[jdk17u-dev] RFR: 8296545: C2 Blackholes should allow load optimizations

Thu Apr 20 10:29:45 UTC 2023

On Wed, 19 Apr 2023 13:36:37 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Unclean backport to improve Blackhole performance and match it to released JDK 20.
> The backport is unclean because there are two little conflicts:
>   1. The context conflict in `MemBarNode::make`, where the `MemBarStoreStore` was moved to another place. I resolved the conflict by hand: accepted only the `Blackhole` case removal.
>   2. IR Framework needs `MUL_I` constant for test to work.
> 
> Additional testing:
>   - [x] macos-aarch64-server-fastdebug, `compiler/irTests/blackhole` (includes new test)
>   - [ ] Eyeballing perfasm outputs with/without this patch

LGTM.

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Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk17u-dev/pull/1273#pullrequestreview-1393693005