[llvm-commits] [llvm] r80907 - /llvm/trunk/lib/Analysis/ProfileInfoLoaderPass.cpp

[Daniel Dunbar]

On Thu, Sep 3, 2009 at 1:32 AM, Andreas Neustifter<astifter-llvm at gmx.at> wrote:
> Hi,
>
> Daniel Dunbar wrote:
>> On Thu, Sep 3, 2009 at 12:53 AM, Andreas Neustifter<astifter-llvm at gmx.at> wrote:
>>> Hi,
>>>
>>> thank you very much for investigating this!
>>>
>>> Daniel Dunbar wrote:
>>>> -  if (weight != (unsigned)MissingValue) {
>>>> +  if (weight != ~0U) {
>>> Since allmost all my other development takes place on platforms that do
>>> not even support floating point my float-typecasting knowledge is a bit
>>> rusty.
>>>
>>> If you have time: can you explain why this is necessary and why the cast
>>> from double to unsigned does not work? (At least not on all platforms...)
>>
>> I didn't know this off the top of my head either, but the relevant
>> language for C99 (I presume C++ is similar is):
>> --
>> 6.3.1.4p1: When a finite value of real floating type is converted to
>> an integer type other than _Bool, the fractional part is discarded
>> (i.e., the value is truncated toward zero). If the value of the
>> integral part cannot be represented by the integer type, the behavior
>> is undefined.
>> --
>
> Thanks, so maybe we should convert all the counters to (signed) int64_t
> to clean up this problem and get larger counters...

Yes, but this particular problem is because some parts of the
interface are using 'unsigned' to represent counts, and other parts
are using double. In this case the comparison was really against the
sentinel value from the file format, not the sentinel value from the
ProfilingInfo interface.

 - Daniel