RFR(XS): 8180036: Guard include of fpu_control.h

[Mikael Vidstedt]

Please review this small change which makes the inclusion of fpu_control.h in os_linux_x86.c conditional:

Bug: https://bugs.openjdk.java.net/browse/JDK-8180036 <https://bugs.openjdk.java.net/browse/JDK-8180036>
Webrev: http://cr.openjdk.java.net/~mikael/webrevs/8180036/webrev.00/hotspot/webrev/ <http://cr.openjdk.java.net/~mikael/webrevs/8180036/webrev.00/hotspot/webrev/>

The reason why the file is included in the first place is that on 32-bit x86 there is some logic in os_linux_x86.c to set/get/change the FPU control word using functions implemented by fpu_control.h. This is only done on 32-bit x86, and the code in question is guarded by #ifndef AMD64. However, the inclusion of the fpu_control.h is unconditional. This change makes that consistent by adding the same #ifndef AMD64 guard around the #include.

Cheers,
Mikael