[llvm-commits] [llvm] r55374 - in /llvm/trunk: lib/Transforms/Scalar/LoopStrengthReduce.cpp test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll

[Nick Lewycky]

Let me try this again, with added sanity this time :-)

Nick Lewycky wrote:
> 
>> +
>> +           for (unsigned i = 0; i < n; ++i) 
>> +             foo((double)i);
>> +
>> +         is trnasformed into
> 
> typo: eliminate

uh huh. typo: transformed

>> +
>> +           double d = 0.0;
>> +           for (unsigned i = 0; i < n; ++i, ++d) 
>> +             foo(d);
>> +      */
> 
> I have a problem with this. Suppose you get:
> 
>    for (unsigned i = x; i != 5, ++i)
>      foo((double)i);
> 
> and SCEV claims the trip count is 10, regardless of what x is equal to. 

Which is, of course, impossible. But suppose it were:
   for (unsigned i = x; i != y; ++i)

then it's possible. Also, 10 would get unrolled, but just work with me 
here. :-)

Nick