From patchwork Tue Jun 10 17:01:00 2014
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X-Patchwork-Submitter: Wilco Dijkstra <wdijkstr@arm.com>
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From: "Wilco" <wdijkstr@arm.com>
To: "GNU C Library" <libc-alpha@sourceware.org>
Subject: [PATCH 5/5] ARM: Cleanup fenv implementation
Date: Tue, 10 Jun 2014 18:01:00 +0100
Message-ID: <003e01cf84cd$8e1cfbe0$aa56f3a0$@com>
MIME-Version: 1.0
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Hi,

This is a series of patches which improves the ARM fenv implementation. Improve fesetenv to use a
similar optimized implementation as feupdateenv.

OK for checkin?

Wilco

ChangeLog:
2014-06-10  Wilco  <wdijkstr@arm.com>

	* sysdeps/arm/fesetenv.c (fesetenv): Optimize implementation.
---
 sysdeps/arm/fesetenv.c |   35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/sysdeps/arm/fesetenv.c b/sysdeps/arm/fesetenv.c
index 62031d5..66b248a 100644
--- a/sysdeps/arm/fesetenv.c
+++ b/sysdeps/arm/fesetenv.c
@@ -17,14 +17,13 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <fenv.h>
-#include <fpu_control.h>
 #include <arm-features.h>
 
 
 int
 fesetenv (const fenv_t *envp)
 {
-  fpu_control_t fpscr;
+  fpu_control_t fpscr, new_fpscr, updated_fpscr;
 
   /* Fail if a VFP unit isn't present.  */
   if (!ARM_HAVE_VFP)
@@ -32,25 +31,31 @@ fesetenv (const fenv_t *envp)
 
   _FPU_GETCW (fpscr);
 
-  /* Preserve the reserved FPSCR flags.  */
-  fpscr &= _FPU_RESERVED;
+  if ((envp != FE_DFL_ENV) && (envp != FE_NOMASK_ENV))
+    {
+      /* The new FPSCR is valid, so don't merge the reserved flags.  */
+      new_fpscr = envp->__cw;
 
-  if (envp == FE_DFL_ENV)
-    fpscr |= _FPU_DEFAULT;
-  else if (envp == FE_NOMASK_ENV)
-    fpscr |= _FPU_IEEE;
-  else
-    fpscr |= envp->__cw & ~_FPU_RESERVED;
+      /* Write new FPSCR if different (ignoring NZCV flags).  */
+      if (((fpscr ^ new_fpscr) & ~_FPU_MASK_NZCV) != 0)
+	_FPU_SETCW (new_fpscr);
 
-  _FPU_SETCW (fpscr);
+      return 0;
+    }
 
-  if (envp == FE_NOMASK_ENV)
+  /* Preserve the reserved FPSCR flags.  */
+  new_fpscr = fpscr & _FPU_RESERVED;
+  new_fpscr |= (envp == FE_DFL_ENV) ? _FPU_DEFAULT : _FPU_IEEE;
+
+  if (((new_fpscr ^ fpscr) & ~_FPU_MASK_NZCV) != 0)
     {
+      _FPU_SETCW (new_fpscr);
+
       /* Not all VFP architectures support trapping exceptions, so
 	 test whether the relevant bits were set and fail if not.  */
-      _FPU_GETCW (fpscr);
-      if ((fpscr & _FPU_IEEE) != _FPU_IEEE)
-	return 1;
+      _FPU_GETCW (updated_fpscr);
+
+      return new_fpscr & ~updated_fpscr;
     }
 
   return 0;