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Re: [PATCH][RFC] Detect and use implementations of BLAS routines


You probably want to disable this transformation when the number of iterations
is predicted to be small, right?

Shouldn't dot product transform be predicated on -fassociative-math?

Do you have a vision of a generalized pattern matcher to allow adding other
routines easily?

I'm curious what gap is between GCC's vectorizer output and fine-tuned BLAS
libraries. [*] Or is the intention here to enable use of accelerated BLAS on
HSA-like architectures?  Or using BLAS when the vectorizer can't possibly
match it (matmult -- but then again it's not easy to pattern-match in the
first place; or non-trivial strides -- but what can a BLAS lib do in that

  [*] The gap is definitely huge on something like ia64 (IIRC vectorization 
  is not important there, but you need to unroll and schedule carefully), but
  I presume you're mostly interested in x86-64.

GCC currently has a somewhat similar in spirit feature for the vectorizer --
-mveclibabi.  Is it known how it is used in practice?



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