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Re: [PATCH v3 7/7] powerpc64le: Enable float128
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:
/* 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. */
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);
Why do you think that isn't the symbol we're using?