[PATCH] [SLPVectorization] Enhance Ability to Vectorize Horizontal Reductions from Consecutive Loads

[suyog]

Hi Michael,

We could add that check for Left[i+1] and Right[i+1] as well.
If we add that, we would have to increase the loop variable by 2 :)
as we are checking both i and i+1 elements.

By the way, The loop will always run for 2 times only in any case,
since the tree which we are considering, will always have only 2 children for a node.

But, this would be a very strict checking. If we skip this checking,
decision to vectorize or not will be taken by cost model as demonstrated earlier.

The only question is to whether to check at this point itself or leave it for
the cost model to decide, which it does very well.

I am of the opinion that we should not check for Left[i+1] and Right[i+1],
since it would hardly make any difference in the logic and the outcome,
and if we include that check, the code would look a bit ugly :)

Removed redundant braces around isConsecutive check.

Regards,
Suyog


REPOSITORY
  rL LLVM

http://reviews.llvm.org/D6675

Files:
  lib/Transforms/Vectorize/SLPVectorizer.cpp
  test/Transforms/SLPVectorizer/AArch64/horizontaladd.ll

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