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Re: [PATCH v3 7/7] powerpc64le: Enable float128
* Peter Bergner:
> On 6/27/17 2:17 PM, Florian Weimer wrote:
>> * Peter Bergner:
>>> bergner@pike:~$ cat float128.c
>>> float128 (void)
>>> return __builtin_cpu_supports ("ieee128");
>>> bergner@pike:~$ gcc -O2 -S float128.c
>>> bergner@pike:~$ cat float128.s
>>> lwz 3,-28776(13)
>>> rldicl 3,3,42,63
>> Nice. I guess the next question is: what would ensure that this code
>> only runs on a glibc which sets up the TCB in the expected way? Is
>> there a symbol reference which prevents that?
>> __parse_hwcap_and_convert_at_platform isn't that symbol, as far as I
>> can tell.
> Yes, we emit a symbol only defined by libcs that support this and
> yes, __parse_hwcap_and_convert_at_platform is that symbol:
> if (cpu_builtin_p)
> /* We have expanded a CPU builtin, so we need to emit a reference to
> the special symbol that LIBC uses to declare it supports the
> AT_PLATFORM and AT_HWCAP/AT_HWCAP2 in the TCB feature. */
> switch_to_section (data_section);
> fprintf (asm_out_file, "\t.align %u\n", TARGET_32BIT ? 2 : 3);
> fprintf (asm_out_file, "\t%s %s\n",
> TARGET_32BIT ? ".long" : ".quad", tcb_verification_symbol);
I see, so everything is fine. Nice!