The counterintuitive one: use TWO distinct locals for the same b*24, because
cse resets at the if-join and the original recomputes the product into a
second register — one shared local cannot reproduce it, and writing it inline
is worse still (cse hoists the %hi/%lo address into a pseudo and changes the
addressing mode). Duplicating a subexpression can be the correct decompile.
Plus: a store-then-read-back turns a redundant load into the target's
register copy; a zero-byte fence stops sched1 hoisting two '= 0' stores into
the load-delay slot; and writing three repeated tails out separately lets
cross_jump merge them, where funnelling them through one variable emits the
arms inverted.
Residual is three allocation facts, incl. a $17 pin that is REQUIRED (else k2
splits across two callee-saved regs and costs a fourth) but drags the shift
chain into $s1.
Drew T
9467db409b