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

[Emanuel Peter]

On Mon, 13 Jan 2025 19:44:10 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.cpp line 38:
> 
>> 36:   MemPointer(MemPointerParser::parse(NOT_PRODUCT(trace COMMA)
>> 37:                                      mem,
>> 38:                                      callback)) {}
> 
> Again. Why not product argument first?

Ah, here I wanted to do the optional parameter `callback` (default `empty()`). You can only put parameters with default at the last position.

I decided to refactor this with 2 constructors, one with and one without `callback` parameter. The one without just delegates to the one with,  passing the default empty parameter. It's a little more code but works.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21926#discussion_r1914337700