[llvm] r179569 - We are not able to bitcast a pointer to an integral value.

[Duncan Sands]

Hi Bill,

On 18/04/13 02:06, Bill Wendling wrote:
> On Apr 16, 2013, at 9:42 AM, Duncan Sands <baldrick at free.fr> wrote:
>
>> Hi Bill,
>>
>> On 16/04/13 00:33, Bill Wendling wrote:
>>> Author: void
>>> Date: Mon Apr 15 17:33:50 2013
>>> New Revision: 179569
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=179569&view=rev
>>> Log:
>>> We are not able to bitcast a pointer to an integral value.
>>>
>>> Two return types are not equivalent if one is a pointer and the other is an
>>> integral. This is because we cannot bitcast a pointer to an integral value.
>>> PR15185
>>
>> you can always ptrtoint it.  I thought the idea of mergefunctions was to
>> ignore types, and consider two values the same if they have the same bits,
>> regardless of whether they are pointers, integers, floats or whatever.  If
>> so, it seems a pity to suddenly decide that type differences matter.
>>
> It wasn't me who decided that, but the bitcast instruction. :-) It expressly prohibits casting a pointer to an integer value.

I meant something a bit different: rather than observe that one function has
an integer return type and the other a pointer return type and decide that the
functions are not equivalent (the fix in your patch), you could instead leave
the old logic for function equivalence (say that they are equivalent), and use
a ptrtoint in the place that converts the pointer return result to the integer
return result.  I.e. rather than just always generate a bitcast, generate one
of: bitcast, ptrtoint or inttoptr as appropriate.

Ciao, Duncan.