Re: [RFC: -mm patch] kcalloc(): INT_MAX -> ULONG_MAX

[Pekka Enberg <penberg@gmail.com>]

On 8/20/05, Adrian Bunk <bunk@stusta.de> wrote:
> This change could (at least in theory) allow a compiler better
> optimization (especially in the n=1 case).
> 
> The practical effect seems to be nearly zero:
>     text           data     bss      dec            hex filename
> 25617207        5850138 1827016 33294361        1fc0819 vmlinux-old
> 25617191        5850138 1827016 33294345        1fc0809 vmlinux-patched
> 
> Is there any reason against this patch?

Looks ok to me.

On 8/20/05, Adrian Bunk <bunk@stusta.de> wrote:
>  static inline void *kcalloc(size_t n, size_t size, unsigned int __nocast flags)
>  {
> -       if (n != 0 && size > INT_MAX / n)
> +       if (n != 0 && size > ULONG_MAX / n)

You'll probably get even better code if you change the above to:

    if (size != 0 && n > ULONG_MAX / size)

Reason being that size is virtually always a constant so the compiler
can evaluate the division at compile-time.

                                  Pekka