[llvm-commits] [PATCH] LoopVectorizer

[Ralf Karrenberg]

On 10/18/12 5:32 AM, Nadav Rotem wrote:
>
> On Oct 17, 2012, at 6:24 PM, Hal Finkel <hfinkel at anl.gov 
> <mailto:hfinkel at anl.gov>> wrote:
>
>> he current pass handles only fixed trip-count (single-exit) loops 
>> without inter-iteration dependencies, correct? For this class of 
>> loops, I believe that what I proposed is correct. Maybe I'm thinking 
>> about this incorrectly, can you please provide a counterexample?
>
> Yes. If there are no cross-iteration dependencies then x equals to the 
> last SIMD lane.  I missed the part which said that there are no 
> cross-iteration deps.
>
I agree. Nadav's comment is correct only if the value forms a 
cross-iteration dependency (read: it is live on the back edge / it is 
the operand of a phi in the loop header).
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