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Add debug option to turn off zero cost phi node inserting in PRE
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Authored by hulx2000 on Jul 15 2015, 11:43 AM.

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Summary

commit 403050abcc091260be2e8f58484e7a39c0782b47
Author: Daniel Berlin <dberlin@dberlin.org>
Date: Tue Feb 3 20:37:08 2015 +0000

Allow PRE to insert no-cost phi nodes

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228024 91177308-0d34-0410-b5e6-96231b3b80d8

Have very broad performance impact to our benchmark, the degradation are up to 30%.

According to owner of this patch, there is no easy fix for now, so I created this patch to add a debug option to allow us to turn this feature off with this debug option, the debug option is off by default.

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rL LLVM

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hulx2000 retitled this revision from to Add debug option to turn off zero cost phi node inserting in PRE.
hulx2000 updated this object.
hulx2000 set the repository for this revision to rL LLVM.
hulx2000 added a subscriber: llvm-commits.
hulx2000 abandoned this revision.Aug 1 2015, 10:28 AM

Opened a bug Bug 24171 - Load PRE inserts badly placed fully-redundant address arithmetic for it Daniel is working on the right solution.