[cfe-dev] [RFC] Introduce overflow builtins

[Dave Zarzycki]

Xi,

Thanks for the update! Have you tried inferring the sign of T* in addition to the size of T* in the API? That would let you simplify this:

	__builtin_sadd_with_overflow()
	__builtin_uadd_with_overflow()
	__builtin_ssub_with_overflow()
	__builtin_usub_with_overflow()
	__builtin_smul_with_overflow()
	__builtin_umul_with_overflow()

To this:

	__builtin_add_with_overflow()
	__builtin_sub_with_overflow()
	__builtin_mul_with_overflow()

Also, have you verified that -Wconversion does the right thing and warns when the sign of the parameters are inconsistent with each other (or the API if you do not make the above simplification)?

davez



On Mar 30, 2012, at 12:24 PM, Xi Wang <xi.wang at gmail.com> wrote:

> Hi,
> 
> I updated the overflow builtins to the form
> 
>    __builtin_*_with_overflow(T*, T, T)
> 
> as suggested by Chris and Dave.
> 
> The patch is still available at
> 
> https://github.com/xiw/clang/compare/master...builtin-overflow
> 
> - xi
>