Integrated: 8365926: RISC-V: Performance regression in renaissance (chi-square)

[Robbin Ehn]

On Tue, 26 Aug 2025 14:43:05 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

> Hey, please consider!
> 
> A bunch of info in JBS entry, please read that also.
> 
> I narrowed this issue down to the old jal optimization, making direct calls when in reach.
> This patch restores them and removes this regression.
> 
> In essence we turn "jalr ra,0(t1)" into a "jal ra,<dest>" if reachable, and restore the jalr if a new destination is not reachable.
> 
> Please test on your hardware!
> 
> 
> Chi Square (100 runs each, 10 fastest iterations of each run, P550)
> JDK-23 (last version with trampoline calls)
> Mean: 3189.5827
> Standard Deviation: 284.6478
> 
> JDK-25
> Mean: 3424.8905
> Standard Deviation: 222.2208
> 
> Patch:
> Mean: 3144.8535
> Standard Deviation: 229.2577
> 
> 
> No issues found in t1, running t2 also. Stress tested on vf2, bpi-f3, p550.

This pull request has now been integrated.

Changeset: 5c1865a4
Author:    Robbin Ehn <rehn at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/5c1865a4fcd5da80ddcc506f4e41aada0fb93970
Stats:     86 lines in 3 files changed: 68 ins; 0 del; 18 mod

8365926: RISC-V: Performance regression in renaissance (chi-square)

Reviewed-by: fyang, mli

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PR: https://git.openjdk.org/jdk/pull/26944