> It's better than the generic branch sequence below, or yours. It still > sucks, obviously.
OK, I thought you were talking about the double-width result. The non-branch sequence I posted is the generic non-branch sequence (that Ada was using). > Let's see. Completely untested. Inputs in regs 3 and 4, output in reg 3. > 32-bit code all the way. > > add: > eqv 9,3,4 > add 3,3,4 > xor 4,3,4 > and. 4,9,4 > blt <overflow> > > sub: > xor 9,3,4 > sub 3,3,4 > eqv 4,3,4 > and. 4,9,4 > blt <overflow> These ones (if correct) are quite better than the generic code! > neg: > neg 3,3 > xoris. 9,3,0x8000 > beq <overflow> > > mul: > mulhw 9,3,4 > mullw 3,3,4 > srawi 4,9,31 > cmpw 4,9 > bne <overflow> These ones are essentially equivalent to the generic code. -- Eric Botcazou
