From the S76 agent, none previously recorded:
1. array[var-K] folds K into the symbol LO16/lhu displacement, and naming
an intermediate idx does NOT stop it (the fold is front-end/combine,
before any steerable register choice). A zero-byte opacity barrier on
idx, one per use site, is what defeats it.
2. The fused sll 16 / sra 15 sign-extend-scale needs the index declared
s16 — confirms §241's recipe reproduces on a fresh case.
3. A mask-then-compare LOCAL cross-jump-merged two case tails and flipped
branch polarity to bne; switching on the expression directly fixed both
and matched the target's forward-beq. The temporary was the defect —
§461 from the other direction.
4. A pointer parameter's SIGNEDNESS decides how -1 is materialized:
s16* gives addiu -1, u16* gives ori 0xffff, because gcc-2.7.2
canonicalizes the RHS constant against the lvalue's signedness when
picking the load-immediate opcode. Invisible in the C, one instruction
in the asm.
Residual is one permuter-class DELAY-SLOT diff two prior attempts also hit.
Drew T
bb36198eea