RFR: 8357554: Enable vectorization of Bool -> CMove with different type size (on riscv) [v2]

[Emanuel Peter]

On Tue, 11 Nov 2025 14:10:47 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Hi,
>> 
>> Can you help to review this patch?
>> 
>> This patch enables the vectorization of statement like `op_1 bop op_2 ? res_f_d_1 : res_f_d_2` in a loop, where op_x's size is different from res_f_d_x's.
>> 
>> To assist with code review, this pr contains only the shared code change, is splitted from https://github.com/openjdk/jdk/pull/28230, which enable & implement the riscv part. The similar optimization could be extended to other platforms. 
>> 
>> ## Some background
>> 
>> Previously, it's https://github.com/openjdk/jdk/pull/25336, which was blocked by unsigned comparison issue. The issue was recently resolved by https://github.com/openjdk/jdk/pull/27942, so I'm re-start working on this optimization.
>> 
>> This pr only relaxes one of the constraints in https://github.com/openjdk/jdk/pull/25336, i.e. transform CMoveF/D to vector operations no matter what's the size of comparison's operator, but remove the optimization of transform CMoveI/L to vector operations which I think need more investigation.
>> 
>> # Test
>> ## Jtreg
>> 
>> in progress...
>> 
>> ## Performance
>> 
>> check the performance data in https://github.com/openjdk/jdk/pull/25341 on riscv.
>> 
>> Thanks
>
> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update src/hotspot/share/opto/superword.cpp
>   
>   refactor `is_velt_basic_type_compatible_use_def`
>   
>   Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>

src/hotspot/cpu/aarch64/matcher_aarch64.hpp line 208:

> 206:   }
> 207: 
> 208:   static bool supports_vector_different_use_def_size() {

This sounds extremely vague. Is this supposed to only be about `CMove`? Because we already have all sorts of instructions that allow different use and def types, such as conversion vectors. Those are already in use on `aarch64` and `x64`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28231#discussion_r2514537193