LoongArch: Add math-barriers.h

This patch implements the LoongArch specific math barriers in order to omit
the store and load from stack if possible.

Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

sysdeps/loongarch/fpu/math-barriers.h

@@ -0,0 +1,28 @@
+/* Control when floating-point expressions are evaluated.  LoongArch version.
+   Copyright (C) 2023 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/>.  */
+
+#ifndef _LOONGARCH_MATH_BARRIERS_H
+#define _LOONGARCH_MATH_BARRIERS_H 1
+
+/* Generic code forces values to memory; we don't need to do that.  */
+#define math_opt_barrier(x)					\
+  ({ __typeof (x) __x = (x); __asm ("" : "+frm" (__x)); __x; })
+#define math_force_eval(x)						\
+  ({ __typeof (x) __x = (x); __asm __volatile__ ("" : : "frm" (__x)); })
+
+#endif /* math-barriers.h */