[LLVMdev] Incompatible types at call site

[Arushi Aggarwal]

On Tue, Apr 5, 2011 at 1:44 PM, Duncan Sands <baldrick at free.fr> wrote:

> Hi Arushi,
>
>
>   %tmp63 = call %struct.TypHeader* (...)* bitcast (%struct.TypHeader*
>> (%struct.TypHeader*, i64, i64)* @Cyclotomic to %struct.TypHeader*
>> (...)*)(%struct.TypHeader* %tmp62, i64 %tmp24, i32 1) nounwind, !dbg !907
>> ;
>> <%struct.TypHeader*> [#uses=1]
>>
>> the 3rd parameter is now used in an srem statement. How do we know what
>> value is
>> used? Does this use decide whether the value is sign extended or zero
>> extended?
>>
>
> inside the called function the 3rd value will contain rubbish.  That's
> because
> the function takes an i64 parameter but via the bitcast you pretend it
> takes an
> i32 parameter, which is wrong.  This is not the correct way to pass an i32
> to a
> function that takes an i64.  Where did you get this IR from?
>

This is unoptimized IR, generated for a SPEC example.

The optimized IR, converts this call to

 %tmp63 = call%struct.TypHeader*
(%struct.TypHeader*, i64, i64)* @Cyclotomic (%struct.TypHeader* %tmp62, i64
%tmp24, i64 1) nounwind
<%struct.TypHeader*> [#uses=1]

I was just wondering what the logic was to infer when such conversions could
be made.

>
> Ciao, Duncan.
>
> PS: It may not contain rubbish in practice, in particular probably the
> lower 32
> bits will have the "right" value, but nothing guarantees that.
>
>
>> Arushi
>>
>> On Tue, Apr 5, 2011 at 1:35 AM, Duncan Sands <baldrick at free.fr
>> <mailto:baldrick at free.fr>> wrote:
>>
>>    Hi Arushi,
>>
>>     > For a call like this,
>>     >
>>     > %tmp6 = call i32 (...)* bitcast (i32 (i8*, i8, i8**)* @ssplit to i32
>>    (...)*)(i8*
>>     > %tmp599, i32 46, i8** %domainv3) nounwind ; <i32>
>>     >
>>     > does the 2nd argument get zero extended or sign extended?
>>
>>    neither since it does not have the zext or sext attribute.
>>
>>    Ciao, Duncan.
>>    _______________________________________________
>>    LLVM Developers mailing list
>>    LLVMdev at cs.uiuc.edu <mailto:LLVMdev at cs.uiuc.edu>
>> http://llvm.cs.uiuc.edu
>>
>>    http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20110405/c73cbade/attachment.html>