* http://bugs.libre-riscv.org/show_bug.cgi?id=44
"""
-from nmigen import Module, Signal
+from nmigen import Module, Signal, Cat, Mux
from nmigen.cli import main, verilog
from math import log
-from nmutil.pipemodbase import FPModBase, FPModBaseChain
+from nmutil.pipemodbase import PipeModBase, PipeModBaseChain
from ieee754.fpcommon.fpbase import FPNumDecode, FPNumBaseRecord
-from ieee754.fpcommon.getop import FPADDBaseData
+from ieee754.fpcommon.basedata import FPBaseData
from ieee754.fpcommon.denorm import (FPSCData, FPAddDeNormMod)
from ieee754.fpmul.align import FPAlignModSingle
from ieee754.div_rem_sqrt_rsqrt.core import DivPipeCoreOperation as DP
-class FPDIVSpecialCasesMod(FPModBase):
+class FPDIVSpecialCasesMod(PipeModBase):
""" special cases: NaNs, infs, zeros, denormalised
see "Special Operations"
https://steve.hollasch.net/cgindex/coding/ieeefloat.html
super().__init__(pspec, "specialcases")
def ispec(self):
- return FPADDBaseData(self.pspec)
+ return FPBaseData(self.pspec)
def ospec(self):
return FPSCData(self.pspec, False)
comb = m.d.comb
# decode: XXX really should move to separate stage
- a1 = FPNumBaseRecord(self.pspec.width, False, name="a1")
- b1 = FPNumBaseRecord(self.pspec.width, False, name="b1")
+ width = self.pspec.width
+ a1 = FPNumBaseRecord(width, False, name="a1")
+ b1 = FPNumBaseRecord(width, False, name="b1")
m.submodules.sc_decode_a = a1 = FPNumDecode(None, a1)
m.submodules.sc_decode_b = b1 = FPNumDecode(None, b1)
comb += [a1.v.eq(self.i.a),
# temporaries (used below)
sabx = Signal(reset_less=True) # sign a xor b (sabx, get it?)
- abnan = Signal(reset_less=True)
- abinf = Signal(reset_less=True)
+ t_abnan = Signal(reset_less=True)
+ t_abinf = Signal(reset_less=True)
+ t_a1inf = Signal(reset_less=True)
+ t_b1inf = Signal(reset_less=True)
+ t_a1nan = Signal(reset_less=True)
+ t_a1zero = Signal(reset_less=True)
+ t_b1zero = Signal(reset_less=True)
+ t_abz = Signal(reset_less=True)
+ t_special_div = Signal(reset_less=True)
+ t_special_sqrt = Signal(reset_less=True)
+ t_special_rsqrt = Signal(reset_less=True)
comb += sabx.eq(a1.s ^ b1.s)
- comb += abnan.eq(a1.is_nan | b1.is_nan)
- comb += abinf.eq(a1.is_inf & b1.is_inf)
-
- # default (overridden if needed)
- comb += self.o.out_do_z.eq(1)
+ comb += t_abnan.eq(a1.is_nan | b1.is_nan)
+ comb += t_abinf.eq(a1.is_inf & b1.is_inf)
+ comb += t_a1inf.eq(a1.is_inf)
+ comb += t_b1inf.eq(b1.is_inf)
+ comb += t_a1nan.eq(a1.is_nan)
+ comb += t_abz.eq(a1.is_zero & b1.is_zero)
+ comb += t_a1zero.eq(a1.is_zero)
+ comb += t_b1zero.eq(b1.is_zero)
+
+ # prepare inf/zero/nans
+ z_zero = FPNumBaseRecord(width, False, name="z_zero")
+ z_zeroa = FPNumBaseRecord(width, False, name="z_zeroa")
+ z_zeroab = FPNumBaseRecord(width, False, name="z_zeroab")
+ z_nan = FPNumBaseRecord(width, False, name="z_nan")
+ z_infa = FPNumBaseRecord(width, False, name="z_infa")
+ z_infb = FPNumBaseRecord(width, False, name="z_infb")
+ z_infab = FPNumBaseRecord(width, False, name="z_infab")
+ comb += z_zero.zero(0)
+ comb += z_zeroa.zero(a1.s)
+ comb += z_zeroab.zero(sabx)
+ comb += z_nan.nan(0)
+ comb += z_infa.inf(a1.s)
+ comb += z_infb.inf(b1.s)
+ comb += z_infab.inf(sabx)
+
+ comb += t_special_div.eq(Cat(t_b1zero, t_a1zero, t_b1inf, t_a1inf,
+ t_abinf, t_abnan).bool())
+ comb += t_special_sqrt.eq(Cat(t_a1zero, a1.s, t_a1inf,
+ t_a1nan).bool())
# select one of 3 different sets of specialcases (DIV, SQRT, RSQRT)
with m.Switch(self.i.ctx.op):
- with m.Case(int(DP.UDivRem)): # DIV
+ ########## DIV ############
+ with m.Case(int(DP.UDivRem)):
- # if a is NaN or b is NaN return NaN
- with m.If(abnan):
- comb += self.o.z.nan(0)
+ # any special cases?
+ comb += self.o.out_do_z.eq(t_special_div)
+ # if a is NaN or b is NaN return NaN
# if a is inf and b is Inf return NaN
- with m.Elif(abinf):
- comb += self.o.z.nan(0)
-
# if a is inf return inf
- with m.Elif(a1.is_inf):
- comb += self.o.z.inf(sabx)
-
# if b is inf return zero
- with m.Elif(b1.is_inf):
- comb += self.o.z.zero(sabx)
-
# if a is zero return zero (or NaN if b is zero)
- with m.Elif(a1.is_zero):
- comb += self.o.z.zero(sabx)
# b is zero return NaN
- with m.If(b1.is_zero):
- comb += self.o.z.nan(0)
-
# if b is zero return Inf
- with m.Elif(b1.is_zero):
- comb += self.o.z.inf(sabx)
- # Denormalised Number checks next, so pass a/b data through
- with m.Else():
- comb += self.o.out_do_z.eq(0)
+ # sigh inverse order on the above, Mux-cascade
+ oz = 0
+ oz = Mux(t_b1zero, z_infab.v, oz)
+ oz = Mux(t_a1zero, Mux(t_b1zero, z_nan.v, z_zeroab.v), oz)
+ oz = Mux(t_b1inf, z_zeroab.v, oz)
+ oz = Mux(t_a1inf, z_infab.v, oz)
+ oz = Mux(t_abinf, z_nan.v, oz)
+ oz = Mux(t_abnan, z_nan.v, oz)
- with m.Case(int(DP.SqrtRem)): # SQRT
+ comb += self.o.oz.eq(oz)
- # if a is zero return zero
- with m.If(a1.is_zero):
- comb += self.o.z.zero(a1.s)
+ ########## SQRT ############
+ with m.Case(int(DP.SqrtRem)):
- # -ve number is NaN
- with m.Elif(a1.s):
- comb += self.o.z.nan(0)
+ # any special cases?
+ comb += self.o.out_do_z.eq(t_special_sqrt)
+ # if a is zero return zero
+ # -ve number is NaN
# if a is inf return inf
- with m.Elif(a1.is_inf):
- comb += self.o.z.inf(sabx)
-
# if a is NaN return NaN
- with m.Elif(a1.is_nan):
- comb += self.o.z.nan(0)
- # Denormalised Number checks next, so pass a/b data through
- with m.Else():
- comb += self.o.out_do_z.eq(0)
+ oz = 0
+ oz = Mux(t_a1nan, z_nan.v, oz)
+ oz = Mux(t_a1inf, z_infab.v, oz)
+ oz = Mux(a1.s, z_nan.v, oz)
+ oz = Mux(t_a1zero, z_zeroa.v, oz)
+
+ comb += self.o.oz.eq(oz)
- with m.Case(int(DP.RSqrtRem)): # RSQRT
+ ########## RSQRT ############
+ with m.Case(int(DP.RSqrtRem)):
# if a is NaN return canonical NaN
with m.If(a1.is_nan):
with m.Else():
comb += self.o.out_do_z.eq(0)
- comb += self.o.oz.eq(self.o.z.v)
+ comb += self.o.oz.eq(self.o.z.v)
+
+ # pass through context
comb += self.o.ctx.eq(self.i.ctx)
return m
-class FPDIVSpecialCasesDeNorm(FPModBaseChain):
+class FPDIVSpecialCasesDeNorm(PipeModBaseChain):
""" special cases: NaNs, infs, zeros, denormalised
"""
projects / ieee754fpu.git / blobdiff