Integrated: 8274130: C2: MulNode::Ideal chained transformations may act on wrong nodes

[Aleksey Shipilev]

On Wed, 22 Sep 2021 10:12:16 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> I was puzzled by it when fixing JDK-8274060. It looks that new optimizations added by [JDK-8273454](https://bugs.openjdk.java.net/browse/JDK-8273454) and [JDK-8263006](https://bugs.openjdk.java.net/browse/JDK-8263006) rewire `in(1)` and `in(2)` in `MulNode::Ideal`, which means the chained transformations should see them? Yet, both inputs and their `Type`-s are cached locally and not refreshed. I have not seen failures due to this yet, but it looks that the current code is subtly incorrect because of this. 
> 
> I thought about doing `return this` instead of `progress = true`, so that we leave `MulNode::Ideal` once we hit any transform and hope to return back, but I wondered if that would expose us to different graph shapes in-between successive `MulNode::Ideal` calls, which might have other unintended consequences. Therefore, I opted to a more conservative patch.
> 
> Additional testing:
>  - [x] `compiler/` tests
>  - [x] `tier1` tests
>  - [x] 100K Fuzzer tests (one unrelated failure)

This pull request has now been integrated.

Changeset: 756d22c3
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/756d22c3563ac92e74bb68d5eecb86d4fbab2c6b
Stats:     12 lines in 1 file changed: 7 ins; 2 del; 3 mod

8274130: C2: MulNode::Ideal chained transformations may act on wrong nodes

Reviewed-by: thartmann, kvn

-------------

PR: https://git.openjdk.java.net/jdk/pull/5631