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[InstCombine] pow(C,x) -> exp2(log2(C)*x)
authorDavid Bolvansky <david.bolvansky@gmail.com>
Wed, 10 Jul 2019 14:43:27 +0000 (14:43 +0000)
committerDavid Bolvansky <david.bolvansky@gmail.com>
Wed, 10 Jul 2019 14:43:27 +0000 (14:43 +0000)
commit0735cc1954d84afa742abadf78e4136489f7cd0d
tree34b46971f5c62bb14fd7ec7df7166e5542b6f988tree | snapshot
parent9cd82a4fbd2ded1e4d6b3815d153b28057ee1e75commit | diff
[InstCombine] pow(C,x) -> exp2(log2(C)*x)

Summary:
Transform
pow(C,x)

To
exp2(log2(C)*x)

if C > 0, C != inf, C != NaN (and C is not power of 2, since we have some fold for such case already).

log(C) is folded by the compiler and exp2 is much faster to compute than pow.

Reviewers: spatel, efriedma, evandro

Reviewed By: evandro

Subscribers: lebedev.ri, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64099

llvm-svn: 365637
llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp diff | blob | history
llvm/test/Transforms/InstCombine/pow-exp.ll diff | blob | history
llvm/test/Transforms/InstCombine/pow_fp_int.ll diff | blob | history
Domain: System / Toolchain;