On 11/10/13 05:34, Eric Botcazou wrote:
But I think that you cannot transform
foo ()
{
*0 = 1;
}
to __builtin_trap as you can catch the trap via an exception handler
in a caller of foo, no?
That is true. OK, I can see an argument that when using
-fnon-call-exceptions that kind of code should not be changed to call
__builtin_trap.
That's exactly the reason why gnat.dg/memtrap.adb started to fail after
Jeff's
patch went it. So, if -fisolate-erroneous-paths isn't amended, we'll need
to
disable it in Ada like in Go.
In that case I think it would be fine to run the isolate paths
optimization, but to not omit the actual dereference of the NULL
pointer (possibly the dereference could be followed by a trap).
This would probably work for Ada as well.
OK. It sounds like there's a pretty general consensus that we ought ot go
ahead and leave in a load/store of a NULL pointer. I'll go ahead and run
with that. I'll probably just emit SSA_NAME = *0, unless someone thinks we
ought ot distinguish between loads and stores, emitting SSA_NAME = *0 and *0
= 0 for the two cases respectively.