[PATCH] D13994: [SimplifyLibCalls] Optimization for pow(x, n) where n is some constant

[Mandeep Singh Grang via llvm-commits]

mgrang updated this revision to Diff 40539.
mgrang added a comment.

Thanks for the suggestions everyone.

I have now implemented Addition-Chains using recursion with memoization. The result being that we do not need to generate extraneous instructions.

Here is an example:

7 --> (2, 5) --> (2, (2, 3)) --> (2, (2, (1, 2)))

We now generate instructions for only the intermediate products needed by our exponent. Storing the results at each step saves us repetitive  recursive calls.

I have also addressed David's comments in this patch (added an assertion for Exp!=0 and removed check-prefix from the test case).

Please let me know your thoughts on this.


http://reviews.llvm.org/D13994

Files:
  lib/Transforms/Utils/SimplifyLibCalls.cpp
  test/Transforms/InstCombine/pow-4.ll

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