mirror of https://github.com/xemu-project/xemu.git
arm/helper.c: re-factor rsqrte and add rsqrte_f16
Much like recpe the ARM ARM has simplified the pseudo code for the calculation which is done on a fixed point 9 bit integer maths. So while adding f16 we can also clean this up to be a little less heavy on the floating point and just return the fractional part and leave the calle's to do the final packing of the result. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-id: 20180227143852.11175-27-alex.bennee@linaro.org Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Alex Bennée
Peter Maydell
parent
b96a54c7e5
commit
d719cbc764
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@ -11756,56 +11756,97 @@ float64 HELPER(recpe_f64)(float64 input, void *fpstp)
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/* The algorithm that must be used to calculate the estimate
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/* The algorithm that must be used to calculate the estimate
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* is specified by the ARM ARM.
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* is specified by the ARM ARM.
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*/
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*/
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static float64 recip_sqrt_estimate(float64 a, float_status *real_fp_status)
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static int do_recip_sqrt_estimate(int a)
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{
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{
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/* These calculations mustn't set any fp exception flags,
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int b, estimate;
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* so we use a local copy of the fp_status.
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*/
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float_status dummy_status = *real_fp_status;
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float_status *s = &dummy_status;
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float64 q;
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int64_t q_int;
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if (float64_lt(a, float64_half, s)) {
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assert(128 <= a && a < 512);
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/* range 0.25 <= a < 0.5 */
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if (a < 256) {
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a = a * 2 + 1;
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/* a in units of 1/512 rounded down */
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/* q0 = (int)(a * 512.0); */
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q = float64_mul(float64_512, a, s);
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q_int = float64_to_int64_round_to_zero(q, s);
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/* reciprocal root r */
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/* r = 1.0 / sqrt(((double)q0 + 0.5) / 512.0); */
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q = int64_to_float64(q_int, s);
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q = float64_add(q, float64_half, s);
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q = float64_div(q, float64_512, s);
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q = float64_sqrt(q, s);
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q = float64_div(float64_one, q, s);
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} else {
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} else {
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/* range 0.5 <= a < 1.0 */
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a = (a >> 1) << 1;
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a = (a + 1) * 2;
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/* a in units of 1/256 rounded down */
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/* q1 = (int)(a * 256.0); */
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q = float64_mul(float64_256, a, s);
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int64_t q_int = float64_to_int64_round_to_zero(q, s);
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/* reciprocal root r */
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/* r = 1.0 /sqrt(((double)q1 + 0.5) / 256); */
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q = int64_to_float64(q_int, s);
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q = float64_add(q, float64_half, s);
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q = float64_div(q, float64_256, s);
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q = float64_sqrt(q, s);
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q = float64_div(float64_one, q, s);
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}
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}
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/* r in units of 1/256 rounded to nearest */
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b = 512;
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/* s = (int)(256.0 * r + 0.5); */
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while (a * (b + 1) * (b + 1) < (1 << 28)) {
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b += 1;
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}
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estimate = (b + 1) / 2;
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assert(256 <= estimate && estimate < 512);
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q = float64_mul(q, float64_256,s );
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return estimate;
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q = float64_add(q, float64_half, s);
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}
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q_int = float64_to_int64_round_to_zero(q, s);
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/* return (double)s / 256.0;*/
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return float64_div(int64_to_float64(q_int, s), float64_256, s);
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static uint64_t recip_sqrt_estimate(int *exp , int exp_off, uint64_t frac)
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{
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int estimate;
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uint32_t scaled;
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if (*exp == 0) {
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while (extract64(frac, 51, 1) == 0) {
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frac = frac << 1;
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*exp -= 1;
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}
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frac = extract64(frac, 0, 51) << 1;
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}
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if (*exp & 1) {
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/* scaled = UInt('01':fraction<51:45>) */
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scaled = deposit32(1 << 7, 0, 7, extract64(frac, 45, 7));
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} else {
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/* scaled = UInt('1':fraction<51:44>) */
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scaled = deposit32(1 << 8, 0, 8, extract64(frac, 44, 8));
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}
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estimate = do_recip_sqrt_estimate(scaled);
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*exp = (exp_off - *exp) / 2;
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return extract64(estimate, 0, 8) << 44;
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}
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float16 HELPER(rsqrte_f16)(float16 input, void *fpstp)
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{
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float_status *s = fpstp;
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float16 f16 = float16_squash_input_denormal(input, s);
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uint16_t val = float16_val(f16);
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bool f16_sign = float16_is_neg(f16);
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int f16_exp = extract32(val, 10, 5);
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uint16_t f16_frac = extract32(val, 0, 10);
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uint64_t f64_frac;
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if (float16_is_any_nan(f16)) {
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float16 nan = f16;
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if (float16_is_signaling_nan(f16, s)) {
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float_raise(float_flag_invalid, s);
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nan = float16_maybe_silence_nan(f16, s);
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}
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if (s->default_nan_mode) {
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nan = float16_default_nan(s);
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}
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return nan;
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} else if (float16_is_zero(f16)) {
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float_raise(float_flag_divbyzero, s);
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return float16_set_sign(float16_infinity, f16_sign);
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} else if (f16_sign) {
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float_raise(float_flag_invalid, s);
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return float16_default_nan(s);
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} else if (float16_is_infinity(f16)) {
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return float16_zero;
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}
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/* Scale and normalize to a double-precision value between 0.25 and 1.0,
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* preserving the parity of the exponent. */
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f64_frac = ((uint64_t) f16_frac) << (52 - 10);
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f64_frac = recip_sqrt_estimate(&f16_exp, 44, f64_frac);
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/* result = sign : result_exp<4:0> : estimate<7:0> : Zeros(2) */
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val = deposit32(0, 15, 1, f16_sign);
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val = deposit32(val, 10, 5, f16_exp);
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val = deposit32(val, 2, 8, extract64(f64_frac, 52 - 8, 8));
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return make_float16(val);
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}
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}
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float32 HELPER(rsqrte_f32)(float32 input, void *fpstp)
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float32 HELPER(rsqrte_f32)(float32 input, void *fpstp)
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@ -11813,13 +11854,10 @@ float32 HELPER(rsqrte_f32)(float32 input, void *fpstp)
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float_status *s = fpstp;
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float_status *s = fpstp;
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float32 f32 = float32_squash_input_denormal(input, s);
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float32 f32 = float32_squash_input_denormal(input, s);
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uint32_t val = float32_val(f32);
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uint32_t val = float32_val(f32);
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uint32_t f32_sbit = 0x80000000 & val;
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uint32_t f32_sign = float32_is_neg(f32);
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int32_t f32_exp = extract32(val, 23, 8);
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int f32_exp = extract32(val, 23, 8);
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uint32_t f32_frac = extract32(val, 0, 23);
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uint32_t f32_frac = extract32(val, 0, 23);
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uint64_t f64_frac;
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uint64_t f64_frac;
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uint64_t val64;
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int result_exp;
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float64 f64;
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if (float32_is_any_nan(f32)) {
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if (float32_is_any_nan(f32)) {
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float32 nan = f32;
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float32 nan = f32;
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@ -11845,32 +11883,13 @@ float32 HELPER(rsqrte_f32)(float32 input, void *fpstp)
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* preserving the parity of the exponent. */
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* preserving the parity of the exponent. */
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f64_frac = ((uint64_t) f32_frac) << 29;
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f64_frac = ((uint64_t) f32_frac) << 29;
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if (f32_exp == 0) {
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while (extract64(f64_frac, 51, 1) == 0) {
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f64_frac = f64_frac << 1;
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f32_exp = f32_exp-1;
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}
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f64_frac = extract64(f64_frac, 0, 51) << 1;
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}
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if (extract64(f32_exp, 0, 1) == 0) {
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f64_frac = recip_sqrt_estimate(&f32_exp, 380, f64_frac);
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f64 = make_float64(((uint64_t) f32_sbit) << 32
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| (0x3feULL << 52)
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| f64_frac);
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} else {
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f64 = make_float64(((uint64_t) f32_sbit) << 32
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| (0x3fdULL << 52)
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| f64_frac);
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}
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result_exp = (380 - f32_exp) / 2;
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/* result = sign : result_exp<4:0> : estimate<7:0> : Zeros(15) */
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val = deposit32(0, 31, 1, f32_sign);
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f64 = recip_sqrt_estimate(f64, s);
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val = deposit32(val, 23, 8, f32_exp);
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val = deposit32(val, 15, 8, extract64(f64_frac, 52 - 8, 8));
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val64 = float64_val(f64);
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val = ((result_exp & 0xff) << 23)
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| ((val64 >> 29) & 0x7fffff);
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return make_float32(val);
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return make_float32(val);
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}
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}
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@ -11879,11 +11898,9 @@ float64 HELPER(rsqrte_f64)(float64 input, void *fpstp)
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float_status *s = fpstp;
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float_status *s = fpstp;
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float64 f64 = float64_squash_input_denormal(input, s);
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float64 f64 = float64_squash_input_denormal(input, s);
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uint64_t val = float64_val(f64);
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uint64_t val = float64_val(f64);
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uint64_t f64_sbit = 0x8000000000000000ULL & val;
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bool f64_sign = float64_is_neg(f64);
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int64_t f64_exp = extract64(val, 52, 11);
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int f64_exp = extract64(val, 52, 11);
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uint64_t f64_frac = extract64(val, 0, 52);
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uint64_t f64_frac = extract64(val, 0, 52);
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int64_t result_exp;
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uint64_t result_frac;
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if (float64_is_any_nan(f64)) {
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if (float64_is_any_nan(f64)) {
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float64 nan = f64;
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float64 nan = f64;
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@ -11905,36 +11922,13 @@ float64 HELPER(rsqrte_f64)(float64 input, void *fpstp)
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return float64_zero;
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return float64_zero;
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}
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}
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/* Scale and normalize to a double-precision value between 0.25 and 1.0,
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f64_frac = recip_sqrt_estimate(&f64_exp, 3068, f64_frac);
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* preserving the parity of the exponent. */
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if (f64_exp == 0) {
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/* result = sign : result_exp<4:0> : estimate<7:0> : Zeros(44) */
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while (extract64(f64_frac, 51, 1) == 0) {
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val = deposit64(0, 61, 1, f64_sign);
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f64_frac = f64_frac << 1;
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val = deposit64(val, 52, 11, f64_exp);
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f64_exp = f64_exp - 1;
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val = deposit64(val, 44, 8, extract64(f64_frac, 52 - 8, 8));
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}
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return make_float64(val);
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f64_frac = extract64(f64_frac, 0, 51) << 1;
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}
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if (extract64(f64_exp, 0, 1) == 0) {
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f64 = make_float64(f64_sbit
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| (0x3feULL << 52)
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| f64_frac);
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} else {
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f64 = make_float64(f64_sbit
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| (0x3fdULL << 52)
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| f64_frac);
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}
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result_exp = (3068 - f64_exp) / 2;
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f64 = recip_sqrt_estimate(f64, s);
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result_frac = extract64(float64_val(f64), 0, 52);
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return make_float64(f64_sbit |
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((result_exp & 0x7ff) << 52) |
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result_frac);
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}
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}
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uint32_t HELPER(recpe_u32)(uint32_t a, void *fpstp)
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uint32_t HELPER(recpe_u32)(uint32_t a, void *fpstp)
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@ -11954,24 +11948,15 @@ uint32_t HELPER(recpe_u32)(uint32_t a, void *fpstp)
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uint32_t HELPER(rsqrte_u32)(uint32_t a, void *fpstp)
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uint32_t HELPER(rsqrte_u32)(uint32_t a, void *fpstp)
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{
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{
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float_status *fpst = fpstp;
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int estimate;
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float64 f64;
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if ((a & 0xc0000000) == 0) {
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if ((a & 0xc0000000) == 0) {
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return 0xffffffff;
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return 0xffffffff;
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}
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}
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if (a & 0x80000000) {
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estimate = do_recip_sqrt_estimate(extract32(a, 23, 9));
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f64 = make_float64((0x3feULL << 52)
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} else { /* bits 31-30 == '01' */
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f64 = make_float64((0x3fdULL << 52)
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}
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f64 = recip_sqrt_estimate(f64, fpst);
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return deposit32(0, 23, 9, estimate);
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return 0x80000000 | ((float64_val(f64) >> 21) & 0x7fffffff);
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}
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}
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/* VFPv4 fused multiply-accumulate */
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/* VFPv4 fused multiply-accumulate */
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@ -195,6 +195,7 @@ DEF_HELPER_3(rsqrts_f32, f32, f32, f32, env)
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DEF_HELPER_FLAGS_2(recpe_f16, TCG_CALL_NO_RWG, f16, f16, ptr)
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DEF_HELPER_FLAGS_2(recpe_f16, TCG_CALL_NO_RWG, f16, f16, ptr)
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DEF_HELPER_FLAGS_2(recpe_f32, TCG_CALL_NO_RWG, f32, f32, ptr)
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DEF_HELPER_FLAGS_2(recpe_f32, TCG_CALL_NO_RWG, f32, f32, ptr)
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DEF_HELPER_FLAGS_2(recpe_f64, TCG_CALL_NO_RWG, f64, f64, ptr)
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DEF_HELPER_FLAGS_2(recpe_f64, TCG_CALL_NO_RWG, f64, f64, ptr)
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DEF_HELPER_FLAGS_2(rsqrte_f16, TCG_CALL_NO_RWG, f16, f16, ptr)
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DEF_HELPER_FLAGS_2(rsqrte_f32, TCG_CALL_NO_RWG, f32, f32, ptr)
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DEF_HELPER_FLAGS_2(rsqrte_f32, TCG_CALL_NO_RWG, f32, f32, ptr)
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DEF_HELPER_FLAGS_2(rsqrte_f64, TCG_CALL_NO_RWG, f64, f64, ptr)
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DEF_HELPER_FLAGS_2(rsqrte_f64, TCG_CALL_NO_RWG, f64, f64, ptr)
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DEF_HELPER_2(recpe_u32, i32, i32, ptr)
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DEF_HELPER_2(recpe_u32, i32, i32, ptr)
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