i386/x86_64: Optimize feholdexcept.

3 files changed, 14 insertions, 29 deletions

diff --git a/ChangeLog b/ChangeLog
index 12a99d2..7efa13b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2012-03-19  Richard Henderson  <rth@twiddle.net>
 
+	* sysdeps/i386/fpu/feholdexcpt.c (feholdexcept): Avoid the fldenv.
+	* sysdeps/x86_64/fpu/feholdexcpt.c (feholdexcept): Likewise.
+
 	* sysdeps/generic/math_private.h (default_libc_feupdateenv_test): New.
 	(libc_feupdateenv_test, libc_feupdateenv_testf): New.
 	(libc_feupdateenv_testl): New.
diff --git a/sysdeps/i386/fpu/feholdexcpt.c b/sysdeps/i386/fpu/feholdexcpt.c
index a09d45e..7e10389 100644
--- a/sysdeps/i386/fpu/feholdexcpt.c
+++ b/sysdeps/i386/fpu/feholdexcpt.c
@@ -1,6 +1,5 @@
 /* Store current floating-point environment and clear exceptions.
-   Copyright (C) 1997, 1999, 2003, 2004, 2005, 2007
-   Free Software Foundation, Inc.
+   Copyright (C) 1997-2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
 
@@ -26,19 +25,9 @@
 int
 feholdexcept (fenv_t *envp)
 {
-  fenv_t temp;
-
-  /* Store the environment.  */
-  __asm__ ("fnstenv %0" : "=m" (temp));
-  *envp = temp;
-
-  /* Now set all exceptions to non-stop.  */
-  temp.__control_word |= 0x3f;
-
-  /* And clear all exceptions.  */
-  temp.__status_word &= ~0x3f;
-
-  __asm__ ("fldenv %0" : : "m" (temp));
+  /* Store the environment.  Recall that fnstenv has a side effect of
+     masking all exceptions.  Then clear all exceptions.  */
+  __asm__ volatile ("fnstenv %0; fnclex" : "=m" (*envp));
 
   /* If the CPU supports SSE we set the MXCSR as well.  */
   if ((GLRO(dl_hwcap) & HWCAP_I386_XMM) != 0)
diff --git a/sysdeps/x86_64/fpu/feholdexcpt.c b/sysdeps/x86_64/fpu/feholdexcpt.c
index b547b34..b380479 100644
--- a/sysdeps/x86_64/fpu/feholdexcpt.c
+++ b/sysdeps/x86_64/fpu/feholdexcpt.c
@@ -1,5 +1,5 @@
 /* Store current floating-point environment and clear exceptions.
-   Copyright (C) 2001, 2005, 2007 Free Software Foundation, Inc.
+   Copyright (C) 2001-2012 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
@@ -22,20 +22,13 @@ int
 feholdexcept (fenv_t *envp)
 {
   unsigned int mxcsr;
-  fenv_t temp;
 
-  /* Store the environment.  */
-  __asm__ ("fnstenv %0\n"
-	   "stmxcsr %1" : "=m" (temp), "=m" (temp.__mxcsr));
-  *envp = temp;
-
-  /* Now set all exceptions to non-stop, first the x87 FPU.  */
-  temp.__control_word |= 0x3f;
-
-  /* And clear all exceptions.  */
-  temp.__status_word &= ~0x3f;
-
-  __asm__ ("fldenv %0" : : "m" (temp));
+  /* Store the environment.  Recall that fnstenv has a side effect of
+     masking all exceptions.  Then clear all exceptions.  */
+  __asm__ ("fnstenv %0\n\t"
+	   "stmxcsr %1\n\t"
+	   "fnclex"
+	   : "=m" (*envp), "=m" (envp->__mxcsr));
 
   /* Set the SSE MXCSR register.  */
   mxcsr = (envp->__mxcsr | 0x1f80) & ~0x3f;