8321003: RISC-V: C2 MulReductionVI

[Hamlin-Li]

Hi, Can you help to review this patch to implement MulReductionVI/MulReductionVL/MulReductionVF/MulReductionVD? On riscv, there is no straightforward instructions to do it, but we can do it with a reduction tree, which could reduce the time complexity to lg(N). Thanks

Performance

TBD

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Progress

• [ ] Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• [x] Change must not contain extraneous whitespace
• [x] Commit message must refer to an issue

Issues

• JDK-8321003: RISC-V: C2 MulReductionVI (Sub-task - P4)
• JDK-8321004: RISC-V: C2 MulReductionVL (Sub-task - P4)
• JDK-8321005: RISC-V: C2 MulReductionVF (Sub-task - P4)
• JDK-8321006: RISC-V: C2 MulReductionVD (Sub-task - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/19015/head:pull/19015
$ git checkout pull/19015

Update a local copy of the PR:
$ git checkout pull/19015
$ git pull https://git.openjdk.org/jdk.git pull/19015/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 19015

View PR using the GUI difftool:
$ git pr show -t 19015

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/19015.diff

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