add fpdiv specialcases

diff --git a/src/ieee754/fpdiv/specialcases.py b/src/ieee754/fpdiv/specialcases.py
new file mode 100644 (file)
index 0000000..5ec3194
--- /dev/null
+++ b/src/ieee754/fpdiv/specialcases.py
@@ -0,0 +1,179 @@
+# IEEE Floating Point Multiplier 
+
+from nmigen import Module, Signal, Cat, Const, Elaboratable
+from nmigen.cli import main, verilog
+from math import log
+
+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)
+
+
+class FPDIVSpecialCasesMod(Elaboratable):
+    """ special cases: NaNs, infs, zeros, denormalised
+        see "Special Operations"
+        https://steve.hollasch.net/cgindex/coding/ieeefloat.html
+    """
+
+    def __init__(self, width, id_wid):
+        self.width = width
+        self.id_wid = id_wid
+        self.i = self.ispec()
+        self.o = self.ospec()
+
+    def ispec(self):
+        return FPADDBaseData(self.width, self.id_wid)
+
+    def ospec(self):
+        return FPSCData(self.width, self.id_wid, 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
+
+        # decode: XXX really should move to separate stage
+        a1 = FPNumBaseRecord(self.width, False)
+        b1 = FPNumBaseRecord(self.width, False)
+        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),
+                     b1.v.eq(self.i.b),
+                     self.o.a.eq(a1),
+                     self.o.b.eq(b1)
+                    ]
+
+        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.mid.eq(self.i.mid)
+
+        return m
+
+
+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
+    """
+
+    def __init__(self, width, id_wid):
+        FPState.__init__(self, "special_cases")
+        self.mod = FPDIVSpecialCasesMod(width)
+        self.out_z = self.mod.ospec()
+        self.out_do_z = Signal(reset_less=True)
+
+    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)
+
+    def action(self, m):
+        self.idsync(m)
+        with m.If(self.out_do_z):
+            m.next = "put_z"
+        with m.Else():
+            m.next = "denormalise"
+
+
+class FPDIVSpecialCasesDeNorm(FPState, SimpleHandshake):
+    """ special cases: NaNs, infs, zeros, denormalised
+    """
+
+    def __init__(self, width, id_wid):
+        FPState.__init__(self, "special_cases")
+        self.width = width
+        self.id_wid = id_wid
+        SimpleHandshake.__init__(self, self) # pipe is its own stage
+        self.out = self.ospec()
+
+    def ispec(self):
+        return FPADDBaseData(self.width, self.id_wid) # SpecialCases ispec
+
+    def ospec(self):
+        return FPSCData(self.width, self.id_wid, False) # DeNorm ospec
+
+    def setup(self, m, i):
+        """ links module to inputs and outputs
+        """
+        smod = FPDIVSpecialCasesMod(self.width, self.id_wid)
+        dmod = FPAddDeNormMod(self.width, self.id_wid, False)
+
+        chain = StageChain([smod, dmod])
+        chain.setup(m, i)
+
+        # only needed for break-out (early-out)
+        # self.out_do_z = smod.o.out_do_z
+
+        self.o = dmod.o
+
+    def process(self, i):
+        return self.o
+
+    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"
+
+