review request for 6792301

[Xiaobin Lu]

6792301:  StackAlignmentInBytes not honored for compiled native methods

Webrev: http://webrev.invokedynamic.info/xiaobin.lu/6792301/webrev/

Details:

Crashes have been observed using SoyLatte and the BSD port of OpenJDK on 
Mac OS X with applications involving many native calls, specifically 
graphical programs. Various parties have identified the reason as 
misalignment of the stack; Mac OS X requires 16-byte alignment of stack 
frames even on 32-bit platforms. While StackAlignmentInBytes is defined 
as 16 in 32-bit x86 HotSpot, the compiled native wrappers for frequently 
invoked JNI methods are not appropriately rounding up the frame size. It 
appears that this is the only place in the VM where the stack alignment 
is not being obeyed. The fix is quite straightforward as indicated in 
generate_native_wrapper method.

Verified by:

The crashes previously seen on Mac OS using Soylatte are gone.
runThese full server

Thanks,
-Xiaobin