Re: Proposal: -O4 -> strict-aliasing

[Marc Espie <espie at quatramaran dot ens dot fr>]

In article <199910281246.OAA15434@aras.mra.man.de> you write:
>>>>>> "Mark" == Mark Mitchell <mark@codesourcery.com> writes:
>    Mark> I'm not sure this is the right thing.  We certainly have
>customers who    Mark> want -O2 and -fstrict-aliasing, but specifically
>don't want function
>    Mark> that aren't marked inline to be inlined.  (And -O3 has some serious
>    Mark> compile-time memory usage implications.)  Basically, I don't think
>    Mark> this optimization falls into a total ordering above
>    Mark> -finline-functions.
>
>Just a thought: Making -O4 imply strict-aliasing as proposed does not mean
>that -O2 -fstrict-aliasing isn't possible any more.
>
making -O4 (arbitrarily) imply -fstrict-aliasing is a kludge-over-a-kludge.

I've been advocating removing -fstrict-aliasing from the default optimizations
for now, as knowledgeable users will turn it back on, and naive users don't
get bitten.

There is ABSOLUTELY *no* rationale to arbitrarily put -fstrict-aliasing at
-O4, or -O42, for that matter.

Right now, the various -O levels are defined in terms of purpose, -O
for simple optimizations, -O2 for good optimisations, -O3 for optimisations
that trade-off speed for size...

The only `dangerous' optimisations (-ffast-math) have their own separate
flags, and nobody ever thought of integrating it into -O42...

This doesn't make any sense.