Re: mark_set_resources does not respect UNSPEC_VOLATILE

[Jim Wilson <wilson at cygnus dot com>]

	I've analyzed the problem, and I'm amazed we haven't seen this more
	often.
	Note the reloading of the `gp' register ($28) about half way through.

The gp register value is always the same, except when we are in shared
libraries.  So the bug won't cause any harm unless this is a shared library
function returning to the main program, or this is a function in the main
program which calls into a shared library routine after the gp restore.
These are going to be uncommon situations, so it isn't all that surprising
that it took us a long time to find the problem.

I was a bit surprised the first time I saw this kind of problem, but I've seen
it happen enough times now that it doesn't surprise me much.

	* resource.c (mark_set_resources): Handle UNSPEC_VOLATILE and
	ASM_INPUT.

This looks pretty reasonable.

You check for ASM_INPUT doesn't work the way you intended.  mark_set_resources
recursively processes RTL, and a extended asm with input operations will have
asm_input rtx inside of it, so your check for ASM_INPUT will catch some
extended asms in addition to all traditional asms.  This can be fixed by
adding explicit support for ASM_OPERANDS as is already done in
mark_used_resources.

I think you should go ahead and add support for TRAP_IF and ASM_OPERANDS to
mark_set_resources similarly to how they are handled in mark_used_resources.

Jim