>>>>> "Nathan" == Nathan Sidwell <[EMAIL PROTECTED]> writes:
Nathan> Dale Johannesen wrote:
>> However, as a QOI issue, I believe the compiler should treat the
>> reference as volatile if either the object or the lvalue is
>> volatile. That is obviously the user's intent.
Nathan> I'm not disagreeing with you, but I wonder at gcc's ability
Nathan> to make good on such a promise. A cast introducing a
Nathan> volatile qualifier will be a NOP_EXPR, and gcc tends to strip
Nathan> those at every opportunity.
Is that true only for casts that add the volatile qualifier but
otherwise do nothing? A quick tests suggests yes.
This change bothers me a lot. It seems likely that this will break
existing code possibly in subtle ways. At least it doesn't do this
when the cast is from a constant integer into a volatile int * --
which is common syntax for CSR references.
Still, never mind what the C spec appears to say, optimizing away the
cast cannot possibly what the user intended. If the standard implies
that this is right, I'd argue that's a standards bug. In any case,
such a transformation should at least generate a warning. Preferably
it should revert to the old semantics.
paul
