@@ -11338,56 +11338,97 @@ float64 HELPER(recpe_f64)(float64 input, void *fpstp)
/* The algorithm that must be used to calculate the estimate
* is specified by the ARM ARM.
*/
-static float64 recip_sqrt_estimate(float64 a, float_status *real_fp_status)
-{
- /* These calculations mustn't set any fp exception flags,
- * so we use a local copy of the fp_status.
- */
- float_status dummy_status = *real_fp_status;
- float_status *s = &dummy_status;
- float64 q;
- int64_t q_int;
-
- if (float64_lt(a, float64_half, s)) {
- /* range 0.25 <= a < 0.5 */
-
- /* a in units of 1/512 rounded down */
- /* q0 = (int)(a * 512.0); */
- q = float64_mul(float64_512, a, s);
- q_int = float64_to_int64_round_to_zero(q, s);
-
- /* reciprocal root r */
- /* r = 1.0 / sqrt(((double)q0 + 0.5) / 512.0); */
- q = int64_to_float64(q_int, s);
- q = float64_add(q, float64_half, s);
- q = float64_div(q, float64_512, s);
- q = float64_sqrt(q, s);
- q = float64_div(float64_one, q, s);
+
+static int do_recip_sqrt_estimate(int a)
+{
+ int b, estimate;
+
+ assert(128 <= a && a < 512);
+ if (a < 256) {
+ a = a * 2 + 1;
} else {
- /* range 0.5 <= a < 1.0 */
+ a = (a >> 1) << 1;
+ a = (a + 1) * 2;
+ }
+ b = 512;
+ while (a * (b + 1) * (b + 1) < (1 << 28)) {
+ b += 1;
+ }
+ estimate = (b + 1) / 2;
+ assert(256 <= estimate && estimate < 512);
+
+ return estimate;
+}
+
- /* a in units of 1/256 rounded down */
- /* q1 = (int)(a * 256.0); */
- q = float64_mul(float64_256, a, s);
- int64_t q_int = float64_to_int64_round_to_zero(q, s);
+static uint64_t recip_sqrt_estimate(int *exp , int exp_off, uint64_t frac)
+{
+ int estimate;
+ uint32_t scaled;
- /* reciprocal root r */
- /* r = 1.0 /sqrt(((double)q1 + 0.5) / 256); */
- q = int64_to_float64(q_int, s);
- q = float64_add(q, float64_half, s);
- q = float64_div(q, float64_256, s);
- q = float64_sqrt(q, s);
- q = float64_div(float64_one, q, s);
+ if (*exp == 0) {
+ while (extract64(frac, 51, 1) == 0) {
+ frac = frac << 1;
+ *exp -= 1;
+ }
+ frac = extract64(frac, 0, 51) << 1;
}
- /* r in units of 1/256 rounded to nearest */
- /* s = (int)(256.0 * r + 0.5); */
- q = float64_mul(q, float64_256,s );
- q = float64_add(q, float64_half, s);
- q_int = float64_to_int64_round_to_zero(q, s);
+ if (*exp & 1) {
+ /* scaled = UInt('01':fraction<51:45>) */
+ scaled = deposit32(1 << 7, 0, 7, extract64(frac, 45, 7));
+ } else {
+ /* scaled = UInt('1':fraction<51:44>) */
+ scaled = deposit32(1 << 8, 0, 8, extract64(frac, 44, 8));
+ }
+ estimate = do_recip_sqrt_estimate(scaled);
- /* return (double)s / 256.0;*/
- return float64_div(int64_to_float64(q_int, s), float64_256, s);
+ *exp = (exp_off - *exp) / 2;
+ return extract64(estimate, 0, 8) << 44;
+}
+
+float16 HELPER(rsqrte_f16)(float16 input, void *fpstp)
+{
+ float_status *s = fpstp;
+ float16 f16 = float16_squash_input_denormal(input, s);
+ uint16_t val = float16_val(f16);
+ bool f16_sign = float16_is_neg(f16);
+ int f16_exp = extract32(val, 10, 5);
+ uint16_t f16_frac = extract32(val, 0, 10);
+ uint64_t f64_frac;
+
+ if (float16_is_any_nan(f16)) {
+ float16 nan = f16;
+ if (float16_is_signaling_nan(f16, s)) {
+ float_raise(float_flag_invalid, s);
+ nan = float16_maybe_silence_nan(f16, s);
+ }
+ if (s->default_nan_mode) {
+ nan = float16_default_nan(s);
+ }
+ return nan;
+ } else if (float16_is_zero(f16)) {
+ float_raise(float_flag_divbyzero, s);
+ return float16_set_sign(float16_infinity, f16_sign);
+ } else if (f16_sign) {
+ float_raise(float_flag_invalid, s);
+ return float16_default_nan(s);
+ } else if (float16_is_infinity(f16)) {
+ return float16_zero;
+ }
+
+ /* Scale and normalize to a double-precision value between 0.25 and 1.0,
+ * preserving the parity of the exponent. */
+
+ f64_frac = ((uint64_t) f16_frac) << (52 - 10);
+
+ f64_frac = recip_sqrt_estimate(&f16_exp, 44, f64_frac);
+
+ /* result = sign : result_exp<4:0> : estimate<7:0> : Zeros(2) */
+ val = deposit32(0, 15, 1, f16_sign);
+ val = deposit32(val, 10, 5, f16_exp);
+ val = deposit32(val, 2, 8, extract64(f64_frac, 52 - 8, 8));
+ return make_float16(val);
}
float32 HELPER(rsqrte_f32)(float32 input, void *fpstp)
@@ -11395,13 +11436,10 @@ float32 HELPER(rsqrte_f32)(float32 input, void *fpstp)
float_status *s = fpstp;
float32 f32 = float32_squash_input_denormal(input, s);
uint32_t val = float32_val(f32);
- uint32_t f32_sbit = 0x80000000 & val;
- int32_t f32_exp = extract32(val, 23, 8);
+ uint32_t f32_sign = float32_is_neg(f32);
+ int f32_exp = extract32(val, 23, 8);
uint32_t f32_frac = extract32(val, 0, 23);
uint64_t f64_frac;
- uint64_t val64;
- int result_exp;
- float64 f64;
if (float32_is_any_nan(f32)) {
float32 nan = f32;
@@ -11427,32 +11465,13 @@ float32 HELPER(rsqrte_f32)(float32 input, void *fpstp)
* preserving the parity of the exponent. */
f64_frac = ((uint64_t) f32_frac) << 29;
- if (f32_exp == 0) {
- while (extract64(f64_frac, 51, 1) == 0) {
- f64_frac = f64_frac << 1;
- f32_exp = f32_exp-1;
- }
- f64_frac = extract64(f64_frac, 0, 51) << 1;
- }
-
- if (extract64(f32_exp, 0, 1) == 0) {
- f64 = make_float64(((uint64_t) f32_sbit) << 32
- | (0x3feULL << 52)
- | f64_frac);
- } else {
- f64 = make_float64(((uint64_t) f32_sbit) << 32
- | (0x3fdULL << 52)
- | f64_frac);
- }
- result_exp = (380 - f32_exp) / 2;
+ f64_frac = recip_sqrt_estimate(&f32_exp, 380, f64_frac);
- f64 = recip_sqrt_estimate(f64, s);
-
- val64 = float64_val(f64);
-
- val = ((result_exp & 0xff) << 23)
- | ((val64 >> 29) & 0x7fffff);
+ /* result = sign : result_exp<4:0> : estimate<7:0> : Zeros(15) */
+ val = deposit32(0, 31, 1, f32_sign);
+ val = deposit32(val, 23, 8, f32_exp);
+ val = deposit32(val, 15, 8, extract64(f64_frac, 52 - 8, 8));
return make_float32(val);
}
@@ -11461,11 +11480,9 @@ float64 HELPER(rsqrte_f64)(float64 input, void *fpstp)
float_status *s = fpstp;
float64 f64 = float64_squash_input_denormal(input, s);
uint64_t val = float64_val(f64);
- uint64_t f64_sbit = 0x8000000000000000ULL & val;
- int64_t f64_exp = extract64(val, 52, 11);
+ bool f64_sign = float64_is_neg(f64);
+ int f64_exp = extract64(val, 52, 11);
uint64_t f64_frac = extract64(val, 0, 52);
- int64_t result_exp;
- uint64_t result_frac;
if (float64_is_any_nan(f64)) {
float64 nan = f64;
@@ -11487,36 +11504,13 @@ float64 HELPER(rsqrte_f64)(float64 input, void *fpstp)
return float64_zero;
}
- /* Scale and normalize to a double-precision value between 0.25 and 1.0,
- * preserving the parity of the exponent. */
-
- if (f64_exp == 0) {
- while (extract64(f64_frac, 51, 1) == 0) {
- f64_frac = f64_frac << 1;
- f64_exp = f64_exp - 1;
- }
- f64_frac = extract64(f64_frac, 0, 51) << 1;
- }
+ f64_frac = recip_sqrt_estimate(&f64_exp, 3068, f64_frac);
- if (extract64(f64_exp, 0, 1) == 0) {
- f64 = make_float64(f64_sbit
- | (0x3feULL << 52)
- | f64_frac);
- } else {
- f64 = make_float64(f64_sbit
- | (0x3fdULL << 52)
- | f64_frac);
- }
-
- result_exp = (3068 - f64_exp) / 2;
-
- f64 = recip_sqrt_estimate(f64, s);
-
- result_frac = extract64(float64_val(f64), 0, 52);
-
- return make_float64(f64_sbit |
- ((result_exp & 0x7ff) << 52) |
- result_frac);
+ /* result = sign : result_exp<4:0> : estimate<7:0> : Zeros(44) */
+ val = deposit64(0, 61, 1, f64_sign);
+ val = deposit64(val, 52, 11, f64_exp);
+ val = deposit64(val, 44, 8, extract64(f64_frac, 52 - 8, 8));
+ return make_float64(val);
}
uint32_t HELPER(recpe_u32)(uint32_t a, void *fpstp)
@@ -11536,24 +11530,15 @@ uint32_t HELPER(recpe_u32)(uint32_t a, void *fpstp)
uint32_t HELPER(rsqrte_u32)(uint32_t a, void *fpstp)
{
- float_status *fpst = fpstp;
- float64 f64;
+ int estimate;
if ((a & 0xc0000000) == 0) {
return 0xffffffff;
}
- if (a & 0x80000000) {
- f64 = make_float64((0x3feULL << 52)
- | ((uint64_t)(a & 0x7fffffff) << 21));
- } else { /* bits 31-30 == '01' */
- f64 = make_float64((0x3fdULL << 52)
- | ((uint64_t)(a & 0x3fffffff) << 22));
- }
-
- f64 = recip_sqrt_estimate(f64, fpst);
+ estimate = do_recip_sqrt_estimate(extract32(a, 23, 9));
- return 0x80000000 | ((float64_val(f64) >> 21) & 0x7fffffff);
+ return deposit32(0, 23, 9, estimate);
}
/* VFPv4 fused multiply-accumulate */
@@ -195,6 +195,7 @@ DEF_HELPER_3(rsqrts_f32, f32, f32, f32, env)
DEF_HELPER_FLAGS_2(recpe_f16, TCG_CALL_NO_RWG, f16, f16, ptr)
DEF_HELPER_FLAGS_2(recpe_f32, TCG_CALL_NO_RWG, f32, f32, ptr)
DEF_HELPER_FLAGS_2(recpe_f64, TCG_CALL_NO_RWG, f64, f64, ptr)
+DEF_HELPER_FLAGS_2(rsqrte_f16, TCG_CALL_NO_RWG, f16, f16, ptr)
DEF_HELPER_FLAGS_2(rsqrte_f32, TCG_CALL_NO_RWG, f32, f32, ptr)
DEF_HELPER_FLAGS_2(rsqrte_f64, TCG_CALL_NO_RWG, f64, f64, ptr)
DEF_HELPER_2(recpe_u32, i32, i32, ptr)
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> --- v2 - checkpatch fixes --- target/arm/helper.c | 221 ++++++++++++++++++++++++---------------------------- target/arm/helper.h | 1 + 2 files changed, 104 insertions(+), 118 deletions(-) -- 2.15.1