[PATCH] [powerpc] get_rounding_mode: utilize faster method to get rounding mode

["Paul A. Clarke" <pc at us dot ibm dot com>]

From: "Paul A. Clarke" <pc@us.ibm.com>

Add support to use 'mffsl' instruction if compiled for POWER9 (or later).

Also, mask the result to avoid bleeding unrelated bits into the result of
_FPU_GET_RC().

2019-06-05  Paul A. Clarke  <pc@us.ibm.com>

	* sysdeps/powerpc/fpu/fegetexcept.c (__fegetexcept): Replace code
	with call to equivalent function.
	* sysdeps/powerpc/fpu/fenv_libc.h (fegetenv_status): New function.
	* sysdeps/powerpc/fpu_control.h (_FPU_MASK_RC): New.
	  (__FPU_MFFS): New.
	  (__FPU_MFFSL): New.
	  (_FPU_GET_RC): New.
	  (_FPU_GETCW): Use __FPU_MFFS().
	* sysdeps/powerpc/powerpc64/get-rounding-mode.h: New file.
---
 sysdeps/powerpc/fpu/fenv_libc.h               | 15 ++++++++++++
 sysdeps/powerpc/fpu_control.h                 | 29 ++++++++++++++++++++---
 sysdeps/powerpc/powerpc64/get-rounding-mode.h | 33 +++++++++++++++++++++++++++
 3 files changed, 74 insertions(+), 3 deletions(-)
 create mode 100644 sysdeps/powerpc/powerpc64/get-rounding-mode.h

diff --git a/sysdeps/powerpc/fpu/fenv_libc.h b/sysdeps/powerpc/fpu/fenv_libc.h
index 8a0bace..621e57f 100644
--- a/sysdeps/powerpc/fpu/fenv_libc.h
+++ b/sysdeps/powerpc/fpu/fenv_libc.h
@@ -34,6 +34,21 @@ extern const fenv_t *__fe_mask_env (void) attribute_hidden;
    pointer.  */
 #define fegetenv_register() __builtin_mffs()
 
+/* Equivalent to fegetenv_register, but only returns bits for
+   status, exception enables, and mode.  */
+#ifdef _ARCH_PWR9
+#define fegetenv_status() \
+  ({union { double __d; unsigned long long __ll; } __u;	\
+    register double __fr;				\
+    __asm__ ("mffsl %0" : "=f" (__fr));			\
+    __u.__d = __fr;					\
+    __u.__ll;						\
+  })
+#else
+#define fegetenv_status() __builtin_mffs()
+#error "power8"
+#endif
+
 /* Equivalent to fesetenv, but takes a fenv_t instead of a pointer.  */
 #define fesetenv_register(env) \
 	do { \
diff --git a/sysdeps/powerpc/fpu_control.h b/sysdeps/powerpc/fpu_control.h
index e0c5cf6..22c52b7 100644
--- a/sysdeps/powerpc/fpu_control.h
+++ b/sysdeps/powerpc/fpu_control.h
@@ -71,6 +71,8 @@ extern fpu_control_t __fpu_control;
 # define _FPU_RC_UP      0x02
 # define _FPU_RC_ZERO    0x01
 
+# define _FPU_MASK_RC (_FPU_RC_NEAREST|_FPU_RC_DOWN|_FPU_RC_UP|_FPU_RC_ZERO)
+
 # define _FPU_MASK_NI  0x04 /* non-ieee mode */
 
 /* masking of interrupts */
@@ -94,15 +96,36 @@ extern fpu_control_t __fpu_control;
 typedef unsigned int fpu_control_t;
 
 /* Macros for accessing the hardware control word.  */
+# define __FPU_MFFS()						\
+  ({register double __fr;					\
+    __asm__ ("mffs %0" : "=f" (__fr));				\
+    __fr;							\
+  })
+
 # define _FPU_GETCW(cw)						\
   ({union { double __d; unsigned long long __ll; } __u;		\
-    register double __fr;					\
-    __asm__ ("mffs %0" : "=f" (__fr));				\
-    __u.__d = __fr;						\
+    __u.__d = __FPU_MFFS();					\
     (cw) = (fpu_control_t) __u.__ll;				\
     (fpu_control_t) __u.__ll;					\
   })
 
+#ifdef _ARCH_PWR9
+# define __FPU_MFFSL()						\
+  ({register double __fr;					\
+    __asm__ ("mffsl %0" : "=f" (__fr));				\
+    __fr;							\
+  })
+#else
+# define __FPU_MFFSL() __FPU_MFFS()
+#endif
+    
+# define _FPU_GET_RC()						\
+  ({union { double __d; unsigned long long __ll; } __u;		\
+    __u.__d = __FPU_MFFSL();					\
+    __u.__ll &= _FPU_MASK_RC;					\
+    (fpu_control_t) __u.__ll;					\
+  })
+
 # define _FPU_SETCW(cw)						\
   { union { double __d; unsigned long long __ll; } __u;		\
     register double __fr;					\
diff --git a/sysdeps/powerpc/powerpc64/get-rounding-mode.h b/sysdeps/powerpc/powerpc64/get-rounding-mode.h
new file mode 100644
index 0000000..e2fdbbb
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/get-rounding-mode.h
@@ -0,0 +1,33 @@
+/* Determine floating-point rounding mode within libc.  powerpc64 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _POWERPC64_GET_ROUNDING_MODE_H
+#define _POWERPC64_GET_ROUNDING_MODE_H	1
+
+#include <fenv.h>
+#include <fpu_control.h>
+
+/* Return the floating-point rounding mode.  */
+
+static inline int
+get_rounding_mode (void)
+{
+  return _FPU_GET_RC ();
+}
+
+#endif /* get-rounding-mode.h */
-- 
1.8.3.1