[Bug inline-asm/11807] GCC should error out when clobbering the stack pointer and frame pointer

["acahalan at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #24 from acahalan at gmail dot com  2006-04-21 02:11 -------
PIC register: while the user could save and restore this, the whole point of
this fancy assembly notation is so that gcc can do nice scheduling and register
allocation. The save and restore should thus be done by gcc. Perhaps the PIC
register won't soon be needed, so gcc could use it for something else until it
gets reloaded with the normal content. At the very least, gcc could pick a good
location for the save/restore operations.

Frame pointer register: this is the same as the PIC register. It's good to
schedule the save/restore nicely.

Stack pointer register: this one is special. For app code, signals may arrive.
For kernel code, interrupts might be delivered without a stack change. Not
supporting a clobbered stack pointer is definitely tolerable. Ideally this case
could be handled (making the code non-reentrant), but the resulting mess is
probably of very limited use. I could imagine abusing push/pop to iterate over
arrays, but that's insane.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11807