In the specializing adatpive interpreter,DEOPT_IFs andEXIT_IFs are synonymous, so we have historically been quite haphazard about which to use.
In the JIT, however, there is an important difference: aDEOPT_IF drops execution back into the interpreter unconditionally, whereas anEXIT_IF causes a side-exit which can warm up and also be jitted.

In some cases, like in aCALL or aSEND, theDEOPT_IF prevents the code from being ever being jitted after the exit. See#145047 for an explanation.

There are currently 109DEOPT_IFs in bytecodes.c. Many of those should beEXIT_IFs.

Specifically,DEOPT_IFs should be converted toEXIT_IFs if they are:

• In a guard (e.g._GUARD_CALLABLE_STR_1)
• In the guard part of a more complex uop (e.g._CHECK_AND_ALLOCATE_OBJECT)

DEOPT_IFs should be left alone if any of these are true:

• It is in teir1-only code
• It is an error, and we are exiting to let the interpeter handle the error
• The interpreter needs to handle something before continuing in jitted code (e.g the eval breaker)
• An optimization is no longer valid and re-specialization/jitting needs to happen

Linked PRs

• GH-145692: Convert DEOPT_IFs to EXIT_IFs #145751