From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Fri, 23 Jan 2026 13:02:21 +0000 (-0300)
Subject: math: Order signed zeros in f{max,min}mag{f,l,f128}
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=822bb1127851fe2b3817481085220cd73a8998ad;p=thirdparty%2Fglibc.git

math: Order signed zeros in f{max,min}mag{f,l,f128}

The functions are documented to behave like fmax/fmin when the
arguments have the same absolute value.

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/manual/arith.texi b/manual/arith.texi
index 7846b6903e..df6d25e0ba 100644
--- a/manual/arith.texi
+++ b/manual/arith.texi
@@ -2201,7 +2201,8 @@ treated as greater than negative zero.
 These functions, from TS 18661-1:2014 and TS 18661-3:2015, return
 whichever of the two values @var{x} and @var{y} has the smaller absolute
 value.  If both have the same absolute value, or either is NaN, they
-behave the same as the @code{fmin} functions.
+behave the same as the @code{fmin} functions (including the order of
+signed zeros).
 @end deftypefun
 
 @deftypefun double fmaxmag (double @var{x}, double @var{y})
diff --git a/math/libm-test-fmaxmag.inc b/math/libm-test-fmaxmag.inc
index 3940a45536..45f3873225 100644
--- a/math/libm-test-fmaxmag.inc
+++ b/math/libm-test-fmaxmag.inc
@@ -22,8 +22,9 @@ static const struct test_ff_f_data fmaxmag_test_data[] =
   {
     TEST_ff_f (fmaxmag, 0, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_ff_f (fmaxmag, minus_zero, minus_zero, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
-    TEST_ff_f (fmaxmag, 0, minus_zero, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED|IGNORE_ZERO_INF_SIGN),
-    TEST_ff_f (fmaxmag, minus_zero, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED|IGNORE_ZERO_INF_SIGN),
+    /* The order signed zeros are implemented as a QoI in the generic implementation.  */
+    TEST_ff_f (fmaxmag, 0, minus_zero, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fmaxmag, minus_zero, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_ff_f (fmaxmag, min_subnorm_value, min_subnorm_value, min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_ff_f (fmaxmag, min_subnorm_value, -min_subnorm_value, min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_ff_f (fmaxmag, -min_subnorm_value, min_subnorm_value, min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
diff --git a/math/libm-test-fminmag.inc b/math/libm-test-fminmag.inc
index 5c80e84de3..979b10eb97 100644
--- a/math/libm-test-fminmag.inc
+++ b/math/libm-test-fminmag.inc
@@ -22,8 +22,9 @@ static const struct test_ff_f_data fminmag_test_data[] =
   {
     TEST_ff_f (fminmag, 0, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_ff_f (fminmag, minus_zero, minus_zero, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
-    TEST_ff_f (fminmag, 0, minus_zero, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED|IGNORE_ZERO_INF_SIGN),
-    TEST_ff_f (fminmag, minus_zero, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED|IGNORE_ZERO_INF_SIGN),
+    /* The order signed zeros are implemented as a QoI in the generic implementation.  */
+    TEST_ff_f (fminmag, 0, minus_zero, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fminmag, minus_zero, 0, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_ff_f (fminmag, min_subnorm_value, min_subnorm_value, min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_ff_f (fminmag, min_subnorm_value, -min_subnorm_value, -min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_ff_f (fminmag, -min_subnorm_value, min_subnorm_value, -min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
diff --git a/math/s_fmaxmag_template.c b/math/s_fmaxmag_template.c
index 915f199283..11df91d092 100644
--- a/math/s_fmaxmag_template.c
+++ b/math/s_fmaxmag_template.c
@@ -26,7 +26,7 @@ M_DECL_FUNC (__fmaxmag) (FLOAT x, FLOAT y)
       FLOAT ax = M_FABS (x);
       FLOAT ay = M_FABS (y);
       if (__glibc_unlikely (ax == ay))
-	return x > y ? x : y;
+        return signbit (x) ? y : x;
       return isgreater (ax, ay) ? x : y;
     }
   else if (issignaling (x) || issignaling (y))
diff --git a/math/s_fminmag_template.c b/math/s_fminmag_template.c
index d4960baefa..88fbac61e5 100644
--- a/math/s_fminmag_template.c
+++ b/math/s_fminmag_template.c
@@ -26,7 +26,7 @@ M_DECL_FUNC (__fminmag) (FLOAT x, FLOAT y)
       FLOAT ax = M_FABS (x);
       FLOAT ay = M_FABS (y);
       if (__glibc_unlikely (ax == ay))
-	return x < y ? x : y;
+        return signbit (x) ? x : y;
       return isless (ax, ay) ? x : y;
     }
   else if (issignaling (x) || issignaling (y))