RFR: 8319822: Use a linear-time algorithm for assert_different_registers() [v12]

[Kim Barrett]

On Fri, 31 May 2024 16:02:40 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> At the present time, `assert_different_registers()` uses an O(N**2) algorithm in assert_different_registers(). We can utilize RegSet to do it in O(N) time. This would be a useful optimization for all builds with assertions enabled.
>> 
>> In addition, it would be useful to be able to static_assert different registers. 
>> 
>> Also, I've taken the opportunity to expand the maximum size of a RegSet to 64 on 64-bit platforms.
>> 
>> I also fixed a bug: sometimes `noreg` is passed to `assert_different_registers()`, but it may only be passed once or a spurious assertion is triggered.
>
> Andrew Haley 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 19 additional commits since the last revision:
> 
>  - Merge branch 'clean' into different-regs
>  - Review feedback
>  - Review feedback
>  - Update src/hotspot/share/asm/register.hpp
>    
>    Co-authored-by: Stefan Karlsson <stefan.karlsson at oracle.com>
>  - Review feedback
>  - Review feedback
>  - Review feedback
>  - Merge branch 'different-regs' of https://github.com/theRealAph/jdk into different-regs
>  - Update src/hotspot/share/asm/register.hpp
>    
>    Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
>  - Merge branch 'clean' into different-regs
>  - ... and 9 more: https://git.openjdk.org/jdk/compare/aaa8ceb4...c9fc63d7

Looks good.

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Marked as reviewed by kbarrett (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16617#pullrequestreview-2091736260