diff options
Diffstat (limited to 'sysdeps/aarch64/fpu/logf_advsimd.c')
| -rw-r--r-- | sysdeps/aarch64/fpu/logf_advsimd.c | 41 |
1 files changed, 24 insertions, 17 deletions
diff --git a/sysdeps/aarch64/fpu/logf_advsimd.c b/sysdeps/aarch64/fpu/logf_advsimd.c index 3c0d0fcdc7..c20dbfd6c0 100644 --- a/sysdeps/aarch64/fpu/logf_advsimd.c +++ b/sysdeps/aarch64/fpu/logf_advsimd.c @@ -21,20 +21,22 @@ static const struct data { - uint32x4_t min_norm; + uint32x4_t off, offset_lower_bound; uint16x8_t special_bound; + uint32x4_t mantissa_mask; float32x4_t poly[7]; - float32x4_t ln2, tiny_bound; - uint32x4_t off, mantissa_mask; + float32x4_t ln2; } data = { /* 3.34 ulp error. */ .poly = { V4 (-0x1.3e737cp-3f), V4 (0x1.5a9aa2p-3f), V4 (-0x1.4f9934p-3f), V4 (0x1.961348p-3f), V4 (-0x1.00187cp-2f), V4 (0x1.555d7cp-2f), V4 (-0x1.ffffc8p-2f) }, .ln2 = V4 (0x1.62e43p-1f), - .tiny_bound = V4 (0x1p-126), - .min_norm = V4 (0x00800000), - .special_bound = V8 (0x7f00), /* asuint32(inf) - min_norm. */ + /* Lower bound is the smallest positive normal float 0x00800000. For + optimised register use subnormals are detected after offset has been + subtracted, so lower bound is 0x0080000 - offset (which wraps around). */ + .offset_lower_bound = V4 (0x00800000 - 0x3f2aaaab), + .special_bound = V8 (0x7f00), /* top16(asuint32(inf) - 0x00800000). */ .off = V4 (0x3f2aaaab), /* 0.666667. */ .mantissa_mask = V4 (0x007fffff) }; @@ -42,32 +44,37 @@ static const struct data #define P(i) d->poly[7 - i] static float32x4_t VPCS_ATTR NOINLINE -special_case (float32x4_t x, float32x4_t y, float32x4_t r2, float32x4_t p, - uint16x4_t cmp) +special_case (float32x4_t p, uint32x4_t u_off, float32x4_t y, float32x4_t r2, + uint16x4_t cmp, const struct data *d) { /* Fall back to scalar code. */ - return v_call_f32 (logf, x, vfmaq_f32 (p, y, r2), vmovl_u16 (cmp)); + return v_call_f32 (logf, vreinterpretq_f32_u32 (vaddq_u32 (u_off, d->off)), + vfmaq_f32 (p, y, r2), vmovl_u16 (cmp)); } float32x4_t VPCS_ATTR NOINLINE V_NAME_F1 (log) (float32x4_t x) { const struct data *d = ptr_barrier (&data); float32x4_t n, p, q, r, r2, y; - uint32x4_t u; + uint32x4_t u, u_off; uint16x4_t cmp; - u = vreinterpretq_u32_f32 (x); - cmp = vcge_u16 (vsubhn_u32 (u, d->min_norm), - vget_low_u16 (d->special_bound)); + /* To avoid having to mov x out of the way, keep u after offset has been + applied, and recover x by adding the offset back in the special-case + handler. */ + u_off = vreinterpretq_u32_f32 (x); /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */ - u = vsubq_u32 (u, d->off); + u_off = vsubq_u32 (u_off, d->off); n = vcvtq_f32_s32 ( - vshrq_n_s32 (vreinterpretq_s32_u32 (u), 23)); /* signextend. */ - u = vandq_u32 (u, d->mantissa_mask); + vshrq_n_s32 (vreinterpretq_s32_u32 (u_off), 23)); /* signextend. */ + u = vandq_u32 (u_off, d->mantissa_mask); u = vaddq_u32 (u, d->off); r = vsubq_f32 (vreinterpretq_f32_u32 (u), v_f32 (1.0f)); + cmp = vcge_u16 (vsubhn_u32 (u_off, d->offset_lower_bound), + vget_low_u16 (d->special_bound)); + /* y = log(1+r) + n*ln2. */ r2 = vmulq_f32 (r, r); /* n*ln2 + r + r2*(P1 + r*P2 + r2*(P3 + r*P4 + r2*(P5 + r*P6 + r2*P7))). */ @@ -80,7 +87,7 @@ float32x4_t VPCS_ATTR NOINLINE V_NAME_F1 (log) (float32x4_t x) p = vfmaq_f32 (r, d->ln2, n); if (__glibc_unlikely (v_any_u16h (cmp))) - return special_case (x, y, r2, p, cmp); + return special_case (p, u_off, y, r2, cmp, d); return vfmaq_f32 (p, y, r2); } libmvec_hidden_def (V_NAME_F1 (log)) |