GNU C Library master sources branch, hjl/pr14117, updated. glibc-2.15-1183-g69033cb

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- Log -----------------------------------------------------------------
http://sources.redhat.com/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=69033cb3ca74283a01301b77d7318c45971fdb1b

commit 69033cb3ca74283a01301b77d7318c45971fdb1b
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Mon Jun 18 11:07:28 2012 -0700

    Update comments

diff --git a/sysdeps/x86_64/fpu_control.h b/sysdeps/x86_64/fpu_control.h
index 7e4366d..605302c 100644
--- a/sysdeps/x86_64/fpu_control.h
+++ b/sysdeps/x86_64/fpu_control.h
@@ -90,11 +90,16 @@
 /* Type of the control word.  */
 typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));
 
-/* Macros for accessing the hardware control word.
+/* Macros for accessing the hardware control word.  "*&" is used to
+   work around a bug in older versions of GCC.  __volatile__ is used
+   to support combination of writing the control register and reading
+   it back.  Without __volatile__, the old value may be used for reading
+   back under compiler optimization.
 
    Note that the use of these macros is not sufficient anymore with
-   recent hardware.  Some floating point operations are executed in
-   the SSE/SSE2 engines which have their own control and status register.  */
+   recent hardware nor on x86-64.  Some floating point operations are
+   executed in the SSE/SSE2 engines which have their own control and
+   status register.  */
 #define _FPU_GETCW(cw) __asm__ __volatile__ ("fnstcw %0" : "=m" (*&cw))
 #define _FPU_SETCW(cw) __asm__ __volatile__ ("fldcw %0" : : "m" (*&cw))
 

-----------------------------------------------------------------------

Summary of changes:
 sysdeps/x86_64/fpu_control.h |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)


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