Counterweight to §3-B, with a precise discriminator. When two arms converge on a shared
block, that block is usually a late cross_jump merge of per-arm DUPLICATED statements
(§298). Spelling it as a real goto is not equivalent when the label sits INSIDE a loop:
the goto becomes a jump into the loop body, jump.c's mark_loop_jump marks it
loop_invalid, cc1 -dL prints 'Loop at N ignored due to multiple entry points', and
loop.c silently drops invariant hoisting — measured: the 1/0x80 constant hoist into
$a0/$a1 vanished, 2 insns plus a spurious andi.
Discriminator: shared tail outside every loop -> fold it (§3-B, and you may free a hard
ABI register). Shared tail inside a loop body -> duplicate per arm and let cross_jump
merge. A -dL line is a free oracle for this.
Also records CdReadSectorReadyCB's three remaining residual clusters as pack fuel so the
next attempt starts from the draft, not from the .s.
Drew T
174f7aaf7a