SS131: `sltiu N` is ground truth in BOTH directions. jtbl_range already EXTENDS a span the
dlabel cut short and WARNS when a span is shorter than the bound, but had no clamp for a
span too LONG for a NON-ZERO reason — and the trailing trim only removes ZERO words, so
ordinary data that spimdisasm ran into the dlabel slipped through and under-filled the piece.
Records the reusable FINGERPRINT of an under-fill, because it does not look like codegen:
hundreds of 1-byte diffs spread over most of the overlay, ~95% at byte 0 (mod 4) = the low
byte of a 16-bit immediate, every one changing by exactly -4. Bucket differing bytes by
offset%4 and decode a few words; uniform small deltas in the immediate field mean LAYOUT,
not codegen. (Measured: 812 of 853 at pos 0 mod 4, all -4.)
The clamp's authorization matches the extension path exactly: unambiguous sltiu bound only,
and REFUSE LOUDLY if any surplus word is a plausible code address.
This was the single instrument failure that survived SS125's retraction round — the one case
where "the tool is broken" was actually true. Now fixed, with the 710-ins behemoth banked.
Drew T
b58fd82068