qemu/include/fpu/softfloat-types.h

/*
 * QEMU float support
 *
 * The code in this source file is derived from release 2a of the SoftFloat
 * IEC/IEEE Floating-point Arithmetic Package. Those parts of the code (and
 * some later contributions) are provided under that license, as detailed below.
 * It has subsequently been modified by contributors to the QEMU Project,
 * so some portions are provided under:
 *  the SoftFloat-2a license
 *  the BSD license
 *  GPL-v2-or-later
 *
 * This header holds definitions for code that might be dealing with
 * softfloat types but not need access to the actual library functions.
 */
/*
===============================================================================
This C header file is part of the SoftFloat IEC/IEEE Floating-point
Arithmetic Package, Release 2a.

Written by John R. Hauser.  This work was made possible in part by the
International Computer Science Institute, located at Suite 600, 1947 Center
Street, Berkeley, California 94704.  Funding was partially provided by the
National Science Foundation under grant MIP-9311980.  The original version
of this code was written as part of a project to build a fixed-point vector
processor in collaboration with the University of California at Berkeley,
overseen by Profs. Nelson Morgan and John Wawrzynek.  More information
is available through the Web page `http://HTTP.CS.Berkeley.EDU/~jhauser/
arithmetic/SoftFloat.html'.

THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE.  Although reasonable effort
has been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT
TIMES RESULT IN INCORRECT BEHAVIOR.  USE OF THIS SOFTWARE IS RESTRICTED TO
PERSONS AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ANY
AND ALL LOSSES, COSTS, OR OTHER PROBLEMS ARISING FROM ITS USE.

Derivative works are acceptable, even for commercial purposes, so long as
(1) they include prominent notice that the work is derivative, and (2) they
include prominent notice akin to these four paragraphs for those parts of
this code that are retained.

===============================================================================
*/

/* BSD licensing:
 * Copyright (c) 2006, Fabrice Bellard
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

/* Portions of this work are licensed under the terms of the GNU GPL,
 * version 2 or later. See the COPYING file in the top-level directory.
 */

#ifndef SOFTFLOAT_TYPES_H
#define SOFTFLOAT_TYPES_H

#include "hw/registerfields.h"

/*
 * Software IEC/IEEE floating-point types.
 */

typedef uint16_t float16;
typedef uint32_t float32;
typedef uint64_t float64;
#define float16_val(x) (x)
#define float32_val(x) (x)
#define float64_val(x) (x)
#define make_float16(x) (x)
#define make_float32(x) (x)
#define make_float64(x) (x)
#define const_float16(x) (x)
#define const_float32(x) (x)
#define const_float64(x) (x)
typedef struct {
    uint64_t low;
    uint16_t high;
} floatx80;
#define make_floatx80(exp, mant) ((floatx80) { mant, exp })
#define make_floatx80_init(exp, mant) { .low = mant, .high = exp }
typedef struct {
#if HOST_BIG_ENDIAN
    uint64_t high, low;
#else
    uint64_t low, high;
#endif
} float128;
#define make_float128(high_, low_) ((float128) { .high = high_, .low = low_ })
#define make_float128_init(high_, low_) { .high = high_, .low = low_ }

/*
 * Software neural-network floating-point types.
 */
typedef uint16_t bfloat16;

/*
 * Software IEC/IEEE floating-point underflow tininess-detection mode.
 */

#define float_tininess_after_rounding  false
#define float_tininess_before_rounding true

/*
 *Software IEC/IEEE floating-point rounding mode.
 */

typedef enum __attribute__((__packed__)) {
    float_round_nearest_even = 0,
    float_round_down         = 1,
    float_round_up           = 2,
    float_round_to_zero      = 3,
    float_round_ties_away    = 4,
    /* Not an IEEE rounding mode: round to closest odd, overflow to max */
    float_round_to_odd       = 5,
    /* Not an IEEE rounding mode: round to closest odd, overflow to inf */
    float_round_to_odd_inf   = 6,
    /* Not an IEEE rounding mode: round to nearest even, overflow to max */
    float_round_nearest_even_max = 7,
} FloatRoundMode;

/*
 * Software IEC/IEEE floating-point exception flags.
 */

enum {
    float_flag_invalid         = 0x0001,
    float_flag_divbyzero       = 0x0002,
    float_flag_overflow        = 0x0004,
    float_flag_underflow       = 0x0008,
    float_flag_inexact         = 0x0010,
    float_flag_input_denormal  = 0x0020,
    float_flag_output_denormal = 0x0040,
    float_flag_invalid_isi     = 0x0080,  /* inf - inf */
    float_flag_invalid_imz     = 0x0100,  /* inf * 0 */
    float_flag_invalid_idi     = 0x0200,  /* inf / inf */
    float_flag_invalid_zdz     = 0x0400,  /* 0 / 0 */
    float_flag_invalid_sqrt    = 0x0800,  /* sqrt(-x) */
    float_flag_invalid_cvti    = 0x1000,  /* non-nan to integer */
    float_flag_invalid_snan    = 0x2000,  /* any operand was snan */
};

/*
 * Rounding precision for floatx80.
 */
typedef enum __attribute__((__packed__)) {
    floatx80_precision_x,
    floatx80_precision_d,
    floatx80_precision_s,
} FloatX80RoundPrec;

/*
 * 2-input NaN propagation rule. Individual architectures have
 * different rules for which input NaN is propagated to the output
 * when there is more than one NaN on the input.
 *
 * If default_nan_mode is enabled then it is valid not to set a
 * NaN propagation rule, because the softfloat code guarantees
 * not to try to pick a NaN to propagate in default NaN mode.
 * When not in default-NaN mode, it is an error for the target
 * not to set the rule in float_status, and we will assert if
 * we need to handle an input NaN and no rule was selected.
 */
typedef enum __attribute__((__packed__)) {
    /* No propagation rule specified */
    float_2nan_prop_none = 0,
    /* Prefer SNaN over QNaN, then operand A over B */
    float_2nan_prop_s_ab,
    /* Prefer SNaN over QNaN, then operand B over A */
    float_2nan_prop_s_ba,
    /* Prefer A over B regardless of SNaN vs QNaN */
    float_2nan_prop_ab,
    /* Prefer B over A regardless of SNaN vs QNaN */
    float_2nan_prop_ba,
    /*
     * This implements x87 NaN propagation rules:
     * SNaN + QNaN => return the QNaN
     * two SNaNs => return the one with the larger significand, silenced
     * two QNaNs => return the one with the larger significand
     * SNaN and a non-NaN => return the SNaN, silenced
     * QNaN and a non-NaN => return the QNaN
     *
     * If we get down to comparing significands and they are the same,
     * return the NaN with the positive sign bit (if any).
     */
    float_2nan_prop_x87,
} Float2NaNPropRule;

/*
 * 3-input NaN propagation rule, for fused multiply-add. Individual
 * architectures have different rules for which input NaN is
 * propagated to the output when there is more than one NaN on the
 * input.
 *
 * If default_nan_mode is enabled then it is valid not to set a NaN
 * propagation rule, because the softfloat code guarantees not to try
 * to pick a NaN to propagate in default NaN mode.  When not in
 * default-NaN mode, it is an error for the target not to set the rule
 * in float_status if it uses a muladd, and we will assert if we need
 * to handle an input NaN and no rule was selected.
 *
 * The naming scheme for Float3NaNPropRule values is:
 *  float_3nan_prop_s_abc:
 *    = "Prefer SNaN over QNaN, then operand A over B over C"
 *  float_3nan_prop_abc:
 *    = "Prefer A over B over C regardless of SNaN vs QNAN"
 *
 * For QEMU, the multiply-add operation is A * B + C.
 */

/*
 * We set the Float3NaNPropRule enum values up so we can select the
 * right value in pickNaNMulAdd in a data driven way.
 */
FIELD(3NAN, 1ST, 0, 2)   /* which operand is most preferred ? */
FIELD(3NAN, 2ND, 2, 2)   /* which operand is next most preferred ? */
FIELD(3NAN, 3RD, 4, 2)   /* which operand is least preferred ? */
FIELD(3NAN, SNAN, 6, 1)  /* do we prefer SNaN over QNaN ? */

#define PROPRULE(X, Y, Z) \
    ((X << R_3NAN_1ST_SHIFT) | (Y << R_3NAN_2ND_SHIFT) | (Z << R_3NAN_3RD_SHIFT))

typedef enum __attribute__((__packed__)) {
    float_3nan_prop_none = 0,     /* No propagation rule specified */
    float_3nan_prop_abc = PROPRULE(0, 1, 2),
    float_3nan_prop_acb = PROPRULE(0, 2, 1),
    float_3nan_prop_bac = PROPRULE(1, 0, 2),
    float_3nan_prop_bca = PROPRULE(1, 2, 0),
    float_3nan_prop_cab = PROPRULE(2, 0, 1),
    float_3nan_prop_cba = PROPRULE(2, 1, 0),
    float_3nan_prop_s_abc = float_3nan_prop_abc | R_3NAN_SNAN_MASK,
    float_3nan_prop_s_acb = float_3nan_prop_acb | R_3NAN_SNAN_MASK,
    float_3nan_prop_s_bac = float_3nan_prop_bac | R_3NAN_SNAN_MASK,
    float_3nan_prop_s_bca = float_3nan_prop_bca | R_3NAN_SNAN_MASK,
    float_3nan_prop_s_cab = float_3nan_prop_cab | R_3NAN_SNAN_MASK,
    float_3nan_prop_s_cba = float_3nan_prop_cba | R_3NAN_SNAN_MASK,
} Float3NaNPropRule;

#undef PROPRULE

/*
 * Rule for result of fused multiply-add 0 * Inf + NaN.
 * This must be a NaN, but implementations differ on whether this
 * is the input NaN or the default NaN.
 *
 * You don't need to set this if default_nan_mode is enabled.
 * When not in default-NaN mode, it is an error for the target
 * not to set the rule in float_status if it uses muladd, and we
 * will assert if we need to handle an input NaN and no rule was
 * selected.
 */
typedef enum __attribute__((__packed__)) {
    /* No propagation rule specified */
    float_infzeronan_none = 0,
    /* Result is never the default NaN (so always the input NaN) */
    float_infzeronan_dnan_never,
    /* Result is always the default NaN */
    float_infzeronan_dnan_always,
    /* Result is the default NaN if the input NaN is quiet */
    float_infzeronan_dnan_if_qnan,
} FloatInfZeroNaNRule;

/*
 * Floating Point Status. Individual architectures may maintain
 * several versions of float_status for different functions. The
 * correct status for the operation is then passed by reference to
 * most of the softfloat functions.
 */

typedef struct float_status {
    uint16_t float_exception_flags;
    FloatRoundMode float_rounding_mode;
    FloatX80RoundPrec floatx80_rounding_precision;
    Float2NaNPropRule float_2nan_prop_rule;
    Float3NaNPropRule float_3nan_prop_rule;
    FloatInfZeroNaNRule float_infzeronan_rule;
    bool tininess_before_rounding;
    /* should denormalised results go to zero and set the inexact flag? */
    bool flush_to_zero;
    /* should denormalised inputs go to zero and set the input_denormal flag? */
    bool flush_inputs_to_zero;
    bool default_nan_mode;
    /*
     * The pattern to use for the default NaN. Here the high bit specifies
     * the default NaN's sign bit, and bits 6..0 specify the high bits of the
     * fractional part. The low bits of the fractional part are copies of bit 0.
     * The exponent of the default NaN is (as for any NaN) always all 1s.
     * Note that a value of 0 here is not a valid NaN. The target must set
     * this to the correct non-zero value, or we will assert when trying to
     * create a default NaN.
     */
    uint8_t default_nan_pattern;
    /*
     * The flags below are not used on all specializations and may
     * constant fold away (see snan_bit_is_one()/no_signalling_nans() in
     * softfloat-specialize.inc.c)
     */
    bool snan_bit_is_one;
    bool no_signaling_nans;
    /* should overflowed results subtract re_bias to its exponent? */
    bool rebias_overflow;
    /* should underflowed results add re_bias to its exponent? */
    bool rebias_underflow;
} float_status;

#endif /* SOFTFLOAT_TYPES_H */