[llvm] r178147 - Cleanup the simplify_type implementation.

[Eli Friedman]

On Tue, Jul 16, 2013 at 8:16 PM, Rafael Espíndola
<rafael.espindola at gmail.com> wrote:
>>>> In terms of the patch itself, if I recall correctly, the enable_ifs
>>>> you're removing are necessary to reject a T* where T is simplifiable.
>>>> I could be wrong, though.
>>>
>>> Sorry, can you give an example of what you want to reject?
>>
>> Something like the following (there are probably better examples, but
>> I can't remember off the top of my head):
>>
>>     llvm::Value *V;
>>     llvm::Use *U = &V->use_begin().getUse();
>>     llvm::Constant *XXX = cast<llvm::Constant>(U);
>
> We used to accept
>
> Constant *foobar(Use *U) {
>   return cast<Constant>(U);
> }
>
> before r178147. Why would you want to reject it?

We want to reject it because it implicitly dereferences the pointer.

IIRC, we still accept the given example if you replace "Use *U" with
"Use ****U".

-Eli