[BUG] JIT bug in older mod "Juvenile Power Fantasy"

[TheKins]

GZDoom version

g4.14.0

Which game are you running with GZDoom?

Doom 2

What Operating System are you using?

Windows 10

Please describe your specific OS version

No response

Relevant hardware info

No response

Have you checked that no other similar issue already exists?

• I have searched and not found similar issues.

A clear and concise description of what the bug is.

When running the old mod Juvenile Power Fantasy, nearly every time the game starts it will stop running during initial startup citing the cryptic error message "Invalid instruction: cmp , 0". Exactly where it hits the error during load seems to change every time, but it seems to most often happen when parsing the first few monster replacements.

A Discord conversation with @RicardoLuis0 suggests that this is a bug in the JIT system being reported at startup instead of when it's hit during gameplay. I am making this Issue by request, to make this bug easier to track and fix.

Steps to reproduce the behaviour.

Explain how to reproduce

1. Download v1.1 of Juvenile Power Fantasy.
2. Attempt to run it in GZDoom g4.14.0, with vm_jit enabled.
3. Watch. In rare cases, the game will reach the titlemap, but in most cases it will hit the error at some point during initial startup.

Your configuration

Provide a Log

No response