diff options
Diffstat (limited to 'sysdeps/aarch64/fpu/exp2f_sve.c')
| -rw-r--r-- | sysdeps/aarch64/fpu/exp2f_sve.c | 35 |
1 files changed, 11 insertions, 24 deletions
diff --git a/sysdeps/aarch64/fpu/exp2f_sve.c b/sysdeps/aarch64/fpu/exp2f_sve.c index fcd7830..989cefb 100644 --- a/sysdeps/aarch64/fpu/exp2f_sve.c +++ b/sysdeps/aarch64/fpu/exp2f_sve.c @@ -18,21 +18,17 @@ <https://www.gnu.org/licenses/>. */ #include "sv_math.h" -#include "poly_sve_f32.h" #define Thres 0x1.5d5e2ap+6f static const struct data { - float c0, c2, c4, c1, c3; - float shift, thres; + float c0, c1, shift, thres; } data = { - /* Coefficients copied from the polynomial in AdvSIMD variant. */ - .c0 = 0x1.62e422p-1f, - .c1 = 0x1.ebf9bcp-3f, - .c2 = 0x1.c6bd32p-5f, - .c3 = 0x1.3ce9e4p-7f, - .c4 = 0x1.59977ap-10f, + /* Coefficients generated using Remez algorithm with minimisation of relative + error. */ + .c0 = 0x1.62e485p-1, + .c1 = 0x1.ebfbe0p-3, /* 1.5*2^17 + 127. */ .shift = 0x1.803f8p17f, /* Roughly 87.3. For x < -Thres, the result is subnormal and not handled @@ -51,16 +47,8 @@ sv_exp2f_inline (svfloat32_t x, const svbool_t pg, const struct data *d) svfloat32_t scale = svexpa (svreinterpret_u32 (z)); - /* Polynomial evaluation: poly(r) ~ exp2(r)-1. - Evaluate polynomial use hybrid scheme - offset ESTRIN by 1 for - coefficients 1 to 4, and apply most significant coefficient directly. */ - svfloat32_t even_coeffs = svld1rq (svptrue_b32 (), &d->c0); - svfloat32_t r2 = svmul_x (svptrue_b32 (), r, r); - svfloat32_t p12 = svmla_lane (sv_f32 (d->c1), r, even_coeffs, 1); - svfloat32_t p34 = svmla_lane (sv_f32 (d->c3), r, even_coeffs, 2); - svfloat32_t p14 = svmla_x (pg, p12, r2, p34); - svfloat32_t p0 = svmul_lane (r, even_coeffs, 0); - svfloat32_t poly = svmla_x (pg, p0, r2, p14); + svfloat32_t poly = svmla_x (pg, sv_f32 (d->c0), r, sv_f32 (d->c1)); + poly = svmul_x (svptrue_b32 (), poly, r); return svmla_x (pg, scale, scale, poly); } @@ -72,11 +60,10 @@ special_case (svfloat32_t x, svbool_t special, const struct data *d) special); } -/* Single-precision SVE exp2f routine. Implements the same algorithm - as AdvSIMD exp2f. - Worst case error is 1.04 ULPs. - _ZGVsMxv_exp2f(-0x1.af994ap-3) got 0x1.ba6a66p-1 - want 0x1.ba6a64p-1. */ +/* Single-precision SVE exp2f routine, based on the FEXPA instruction. + Worst case error is 1.09 ULPs. + _ZGVsMxv_exp2f (0x1.9a2a94p-1) got 0x1.be1054p+0 + want 0x1.be1052p+0. */ svfloat32_t SV_NAME_F1 (exp2) (svfloat32_t x, const svbool_t pg) { const struct data *d = ptr_barrier (&data); |