On Thu, Dec 02, 2021 at 09:23:20AM -0500, Vladimir Makarov wrote:
>
> On 2021-12-02 09:00, Jakub Jelinek wrote:
> > On Thu, Dec 02, 2021 at 08:53:31AM -0500, Vladimir Makarov via Gcc-patches
> > wrote:
> > > The following patch fixes
> > >
> > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103437
> > >
> > > The patch was successfully bootstrapped and tested on x86-64. There is no
> > > test as the bug occurs on GCC built with sanitizing for an existing go
> > > test.
> > I'm afraid we can't use __builtin_smul_overflow, not all system compilers
> > will have that.
> > But, as it is done in int and we kind of rely on int being 32-bit on host
> > and rely on long long being 64-bit, I think you can do something like:
> > long long priorityll = (long long) mult * diff;
> > priority = priorityll;
> > if (priorityll != priority
> > ...
> >
> >
> My 1st version of the patch was based on long long but the standard does not
> guarantee that int size is smaller than long long size. Although it is true
> for all targets supported by GCC.
>
> Another solution would be to switching to int32_t instead of int for costs
> but it will require a lot of changes in RA code.
>
> I see your point for usage system compiler different from GCC and LLVM. I
> guess I could change it to
>
> #if __GNUC__ >= 5
#ifdef __has_builtin
# if __has_builtin(__builtin_smul_overflow)
would be the best check.
And you can just gcc_assert (sizeof (long long) >= 2 * sizeof (int));
in the fallback code ;)
Jakub
