1 # IEEE Floating Point Adder (Single Precision)
2 # Copyright (C) Jonathan P Dawson 2013
5 from nmigen
import Module
, Signal
, Cat
, Const
, Elaboratable
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
, FPNumBaseRecord
13 from ieee754
.fpcommon
.getop
import FPADDBaseData
14 from ieee754
.fpcommon
.denorm
import (FPSCData
, FPAddDeNormMod
)
17 class FPAddSpecialCasesMod(Elaboratable
):
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
, pspec
):
29 return FPADDBaseData(self
.pspec
)
32 return FPSCData(self
.pspec
, True)
34 def setup(self
, m
, i
):
35 """ links module to inputs and outputs
37 m
.submodules
.specialcases
= self
38 m
.d
.comb
+= self
.i
.eq(i
)
43 def elaborate(self
, platform
):
46 #m.submodules.sc_out_z = self.o.z
48 # decode: XXX really should move to separate stage
49 width
= self
.pspec
.width
50 a1
= FPNumBaseRecord(width
)
51 b1
= FPNumBaseRecord(width
)
52 m
.submodules
.sc_decode_a
= a1
= FPNumDecode(None, a1
)
53 m
.submodules
.sc_decode_b
= b1
= FPNumDecode(None, 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
)
82 m
.d
.comb
+= self
.o
.out_do_z
.eq(1)
84 # if a is NaN or b is NaN return NaN
86 m
.d
.comb
+= self
.o
.z
.nan(0)
88 # XXX WEIRDNESS for FP16 non-canonical NaN handling
91 ## if a is zero and b is NaN return -b
92 #with m.If(a.is_zero & (a.s==0) & b.is_nan):
93 # m.d.comb += self.o.out_do_z.eq(1)
94 # m.d.comb += z.create(b.s, b.e, Cat(b.m[3:-2], ~b.m[0]))
96 ## if b is zero and a is NaN return -a
97 #with m.Elif(b.is_zero & (b.s==0) & a.is_nan):
98 # m.d.comb += self.o.out_do_z.eq(1)
99 # m.d.comb += z.create(a.s, a.e, Cat(a.m[3:-2], ~a.m[0]))
101 ## if a is -zero and b is NaN return -b
102 #with m.Elif(a.is_zero & (a.s==1) & b.is_nan):
103 # m.d.comb += self.o.out_do_z.eq(1)
104 # m.d.comb += z.create(a.s & b.s, b.e, Cat(b.m[3:-2], 1))
106 ## if b is -zero and a is NaN return -a
107 #with m.Elif(b.is_zero & (b.s==1) & a.is_nan):
108 # m.d.comb += self.o.out_do_z.eq(1)
109 # m.d.comb += z.create(a.s & b.s, a.e, Cat(a.m[3:-2], 1))
111 # if a is inf return inf (or NaN)
112 with m
.Elif(a1
.is_inf
):
113 m
.d
.comb
+= self
.o
.z
.inf(a1
.s
)
114 # if a is inf and signs don't match return NaN
116 m
.d
.comb
+= self
.o
.z
.nan(0)
118 # if b is inf return inf
119 with m
.Elif(b1
.is_inf
):
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
.z
.create(a1
.s
& b1
.s
, b1
.e
, b1
.m
[3:-1])
126 # if a is zero return b
127 with m
.Elif(a1
.is_zero
):
128 m
.d
.comb
+= self
.o
.z
.create(b1
.s
, b1
.e
, b1
.m
[3:-1])
130 # if b is zero return a
131 with m
.Elif(b1
.is_zero
):
132 m
.d
.comb
+= self
.o
.z
.create(a1
.s
, a1
.e
, a1
.m
[3:-1])
134 # if a equal to -b return zero (+ve zero)
136 m
.d
.comb
+= self
.o
.z
.zero(0)
138 # Denormalised Number checks next, so pass a/b data through
140 m
.d
.comb
+= self
.o
.out_do_z
.eq(0)
142 m
.d
.comb
+= self
.o
.oz
.eq(self
.o
.z
.v
)
143 m
.d
.comb
+= self
.o
.ctx
.eq(self
.i
.ctx
)
148 class FPAddSpecialCases(FPState
):
149 """ special cases: NaNs, infs, zeros, denormalised
150 NOTE: some of these are unique to add. see "Special Operations"
151 https://steve.hollasch.net/cgindex/coding/ieeefloat.html
154 def __init__(self
, width
, id_wid
):
155 FPState
.__init
__(self
, "special_cases")
156 self
.mod
= FPAddSpecialCasesMod(width
)
157 self
.out_z
= self
.mod
.ospec()
158 self
.out_do_z
= Signal(reset_less
=True)
160 def setup(self
, m
, i
):
161 """ links module to inputs and outputs
163 self
.mod
.setup(m
, i
, self
.out_do_z
)
164 m
.d
.sync
+= self
.out_z
.v
.eq(self
.mod
.out_z
.v
) # only take the output
165 m
.d
.sync
+= self
.out_z
.ctx
.eq(self
.mod
.o
.ctx
) # (and mid)
169 with m
.If(self
.out_do_z
):
172 m
.next
= "denormalise"
175 class FPAddSpecialCasesDeNorm(FPState
, SimpleHandshake
):
176 """ special cases: NaNs, infs, zeros, denormalised
177 NOTE: some of these are unique to add. see "Special Operations"
178 https://steve.hollasch.net/cgindex/coding/ieeefloat.html
181 def __init__(self
, pspec
):
182 FPState
.__init
__(self
, "special_cases")
184 SimpleHandshake
.__init
__(self
, self
) # pipe is its own stage
185 self
.out
= self
.ospec()
188 return FPADDBaseData(self
.pspec
) # SC ispec
191 return FPSCData(self
.pspec
, True) # DeNorm
193 def setup(self
, m
, i
):
194 """ links module to inputs and outputs
196 smod
= FPAddSpecialCasesMod(self
.pspec
)
197 dmod
= FPAddDeNormMod(self
.pspec
, True)
199 chain
= StageChain([smod
, dmod
])
202 # only needed for break-out (early-out)
203 # self.out_do_z = smod.o.out_do_z
207 def process(self
, i
):
211 # for break-out (early-out)
212 #with m.If(self.out_do_z):
215 m
.d
.sync
+= self
.out
.eq(self
.process(None))