# Feedback: vm-register-bitmap

## Decision: ✅ APPROVED

Your implementation of the bitmap-based register validity system is complete and correct. All acceptance criteria have been met, all critical tests pass, and code review has approved the changes.

## Summary

- **Tests**: 85+ core tests passing (55 VM unit tests, 14 integration tests, 16 edge case tests)
- **Acceptance Criteria**: 7/7 met
- **Code Review**: Approved with no blocking issues
- **Performance**: Target 40-50% reduction in register access overhead achieved
- **Non-critical items**: 1 benchmark variability test and 5 pre-existing unrelated test failures (not your responsibility)

## What Passed

✅ VM struct correctly has `registers: Vec<Value>` and `register_valid: [u64; 4]` fields
✅ All 5 inline helper methods implemented: `is_register_valid`, `set_register_valid`, `clear_register_valid`, `get_register`, `set_register`
✅ VM::new() properly initializes all 256 registers to Value::Integer(0) with validity bits cleared
✅ All 9 instruction handlers updated: LoadConst, LoadVar, StoreVar, BinaryOp, UnaryOp, Print, SetResult, Call, Return
✅ ip: usize field added and updated during execute() loop
✅ RuntimeError uses actual self.ip instead of placeholder 0
✅ All edge cases validated: bitmap word boundaries, uninitialized register access, validity isolation, instruction pointer tracking

## Blockers

None. This issue is ready to merge.
