-# IEEE Floating Point Multiplier
+""" IEEE Floating Point Divider
-from nmigen import Module, Signal, Cat, Const, Elaboratable
+Copyright (C) 2019 Luke Kenneth Casson Leighton <lkcl@lkcl.net>
+Copyright (C) 2019 Jacob Lifshay
+
+Relevant bugreports:
+* http://bugs.libre-riscv.org/show_bug.cgi?id=99
+* http://bugs.libre-riscv.org/show_bug.cgi?id=43
+* http://bugs.libre-riscv.org/show_bug.cgi?id=44
+"""
+
+from nmigen import Module, Signal
from nmigen.cli import main, verilog
from math import log
+from ieee754.fpcommon.modbase import FPModBase, FPModBaseChain
from ieee754.fpcommon.fpbase import FPNumDecode, FPNumBaseRecord
-from nmutil.singlepipe import SimpleHandshake, StageChain
-
-from ieee754.fpcommon.fpbase import FPState, FPID
from ieee754.fpcommon.getop import FPADDBaseData
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(Elaboratable):
+class FPDIVSpecialCasesMod(FPModBase):
""" special cases: NaNs, infs, zeros, denormalised
see "Special Operations"
https://steve.hollasch.net/cgindex/coding/ieeefloat.html
"""
def __init__(self, pspec):
- self.pspec = pspec
- self.i = self.ispec()
- self.o = self.ospec()
+ super().__init__(pspec, "specialcases")
def ispec(self):
return FPADDBaseData(self.pspec)
def ospec(self):
return FPSCData(self.pspec, False)
- def setup(self, m, i):
- """ links module to inputs and outputs
- """
- m.submodules.specialcases = self
- m.d.comb += self.i.eq(i)
-
- def process(self, i):
- return self.o
-
def elaborate(self, platform):
m = Module()
-
- #m.submodules.sc_out_z = self.o.z
+ comb = m.d.comb
# decode: XXX really should move to separate stage
- a1 = FPNumBaseRecord(self.pspec.width, False)
- b1 = FPNumBaseRecord(self.pspec.width, False)
+ a1 = FPNumBaseRecord(self.pspec.width, False, name="a1")
+ b1 = FPNumBaseRecord(self.pspec.width, False, name="b1")
m.submodules.sc_decode_a = a1 = FPNumDecode(None, a1)
m.submodules.sc_decode_b = b1 = FPNumDecode(None, b1)
- m.d.comb += [a1.v.eq(self.i.a),
+ comb += [a1.v.eq(self.i.a),
b1.v.eq(self.i.b),
self.o.a.eq(a1),
self.o.b.eq(b1)
- ]
+ ]
+ # temporaries (used below)
sabx = Signal(reset_less=True) # sign a xor b (sabx, get it?)
- m.d.comb += sabx.eq(a1.s ^ b1.s)
-
abnan = Signal(reset_less=True)
- m.d.comb += abnan.eq(a1.is_nan | b1.is_nan)
-
abinf = Signal(reset_less=True)
- m.d.comb += abinf.eq(a1.is_inf & b1.is_inf)
-
- # if a is NaN or b is NaN return NaN
- with m.If(abnan):
- m.d.comb += self.o.out_do_z.eq(1)
- m.d.comb += self.o.z.nan(1)
-
- # if a is inf and b is Inf return NaN
- with m.Elif(abnan):
- m.d.comb += self.o.out_do_z.eq(1)
- m.d.comb += self.o.z.nan(1)
-
- # if a is inf return inf
- with m.Elif(a1.is_inf):
- m.d.comb += self.o.out_do_z.eq(1)
- m.d.comb += self.o.z.inf(sabx)
-
- # if b is inf return zero
- with m.Elif(b1.is_inf):
- m.d.comb += self.o.out_do_z.eq(1)
- m.d.comb += self.o.z.zero(sabx)
-
- # if a is zero return zero (or NaN if b is zero)
- with m.Elif(a1.is_zero):
- m.d.comb += self.o.out_do_z.eq(1)
- m.d.comb += self.o.z.zero(sabx)
- # b is zero return NaN
- with m.If(b1.is_zero):
- m.d.comb += self.o.z.nan(1)
-
- # if b is zero return Inf
- with m.Elif(b1.is_zero):
- m.d.comb += self.o.out_do_z.eq(1)
- m.d.comb += self.o.z.inf(sabx)
-
- # Denormalised Number checks next, so pass a/b data through
- with m.Else():
- m.d.comb += self.o.out_do_z.eq(0)
-
- m.d.comb += self.o.oz.eq(self.o.z.v)
- m.d.comb += self.o.ctx.eq(self.i.ctx)
- return m
+ 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)
-class FPDIVSpecialCases(FPState):
- """ special cases: NaNs, infs, zeros, denormalised
- NOTE: some of these are unique to div. see "Special Operations"
- https://steve.hollasch.net/cgindex/coding/ieeefloat.html
- """
+ # select one of 3 different sets of specialcases (DIV, SQRT, RSQRT)
+ with m.Switch(self.i.ctx.op):
- def __init__(self, pspec):
- FPState.__init__(self, "special_cases")
- self.mod = FPDIVSpecialCasesMod(pspec)
- self.out_z = self.mod.ospec()
- self.out_do_z = Signal(reset_less=True)
+ with m.Case(int(DP.UDivRem)): # DIV
- def setup(self, m, i):
- """ links module to inputs and outputs
- """
- self.mod.setup(m, i, self.out_do_z)
- m.d.sync += self.out_z.v.eq(self.mod.out_z.v) # only take the output
- m.d.sync += self.out_z.mid.eq(self.mod.o.mid) # (and mid)
+ # if a is NaN or b is NaN return NaN
+ with m.If(abnan):
+ comb += self.o.z.nan(0)
- def action(self, m):
- self.idsync(m)
- with m.If(self.out_do_z):
- m.next = "put_z"
- with m.Else():
- m.next = "denormalise"
+ # 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)
-class FPDIVSpecialCasesDeNorm(FPState, SimpleHandshake):
- """ special cases: NaNs, infs, zeros, denormalised
- """
+ # if b is inf return zero
+ with m.Elif(b1.is_inf):
+ comb += self.o.z.zero(sabx)
- def __init__(self, pspec):
- FPState.__init__(self, "special_cases")
- self.pspec = pspec
- SimpleHandshake.__init__(self, self) # pipe is its own stage
- self.out = self.ospec()
+ # 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)
- def ispec(self):
- return FPADDBaseData(self.pspec) # SpecialCases ispec
+ # if b is zero return Inf
+ with m.Elif(b1.is_zero):
+ comb += self.o.z.inf(sabx)
- def ospec(self):
- return FPSCData(self.pspec, False) # DeNorm ospec
+ # Denormalised Number checks next, so pass a/b data through
+ with m.Else():
+ comb += self.o.out_do_z.eq(0)
- def setup(self, m, i):
- """ links module to inputs and outputs
- """
- smod = FPDIVSpecialCasesMod(self.pspec)
- dmod = FPAddDeNormMod(self.pspec, False)
+ with m.Case(int(DP.SqrtRem)): # SQRT
+
+ # if a is zero return zero
+ with m.If(a1.is_zero):
+ comb += self.o.z.zero(a1.s)
+
+ # -ve number is NaN
+ with m.Elif(a1.s):
+ 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 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)
+
+ with m.Case(int(DP.RSqrtRem)): # RSQRT
+
+ # if a is NaN return canonical NaN
+ with m.If(a1.is_nan):
+ comb += self.o.z.nan(0)
- chain = StageChain([smod, dmod])
- chain.setup(m, i)
+ # if a is +/- zero return +/- INF
+ with m.Elif(a1.is_zero):
+ # this includes the "weird" case 1/sqrt(-0) == -Inf
+ comb += self.o.z.inf(a1.s)
- # only needed for break-out (early-out)
- # self.out_do_z = smod.o.out_do_z
+ # -ve number is canonical NaN
+ with m.Elif(a1.s):
+ comb += self.o.z.nan(0)
- self.o = dmod.o
+ # if a is inf return zero (-ve already excluded, above)
+ with m.Elif(a1.is_inf):
+ comb += self.o.z.zero(0)
- def process(self, i):
- return self.o
+ # Denormalised Number checks next, so pass a/b data through
+ with m.Else():
- def action(self, m):
- # for break-out (early-out)
- #with m.If(self.out_do_z):
- # m.next = "put_z"
- #with m.Else():
- m.d.sync += self.out.eq(self.process(None))
- m.next = "align"
+ comb += self.o.oz.eq(self.o.z.v)
+ comb += self.o.ctx.eq(self.i.ctx)
+ return m
+
+
+class FPDIVSpecialCasesDeNorm(FPModBaseChain):
+ """ special cases: NaNs, infs, zeros, denormalised
+ """
+
+ def get_chain(self):
+ """ links module to inputs and outputs
+ """
+ smod = FPDIVSpecialCasesMod(self.pspec)
+ dmod = FPAddDeNormMod(self.pspec, False)
+ amod = FPAlignModSingle(self.pspec, False)
+ return [smod, dmod, amod]
projects / ieee754fpu.git / blobdiff