Aarch64: Improve codegen in SVE exp and users, and update expf_inline

Use unpredicted muls, and improve memory access.
7%, 3% and 1% improvement in throughput microbenchmark on Neoverse V1,
for exp, exp2 and cosh respectively.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

1 files changed, 14 insertions, 12 deletions

diff --git a/sysdeps/aarch64/fpu/exp2_sve.c b/sysdeps/aarch64/fpu/exp2_sve.c
index a37c33092a..6db85266ca 100644
--- a/sysdeps/aarch64/fpu/exp2_sve.c
+++ b/sysdeps/aarch64/fpu/exp2_sve.c
@@ -18,7 +18,6 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include "sv_math.h"
-#include "poly_sve_f64.h"
 
 #define N (1 << V_EXP_TABLE_BITS)
 
@@ -27,15 +26,15 @@
 
 static const struct data
 {
-  double poly[4];
+  double c0, c2;
+  double c1, c3;
   double shift, big_bound, uoflow_bound;
 } data = {
   /* Coefficients are computed using Remez algorithm with
      minimisation of the absolute error.  */
-  .poly = { 0x1.62e42fefa3686p-1, 0x1.ebfbdff82c241p-3, 0x1.c6b09b16de99ap-5,
-	    0x1.3b2abf5571ad8p-7 },
-  .shift = 0x1.8p52 / N,
-  .uoflow_bound = UOFlowBound,
+  .c0 = 0x1.62e42fefa3686p-1, .c1 = 0x1.ebfbdff82c241p-3,
+  .c2 = 0x1.c6b09b16de99ap-5, .c3 = 0x1.3b2abf5571ad8p-7,
+  .shift = 0x1.8p52 / N,      .uoflow_bound = UOFlowBound,
   .big_bound = BigBound,
 };
 
@@ -67,9 +66,9 @@ special_case (svbool_t pg, svfloat64_t s, svfloat64_t y, svfloat64_t n,
   /* |n| > 1280 => 2^(n) overflows.  */
   svbool_t p_cmp = svacgt (pg, n, d->uoflow_bound);
 
-  svfloat64_t r1 = svmul_x (pg, s1, s1);
+  svfloat64_t r1 = svmul_x (svptrue_b64 (), s1, s1);
   svfloat64_t r2 = svmla_x (pg, s2, s2, y);
-  svfloat64_t r0 = svmul_x (pg, r2, s1);
+  svfloat64_t r0 = svmul_x (svptrue_b64 (), r2, s1);
 
   return svsel (p_cmp, r1, r0);
 }
@@ -99,11 +98,14 @@ svfloat64_t SV_NAME_D1 (exp2) (svfloat64_t x, svbool_t pg)
   svuint64_t top = svlsl_x (pg, ki, 52 - V_EXP_TABLE_BITS);
   svfloat64_t scale = svreinterpret_f64 (svadd_x (pg, sbits, top));
 
+  svfloat64_t c13 = svld1rq (svptrue_b64 (), &d->c1);
   /* Approximate exp2(r) using polynomial.  */
-  svfloat64_t r2 = svmul_x (pg, r, r);
-  svfloat64_t p = sv_pairwise_poly_3_f64_x (pg, r, r2, d->poly);
-  svfloat64_t y = svmul_x (pg, r, p);
-
+  /* y = exp2(r) - 1 ~= C0 r + C1 r^2 + C2 r^3 + C3 r^4.  */
+  svfloat64_t r2 = svmul_x (svptrue_b64 (), r, r);
+  svfloat64_t p01 = svmla_lane (sv_f64 (d->c0), r, c13, 0);
+  svfloat64_t p23 = svmla_lane (sv_f64 (d->c2), r, c13, 1);
+  svfloat64_t p = svmla_x (pg, p01, p23, r2);
+  svfloat64_t y = svmul_x (svptrue_b64 (), r, p);
   /* Assemble exp2(x) = exp2(r) * scale.  */
   if (__glibc_unlikely (svptest_any (pg, special)))
     return special_case (pg, scale, y, kd, d);