[PATCH, LIBGCC] Avoid count_leading_zeros with undefined result (PR 78067)

[Bernd Edlinger]

On 10/27/16 22:23, Joseph Myers wrote:
> On Thu, 27 Oct 2016, Bernd Edlinger wrote:
>
>> Hi,
>>
>> by code reading I became aware that libgcc can call count_leading_zeros
>> in certain cases which can give undefined results.  This happens on
>> signed int128 -> float or double conversions, when the int128 is in the range
>> INT64_MAX+1 to UINT64_MAX.
>
> I'd expect testcases added to the testsuite that exercise this case at
> runtime, if not already present.
>

Yes, thanks.  I somehow expected there were already test cases,
somewhere, but now when you ask that, I begin to doubt as well...

I will try to add an asm("int 3") and see if that gets hit at all.


Bernd.