search for: selectunrollfactor

Hey Arnold, I have run into this situation many times while benchmarking. I think it is best if this is addressed using a simple heuristic. For that, we need to identify the loop cost and decide if it makes sense to completely unroll the loop, or partially unroll. I am unsure of the optimal way to implement this though. I want to run it by the list to get any ideas floating around :) Thanks

On Sep 27, 2013, at 12:47 PM, Arnold Schwaighofer <aschwaighofer at apple.com> wrote: > so you could infer that n must be smaller than 8 (because you know the range of the other dimension). The question is how often does such an example occur, where this is possible, to make such an effort justifiable? smaller equal, of course ;)

...ely to be unrolled. diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp index 7867495..978c5a1 100644 --- a/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -5142,8 +5142,8 @@ LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize, // fit without causing spills. All of this is rounded down if necessary to be // a power of two. We want power of two unroll factors to simplify any // addressing operations or alignment considerations. - unsigned UF = PowerOf2Floor((TargetNumRegisters - R.LoopInvariantRe...

On 16/01/2014, 23:47 , Andrew Trick wrote: > > On Jan 15, 2014, at 4:13 PM, Diego Novillo <dnovillo at google.com > <mailto:dnovillo at google.com>> wrote: > >> Chandler also pointed me at the vectorizer, which has its own >> unroller. However, the vectorizer only unrolls enough to serve the >> target, it's not as general as the runtime-triggered