diff options
Diffstat (limited to 'contrib/arm-optimized-routines/pl/math/v_atan_2u5.c')
| -rw-r--r-- | contrib/arm-optimized-routines/pl/math/v_atan_2u5.c | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/contrib/arm-optimized-routines/pl/math/v_atan_2u5.c b/contrib/arm-optimized-routines/pl/math/v_atan_2u5.c new file mode 100644 index 000000000000..ba68cc3cc720 --- /dev/null +++ b/contrib/arm-optimized-routines/pl/math/v_atan_2u5.c @@ -0,0 +1,104 @@ +/* + * Double-precision vector atan(x) function. + * + * Copyright (c) 2021-2023, Arm Limited. + * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception + */ + +#include "v_math.h" +#include "pl_sig.h" +#include "pl_test.h" +#include "poly_advsimd_f64.h" + +static const struct data +{ + float64x2_t pi_over_2; + float64x2_t poly[20]; +} data = { + /* Coefficients of polynomial P such that atan(x)~x+x*P(x^2) on + [2**-1022, 1.0]. */ + .poly = { V2 (-0x1.5555555555555p-2), V2 (0x1.99999999996c1p-3), + V2 (-0x1.2492492478f88p-3), V2 (0x1.c71c71bc3951cp-4), + V2 (-0x1.745d160a7e368p-4), V2 (0x1.3b139b6a88ba1p-4), + V2 (-0x1.11100ee084227p-4), V2 (0x1.e1d0f9696f63bp-5), + V2 (-0x1.aebfe7b418581p-5), V2 (0x1.842dbe9b0d916p-5), + V2 (-0x1.5d30140ae5e99p-5), V2 (0x1.338e31eb2fbbcp-5), + V2 (-0x1.00e6eece7de8p-5), V2 (0x1.860897b29e5efp-6), + V2 (-0x1.0051381722a59p-6), V2 (0x1.14e9dc19a4a4ep-7), + V2 (-0x1.d0062b42fe3bfp-9), V2 (0x1.17739e210171ap-10), + V2 (-0x1.ab24da7be7402p-13), V2 (0x1.358851160a528p-16), }, + .pi_over_2 = V2 (0x1.921fb54442d18p+0), +}; + +#define SignMask v_u64 (0x8000000000000000) +#define TinyBound 0x3e10000000000000 /* asuint64(0x1p-30). */ +#define BigBound 0x4340000000000000 /* asuint64(0x1p53). */ + +/* Fast implementation of vector atan. + Based on atan(x) ~ shift + z + z^3 * P(z^2) with reduction to [0,1] using + z=1/x and shift = pi/2. Maximum observed error is 2.27 ulps: + _ZGVnN2v_atan (0x1.0005af27c23e9p+0) got 0x1.9225645bdd7c1p-1 + want 0x1.9225645bdd7c3p-1. */ +float64x2_t VPCS_ATTR V_NAME_D1 (atan) (float64x2_t x) +{ + const struct data *d = ptr_barrier (&data); + + /* Small cases, infs and nans are supported by our approximation technique, + but do not set fenv flags correctly. Only trigger special case if we need + fenv. */ + uint64x2_t ix = vreinterpretq_u64_f64 (x); + uint64x2_t sign = vandq_u64 (ix, SignMask); + +#if WANT_SIMD_EXCEPT + uint64x2_t ia12 = vandq_u64 (ix, v_u64 (0x7ff0000000000000)); + uint64x2_t special = vcgtq_u64 (vsubq_u64 (ia12, v_u64 (TinyBound)), + v_u64 (BigBound - TinyBound)); + /* If any lane is special, fall back to the scalar routine for all lanes. */ + if (unlikely (v_any_u64 (special))) + return v_call_f64 (atan, x, v_f64 (0), v_u64 (-1)); +#endif + + /* Argument reduction: + y := arctan(x) for x < 1 + y := pi/2 + arctan(-1/x) for x > 1 + Hence, use z=-1/a if x>=1, otherwise z=a. */ + uint64x2_t red = vcagtq_f64 (x, v_f64 (1.0)); + /* Avoid dependency in abs(x) in division (and comparison). */ + float64x2_t z = vbslq_f64 (red, vdivq_f64 (v_f64 (1.0), x), x); + float64x2_t shift = vreinterpretq_f64_u64 ( + vandq_u64 (red, vreinterpretq_u64_f64 (d->pi_over_2))); + /* Use absolute value only when needed (odd powers of z). */ + float64x2_t az = vbslq_f64 ( + SignMask, vreinterpretq_f64_u64 (vandq_u64 (SignMask, red)), z); + + /* Calculate the polynomial approximation. + Use split Estrin scheme for P(z^2) with deg(P)=19. Use split instead of + full scheme to avoid underflow in x^16. + The order 19 polynomial P approximates + (atan(sqrt(x))-sqrt(x))/x^(3/2). */ + float64x2_t z2 = vmulq_f64 (z, z); + float64x2_t x2 = vmulq_f64 (z2, z2); + float64x2_t x4 = vmulq_f64 (x2, x2); + float64x2_t x8 = vmulq_f64 (x4, x4); + float64x2_t y + = vfmaq_f64 (v_estrin_7_f64 (z2, x2, x4, d->poly), + v_estrin_11_f64 (z2, x2, x4, x8, d->poly + 8), x8); + + /* Finalize. y = shift + z + z^3 * P(z^2). */ + y = vfmaq_f64 (az, y, vmulq_f64 (z2, az)); + y = vaddq_f64 (y, shift); + + /* y = atan(x) if x>0, -atan(-x) otherwise. */ + y = vreinterpretq_f64_u64 (veorq_u64 (vreinterpretq_u64_f64 (y), sign)); + return y; +} + +PL_SIG (V, D, 1, atan, -10.0, 10.0) +PL_TEST_ULP (V_NAME_D1 (atan), 1.78) +PL_TEST_EXPECT_FENV (V_NAME_D1 (atan), WANT_SIMD_EXCEPT) +PL_TEST_INTERVAL (V_NAME_D1 (atan), 0, 0x1p-30, 10000) +PL_TEST_INTERVAL (V_NAME_D1 (atan), -0, -0x1p-30, 1000) +PL_TEST_INTERVAL (V_NAME_D1 (atan), 0x1p-30, 0x1p53, 900000) +PL_TEST_INTERVAL (V_NAME_D1 (atan), -0x1p-30, -0x1p53, 90000) +PL_TEST_INTERVAL (V_NAME_D1 (atan), 0x1p53, inf, 10000) +PL_TEST_INTERVAL (V_NAME_D1 (atan), -0x1p53, -inf, 1000) |