RFR: 8342156: C2: Compilation failure with fewer arguments after JDK-8329032 [v5]

[Daniel Lundén]

> Adding C2 register allocation support for APX EGPRs ([JDK-8329032](https://bugs.openjdk.org/browse/JDK-8329032)) reduced, due to unfortunate rounding in the register mask size computation, the available space for incoming/outgoing method arguments in register masks.
> 
> ### Changeset
> 
> - Bump the number of 32-bit words dedicated to incoming/outgoing arguments in register masks from 3 to 4.
> - Add a regression test.
> 
> ### Testing
> 
> - [GitHub Actions](https://github.com/dlunde/jdk/actions/runs/11436050131)
> - `tier1` to `tier4` (and additional Oracle-internal testing) on Windows x64, Linux x64, Linux aarch64, macOS x64, and macOS aarch64.
> - C2 compilation time benchmarking for DaCapo on Windows x64, Linux x64, Linux aarch64, macOS x64, and macOS aarch64. There is no observable difference in C2 compilation time.

Daniel Lundén has updated the pull request incrementally with one additional commit since the last revision:

  Update src/hotspot/share/adlc/formsopt.cpp
  
  Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/21612/files
  - new: https://git.openjdk.org/jdk/pull/21612/files/33809e9b..87745d69

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21612&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21612&range=03-04

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21612.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21612/head:pull/21612

PR: https://git.openjdk.org/jdk/pull/21612