RFR: 8291302: ARM32: nmethod entry barriers support [v4]

[Andrew Haley]

On Thu, 8 Dec 2022 15:02:18 GMT, Aleksei Voitylov <avoitylov at openjdk.org> wrote:

>> This PR implements nmethod entry barriers for ARM32. It has already been implemented for other ports and is related with JDK-8290025 "Remove the Sweeper".
>
> Aleksei Voitylov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8291302-3
>  - remove membar
>  - save float registers
>  - 8291302: ARM32: nmethod entry barriers support

src/hotspot/cpu/arm/gc/shared/barrierSetAssembler_arm.cpp line 207:

> 205: 
> 206:   Register tmp0 = Rtemp;
> 207:   Register tmp1 = R5; // wrong register here will lead to crash

Why specifically `R5` ? Please add a comment.

src/hotspot/cpu/arm/gc/shared/barrierSetAssembler_arm.cpp line 214:

> 212: 
> 213:   // The are no GCs that require memory barrier on arm32 now
> 214: #ifndef PRODUCT

Suggestion:

#ifdef ASSERT

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PR: https://git.openjdk.org/jdk/pull/11442