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

[Hamlin Li]

On Mon, 17 Nov 2025 07:39:19 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/TestScalarConditionalMoveCmpObj.java line 131:
> 
>> 129:     //     applyIf = {"UseCompressedOops", "false"})
>> 130:     // @IR(counts = {IRNode.CMOVE_L, ">0", IRNode.CMP_N, ">0"},
>> 131:     //     applyIf = {"UseCompressedOops", "true"})
> 
> Do you plan to still do this in this PR? Probably a future RFE would be better. It could be nice if you could link to the RFE with the issue number from this comment.

In this PR, no, this one will only implement CMoveF/D and enable the vectorization of CMoveF/D, so do some preparation for https://github.com/openjdk/jdk/pull/28231.
To guarantee the generation of CMoveI/L, seems to me we need to improve the cost model when transfrom a phi to a conditional move. I can have a invetigation later, as this impact how & whether CMoveL/I can be generated and be vectorized accordingly. File https://bugs.openjdk.org/browse/JDK-8371984 to track it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28309#discussion_r2533384835