Jingyue Wu 1d56cda023 Partially revert r210444 due to performance regression
Summary:
Converting outermost zext(a) to sext(a) causes worse code when the
computation of zext(a) could be reused. For example, after converting

... = array[zext(a)]
... = array[zext(a) + 1]

to

... = array[sext(a)]
... = array[zext(a) + 1],

the program computes sext(a), which is actually unnecessary. I added one
test in split-gep-and-gvn.ll to illustrate this scenario.

Also, with r211281 and r211084, we annotate more "nuw" tags to
computation involving CUDA intrinsics such as threadIdx.x. These
annotations help with splitting GEP a lot, rendering the benefit we get
from this reverted optimization only marginal.

Test Plan: make check-all

Reviewers: eliben, meheff

Reviewed By: meheff

Subscribers: jholewinski, llvm-commits

Differential Revision: http://reviews.llvm.org/D4542

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213209 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-16 23:25:00 +00:00
2014-07-16 16:50:34 +00:00
2014-07-14 05:01:53 +00:00
2014-06-25 13:13:36 +00:00
2014-05-29 19:59:58 +00:00
2014-07-16 16:50:34 +00:00

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