helping the compiler with asserts-hints to optimize

[Jeff Law]

On 04/24/14 06:40, Agustin Perez Paladini wrote:
>
> int
> fun_module(int a)
> {
>      ASSUME(a % 4 == 0);
>
>      if (a == 3) {
>          return 123;
>      }
>      return 789;
> }
>
> giving this asm
>
> fun_module:
>      .LFB3:
>      .cfi_startproc
>      cmpl $3, 4(%esp)
>      movl $789, %edx
>      movl $123, %eax
>      cmovne %edx, %eax
>      ret
>      .cfi_endproc
>
>
> Anyway, I think its pretty much what I was looking for.
Feel free to file a bug report for this one.  VRP doesn't have a 
nonzero/zero bits tracking lattice, but it's something I can see being 
added at some point and having examples like this in the BZ database is 
often helpful when doing that kind of optimization work.

Thanks,

Jeff