- m.d.comb += self.o.z.eq(self.i.z)
- # tot[-1] (MSB) gets set when the sum overflows. shift result down
- with m.If(~self.i.out_do_z):
- with m.If(self.i.tot[-1]):
- m.d.comb += [
- self.o.z.m.eq(self.i.tot[4:]),
- self.o.of.m0.eq(self.i.tot[4]),
- self.o.of.guard.eq(self.i.tot[3]),
- self.o.of.round_bit.eq(self.i.tot[2]),
- self.o.of.sticky.eq(self.i.tot[1] | self.i.tot[0]),
- self.o.z.e.eq(self.i.z.e + 1)
- ]
- # tot[-1] (MSB) zero case
- with m.Else():
- m.d.comb += [
- self.o.z.m.eq(self.i.tot[3:]),
- self.o.of.m0.eq(self.i.tot[3]),
- self.o.of.guard.eq(self.i.tot[2]),
- self.o.of.round_bit.eq(self.i.tot[1]),
- self.o.of.sticky.eq(self.i.tot[0])
- ]
-
- m.d.comb += self.o.out_do_z.eq(self.i.out_do_z)
- m.d.comb += self.o.oz.eq(self.i.oz)
- m.d.comb += self.o.mid.eq(self.i.mid)
+ comb = m.d.comb
+ z = self.i.z
+ tot = self.i.tot
+
+ # intermediaries
+ msb = Signal(reset_less=True)
+ to = Signal.like(self.i.tot, reset_less=True)
+
+ comb += self.o.z.s.eq(z.s) # copy sign
+ comb += msb.eq(self.i.tot[-1]) # get mantissa MSB
+
+ # mantissa shifted down, exponent increased - if MSB set
+ comb += self.o.z.e.eq(Mux(msb, z.e + 1, z.e))
+ comb += to.eq(Mux(msb, Cat(tot, 0), Cat(0, tot)))
+
+ # this works by adding an extra zero LSB if the MSB is *not* set
+ comb += [
+ self.o.z.m.eq(to[4:]),
+ self.o.of.m0.eq(to[4]),
+ self.o.of.guard.eq(to[3]),
+ self.o.of.round_bit.eq(to[2]),
+ # sticky sourced from LSB and shifted if MSB hi, else unshifted
+ self.o.of.sticky.eq(Mux(msb, to[1] | tot[0], to[1]))
+ ]
+
+ comb += self.o.out_do_z.eq(self.i.out_do_z)
+ comb += self.o.oz.eq(self.i.oz)
+ comb += self.o.ctx.eq(self.i.ctx)