RFR: 8357551: RISC-V: support CMoveF/D vectorization [v2]

[Hamlin Li]

On Fri, 14 Nov 2025 15:59:18 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Hamlin Li has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - add CMove+CmpP/N tests
>>  - fix cmovF/D_cmpP
>
> test/hotspot/jtreg/compiler/c2/irTests/TestScalarConditionalMove.java line 36:
> 
>> 34:  * @test
>> 35:  * @summary Test conditional move.
>> 36:  * @requires vm.simpleArch == "riscv64"
> 
> I would prefer if you could enable the test on all platforms, but just require the specific platform on the IR rules.
> What would be even more fantastic: if you were able to also enable the IR rules for `x64` and `aarch64`, but we can also file a follow-up RFE for that.

Make sense. I filed https://bugs.openjdk.org/browse/JDK-8371920 to track the task, will do it later after this pr.

> test/hotspot/jtreg/compiler/c2/irTests/TestScalarConditionalMove.java line 49:
> 
>> 47:                                    "-XX:+UnlockExperimentalVMOptions", "-XX:-UseCompactObjectHeaders");
>> 48:         TestFramework.runWithFlags("-XX:+UseCMoveUnconditionally", "-XX:-UseVectorCmov",
>> 49:                                    "-XX:+UnlockExperimentalVMOptions", "-XX:+UseCompactObjectHeaders");
> 
> Wait. Is this just a copy of the existing vector test, but run with CMove vectorization disabled?
> If so, we could just add these additional runs to the existing test, and guard the IR test with corresponding flags:
> Have an IR rule for `-XX:-UseVectorCmov` and one for `-XX:+UseVectorCmov`.
> 
> That would allow us to reduce some code duplication. And it would also avoid letting the two tests go out of sync when people add more to one but not the other.
> 
> What do you think?

Good idea!
I can do it. What do you think about the name of the merged tests? `TestConditionalMove.java` or `TestScalarAndVectorConditionalMove.java`

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PR Review Comment: https://git.openjdk.org/jdk/pull/28309#discussion_r2528463608
PR Review Comment: https://git.openjdk.org/jdk/pull/28309#discussion_r2528467634