Backport [LoopReroll] Fix rerolling loop with extra instructions to 12.0.1

[kawashima-fj]

Bugzilla Link	50093
Resolution	FIXED
Resolved on	May 06, 2021 17:17
Version	trunk
OS	Linux
Blocks	#48661
CC	@kawashima-fj,@tstellar
Fixed by commit(s)	d9a9c99 ac593de

Extended Description

Please backport the following commit to version 12.0.1.
It is a fix for the data corruption bug #46971 .

commit d9a9c992d190dd6645ea911b66cf0cadba0dadc3
Author: KAWASHIMA Takahiro <t-kawashima@fujitsu.com>
Date:   2021-04-08 12:33:25 +0900

    [LoopReroll] Fix rerolling loop with extra instructions

I forgot to add Differential Revision: line in the commit message.
It is https://reviews.llvm.org/D88395 .

[kawashima-fj]

assigned to @Meinersbur

[tstellar]

Hi Michael,

What is your opinion on backporting this?

https://reviews.llvm.org/rGd9a9c992d190dd6645ea911b66cf0cadba0dadc3

[Meinersbur]

Original bug is #46971

I suggested the backporting myself in the discussion of D88395. It's a miscompile bug with straightforward fix (instructions with side effects must not be skipped during legality checks).

[tstellar]

Merged: ac593de