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Re: type based aliasing again
Mark Mitchell wrote:
> >>>>> "David" == David Edelsohn <dje@watson.ibm.com> writes:
>
> David> FYI, IBM's AIX compiler does not enable "ANSI
> David> aliasing" by default when the compiler is invoked with
>
> Someone reported something similar for the DEC copmiler; `cc' is
> -fno-strict-aliasing, while some more progressive-sounding compiler
> name is -fstrict-aliasing.
>
> One thing important about these data points, though, is that major
> vendors must be finding that not too many programs use the invalid
> constructs in question. Otherwise, they would not have dared to
> enable these options. (Of course, they could have the kind of
The SCO UnixWare (and therefore, UDK) compilers for IA32 do perform this
at high levels of optimization.
The Intel C Compiler performs this optimization, but only if you
explictly add the '-distype' flag.
I can't recall having been bitten by either (I uses the UW compiler much
more than icc) but I don't really know how aggressively either optimizes
this specific construct. OTOH, the UW compiler frequently generates
better code than GCC so I'm inclined to say if there's an optimization
opportunity it probably grabs it.
RJL