RFR: 8318959: C2: define MachNode::fill_new_machnode() statically

[Vladimir Kozlov]

On Wed, 1 Nov 2023 07:27:09 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> This changeset makes the implementation of `MachNode::fill_new_machnode()` static instead of ADLC-generated, for better maintainability. The original motivation to generate this function was to replace its logic with a `ShouldNotCallThis()` call for targets that do not define CISC spill or short branch instruction versions. However, most targets (including x64 and aarch64) feature at least one of these and hence do not make use of the ADLC specialization. For those that do, the savings (approximately 140 bytes on a x64 build of `libjvm.so`) are marginal and (arguably) not worth the additional code complexity.
> 
> See motivating discussion in https://mail.openjdk.org/pipermail/hotspot-compiler-dev/2023-October/thread.html#69348.
> 
> #### Testing
> - tier1-3 (windows-x64, linux-x64, linux-aarch64, macosx-x64, macosx-aarch64; release and debug mode)

src/hotspot/share/adlc/output_c.cpp line 3218:

> 3216: 
> 3217:     // Output code to convert to the short branch version, if applicable
> 3218:     instr->define_short_branch_methods(*this, fp);

Should you update these 2 methods since their return value is not used anymore anywhere?

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PR Review Comment: https://git.openjdk.org/jdk/pull/16444#discussion_r1379021697