RFR: 8343685: C2 SuperWord: refactor VPointer with MemPointer [v4]

[Emanuel Peter]

On Mon, 13 Jan 2025 20:03:38 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 116 commits:
>> 
>>  - copyright 2025
>>  - Merge branch 'master' into JDK-8343685-VPointer-MemPointer
>>  - manual merge
>>  - fix printing
>>  - rename
>>  - fix up print
>>  - add TestEquivalentInvariants.java
>>  - improve documentation
>>  - hide parser via delegation
>>  - Merge branch 'master' into JDK-8343685-VPointer-MemPointer
>>  - ... and 106 more: https://git.openjdk.org/jdk/compare/84e6432b...b64f9295
>
> src/hotspot/share/opto/mempointer.hpp line 677:
> 
>> 675:     assert(pos == summands.length(), "copied all summands");
>> 676: 
>> 677:     assert(1 <= _size && _size <= 2048 && is_power_of_2(_size), "valid size");
> 
> Where 2048 comes from? Do you have a runtime check somewhere too?

It is just a sanity check: currently no platform has vectors larger than 2048. Replaced the assert with:
`assert(1 <= _size && _size <= 2048 && is_power_of_2(_size), "sanity: no vector is expected to be larger");`

> test/hotspot/jtreg/compiler/loopopts/superword/TestEquivalentInvariants.java line 2:
> 
>> 1: /*
>> 2:  * Copyright (c) 2024, 2025, Oracle and/or its affiliates. All rights reserved.
> 
> This is new file. Why two years?

Nice catch. I must have just blindly extended it when I updated the copyright year.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21926#discussion_r1914321984
PR Review Comment: https://git.openjdk.org/jdk/pull/21926#discussion_r1914323015