Re: [PATCH] Make memset in calloc a tail call.

[Andrew Pinski <pinskia at gmail dot com>]

On Thu, Nov 7, 2013 at 12:31 PM, OndÅej BÃlka <neleai@seznam.cz> wrote:
> Hi, after reading a calloc code I found that we do not return memset
> value. Unless compiler can recognize that memset result and return value
> are same it will be used as normal call but a tail call is faster.

It can and does in 4.8 and above but that is after the tail call
optimization happens.

Thanks,
Andrew Pinski


>
> OK to commit?
>
>         * malloc/malloc.c (calloc): Make memset a tail call.
>
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index 897c43a..3fac780 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -3214,7 +3214,7 @@ __libc_calloc(size_t n, size_t elem_size)
>    if (chunk_is_mmapped (p))
>      {
>        if (__builtin_expect (perturb_byte, 0))
> -       MALLOC_ZERO (mem, sz);
> +       return MALLOC_ZERO (mem, sz);
>        return mem;
>      }
>
> @@ -3236,7 +3236,7 @@ __libc_calloc(size_t n, size_t elem_size)
>    assert(nclears >= 3);
>
>    if (nclears > 9)
> -    MALLOC_ZERO(d, clearsize);
> +    return MALLOC_ZERO(d, clearsize);
>
>    else {
>      *(d+0) = 0;