From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Fri, 10 Oct 2025 17:49:20 +0000 (-0300)
Subject: math: Optimize fma call on acospif
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c075ff00a63bc1f0428cbf6c53e930fbbc6ef5c2;p=thirdparty%2Fglibc.git

math: Optimize fma call on acospif

The fma is required only for inputs less than 0x1.0fd288p-127.  Also
only add the extra check for !__FP_FAST_FMA targets.

Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: Paul Zimmermann <Paul.Zimmermann@inria.fr>
---

diff --git a/sysdeps/ieee754/flt-32/s_acospif.c b/sysdeps/ieee754/flt-32/s_acospif.c
index caf65d42f3..63230bd3b3 100644
--- a/sysdeps/ieee754/flt-32/s_acospif.c
+++ b/sysdeps/ieee754/flt-32/s_acospif.c
@@ -67,7 +67,12 @@ __acospif (float x)
       /* For |x| <= 0x1.0fd288p-127, c0 += c4*(z4*z4) would raise a spurious
 	 underflow exception, we use an FMA instead, where c4 * z4 does not
 	 underflow. */
-      c0 = fma (c4 * z4, z4, c0);
+#ifndef __FP_FAST_FMA
+      if (__glibc_likely (ax > 0x1.0fd288p-127))
+	c0 = (c4 * z4) * z4 + c0;
+      else
+#endif
+	c0 = fma (c4 * z4, z4, c0);
       return 0.5 - z * c0;
     }
   else