounding results from the largest
/// supported mode.
static constexpr uint32_t ExtendedFltRoundOffset = 4;

/// Offset in mode register of f32 rounding mode.
static constexpr uint32_t F32FltRoundOffset = 0;

/// Offset in mode register of f64/f16 rounding mode.
static constexpr uint32_t F64FltRoundOffset = 2;

// Bit indexed table to convert from hardware rounding mode values to FLT_ROUNDS
// values.
extern const uint64_t FltRoundConversionTable;

// Bit indexed table to convert from FLT_ROUNDS values to hardware rounding mode
// values
extern const uint64_t FltRoundToHWConversionTable;

/// Read the hardware rounding mode equivalent of a AMDGPUFltRounds value.
uint32_t decodeFltRoundToHWConversionTable(uint32_t FltRounds);

} // end namespace AMDGPU

} // end namespace llvm

#endif // LLVM_LIB_TARGET_AMDGPU_SIMODEREGISTERDEFAULTS_H