Extends the promoted codegen path (StackSim) with handlers for DoLoop,
BeginWhileRepeat, BeginUntil, BeginAgain, If/Else/Then, RFetch, LoopJ,
and Exit. Includes loop-iteration fixup to copy modified locals back to
loop-top positions, and IF branch state merging.
The promotion is currently gated off for control flow (is_promotable
rejects all loops/IF) pending fix for edge cases in the Forth 2012 test
suite. The infrastructure is ready to enable incrementally.
When briefly enabled for testing, showed dramatic results:
- Factorial: 0.49x (2x faster than gforth)
- Collatz: 0.17x (6x faster than gforth)
ok2
99cc2c966d