[LLVMdev] [LLVMDev] trouble building gcc-frontend from source

[Dale Johannesen]

On Mar 13, 2009, at 10:45 PM, Gautam Sewani wrote:

> On Fri, Mar 13, 2009 at 8:09 PM, John Criswell  
> <criswell at cs.uiuc.edu> wrote:
>> Gautam Sewani wrote:
>>> On Fri, Mar 13, 2009 at 2:38 PM, Duncan Sands <baldrick at free.fr>  
>>> wrote:
>>>
>>>> Hi, the versions of llvm-gcc and llvm you are using are
>>>> not synchronized.  Probably one is from subversion while
>>>> the other is not.
>>>>
>> I've run into this, too.  The problem is that the inliner pass uses  
>> a 30
>> bit integer to store the inline cost; the code that calculates the
>> inline cost generates a cost that is too large, and so you hit the
>> assertion.
>>
>> I haven't yet distilled a test case for this yet (had some problems  
>> with
>> bugpoint for some mysterious reason), but I do have a work-around: go
>> into include/llvm/Transforms/Utils/InlineCost.h and make the  
>> following
>> change:

Glad that works for you, but it means that if the 32-bit cost  
computation overflows, we won't be told about it.   I think the right  
thing is to make sure the computation saturates at 30 bits instead of  
overflowing.  Am I going to talk myself into overloading operator+ ?

>> Index: InlineCost.h
>> ===================================================================
>> --- InlineCost.h        (revision 66848)
>> +++ InlineCost.h        (working copy)
>> @@ -37,8 +37,13 @@
>>      Never
>>    };
>>
>> +#if 0
>>    int Cost : 30;
>>    unsigned Type :  2;
>> +#else
>> +    int Cost;
>> +    unsigned Type :  2;
>> +#endif
>>
>>    InlineCost(int C, int T) : Cost(C), Type(T) {
>>      assert(Cost == C && "Cost exceeds InlineCost precision");
>>
>> Basically, you're changing the inline cost variable from 30 to 32  
>> bits.
>> After that, do a RELEASE build of LLVM and retry building llvm-gcc.
>>
>> -- John T.
>>
>
> That worked like a charm. Thanks a lot!
>
> Gautam
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