[PATCH 1/5] riscv: Optimize fmaximum_num and fminimum_num

[Julian Zhu]

Implement the C23 maximumNumber and minimumNumber operations with the RISC-V fmax and fmin instructions for float and double.  These instructions provide the required NaN and signed-zero semantics using the base F and D extensions.

Signed-off-by: Julian Zhu <jz531210@gmail.com>
---
 sysdeps/riscv/rvd/s_fmaximum_num.c  | 37 +++++++++++++++++++++++++++++
 sysdeps/riscv/rvd/s_fminimum_num.c  | 37 +++++++++++++++++++++++++++++
 sysdeps/riscv/rvf/s_fmaximum_numf.c | 32 +++++++++++++++++++++++++
 sysdeps/riscv/rvf/s_fminimum_numf.c | 32 +++++++++++++++++++++++++
 4 files changed, 138 insertions(+)
 create mode 100644 sysdeps/riscv/rvd/s_fmaximum_num.c
 create mode 100644 sysdeps/riscv/rvd/s_fminimum_num.c
 create mode 100644 sysdeps/riscv/rvf/s_fmaximum_numf.c
 create mode 100644 sysdeps/riscv/rvf/s_fminimum_numf.c

diff --git a/sysdeps/riscv/rvd/s_fmaximum_num.c b/sysdeps/riscv/rvd/s_fmaximum_num.c
new file mode 100644
index 0000000000..0203329935
--- /dev/null
+++ b/sysdeps/riscv/rvd/s_fmaximum_num.c
@@ -0,0 +1,37 @@
+/* fmaximum_num().  RISC-V version.
+   Copyright (C) 2026 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 <math.h>
+#include <libm-alias-double.h>
+
+/* fmaximum_num is the IEEE 754-2019 maximumNumber operation: it returns
+   the larger operand, treats a NaN operand as if it were absent (so a
+   NaN and a number yield the number), returns a quiet NaN only when both
+   operands are NaN, and orders +0 above -0.  The RISC-V fmax.d
+   instruction implements exactly these semantics and raises the invalid
+   exception for a signaling NaN input, so unlike fmax it needs no NaN
+   pre-check.  */
+
+double
+__fmaximum_num (double x, double y)
+{
+  double res;
+  asm ("fmax.d %0, %1, %2" : "=f" (res) : "f" (x), "f" (y));
+  return res;
+}
+libm_alias_double (__fmaximum_num, fmaximum_num)
diff --git a/sysdeps/riscv/rvd/s_fminimum_num.c b/sysdeps/riscv/rvd/s_fminimum_num.c
new file mode 100644
index 0000000000..7875f3cb8e
--- /dev/null
+++ b/sysdeps/riscv/rvd/s_fminimum_num.c
@@ -0,0 +1,37 @@
+/* fminimum_num().  RISC-V version.
+   Copyright (C) 2026 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 <math.h>
+#include <libm-alias-double.h>
+
+/* fminimum_num is the IEEE 754-2019 minimumNumber operation: it returns
+   the smaller operand, treats a NaN operand as if it were absent (so a
+   NaN and a number yield the number), returns a quiet NaN only when both
+   operands are NaN, and orders -0 below +0.  The RISC-V fmin.d
+   instruction implements exactly these semantics and raises the invalid
+   exception for a signaling NaN input, so unlike fmin it needs no NaN
+   pre-check.  */
+
+double
+__fminimum_num (double x, double y)
+{
+  double res;
+  asm ("fmin.d %0, %1, %2" : "=f" (res) : "f" (x), "f" (y));
+  return res;
+}
+libm_alias_double (__fminimum_num, fminimum_num)
diff --git a/sysdeps/riscv/rvf/s_fmaximum_numf.c b/sysdeps/riscv/rvf/s_fmaximum_numf.c
new file mode 100644
index 0000000000..334a177f63
--- /dev/null
+++ b/sysdeps/riscv/rvf/s_fmaximum_numf.c
@@ -0,0 +1,32 @@
+/* fmaximum_numf().  RISC-V version.
+   Copyright (C) 2026 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 <math.h>
+#include <libm-alias-float.h>
+
+/* See s_fmaximum_num.c for a description of the semantics; the RISC-V
+   fmax.s instruction implements maximumNumber for single precision.  */
+
+float
+__fmaximum_numf (float x, float y)
+{
+  float res;
+  asm ("fmax.s %0, %1, %2" : "=f" (res) : "f" (x), "f" (y));
+  return res;
+}
+libm_alias_float (__fmaximum_num, fmaximum_num)
diff --git a/sysdeps/riscv/rvf/s_fminimum_numf.c b/sysdeps/riscv/rvf/s_fminimum_numf.c
new file mode 100644
index 0000000000..71d2683a97
--- /dev/null
+++ b/sysdeps/riscv/rvf/s_fminimum_numf.c
@@ -0,0 +1,32 @@
+/* fminimum_numf().  RISC-V version.
+   Copyright (C) 2026 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 <math.h>
+#include <libm-alias-float.h>
+
+/* See s_fminimum_num.c for a description of the semantics; the RISC-V
+   fmin.s instruction implements minimumNumber for single precision.  */
+
+float
+__fminimum_numf (float x, float y)
+{
+  float res;
+  asm ("fmin.s %0, %1, %2" : "=f" (res) : "f" (x), "f" (y));
+  return res;
+}
+libm_alias_float (__fminimum_num, fminimum_num)
-- 
2.53.0