Figure 3 — LAMBDA Machine-Status Fast Path
Patent Figure: LAMBDA entry, body execution, and RETURN with fast-path vs stack-path decision
LAMBDA ENTRY
~2 cycles
BODY EXECUTION
N cycles
RETURN
1 cycle (fast) / 5+ cycles (stack)
LAMBDA CRn, x
CRn.Type =
Inform (00)?
FAULT
No
Yes
X perm
set?
No
Yes
LAMBDA-active
already set?
Yes
No (clear)
Save PC+4 to
LAMBDA_PC reg
Set
LAMBDA-active = 1
Branch to
CRn entry point
Body executes: args/results in DRs
CR6, CR14 unchanged — same protection domain
RETURN
LAMBDA-active
flag set?
Yes
FAST PATH
Restore PC from
LAMBDA_PC
Clear LAMBDA-active
DONE
Zero stack access
~1 cycle total
No
STACK PATH
Pop stack frame
Tag
bit?
Tag = 0
CALL frame
Restore CR5, CR6, CR14
via mLoad revalidation
DONE
Full domain restore
5+ cycles total
Tag = 1
LAMBDA frame
Restore PC only
~2 cycles
No CR writes. No mLoad.
Flow
Yes / Fast path (~1 cycle)
No / Fault
Stack path (5+ cycles)
Decision