On Tue, 2 Dec 2025 08:34:50 GMT, Marc Chevalier <[email protected]> wrote:
> In > https://github.com/openjdk/valhalla/blob/acb511a9f5c7b750b41e1ce77aab3d1a59613097/test/hotspot/jtreg/compiler/c2/irTests/scalarReplacement/ScalarReplacementWithGCBarrierTests.java#L98-L116 > > we have 2 allocations: `Iter` and `Integer`. Scalar replacement allows to > eliminate the allocation of `Iter`, but we still had the allocation of > `Integer`. With value classes, we can also save the allocation of `Integer` > since it is a value class. Adapting expectations is enough. > > To keep the test robust, I prefered to expect the exact amount, and not > something like > > @IR(phase = { CompilePhase.PHASEIDEAL_BEFORE_EA }, counts = { IRNode.ALLOC, > "<= 2" }) > @IR(phase = { CompilePhase.ITER_GVN_AFTER_ELIMINATION }, counts = { > IRNode.ALLOC, "<= 1" }) > > Since that would allow the respective counts 1 and 1 (for instance, if > `Integer` allocation is being removed as a value class, but `Iter` is not > because EA would be broken with Valhalla). > > To allow the test to work precisely with and without Valhalla, I propose a > fake flag `enable-valhalla` that checks whether `Integer` is a value class. I > preferred that over more generally "enable-preview" because it lacks > granularity with respect to other preview features, and > `PreviewFeatures.isEnabled()` is internal and not accessible anyway. It's a > little hack, but I think the usage is very natural. It would be good if > @chhagedorn could take a look at it. > > Thanks, > Marc Thanks for doing this! I left some comments on the feature flag since I'm working on that right now. test/hotspot/jtreg/compiler/c2/irTests/scalarReplacement/ScalarReplacementWithGCBarrierTests.java line 108: > 106: // could not be eliminated. > 107: @Test > 108: @IR(applyIf = {"enable-valhalla", "false"}, phase = { > CompilePhase.PHASEIDEAL_BEFORE_EA }, counts = { IRNode.ALLOC, "2" }) With `EnableValhalla` being removed in favour of `--enable-preview`, I think it would make sense if we transition to a preview on/off state rather than the fine-grained one we have right now. ------------- PR Review: https://git.openjdk.org/valhalla/pull/1767#pullrequestreview-3528932060 PR Review Comment: https://git.openjdk.org/valhalla/pull/1767#discussion_r2580224094
