Optimize GDScript VM codegen for MSVC

[RandomShaper]

This allegedly leads to less optimal code than in the case of GCC/Clang's computed gotos, but is an improvement for those building with MSVC. I haven't benchmarked myself, so TIWAGOS.

[Calinou]

That reminds me, could we use likely()/unlikely() hints with GCC/Clang here? We do this in error macros already.

[RandomShaper]

That reminds me, could we use likely()/unlikely() hints with GCC/Clang here? We do this in error macros already.

If you mean using them for dispatching opcodes, there's the computed gotos optimization already in place for them, for which there's no point in mixing with (un)likely. Or are you talking about other spot?

[akien-mga]

Would be interesting to check how this affects build time for this file, both with and without exceptions enabled (see #80513).

[akien-mga]

Looks good to me.

Would like to have some numbers so we know exactly what we gain, but it's not blocking.

[akien-mga]

Thanks!

[Faless]

For posterity, I did run some benchmarks on this.

The MSVC build is much faster with this patch but still noticeably slower than the GCC/MinGW version using the synthetic test in #11518 adapted to 4.x ( test.zip ).

Here are the hyperfine results for 549fcce (+ patch) built with target=template_release production=yes

$ hyperfine.exe -w 1 -r 5 .\test\msvc_base\test.exe .\test\msvc_opt\test.exe .\test\mingw\test.exe
Benchmark 1: .\test\msvc_base\test.exe
  Time (mean ± σ):     22.410 s ±  0.312 s    [User: 22.251 s, System: 0.040 s]
  Range (min … max):   22.075 s … 22.911 s    5 runs

Benchmark 2: .\test\msvc_opt\test.exe
  Time (mean ± σ):     16.885 s ±  0.078 s    [User: 16.701 s, System: 0.052 s]
  Range (min … max):   16.774 s … 16.960 s    5 runs

Benchmark 3: .\test\mingw\test.exe
  Time (mean ± σ):     15.021 s ±  0.103 s    [User: 14.892 s, System: 0.021 s]
  Range (min … max):   14.915 s … 15.194 s    5 runs

Summary
  .\test\mingw\test.exe ran
    1.12 ± 0.01 times faster than .\test\msvc_opt\test.exe
    1.49 ± 0.02 times faster than .\test\msvc_base\test.exe