[llvm] r309651 - [StackColoring] Update AliasAnalysis information in stack coloring pass

[Hans Wennborg via llvm-commits]

Matthias, the PR for this was marked as a release blocker for 5.0.
What do you think about merging this?

On Mon, Jul 31, 2017 at 8:32 PM, Hiroshi Inoue via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: inouehrs
> Date: Mon Jul 31 20:32:15 2017
> New Revision: 309651
>
> URL: http://llvm.org/viewvc/llvm-project?rev=309651&view=rev
> Log:
> [StackColoring] Update AliasAnalysis information in stack coloring pass
>
> Stack coloring pass need to maintain AliasAnalysis information when merging stack slots of different types.
> Actually, there is a FIXME comment in StackColoring.cpp
>
> // FIXME: In order to enable the use of TBAA when using AA in CodeGen,
> // we'll also need to update the TBAA nodes in MMOs with values
> // derived from the merged allocas.
>
> But, TBAA has been already enabled in CodeGen without fixing this pass.
> The incorrect TBAA metadata results in recent failures in bootstrap test on ppc64le (PR33928) by allowing unsafe instruction scheduling.
> Although we observed the problem on ppc64le, this is a platform neutral issue.
>
> This patch makes the stack coloring pass maintains AliasAnalysis information when merging multiple stack slots.

(This is https://reviews.llvm.org/D35907)