Re: [PATCH] expr.cc: avoid unexpected side effects in expand_expr_divmod optimization

[Jeff Law <jeffreyalaw@gmail.com>]

On 1/9/23 02:57, Jakub Jelinek via Gcc-patches wrote:
> On Mon, Jan 09, 2023 at 09:05:26AM +0100, Richard Biener wrote:
>> On Wed, Jan 4, 2023 at 9:54 AM Jose E. Marchesi via Gcc-patches
>> <gcc-patches@gcc.gnu.org> wrote:
>>>
>>>
>>> ping.
>>> Would this be a good approach for fixing the issue?
>>
>> adding the is_libcall bit enlarges rtx_def by 8 bytes - there's no room for more
>> bits here.
> 
> That is obviously not the way to go, sure.
> 
>> I really wonder how other targets avoid the issue you are pointing out?
>> Do their assemblers prune unused (extern) .global?
> 
> I think no target solves this, if they see an extern call during expansion
> and emit some directive for those, they emit the global or whatever directive
> which remains there.
> 
> If all bits for CALL_INSN are taken, can't we add a flag on the CALL
> rtx inside of the CALL_INSN pattern?  Or a flag on the SYMBOL_REF inside of
> it (libcalls are always direct calls, aren't they) or SYMBOL_REF_FLAGS ?
You might look at 32bit PA SOM.  It was always a bit odd in this respect.

You had to import every external symbol explicitly and it disliked 
importing something that wasn't used.  I recall some special handling 
for libcalls as well.

Jeff