- am0 = Signal(len(self.i.a.m)+1, reset_less=True)
- bm0 = Signal(len(self.i.b.m)+1, reset_less=True)
- # same-sign (both negative or both positive) add mantissas
- comb += [seq.eq(self.i.a.s == self.i.b.s),
- mge.eq(self.i.a.m >= self.i.b.m),
- am0.eq(Cat(self.i.a.m, 0)),
- bm0.eq(Cat(self.i.b.m, 0))
+ sm = Signal(reset_less=True)
+ op1 = Signal(len(a.m)+1, reset_less=True)
+ op2 = Signal(len(b.m)+1, reset_less=True)
+
+ # logic is as follows:
+ # * same-sign (both negative or both positive) add mantissas
+ # * opposite sign, subtract b mantissa from a
+ # * a mantissa greater than b, use a
+ # * b mantissa greater than a, use b
+ comb += [seq.eq(a.s == b.s),
+ mge.eq(a.m >= b.m),
+ sm.eq(seq | mge),
+ op1.eq(Cat(Mux(sm, a.m, b.m), 0)), # swap a and b
+ op2.eq(Cat(Mux(sm, b.m, a.m), 0)), # swap b and a