aarch64: Add vector implementations of exp2 routines

Some routines reuse table from v_exp_data.c

1 files changed, 124 insertions, 0 deletions

diff --git a/sysdeps/aarch64/fpu/exp2f_advsimd.c b/sysdeps/aarch64/fpu/exp2f_advsimd.c
new file mode 100644
index 0000000000..70b3ab66c1
--- /dev/null
+++ b/sysdeps/aarch64/fpu/exp2f_advsimd.c
@@ -0,0 +1,124 @@
+/* Single-precision vector (AdvSIMD) exp2 function
+
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include "v_math.h"
+
+static const struct data
+{
+  float32x4_t poly[5];
+  uint32x4_t exponent_bias;
+#if !WANT_SIMD_EXCEPT
+  float32x4_t special_bound, scale_thresh;
+#endif
+} data = {
+  /* maxerr: 1.962 ulp.  */
+  .poly = { V4 (0x1.59977ap-10f), V4 (0x1.3ce9e4p-7f), V4 (0x1.c6bd32p-5f),
+	    V4 (0x1.ebf9bcp-3f), V4 (0x1.62e422p-1f) },
+  .exponent_bias = V4 (0x3f800000),
+#if !WANT_SIMD_EXCEPT
+  .special_bound = V4 (126.0f),
+  .scale_thresh = V4 (192.0f),
+#endif
+};
+
+#define C(i) d->poly[i]
+
+#if WANT_SIMD_EXCEPT
+
+# define TinyBound v_u32 (0x20000000)	  /* asuint (0x1p-63).  */
+# define BigBound v_u32 (0x42800000)	  /* asuint (0x1p6).  */
+# define SpecialBound v_u32 (0x22800000) /* BigBound - TinyBound.  */
+
+static float32x4_t VPCS_ATTR NOINLINE
+special_case (float32x4_t x, float32x4_t y, uint32x4_t cmp)
+{
+  /* If fenv exceptions are to be triggered correctly, fall back to the scalar
+     routine for special lanes.  */
+  return v_call_f32 (exp2f, x, y, cmp);
+}
+
+#else
+
+# define SpecialOffset v_u32 (0x82000000)
+# define SpecialBias v_u32 (0x7f000000)
+
+static float32x4_t VPCS_ATTR NOINLINE
+special_case (float32x4_t poly, float32x4_t n, uint32x4_t e, uint32x4_t cmp1,
+	      float32x4_t scale, const struct data *d)
+{
+  /* 2^n may overflow, break it up into s1*s2.  */
+  uint32x4_t b = vandq_u32 (vclezq_f32 (n), SpecialOffset);
+  float32x4_t s1 = vreinterpretq_f32_u32 (vaddq_u32 (b, SpecialBias));
+  float32x4_t s2 = vreinterpretq_f32_u32 (vsubq_u32 (e, b));
+  uint32x4_t cmp2 = vcagtq_f32 (n, d->scale_thresh);
+  float32x4_t r2 = vmulq_f32 (s1, s1);
+  float32x4_t r1 = vmulq_f32 (vfmaq_f32 (s2, poly, s2), s1);
+  /* Similar to r1 but avoids double rounding in the subnormal range.  */
+  float32x4_t r0 = vfmaq_f32 (scale, poly, scale);
+  float32x4_t r = vbslq_f32 (cmp1, r1, r0);
+  return vbslq_f32 (cmp2, r2, r);
+}
+
+#endif
+
+float32x4_t VPCS_ATTR V_NAME_F1 (exp2) (float32x4_t x)
+{
+  const struct data *d = ptr_barrier (&data);
+  float32x4_t n, r, r2, scale, p, q, poly;
+  uint32x4_t cmp, e;
+
+#if WANT_SIMD_EXCEPT
+  /* asuint(|x|) - TinyBound >= BigBound - TinyBound.  */
+  uint32x4_t ia = vreinterpretq_u32_f32 (vabsq_f32 (x));
+  cmp = vcgeq_u32 (vsubq_u32 (ia, TinyBound), SpecialBound);
+  float32x4_t xm = x;
+  /* If any lanes are special, mask them with 1 and retain a copy of x to allow
+     special_case to fix special lanes later. This is only necessary if fenv
+     exceptions are to be triggered correctly.  */
+  if (__glibc_unlikely (v_any_u32 (cmp)))
+    x = vbslq_f32 (cmp, v_f32 (1), x);
+#endif
+
+    /* exp2(x) = 2^n (1 + poly(r)), with 1 + poly(r) in [1/sqrt(2),sqrt(2)]
+       x = n + r, with r in [-1/2, 1/2].  */
+  n = vrndaq_f32 (x);
+  r = vsubq_f32 (x, n);
+  e = vshlq_n_u32 (vreinterpretq_u32_s32 (vcvtaq_s32_f32 (x)), 23);
+  scale = vreinterpretq_f32_u32 (vaddq_u32 (e, d->exponent_bias));
+
+#if !WANT_SIMD_EXCEPT
+  cmp = vcagtq_f32 (n, d->special_bound);
+#endif
+
+  r2 = vmulq_f32 (r, r);
+  p = vfmaq_f32 (C (1), C (0), r);
+  q = vfmaq_f32 (C (3), C (2), r);
+  q = vfmaq_f32 (q, p, r2);
+  p = vmulq_f32 (C (4), r);
+  poly = vfmaq_f32 (p, q, r2);
+
+  if (__glibc_unlikely (v_any_u32 (cmp)))
+#if WANT_SIMD_EXCEPT
+    return special_case (xm, vfmaq_f32 (scale, poly, scale), cmp);
+#else
+    return special_case (poly, n, e, cmp, scale, d);
+#endif
+
+  return vfmaq_f32 (scale, poly, scale);
+}