Re: [google][4.8] Expose all target specific builtins unconditionally for LIPO builds

[Sriraman Tallam <tmsriram at google dot com>]

On Wed, Jul 24, 2013 at 3:21 PM, Xinliang David Li <davidxl@google.com> wrote:
> Can you collect some number on ggc_memory increase  with this change
> in profile_gen build -- the value is recorded gcov_module_info object
> in coverage.c.

The ggc_memory increase if < 0.2% for large modules (initial usage
around 100MB and greater).  For some small modules, whose initial
parser memory usage is around 2MB, I see a 80% increase.

Thanks
Sri

>
> thanks,
>
> David
>
> On Wed, Jul 24, 2013 at 3:14 PM, Sriraman Tallam <tmsriram@google.com> wrote:
>> The following test-case fails in LIPO mode during profile-use build:
>>
>> main.ccthe
>> ------------
>> __attribute__((target("sse4.2")))
>> unsigned int problem_aux (unsigned int A, unsigned int B);
>>
>>
>> int main (int argc, char *argv[])
>> {
>>   return problem_aux (0, 0);
>> }
>>
>> aux.cc
>> ---------
>> __attribute__((target("sse4.2")))
>> unsigned int problem_aux (unsigned int A, unsigned int B)
>> {
>>   return __builtin_ia32_crc32qi (A, B);
>> }
>>
>> $ g++ -O2 -fprofile-generate main.cc aux.cc
>> $ ./a.out
>> $ g++ -O2 -fprofile-use main.cc
>> error: '__builtin_ia32_crc32qi' was not declared in this scope
>>
>> This happens when parsing the auxiliary module. __builtin_ia32_crc32qi
>> is a target specific builtin that gets created after the target
>> attribute is seen in the declaration of problem_aux in the primary
>> module. This is too late for adding theisbuiltin to the list of
>> knowns, the buitlins get saved when cp_save_built_in_decl_pre_parsing
>> in cp/cp-objcp-common.c is called much earlier.  Hence, this builtin
>> which is created during primary module parsing is not available when
>> parsing the auxiliary module.
>>
>> A simple fix is to expose all target builtins unconditionally in LIPO
>> mode. Patch:
>>
>>
>> Index: config/i386/i386.c
>> ===================================================================
>> --- config/i386/i386.c  (revision 201046)
>> +++ config/i386/i386.c  (working copy)
>> @@ -26957,7 +26957,8 @@ def_builtin (HOST_WIDE_INT mask, const char *name,
>>        ix86_builtins_isa[(int) code].isa = mask;
>>
>>        mask &= ~OPTION_MASK_ISA_64BIT;
>> -      if (mask == 0
>> +      if (flag_dyn_ipa
>> +         || mask == 0
>>           || (mask & ix86_isa_flags) != 0
>>           || (lang_hooks.builtin_function
>>               == lang_hooks.builtin_function_ext_scope))
>>
>>
>> Is this ok?
>>
>> Thanks
>> Sri