Phase 6 graded function starts and left every end to be derived by hand. This
adds tools/sf3_extents, which explores all reachable control flow from each hard
start (jal/entry) and reports an extent plus how far it can be trusted.
Measured decisions, not stylistic ones:
- Soft starts are not walk boundaries. A body's second instruction can satisfy
the prologue grade exactly (0x800152AC is lw v1,8(gp) / addiu sp,sp,-176, so
0x800152B0 looks like a start). Enforcing soft boundaries stopped 155 of 416
walks inside a real body.
- The walk is a full reachability computation, not a first-terminal search: a
function whose paths return at different addresses must report the whole body.
Grades: exact 1940 (1666 packed, gap=0), fallthrough 256, indirect 73,
escape 15, contained 153, standalone 438; 63.8% of the payload covered.
Verification: all 12 registered regions reproduce exactly (make extents-verify,
now part of make check), 29 new synthetic tests (115 total), byte-identical
across two runs, and Ghidra's independent body for FUN_80017ad4 agrees. Two
defects were caught by writing the tests first and are recorded: reach had to be
an exclusive end, and a terminal j's delay slot must not continue linearly.
The table holds addresses, sizes, grades and site addresses only -- no bytes.
Christopher Williams
6988ca96b0