[glibc] LoongArch: Add support for ilogb[f]

[Yinyu Cai <caiyinyu@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=885d340f20aab989482b8a1f844a224a1656d52c

commit 885d340f20aab989482b8a1f844a224a1656d52c
Author: Xiaolin Tang <tangxiaolin@loongson.cn>
Date:   Wed Nov 23 11:49:26 2022 +0800

    LoongArch: Add support for ilogb[f]
    
    Add inline assembler for the ilogb functions. Passes GLIBC regression.

Diff:
---
 sysdeps/loongarch/fpu/e_ilogb.c  | 39 +++++++++++++++++++++++++++++++++++++++
 sysdeps/loongarch/fpu/e_ilogbf.c | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)

diff --git a/sysdeps/loongarch/fpu/e_ilogb.c b/sysdeps/loongarch/fpu/e_ilogb.c
new file mode 100644
index 0000000000..f9ada6921a
--- /dev/null
+++ b/sysdeps/loongarch/fpu/e_ilogb.c
@@ -0,0 +1,39 @@
+/* __ieee754_ilogb().  LoongArch version.
+   Copyright (C) 2022 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/>.  */
+
+#define NO_MATH_REDIRECT
+#include <math.h>
+#include <fpu_control.h>
+
+int
+__ieee754_ilogb (double x)
+{
+  int x_cond;
+  asm volatile ("fclass.d \t%0, %1" : "=f" (x_cond) : "f" (x));
+
+  if (__glibc_unlikely (x_cond & _FCLASS_ZERO))
+      return FP_ILOGB0;
+  else if (__glibc_unlikely (x_cond & ( _FCLASS_NAN | _FCLASS_INF)))
+      return FP_ILOGBNAN;
+  else
+    {
+      asm volatile ("fabs.d \t%0, %1" : "=f" (x) : "f" (x));
+      asm volatile ("flogb.d \t%0, %1" : "=f" (x) : "f" (x));
+      return x;
+    }
+}
diff --git a/sysdeps/loongarch/fpu/e_ilogbf.c b/sysdeps/loongarch/fpu/e_ilogbf.c
new file mode 100644
index 0000000000..e1da48ecfc
--- /dev/null
+++ b/sysdeps/loongarch/fpu/e_ilogbf.c
@@ -0,0 +1,39 @@
+/* __ieee754_ilogbf().  LoongArch version.
+   Copyright (C) 2022 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/>.  */
+
+#define NO_MATH_REDIRECT
+#include <math.h>
+#include <fpu_control.h>
+
+int
+__ieee754_ilogbf (float x)
+{
+  int x_cond;
+  asm volatile ("fclass.s \t%0, %1" : "=f" (x_cond) : "f" (x));
+
+  if (__glibc_unlikely (x_cond & _FCLASS_ZERO))
+      return FP_ILOGB0;
+  else if (__glibc_unlikely (x_cond & ( _FCLASS_NAN | _FCLASS_INF)))
+      return FP_ILOGBNAN;
+  else
+    {
+      asm volatile ("fabs.s \t%0, %1" : "=f" (x) : "f" (x));
+      asm volatile ("flogb.s \t%0, %1" : "=f" (x) : "f" (x));
+      return x;
+    }
+}