On Fri, Aug 21, 2015 at 03:37:38PM +0200, Richard Biener wrote:
> On Fri, Aug 21, 2015 at 2:49 PM, Marek Polacek <pola...@redhat.com> wrote:
> > On Fri, Aug 21, 2015 at 01:27:43PM +0200, Richard Biener wrote:
> >> On Fri, Aug 21, 2015 at 12:52 PM, Marek Polacek <pola...@redhat.com> wrote:
> >> > This fixes the libgo breakage. Seems I really should have removed the
> >> > edge after we split the block with null dereference after __builtin_trap
> >> > statement so that it's unreachable.
> >> >
> >> > Bootstrapped/regtested on x86_64-linux + ppc64-linux + bootstrapped on
> >> > aarch64-linux, ok for trunk?
> >>
> >> Hum. I don't see why this is needed - CFG cleanup (which of course needs
> >> to run!) should do this for you. In fact stray unreachable blocks are
> >> usually
> >> more of a problem.
> >
> > Aha. It seems cleanup does that if I change the code to generate
> > __builtin_unreachable instead of __builtin_trap. A hint maybe? ;)
>
> Not really...
>
> static bool
> cleanup_control_flow_bb (basic_block bb)
> {
> ...
> /* Check for indirect calls that have been turned into
> noreturn calls. */
> else if (is_gimple_call (stmt)
> && gimple_call_noreturn_p (stmt)
> && remove_fallthru_edge (bb->succs))
> retval = true;
>
> and __builtin_trap is NORETURN. But there is the hint where to debug.
Yes, but gimple_call_noreturn_p is false on __builtin_trap. That's quite
confusing... but flags_from_decl_or_type really returns 0 for __builtin_trap.
So can't we use __builtin_unreachable in isolate-path code?
Marek
