Re: dejagnu multilib options and dg-{add|additional-}options

[Janis Johnson <janis_johnson at mentor dot com>]

On 08/27/2013 06:52 AM, Marcus Shawcroft wrote:
> On 23 July 2013 17:40, Janis Johnson <janis_johnson@mentor.com> wrote:
>> On 07/22/2013 02:59 AM, Vidya Praveen wrote:
>>> Hello,
>>>
>>> There are 42 test files (25 under gcc.dg) that specifies
>>>
>>> { dg-add-options bind_pic_locally }
>>>
>>> in the regression testsuite. The procedure add_options_for_bind_pic_locally
>>> from lib/target-supports.exp adds -fPIE or -fpie when -fPIC or -fpic is passed
>>> respectively. But this is added before the dejagnu multilib options are added.
>>> So when -fPIC is passed as a multilib option, -fPIE will be unset by -fPIC
>>> (see gcc/common.opt). This should have been the behaviour since the patch
>>> http://gcc.gnu.org/ml/gcc-patches/2012-11/msg01026.html that brings all -fPIC
>>> & -fPIE variants in a Negative loop, was applied.
>>>
>>> I tried fixing this in dejagnu/target.exp by adding the multilib options before
>>> the other options:
>>>
>>> default_target_compile:
>>>
>>> <       append add_flags " [board_info $dest multilib_flags]"
>>> ---
>>>>       set add_flags " [board_info $dest multilib_flags] $add_flags"
>>>
>>> and ran regressions for x86_64-unknown-linux-gnu before and after the change.
>>> The only difference in the results after the change was 24 new PASSes which
>>> are from the testcases which either use bind_pic_locally or that use -fno-pic.
>>>
>>> (Interestingly, there are many test files that bind_pic_locally pass without
>>> any issue before and after the change.)
>>>
>>> I tend to think that the options added from the test files should always win.
>>> Please correct me if I'm wrong. If I'm right, is dejagnu/target.exp is the
>>> best place to fix this and the way it tried to fix? Any better suggestions?
>>>
>>> Though this case is to do with -fPIC, I'm sure there are other options which
>>> when they come as multilib options might have same issue with the some of the
>>> options added by the test files or the default options.
>>>
>>> Regards
>>> VP
>>
>> Ideally we would ask for that change in DejaGnu, but relying on such a
>> change would require everyone testing GCC to upgrade to a version of
>> DejaGnu with that fix, and I don't think we're ready to do that.
>>
>> Tests that add options that might override or conflict with multilib
>> flags should check for those flags first and skip the test if they are
>> used.  For examples, see tests in gcc.target/arm that use dg-skip-if.
> 
> Umm, the purpose of bind_pic_locally appears to be to detect the use
> of -fPIC and override that behavior with -fPIE.  If I understand the
> above paragraph correctly then bind_pic_locally is fundamentally
> broken and all of the tests that use it need rewriting to skip if
> -fPIC or -fpic is in use?
> 
> Cheers
> /Marcus
> 

That is correct.  There should probably be an effective-target check
bind_pic_locally_ok that fails if adding -fpie or -fPIE doesn't have the
expected result, and the tests that use "dg-add-options bind_pic_locally"
should be skipped if bind_pic_locally_ok fails.

Janis