[PATCH] Fix libgo breakage (PR tree-optimization/67284)
Richard Biener
rguenther@suse.de
Fri Aug 21 16:23:00 GMT 2015
On August 21, 2015 5:09:46 PM GMT+02:00, Jeff Law <law@redhat.com> wrote:
>On 08/21/2015 08:41 AM, Marek Polacek wrote:
>> On Fri, Aug 21, 2015 at 03:37:38PM +0200, Richard Biener wrote:
>>> On Fri, Aug 21, 2015 at 2:49 PM, Marek Polacek <polacek@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
><polacek@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.
>Well, if that's intentional (and offhand I have no idea if it is), then
>
>you could emit a __builtin_trap followed by a __builtin_unreachable.
Looking at builtins.def I'd say it should be no return.
Richard.
>jeff
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