[glibc] S390: Implement math-barriers math_opt_barrier and math_force_eval.

[glibc] S390: Implement math-barriers math_opt_barrier and math_force_eval.

[Stefan Liebler]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=433a2ba68cd91842546e0f0d43d65835634d570d

commit 433a2ba68cd91842546e0f0d43d65835634d570d
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Wed Dec 11 15:09:32 2019 +0100

    S390: Implement math-barriers math_opt_barrier and math_force_eval.
    
    This patch implements the s390 specific math barriers in order
    to omit the store and load from stack if possible.

Diff:
---
 sysdeps/s390/fpu/math-barriers.h | 46 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/sysdeps/s390/fpu/math-barriers.h b/sysdeps/s390/fpu/math-barriers.h
new file mode 100644
index 0000000..7c3e6b1
--- /dev/null
+++ b/sysdeps/s390/fpu/math-barriers.h
@@ -0,0 +1,46 @@
+/* Control when floating-point expressions are evaluated.  s390 version.
+   Copyright (C) 2019 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 S390_MATH_BARRIERS_H
+#define S390_MATH_BARRIERS_H 1
+
+#ifdef HAVE_S390_VX_GCC_SUPPORT
+# define ASM_CONSTRAINT_VR "v"
+#else
+# define ASM_CONSTRAINT_VR
+#endif
+
+#define math_opt_barrier(x)						\
+  ({ __typeof (x) __x = (x);						\
+    if (__builtin_types_compatible_p (__typeof (x), _Float128))		\
+      __asm__ ("# math_opt_barrier_f128 %0" : "+fm" (__x));		\
+    else								\
+      __asm__ ("# math_opt_barrier %0"					\
+	       : "+f" ASM_CONSTRAINT_VR "m" (__x));			\
+    __x; })
+#define math_force_eval(x)						\
+  ({ __typeof (x) __x = (x);						\
+    if (__builtin_types_compatible_p (__typeof (x), _Float128))		\
+      __asm__ __volatile__ ("# math_force_eval_f128 %0"			\
+			    : : "fm" (__x));				\
+    else								\
+      __asm__ __volatile__ ("# math_force_eval %0"			\
+			    : : "f" ASM_CONSTRAINT_VR "m" (__x));	\
+  })
+
+#endif