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fpu/softfloat: re-factor add/sub
We can now add float16_add/sub and use the common decompose and canonicalize functions to have a single implementation for float16/32/64 add and sub functions. Backports commit 6fff216769cf7eaa3961c85dee7a72838696d365 from qemu
This commit is contained in:
Alex Bennée
Lioncash
parent
d80f1ea222
commit
b1884d0685
@ -83,7 +83,7 @@ this code that are retained.
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* target-dependent and needs the TARGET_* macros.
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*/
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#include "qemu/osdep.h"
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#include "qemu/bitops.h"
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#include "fpu/softfloat.h"
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/* We only need stdlib for abort() */
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@ -271,6 +271,470 @@ static const FloatFmt float64_params = {
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FLOAT_PARAMS(11, 52)
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};
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/* Unpack a float to parts, but do not canonicalize. */
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static inline FloatParts unpack_raw(FloatFmt fmt, uint64_t raw)
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{
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const int sign_pos = fmt.frac_size + fmt.exp_size;
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FloatParts result;
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result.cls = float_class_unclassified;
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result.sign = extract64(raw, sign_pos, 1);
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result.exp = extract64(raw, fmt.frac_size, fmt.exp_size);
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result.frac = extract64(raw, 0, fmt.frac_size);
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return result;
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}
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static inline FloatParts float16_unpack_raw(float16 f)
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{
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return unpack_raw(float16_params, f);
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}
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static inline FloatParts float32_unpack_raw(float32 f)
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{
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return unpack_raw(float32_params, f);
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}
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static inline FloatParts float64_unpack_raw(float64 f)
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{
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return unpack_raw(float64_params, f);
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}
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/* Pack a float from parts, but do not canonicalize. */
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static inline uint64_t pack_raw(FloatFmt fmt, FloatParts p)
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{
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const int sign_pos = fmt.frac_size + fmt.exp_size;
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uint64_t ret = deposit64(p.frac, fmt.frac_size, fmt.exp_size, p.exp);
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return deposit64(ret, sign_pos, 1, p.sign);
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}
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static inline float16 float16_pack_raw(FloatParts p)
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{
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return make_float16(pack_raw(float16_params, p));
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}
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static inline float32 float32_pack_raw(FloatParts p)
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{
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return make_float32(pack_raw(float32_params, p));
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}
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static inline float64 float64_pack_raw(FloatParts p)
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{
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return make_float64(pack_raw(float64_params, p));
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}
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/* Canonicalize EXP and FRAC, setting CLS. */
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static FloatParts canonicalize(FloatParts part, const FloatFmt *parm,
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float_status *status)
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{
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if (part.exp == parm->exp_max) {
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if (part.frac == 0) {
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part.cls = float_class_inf;
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} else {
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#ifdef NO_SIGNALING_NANS
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part.cls = float_class_qnan;
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#else
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int64_t msb = part.frac << (parm->frac_shift + 2);
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if ((msb < 0) == status->snan_bit_is_one) {
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part.cls = float_class_snan;
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} else {
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part.cls = float_class_qnan;
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}
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#endif
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}
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} else if (part.exp == 0) {
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if (likely(part.frac == 0)) {
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part.cls = float_class_zero;
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} else if (status->flush_inputs_to_zero) {
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float_raise(float_flag_input_denormal, status);
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part.cls = float_class_zero;
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part.frac = 0;
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} else {
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int shift = clz64(part.frac) - 1;
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part.cls = float_class_normal;
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part.exp = parm->frac_shift - parm->exp_bias - shift + 1;
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part.frac <<= shift;
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}
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} else {
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part.cls = float_class_normal;
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part.exp -= parm->exp_bias;
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part.frac = DECOMPOSED_IMPLICIT_BIT + (part.frac << parm->frac_shift);
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}
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return part;
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}
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/* Round and uncanonicalize a floating-point number by parts. There
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* are FRAC_SHIFT bits that may require rounding at the bottom of the
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* fraction; these bits will be removed. The exponent will be biased
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* by EXP_BIAS and must be bounded by [EXP_MAX-1, 0].
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*/
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static FloatParts round_canonical(FloatParts p, float_status *s,
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const FloatFmt *parm)
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{
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const uint64_t frac_lsbm1 = parm->frac_lsbm1;
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const uint64_t round_mask = parm->round_mask;
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const uint64_t roundeven_mask = parm->roundeven_mask;
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const int exp_max = parm->exp_max;
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const int frac_shift = parm->frac_shift;
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uint64_t frac, inc;
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int exp, flags = 0;
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bool overflow_norm;
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frac = p.frac;
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exp = p.exp;
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switch (p.cls) {
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case float_class_normal:
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switch (s->float_rounding_mode) {
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case float_round_nearest_even:
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overflow_norm = false;
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inc = ((frac & roundeven_mask) != frac_lsbm1 ? frac_lsbm1 : 0);
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break;
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case float_round_ties_away:
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overflow_norm = false;
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inc = frac_lsbm1;
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break;
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case float_round_to_zero:
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overflow_norm = true;
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inc = 0;
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break;
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case float_round_up:
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inc = p.sign ? 0 : round_mask;
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overflow_norm = p.sign;
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break;
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case float_round_down:
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inc = p.sign ? round_mask : 0;
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overflow_norm = !p.sign;
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break;
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default:
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g_assert_not_reached();
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}
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exp += parm->exp_bias;
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if (likely(exp > 0)) {
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if (frac & round_mask) {
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flags |= float_flag_inexact;
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frac += inc;
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if (frac & DECOMPOSED_OVERFLOW_BIT) {
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frac >>= 1;
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exp++;
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}
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}
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frac >>= frac_shift;
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if (unlikely(exp >= exp_max)) {
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flags |= float_flag_overflow | float_flag_inexact;
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if (overflow_norm) {
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exp = exp_max - 1;
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frac = -1;
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} else {
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p.cls = float_class_inf;
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goto do_inf;
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}
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}
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} else if (s->flush_to_zero) {
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flags |= float_flag_output_denormal;
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p.cls = float_class_zero;
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goto do_zero;
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} else {
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bool is_tiny = (s->float_detect_tininess
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== float_tininess_before_rounding)
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|| (exp < 0)
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|| !((frac + inc) & DECOMPOSED_OVERFLOW_BIT);
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shift64RightJamming(frac, 1 - exp, &frac);
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if (frac & round_mask) {
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/* Need to recompute round-to-even. */
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if (s->float_rounding_mode == float_round_nearest_even) {
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inc = ((frac & roundeven_mask) != frac_lsbm1
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? frac_lsbm1 : 0);
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}
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flags |= float_flag_inexact;
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frac += inc;
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}
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exp = (frac & DECOMPOSED_IMPLICIT_BIT ? 1 : 0);
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frac >>= frac_shift;
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if (is_tiny && (flags & float_flag_inexact)) {
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flags |= float_flag_underflow;
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}
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if (exp == 0 && frac == 0) {
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p.cls = float_class_zero;
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}
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}
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break;
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case float_class_zero:
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do_zero:
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exp = 0;
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frac = 0;
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break;
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case float_class_inf:
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do_inf:
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exp = exp_max;
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frac = 0;
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break;
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case float_class_qnan:
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case float_class_snan:
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exp = exp_max;
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break;
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default:
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g_assert_not_reached();
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}
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float_raise(flags, s);
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p.exp = exp;
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p.frac = frac;
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return p;
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}
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static FloatParts float16_unpack_canonical(float16 f, float_status *s)
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{
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return canonicalize(float16_unpack_raw(f), &float16_params, s);
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}
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static float16 float16_round_pack_canonical(FloatParts p, float_status *s)
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{
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switch (p.cls) {
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case float_class_dnan:
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return float16_default_nan(s);
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case float_class_msnan:
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return float16_maybe_silence_nan(float16_pack_raw(p), s);
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default:
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p = round_canonical(p, s, &float16_params);
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return float16_pack_raw(p);
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}
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}
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static FloatParts float32_unpack_canonical(float32 f, float_status *s)
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{
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return canonicalize(float32_unpack_raw(f), &float32_params, s);
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}
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static float32 float32_round_pack_canonical(FloatParts p, float_status *s)
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{
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switch (p.cls) {
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case float_class_dnan:
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return float32_default_nan(s);
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case float_class_msnan:
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return float32_maybe_silence_nan(float32_pack_raw(p), s);
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default:
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p = round_canonical(p, s, &float32_params);
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return float32_pack_raw(p);
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}
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}
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static FloatParts float64_unpack_canonical(float64 f, float_status *s)
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{
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return canonicalize(float64_unpack_raw(f), &float64_params, s);
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}
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static float64 float64_round_pack_canonical(FloatParts p, float_status *s)
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{
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switch (p.cls) {
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case float_class_dnan:
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return float64_default_nan(s);
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case float_class_msnan:
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return float64_maybe_silence_nan(float64_pack_raw(p), s);
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default:
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p = round_canonical(p, s, &float64_params);
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return float64_pack_raw(p);
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}
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}
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/* Simple helpers for checking if what NaN we have */
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static bool is_nan(FloatClass c)
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{
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return unlikely(c >= float_class_qnan);
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}
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static bool is_snan(FloatClass c)
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{
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return c == float_class_snan;
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}
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static bool is_qnan(FloatClass c)
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{
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return c == float_class_qnan;
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}
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static FloatParts pick_nan(FloatParts a, FloatParts b, float_status *s)
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{
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if (is_snan(a.cls) || is_snan(b.cls)) {
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s->float_exception_flags |= float_flag_invalid;
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}
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if (s->default_nan_mode) {
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a.cls = float_class_dnan;
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} else {
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if (pickNaN(is_qnan(a.cls), is_snan(a.cls),
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is_qnan(b.cls), is_snan(b.cls),
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a.frac > b.frac ||
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(a.frac == b.frac && a.sign < b.sign))) {
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a = b;
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}
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a.cls = float_class_msnan;
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}
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return a;
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}
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/*
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* Returns the result of adding or subtracting the values of the
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* floating-point values `a' and `b'. The operation is performed
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* according to the IEC/IEEE Standard for Binary Floating-Point
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* Arithmetic.
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*/
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static FloatParts addsub_floats(FloatParts a, FloatParts b, bool subtract,
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float_status *s)
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{
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bool a_sign = a.sign;
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bool b_sign = b.sign ^ subtract;
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if (a_sign != b_sign) {
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/* Subtraction */
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if (a.cls == float_class_normal && b.cls == float_class_normal) {
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if (a.exp > b.exp || (a.exp == b.exp && a.frac >= b.frac)) {
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shift64RightJamming(b.frac, a.exp - b.exp, &b.frac);
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a.frac = a.frac - b.frac;
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} else {
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shift64RightJamming(a.frac, b.exp - a.exp, &a.frac);
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a.frac = b.frac - a.frac;
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a.exp = b.exp;
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a_sign ^= 1;
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}
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if (a.frac == 0) {
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a.cls = float_class_zero;
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a.sign = s->float_rounding_mode == float_round_down;
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} else {
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int shift = clz64(a.frac) - 1;
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a.frac = a.frac << shift;
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a.exp = a.exp - shift;
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a.sign = a_sign;
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}
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return a;
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}
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if (is_nan(a.cls) || is_nan(b.cls)) {
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return pick_nan(a, b, s);
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}
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if (a.cls == float_class_inf) {
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if (b.cls == float_class_inf) {
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float_raise(float_flag_invalid, s);
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a.cls = float_class_dnan;
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}
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return a;
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}
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if (a.cls == float_class_zero && b.cls == float_class_zero) {
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a.sign = s->float_rounding_mode == float_round_down;
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return a;
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}
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if (a.cls == float_class_zero || b.cls == float_class_inf) {
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b.sign = a_sign ^ 1;
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return b;
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}
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if (b.cls == float_class_zero) {
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return a;
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}
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} else {
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/* Addition */
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if (a.cls == float_class_normal && b.cls == float_class_normal) {
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if (a.exp > b.exp) {
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shift64RightJamming(b.frac, a.exp - b.exp, &b.frac);
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} else if (a.exp < b.exp) {
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shift64RightJamming(a.frac, b.exp - a.exp, &a.frac);
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a.exp = b.exp;
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}
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a.frac += b.frac;
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if (a.frac & DECOMPOSED_OVERFLOW_BIT) {
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a.frac >>= 1;
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a.exp += 1;
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}
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return a;
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}
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if (is_nan(a.cls) || is_nan(b.cls)) {
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return pick_nan(a, b, s);
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}
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if (a.cls == float_class_inf || b.cls == float_class_zero) {
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return a;
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}
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if (b.cls == float_class_inf || a.cls == float_class_zero) {
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b.sign = b_sign;
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return b;
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}
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}
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g_assert_not_reached();
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}
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/*
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* Returns the result of adding or subtracting the floating-point
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* values `a' and `b'. The operation is performed according to the
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* IEC/IEEE Standard for Binary Floating-Point Arithmetic.
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*/
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float16 QEMU_FLATTEN float16_add(float16 a, float16 b,
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float_status *status)
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{
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FloatParts pa = float16_unpack_canonical(a, status);
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FloatParts pb = float16_unpack_canonical(b, status);
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FloatParts pr = addsub_floats(pa, pb, false, status);
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return float16_round_pack_canonical(pr, status);
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}
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float32 QEMU_FLATTEN float32_add(float32 a, float32 b,
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float_status *status)
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{
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FloatParts pa = float32_unpack_canonical(a, status);
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FloatParts pb = float32_unpack_canonical(b, status);
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FloatParts pr = addsub_floats(pa, pb, false, status);
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return float32_round_pack_canonical(pr, status);
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}
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float64 QEMU_FLATTEN float64_add(float64 a, float64 b,
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float_status *status)
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{
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FloatParts pa = float64_unpack_canonical(a, status);
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FloatParts pb = float64_unpack_canonical(b, status);
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FloatParts pr = addsub_floats(pa, pb, false, status);
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return float64_round_pack_canonical(pr, status);
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}
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float16 QEMU_FLATTEN float16_sub(float16 a, float16 b,
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float_status *status)
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{
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FloatParts pa = float16_unpack_canonical(a, status);
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FloatParts pb = float16_unpack_canonical(b, status);
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FloatParts pr = addsub_floats(pa, pb, true, status);
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return float16_round_pack_canonical(pr, status);
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}
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float32 QEMU_FLATTEN float32_sub(float32 a, float32 b,
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float_status *status)
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{
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FloatParts pa = float32_unpack_canonical(a, status);
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FloatParts pb = float32_unpack_canonical(b, status);
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FloatParts pr = addsub_floats(pa, pb, true, status);
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return float32_round_pack_canonical(pr, status);
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}
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float64 QEMU_FLATTEN float64_sub(float64 a, float64 b,
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float_status *status)
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{
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FloatParts pa = float64_unpack_canonical(a, status);
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FloatParts pb = float64_unpack_canonical(b, status);
|
||||
FloatParts pr = addsub_floats(pa, pb, true, status);
|
||||
|
||||
return float64_round_pack_canonical(pr, status);
|
||||
}
|
||||
|
||||
/*----------------------------------------------------------------------------
|
||||
| Takes a 64-bit fixed-point value `absZ' with binary point between bits 6
|
||||
| and 7, and returns the properly rounded 32-bit integer corresponding to the
|
||||
|
||||
@ -58,6 +58,9 @@ static union MSVC_FLOAT_HACK __NAN = {{0x00, 0x00, 0xC0, 0x7F}};
|
||||
|
||||
#define QEMU_ALIGNED(A, B) __declspec(align(A)) B
|
||||
|
||||
// Unicorn: Initially added to abstract away GCC's flatten attribute in softfloat.c
|
||||
#define QEMU_FLATTEN
|
||||
|
||||
// Unicorn: Addition for thread-local variables
|
||||
#define QEMU_THREAD_LOCAL_VAR __declspec(thread)
|
||||
|
||||
@ -123,6 +126,9 @@ static union MSVC_FLOAT_HACK __NAN = {{0x00, 0x00, 0xC0, 0x7F}};
|
||||
|
||||
#define QEMU_ALIGNED(A, B) B __attribute__((aligned(A)))
|
||||
|
||||
// Unicorn: Initially added to abstract away GCC's flatten attribute in softfloat.c
|
||||
#define QEMU_FLATTEN __attribute__((flatten))
|
||||
|
||||
// Unicorn: Addition for thread-local variables
|
||||
#define QEMU_THREAD_LOCAL_VAR __thread
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user