[llvm] r302938 - Add LiveRangeShrink pass to shrink live range within BB.

[Hans Wennborg via llvm-commits]

On Fri, May 12, 2017 at 12:29 PM, Dehao Chen via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: dehao
> Date: Fri May 12 14:29:27 2017
> New Revision: 302938
>
> URL: http://llvm.org/viewvc/llvm-project?rev=302938&view=rev
> Log:
> Add LiveRangeShrink pass to shrink live range within BB.
>
> Summary: LiveRangeShrink pass moves instruction right after the definition with the same BB if the instruction and its operands all have more than one use. This pass is inexpensive and guarantees optimal live-range within BB.
>
> Reviewers: davidxl, wmi, hfinkel, MatzeB, andreadb
>
> Reviewed By: MatzeB, andreadb
>
> Subscribers: hiraditya, jyknight, sanjoy, skatkov, gberry, jholewinski, qcolombet, javed.absar, krytarowski, atrick, spatel, RKSimon, andreadb, MatzeB, mehdi_amini, mgorny, efriedma, davide, dberlin, llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D32563

This broke some tests in Chromium under MSan:
https://bugs.chromium.org/p/chromium/issues/detail?id=724156
And also internally at Google: b/38418215

I've gone ahead and reverted in r303369.