[Valgrind-developers] better coordination with user stack switching

[John R. <jr...@Bi...>]

The attached patch introduces new internal calls which give
better coordination with explicit user stack switching:
   VG_USERREQ__STACK_SWITCH   notify V of explicit switch
   VG_USERREQ__STACK_DEREGADDR   de-register by address (not id)
The patch is against valgrind-3.2.3.

The patch also strengthens the logic of VG_(switch_stack):
   the new stack always becomes current_stack
   allow old and new to be the same

An example implementation of longjmp() for x86 is included.
Perhaps VEX could be enhanced later so that "movl ...,%esp"
(or any non-incremental operation with stack pointer as destination)
generated VG_USERREQ__STACK_SWITCH automatically, but not now.

-- 
John Reiser, jr...@Bi...