Re: [PATCH v6 5/5] riscv: Add and use alignment-ignorant memcpy

[Richard Henderson <richard.henderson@linaro.org>]

On 8/3/23 00:25, Florian Weimer via Libc-alpha wrote:
> * Evan Green:
> 
>> +static inline __typeof (__redirect_memcpy) *
>> +select_memcpy_ifunc (uint64_t dl_hwcap, __riscv_hwprobe_t hwprobe_func)
>> +{
>> +  INIT_ARCH ();
>> +
>> +  struct riscv_hwprobe pair;
>> +
>> +  pair.key = RISCV_HWPROBE_KEY_CPUPERF_0;
>> +  if (!hwprobe_func || hwprobe_func(&pair, 1, 0, NULL, 0) != 0)
>> +    return __memcpy_generic;
>> +
>> +  if ((pair.key > 0) &&
>> +      (pair.value & RISCV_HWPROBE_MISALIGNED_MASK) ==
>> +       RISCV_HWPROBE_MISALIGNED_FAST)
>> +    return __memcpy_noalignment;
>> +
>> +  return __memcpy_generic;
>> +}
> 
> In libc, you could call __riscv_hwprobe directly, so the additional
> argument isn't needed after all.

Outside libc something is required.

An extra parameter to ifunc is surprising though, and clearly not ideal per the extra 
hoops above.  I would hope for something with hidden visibility in libc_nonshared.a that 
could always be called directly.


r~