Done.
--Josh
At 22:57 on 12/31/2002 GMT, Nicholas Clark <[EMAIL PROTECTED]> wrote:
> Currently Parrot is picking up Perl's C compiler flags. Perl is quite
> deliberately attempting to set -fno-strict-aliasing, to stop gcc using
> ANSI's aliasing rules to infer possible optimisations; optimisations that
> will actually break Perl's code.
>
> (Don't ask me to remember exactly what the aliasing rules are, let alone
> explain them correctly, but it's something to do with more than one type of
> pointer not being allowed to point at the same thing (except via a union,
> and where char pointers are exempt) in a strictly conformant ANSI C
> program. Providing this holds true in the C source, the compiler can safely
> reorder memory access and potentially gain speedups. Perl's source isn't
> ANSI conformant in this way. Well, you can ask what the aliasing rules are,
> but I won't answer)
>
> The upshot is that you can't guarantee that any compiler won't be optimising
> based on aliasing assumptions, because, hell, it's allowed to. And we may
> not be able to turn it off. So we ought to be writing code that doesn't make
> aliasing assumptions. Hence we ought to remove -fno-strict-aliasing from
> Parrot's cflags. And as Dan put it "see what breaks". So far nothing, at
> least for a test build on Debian/x86. And as we're now letting gcc make
> aliasing based optimisations, we might see more speed. (And maybe unicorns,
> flying pigs, and round tuits)
>
> Nicholas Clark
>
> --- config/inter/progs.pl~ Fri Oct 25 11:23:17 2002
> +++ config/inter/progs.pl Tue Dec 31 21:18:24 2002
> @@ -15,6 +15,7 @@ sub runstep {
> my($cc, $link, $ld, $ccflags, $linkflags, $ldflags, $libs) =
> Configure::Data->get(qw(cc link ld ccflags linkflags ldflags libs));
> $ccflags =~ s/-D(PERL|HAVE)_\w+\s*//g;
> + $ccflags =~ s/-fno-strict-aliasing//g;
> $linkflags =~ s/-libpath:\S+//g;
> $ldflags =~ s/-libpath:\S+//g;
> my $debug='n';
