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Re: [PATCH 6/6] Compile sched_getaffinity.c with -fno-builtin-memset

On Fri, Aug 14, 2015 at 9:02 AM, Joseph Myers <> wrote:
> On Fri, 14 Aug 2015, H.J. Lu wrote:
>> > point to the GOT as it would for a call through the PLT.  I don't know
>> > whether this gets optimized for built-in function calls using
>> > libc_hidden_builtin_proto, but if it doesn't, that seems like a missed
>> > optimization that should be addressed in the compiler not in glibc.
>> >
>> It is hard to say it is a GCC issue when we are kind of doing this behind
>> the back of GCC unless there is a way to tell GCC that the libcall of
>> a builtin function is hidden.
> We're declaring (essentially, though a load of macros):
> extern __typeof (memset) memset __asm__ ("__GI_memset") __attribute__ ((visibility ("hidden")));
> GCC is using the __asm__ information to compile calls to __builtin_memset
> to use the assembler name __GI_memset - that is, in that regard our
> declaration is being taken as applying to the libcall.  If it's not also
> using the visibility information to know that those are calls within the
> library and don't need to set up %ebx, that's a clear inconsistency; all
> pieces of information from an explicit declaration of a built-in function
> should be treated the same unless there is a clear reason not to do so.

Should I open a GCC bug?


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