1 # IEEE Floating Point Adder (Single Precision)
2 # Copyright (C) Jonathan P Dawson 2013
5 from nmigen
import Module
, Signal
, Cat
, Const
6 from nmigen
.cli
import main
, verilog
9 from ieee754
.fpcommon
.fpbase
import FPNumDecode
10 from nmutil
.singlepipe
import SimpleHandshake
, StageChain
12 from ieee754
.fpcommon
.fpbase
import FPState
, FPID
13 from ieee754
.fpcommon
.getop
import FPADDBaseData
14 from ieee754
.fpcommon
.denorm
import (FPSCData
, FPAddDeNormMod
)
17 class FPAddSpecialCasesMod
:
18 """ special cases: NaNs, infs, zeros, denormalised
19 NOTE: some of these are unique to add. see "Special Operations"
20 https://steve.hollasch.net/cgindex/coding/ieeefloat.html
23 def __init__(self
, width
, id_wid
):
30 return FPADDBaseData(self
.width
, self
.id_wid
)
33 return FPSCData(self
.width
, self
.id_wid
)
35 def setup(self
, m
, i
):
36 """ links module to inputs and outputs
38 m
.submodules
.specialcases
= self
39 m
.d
.comb
+= self
.i
.eq(i
)
44 def elaborate(self
, platform
):
47 m
.submodules
.sc_out_z
= self
.o
.z
49 # decode: XXX really should move to separate stage
50 a1
= FPNumDecode(None, self
.width
)
51 b1
= FPNumDecode(None, self
.width
)
52 m
.submodules
.sc_decode_a
= a1
53 m
.submodules
.sc_decode_b
= b1
54 m
.d
.comb
+= [a1
.v
.eq(self
.i
.a
),
60 s_nomatch
= Signal(reset_less
=True)
61 m
.d
.comb
+= s_nomatch
.eq(a1
.s
!= b1
.s
)
63 m_match
= Signal(reset_less
=True)
64 m
.d
.comb
+= m_match
.eq(a1
.m
== b1
.m
)
66 e_match
= Signal(reset_less
=True)
67 m
.d
.comb
+= e_match
.eq(a1
.e
== b1
.e
)
69 aeqmb
= Signal(reset_less
=True)
70 m
.d
.comb
+= aeqmb
.eq(s_nomatch
& m_match
& e_match
)
72 abz
= Signal(reset_less
=True)
73 m
.d
.comb
+= abz
.eq(a1
.is_zero
& b1
.is_zero
)
75 abnan
= Signal(reset_less
=True)
76 m
.d
.comb
+= abnan
.eq(a1
.is_nan | b1
.is_nan
)
78 bexp128s
= Signal(reset_less
=True)
79 m
.d
.comb
+= bexp128s
.eq(b1
.exp_128
& s_nomatch
)
81 # if a is NaN or b is NaN return NaN
83 m
.d
.comb
+= self
.o
.out_do_z
.eq(1)
84 m
.d
.comb
+= self
.o
.z
.nan(0)
86 # XXX WEIRDNESS for FP16 non-canonical NaN handling
89 ## if a is zero and b is NaN return -b
90 #with m.If(a.is_zero & (a.s==0) & b.is_nan):
91 # m.d.comb += self.o.out_do_z.eq(1)
92 # m.d.comb += z.create(b.s, b.e, Cat(b.m[3:-2], ~b.m[0]))
94 ## if b is zero and a is NaN return -a
95 #with m.Elif(b.is_zero & (b.s==0) & a.is_nan):
96 # m.d.comb += self.o.out_do_z.eq(1)
97 # m.d.comb += z.create(a.s, a.e, Cat(a.m[3:-2], ~a.m[0]))
99 ## if a is -zero and b is NaN return -b
100 #with m.Elif(a.is_zero & (a.s==1) & b.is_nan):
101 # m.d.comb += self.o.out_do_z.eq(1)
102 # m.d.comb += z.create(a.s & b.s, b.e, Cat(b.m[3:-2], 1))
104 ## if b is -zero and a is NaN return -a
105 #with m.Elif(b.is_zero & (b.s==1) & a.is_nan):
106 # m.d.comb += self.o.out_do_z.eq(1)
107 # m.d.comb += z.create(a.s & b.s, a.e, Cat(a.m[3:-2], 1))
109 # if a is inf return inf (or NaN)
110 with m
.Elif(a1
.is_inf
):
111 m
.d
.comb
+= self
.o
.out_do_z
.eq(1)
112 m
.d
.comb
+= self
.o
.z
.inf(a1
.s
)
113 # if a is inf and signs don't match return NaN
115 m
.d
.comb
+= self
.o
.z
.nan(0)
117 # if b is inf return inf
118 with m
.Elif(b1
.is_inf
):
119 m
.d
.comb
+= self
.o
.out_do_z
.eq(1)
120 m
.d
.comb
+= self
.o
.z
.inf(b1
.s
)
122 # if a is zero and b zero return signed-a/b
124 m
.d
.comb
+= self
.o
.out_do_z
.eq(1)
125 m
.d
.comb
+= self
.o
.z
.create(a1
.s
& b1
.s
, b1
.e
, b1
.m
[3:-1])
127 # if a is zero return b
128 with m
.Elif(a1
.is_zero
):
129 m
.d
.comb
+= self
.o
.out_do_z
.eq(1)
130 m
.d
.comb
+= self
.o
.z
.create(b1
.s
, b1
.e
, b1
.m
[3:-1])
132 # if b is zero return a
133 with m
.Elif(b1
.is_zero
):
134 m
.d
.comb
+= self
.o
.out_do_z
.eq(1)
135 m
.d
.comb
+= self
.o
.z
.create(a1
.s
, a1
.e
, a1
.m
[3:-1])
137 # if a equal to -b return zero (+ve zero)
139 m
.d
.comb
+= self
.o
.out_do_z
.eq(1)
140 m
.d
.comb
+= self
.o
.z
.zero(0)
142 # Denormalised Number checks next, so pass a/b data through
144 m
.d
.comb
+= self
.o
.out_do_z
.eq(0)
146 m
.d
.comb
+= self
.o
.oz
.eq(self
.o
.z
.v
)
147 m
.d
.comb
+= self
.o
.mid
.eq(self
.i
.mid
)
152 class FPAddSpecialCases(FPState
):
153 """ special cases: NaNs, infs, zeros, denormalised
154 NOTE: some of these are unique to add. see "Special Operations"
155 https://steve.hollasch.net/cgindex/coding/ieeefloat.html
158 def __init__(self
, width
, id_wid
):
159 FPState
.__init
__(self
, "special_cases")
160 self
.mod
= FPAddSpecialCasesMod(width
)
161 self
.out_z
= self
.mod
.ospec()
162 self
.out_do_z
= Signal(reset_less
=True)
164 def setup(self
, m
, i
):
165 """ links module to inputs and outputs
167 self
.mod
.setup(m
, i
, self
.out_do_z
)
168 m
.d
.sync
+= self
.out_z
.v
.eq(self
.mod
.out_z
.v
) # only take the output
169 m
.d
.sync
+= self
.out_z
.mid
.eq(self
.mod
.o
.mid
) # (and mid)
173 with m
.If(self
.out_do_z
):
176 m
.next
= "denormalise"
179 class FPAddSpecialCasesDeNorm(FPState
, SimpleHandshake
):
180 """ special cases: NaNs, infs, zeros, denormalised
181 NOTE: some of these are unique to add. see "Special Operations"
182 https://steve.hollasch.net/cgindex/coding/ieeefloat.html
185 def __init__(self
, width
, id_wid
):
186 FPState
.__init
__(self
, "special_cases")
189 SimpleHandshake
.__init
__(self
, self
) # pipe is its own stage
190 self
.out
= self
.ospec()
193 return FPADDBaseData(self
.width
, self
.id_wid
) # SpecialCases ispec
196 return FPSCData(self
.width
, self
.id_wid
) # DeNorm ospec
198 def setup(self
, m
, i
):
199 """ links module to inputs and outputs
201 smod
= FPAddSpecialCasesMod(self
.width
, self
.id_wid
)
202 dmod
= FPAddDeNormMod(self
.width
, self
.id_wid
)
204 chain
= StageChain([smod
, dmod
])
207 # only needed for break-out (early-out)
208 # self.out_do_z = smod.o.out_do_z
212 def process(self
, i
):
216 # for break-out (early-out)
217 #with m.If(self.out_do_z):
220 m
.d
.sync
+= self
.out
.eq(self
.process(None))