RFR: 8356924: RISC-V: Clean up cost for vector instructions

[Gui Cao]

On Wed, 14 May 2025 04:04:11 GMT, Dingli Zhang <dzhang at openjdk.org> wrote:

> As mentioned in https://bugs.openjdk.org/browse/JDK-8285790 regarding the ARM64 vector instruct modifications:
> Since the new rules are unique and setting different "ins_cost" makes no sense, we have switched to using the default cost.
> 
> Currently, there is a similar situation on RISC-V. Over half of the instructions in riscv_v.ad do not include ins_cost definitions. Additionally, as RVV nodes are also unique, we can unify the format by removing these ins_cost entries from riscv_v.ad.
> 
> ### Testing
> qemu-system 9.1.0 with UseRVV (ubuntu24.10):
> * [x]  Run test/jdk/jdk/incubator/vector (fastdebug)
> * [x]  Run test/hotspot/jtreg/compiler/vectorapi (fastdebug)

LGTM.

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Marked as reviewed by gcao (Author).

PR Review: https://git.openjdk.org/jdk/pull/25221#pullrequestreview-2839130010