From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Fri, 23 Jan 2026 13:02:17 +0000 (-0300)
Subject: math: Simplify f{max,min}mag template
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6bbe7ae5f3a7ebda2c559de1b8d21f738633d3d2;p=thirdparty%2Fglibc.git

math: Simplify f{max,min}mag template

On aarch64 with gcc-15 it optimizes the fast-path slightly, for fmaxmag:

* master

0000000000000000 <__fmaxmag>:
   0:   d503245f        bti     c
   4:   1e60c01e        fabs    d30, d0
   8:   1e60c03f        fabs    d31, d1
   c:   1e7f23c0        fcmp    d30, d31
  10:   5400004d        b.le    18 <__fmaxmag+0x18>
  14:   d65f03c0        ret
  18:   54000065        b.pl    24 <__fmaxmag+0x24>  // b.nfrst
  1c:   1e604020        fmov    d0, d1
  20:   d65f03c0        ret
  24:   540001e0        b.eq    60 <__fmaxmag+0x60>  // b.none
  [...]
  60:   1e612010        fcmpe   d0, d1
  64:   1e61cc00        fcsel   d0, d0, d1, gt
  68:   d65f03c0        ret

* patch:

0000000000000000 <__fmaxmag>:
   0:   d503245f        bti     c
   4:   1e612000        fcmp    d0, d1
   8:   540000e6        b.vs    24 <__fmaxmag+0x24>
   c:   1e60c01f        fabs    d31, d0
  10:   1e60c03e        fabs    d30, d1
  14:   1e7e23e0        fcmp    d31, d30
  18:   540001c0        b.eq    50 <__fmaxmag+0x50>  // b.none
  1c:   1e60dc20        fcsel   d0, d1, d0, le
  20:   d65f03c0        ret
  [...]
  50:   1e612010        fcmpe   d0, d1
  54:   1e61cc00        fcsel   d0, d0, d1, gt
  58:   d65f03c0        ret
  [...]

Checked on x86_64-linux-gnu, aarch64-linux-gnu, i686-linux-gnu,
arm-linux-gnueabihf, powerpc64le-linux-gnu,
riscv64-linux-gnu-rv64imafdc-lp64d, and loongarch64-linux-gnuf64.

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

diff --git a/math/s_fmaxmag_template.c b/math/s_fmaxmag_template.c
index dc4be5eb18..915f199283 100644
--- a/math/s_fmaxmag_template.c
+++ b/math/s_fmaxmag_template.c
@@ -21,14 +21,14 @@
 FLOAT
 M_DECL_FUNC (__fmaxmag) (FLOAT x, FLOAT y)
 {
-  FLOAT ax = M_FABS (x);
-  FLOAT ay = M_FABS (y);
-  if (isgreater (ax, ay))
-    return x;
-  else if (isless (ax, ay))
-    return y;
-  else if (ax == ay)
-    return x > y ? x : y;
+  if (__glibc_likely (!isunordered (x, y)))
+    {
+      FLOAT ax = M_FABS (x);
+      FLOAT ay = M_FABS (y);
+      if (__glibc_unlikely (ax == ay))
+	return x > y ? x : y;
+      return isgreater (ax, ay) ? x : y;
+    }
   else if (issignaling (x) || issignaling (y))
     return x + y;
   else
diff --git a/math/s_fminmag_template.c b/math/s_fminmag_template.c
index 3c1bdc47f0..d4960baefa 100644
--- a/math/s_fminmag_template.c
+++ b/math/s_fminmag_template.c
@@ -21,14 +21,14 @@
 FLOAT
 M_DECL_FUNC (__fminmag) (FLOAT x, FLOAT y)
 {
-  FLOAT ax = M_FABS (x);
-  FLOAT ay = M_FABS (y);
-  if (isless (ax, ay))
-    return x;
-  else if (isgreater (ax, ay))
-    return y;
-  else if (ax == ay)
-    return x < y ? x : y;
+  if (__glibc_likely (!isunordered (x, y)))
+    {
+      FLOAT ax = M_FABS (x);
+      FLOAT ay = M_FABS (y);
+      if (__glibc_unlikely (ax == ay))
+	return x < y ? x : y;
+      return isless (ax, ay) ? x : y;
+    }
   else if (issignaling (x) || issignaling (y))
     return x + y;
   else