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

[Xiaohong Gong]

On Tue, 20 May 2025 19:39:30 GMT, Hamlin Li <mli at openjdk.org> wrote:

> Hi,
> Can you help to review this patch?
> This pr is splited from https://github.com/openjdk/jdk/pull/25341, and contains only share code change.
> 
> This patch enable the vectorization of statement like `fd_1 bop fd_2 ? res_1 : res_2` in a loop.
> 
> The current behaviour on other platforms support vecatorization of `fd_1 bop fd_2 ? res_1 : res_2` in a loop only when `fd` and `res` have the same size, but this constraint seems not necessary at least not necessary on riscv, so I relax this constraint on riscv, maybe on other platforms it can be relaxed too, but currently I only made it work on riscv.
> Besides of this, I also relax the constraint on transforming Op_CMoveI/L to Op_VectorBlend on riscv, this bring some extra benefit when the `res` is not float or double types.
> Both relaxation bring performance benefit via vectorization.
> 
> Compared with other runs (master, master with `-XX:+UseVectorCmov -XX:+UseCMoveUnconditionally` turned on, patch without flags turned on), average improvement introduced by the patch with `-XX:+UseVectorCmov -XX:+UseCMoveUnconditionally` turned on is more than 2.1 times, in some cases it can bring more than 4 times improvement.
> When `-XX:-UseVectorCmov -XX:-UseCMoveUnconditionally` turned off, there is no regression on average.
> 
> Check more details at: https://github.com/openjdk/jdk/pull/25341.
> 
> Thanks

src/hotspot/share/opto/vectornode.cpp line 438:

> 436:     if (vopc == Op_VectorBlend) {
> 437:       return VectorBlendNode::implemented(opc);
> 438:     }

To keep the same code style with other ops, maybe we can directly use the body of `VectorBlendNode::implemented()` here.  Or making `VectorBlendNode::implemented()` as a static method of `VectorNode` like other ops.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25336#discussion_r2170692996