**670 bodies / 680 regions. Phase: 602 -> 670 = +68.**
**+3 bodies, all verified by me from fresh --work dirs at their REAL extents:**
0x80107CCC (76 B, cc1bin=gcc-2.8.1-psx) -- A's row, unlocked by the tool fix below
0x8002D060 (72 B, D) 0x8006FAEC (88 B, D)
And +2 earlier this round: 0x8004D7C8 (220 B, B), 0x8003A9C8 (240 B, B).
**WORKER A FOUND A REAL BUG IN tools/sf3_match AND I FIXED IT.** `rewrite_gp_accesses`'s `_GP_LO`
branch rewrote `lw $2,%lo(SYM)($R)` to `lw $2,%gp_rel(SYM)($gp)` and then `continue`d WITHOUT recording
that the rewrite redefines its destination register. `carrying` kept the stale `%hi`, the register's
next use was scored as an unrewritten use, and the `%hi` was deliberately kept -- so the region came
out exactly 4 bytes long, one instruction.
I reproduced the evidence independently before touching the code, in 0x80107CCC's pre-fix output:
lui $2,%hi(D_801221CC) # high
lw $2,%gp_rel(D_801221CC)($gp)
The same failure the docstring says was fixed for the adjacent-lines case, still live for the
load-whose-result-is-used-later case. One-line fix, A's reasoning and name in the comment, plus why it
stayed invisible: nothing breaks until a gp-marked LOAD feeds something.
Measured: 80/LENGTH-MISMATCH -> 76/0/MATCH. **The tool change was GATED, not trusted**: the pass
touches every gp region, so the full gate was re-run -- c_regions=678, differing_bytes=0, MATCH. That
also answers A, which asked whether the four merged cc1bin rows needed re-verification; the gate is
what proves it and it was green.
**AND WORKER D FOUND THE SAME PASS FROM THE OPPOSITE DIRECTION** on 0x800FFBBC: cc1 2.8.1 puts a safe
`lui $2,%hi(...)` in a branch delay slot, the rewrite folds the hi/lo pair to gp-relative, the lui
DISAPPEARS and the store slides into the delay slot (48 -> 44). So A's case is the rewrite failing to
fire and D's is the rewrite firing and changing a schedule -- two faces of one pass, on two rows, found
by two workers who could not see each other's row. D's framing is the open item: a maspsx mode that
re-derives the delay slot after the gp-relative rewrite would likely close a class.
**cc1bin's measured boundary, and a correction to my own guidance.** B swept the compilers: 2.5.7 /
2.6.0 / 2.6.3 / 2.7.2 / 2.7.2-cdk / 2.7.2-psx give a MERGED epilogue; 2.8.0-psx / 2.8.1-psx give
SEPARATE jr $31 per return. So return merging is a 2.7.2-family behaviour. BUT 2.8.x also changes the
GLOBAL ACCESS FORM (explicit lui %hi / lw %lo pair instead of the symbolic load maspsx turns into
lw v0,2080(gp)). **The lever moves two axes at once and is not free** -- which corrects what I told A,
B and D when routing the multi-exit rows.
**0x80107D7C sits BETWEEN the compilers and is a genuine open question.** B: default 112, 2.8.1 104,
target 108. I swept all TEN vendored builds because B's table listed eight: only 2.7.2-cdk produces 108
bytes, and it is 30 bytes off in content. 2.91.66 and 2.95.2 give 100. So the length is reachable and
the content is not, on any vendored compiler.
**Two corrections of record, both mine:** I guessed extents instead of reading
config/function_extents.tsv (testing A's 76-byte row against an 80-byte extent and reporting
LENGTH-MISMATCH from a correct candidate); and I told three workers cc1bin was a clean lever for the
multi-exit rows when B's sweep shows it moves two axes.
**Ruling on A's per-region codegen flag request (0x800AB504): (b) class-bound, with the diagnosis
kept** -- because `-fno-strength-reduce` gives 152 against a 148 target. A flag that closes a row is a
lever; one that moves a row 16 bytes closer to a different number is a diagnosis. But the PRINCIPLE is
recorded for the next such row: a codegen flag is admissible on the same terms as cc1bin, i.e. a named
mechanism in the bytes, and A has one (address normalisation creating a second loop-carried pointer).
**D: the indexed and pointer loop forms COEXIST and neither carries across rows.** 0x8002D060 matches
only as an INDEXED loop; 0x80107B40 wants the pointer form. A direct refutation of pattern-carrying
from the worker with the most reason to trust a pattern. Also: the both-sides-volatile rule TRANSFERS
(0x8006FAEC), with the narrowing measured (only interleaved accesses need it); and READ the displacement
and compute the symbol rather than inferring it from an adjacent symbol's name (gp+0xBA4 -> 0x801224DC).
**Charter note: `--cc1-flag=X` REPLACES the default `-quiet -O2 -G0` set**, so a diagnosis run must
pass all four explicitly. A's first -fthread-jumps probe read 200 B purely because -O2 was dropped.
Christopher Williams
354e90d5e5