src/add/fmul.py

   1 from nmigen import Module, Signal
   2 from nmigen.cli import main, verilog
   3
   4 from fpbase import FPNum, FPOp, Overflow, FPBase
   5
   6
   7 class FPMUL(FPBase):
   8
   9     def __init__(self, width):
  10         FPBase.__init__(self)
  11         self.width = width
  12
  13         self.in_a  = FPOp(width)
  14         self.in_b  = FPOp(width)
  15         self.out_z = FPOp(width)
  16
  17     def get_fragment(self, platform=None):
  18         """ creates the HDL code-fragment for FPMUL
  19         """
  20         m = Module()
  21
  22         # Latches
  23         a = FPNum(self.width)
  24         b = FPNum(self.width)
  25         z = FPNum(self.width, False)
  26
  27         tot = Signal(28)     # sticky/round/guard bits, 23 result, 1 overflow
  28
  29         of = Overflow()
  30
  31         with m.FSM() as fsm:
  32
  33                 with m.State("get_a"):
  34                         m.next += "get_b"
  35                         m.d.sync += s.in_a.ack.eq(1)
  36                         with m.If(s.in_a.ack & in_a.stb):
  37                                 m.d.sync += [
  38                                 a.eq(in_a),
  39                                 s.in_a.ack(0)
  40                         ]
  41
  42                 with m.State("get_b"):
  43                         m.next += "unpack"
  44                         m.d.sync += s.in_b.ack.eq(1)
  45                         with m.If(s.in_b.ack & in_b.stb):
  46                                 m.d.sync += [
  47                                 b.eq(in_b),
  48                                 s.in_b.ack(0)
  49                         ]
  50
  51                 with m.State("unpack"):
  52                         m.next += "special_cases"
  53                         m.d.sync += [
  54                         a.m.eq(a[0:22]),
  55                         b.m.eq(b[0:22]),
  56                         a.e.eq(a[23:31] - 127),
  57                         b.e.eq(b[23:31] - 127),
  58                         a.s.eq(a[31]),
  59                         b.s.eq(b[31])
  60                         ]
  61
  62                 with m.State("special_cases"):
  63                         m.next = "normalise_a"
  64                         #if a or b is NaN return NaN
  65                         with m.If(a.is_nan() | b.is_nan()):
  66                                 m.next += "put_z"
  67                                 m.d.sync += z.nan(1)
  68                         #if a is inf return inf
  69                         with m.Elif(a.is_inf()):
  70                                 m.next += "put_z"
  71                                 m.d.sync += z.inf(0)
  72                         #if b is zero return NaN
  73                         with m.If(b.is_zero()):
  74                                 m.d.sync += z.nan(1)
  75                         #if b is inf return inf
  76                         with m.Elif(b.is_inf()):
  77                                 m.next += "put_z"
  78                                 m.d.sync += z.inf(0)
  79                         #if a is zero return NaN
  80                         with m.If(a.is_zero()):
  81                                 m.next += "put_z"
  82                                 m.d.sync += z.nan(1)
  83                         #if a is zero return zero
  84                         with m.Elif(a.is_zero()):
  85                                 m.next += "put_z"
  86                                 m.d.sync += z.zero(0)
  87                         #if b is zero return zero
  88                         with m.Elif(b.is_zero()):
  89                                 m.next += "put_z"
  90                                 m.d.sync += z.zero(0)
  91                 # Denormalised Number checks
  92                                 with m.Else():
  93                         m.next = "normalise_a"
  94                     self.denormalise(m, a)
  95                     self.denormalise(m, b)
  96
  97             # ******
  98             # normalise_a
  99
 100             with m.State("normalise_a"):
 101                 self.op_normalise(m, a, "normalise_b")
 102
 103             # ******
 104             # normalise_b
 105
 106             with m.State("normalise_b"):
 107                 self.op_normalise(m, b, "multiply_0")
 108
 109
 110
 111 """
 112 special_cases:
 113       begin
 114         //if a is NaN or b is NaN return NaN
 115         if ((a_e == 128 && a_m != 0) || (b_e == 128 && b_m != 0)) begin
 116           z[31] <= 1;
 117           z[30:23] <= 255;
 118           z[22] <= 1;
 119           z[21:0] <= 0;
 120           state <= put_z;
 121         //if a is inf return inf
 122         end else if (a_e == 128) begin
 123           z[31] <= a_s ^ b_s;
 124           z[30:23] <= 255;
 125           z[22:0] <= 0;
 126           //if b is zero return NaN
 127           if (($signed(b_e) == -127) && (b_m == 0)) begin
 128             z[31] <= 1;
 129             z[30:23] <= 255;
 130             z[22] <= 1;
 131             z[21:0] <= 0;
 132           end
 133           state <= put_z;
 134         //if b is inf return inf
 135         end else if (b_e == 128) begin
 136           z[31] <= a_s ^ b_s;
 137           z[30:23] <= 255;
 138           z[22:0] <= 0;
 139           //if a is zero return NaN
 140           if (($signed(a_e) == -127) && (a_m == 0)) begin
 141             z[31] <= 1;
 142             z[30:23] <= 255;
 143             z[22] <= 1;
 144             z[21:0] <= 0;
 145           end
 146           state <= put_z;
 147         //if a is zero return zero
 148         end else if (($signed(a_e) == -127) && (a_m == 0)) begin
 149           z[31] <= a_s ^ b_s;
 150           z[30:23] <= 0;
 151           z[22:0] <= 0;
 152           state <= put_z;
 153         //if b is zero return zero
 154         end else if (($signed(b_e) == -127) && (b_m == 0)) begin
 155           z[31] <= a_s ^ b_s;
 156           z[30:23] <= 0;
 157           z[22:0] <= 0;
 158           state <= put_z;
 159           //^ done up to here
 160         end else begin
 161           //Denormalised Number
 162           if ($signed(a_e) == -127) begin
 163             a_e <= -126;
 164           end else begin
 165             a_m[23] <= 1;
 166           end
 167           //Denormalised Number
 168           if ($signed(b_e) == -127) begin
 169             b_e <= -126;
 170           end else begin
 171             b_m[23] <= 1;
 172           end
 173           state <= normalise_a;
 174         end
 175       end
 176
 177       normalise_a:
 178       begin
 179         if (a_m[23]) begin
 180           state <= normalise_b;
 181         end else begin
 182           a_m <= a_m << 1;
 183           a_e <= a_e - 1;
 184         end
 185       end
 186
 187       normalise_b:
 188       begin
 189         if (b_m[23]) begin
 190           state <= multiply_0;
 191         end else begin
 192           b_m <= b_m << 1;
 193           b_e <= b_e - 1;
 194         end
 195       end
 196
 197       multiply_0:
 198       begin
 199         z_s <= a_s ^ b_s;
 200         z_e <= a_e + b_e + 1;
 201         product <= a_m * b_m * 4;
 202         state <= multiply_1;
 203       end
 204
 205       multiply_1:
 206       begin
 207         z_m <= product[49:26];
 208         guard <= product[25];
 209         round_bit <= product[24];
 210         sticky <= (product[23:0] != 0);
 211         state <= normalise_1;
 212       end
 213
 214       normalise_1:
 215       begin
 216         if (z_m[23] == 0) begin
 217           z_e <= z_e - 1;
 218           z_m <= z_m << 1;
 219           z_m[0] <= guard;
 220           guard <= round_bit;
 221           round_bit <= 0;
 222         end else begin
 223           state <= normalise_2;
 224         end
 225       end
 226
 227       normalise_2:
 228       begin
 229         if ($signed(z_e) < -126) begin
 230           z_e <= z_e + 1;
 231           z_m <= z_m >> 1;
 232           guard <= z_m[0];
 233           round_bit <= guard;
 234           sticky <= sticky | round_bit;
 235         end else begin
 236           state <= round;
 237         end
 238       end
 239
 240       round:
 241       begin
 242         if (guard && (round_bit | sticky | z_m[0])) begin
 243           z_m <= z_m + 1;
 244           if (z_m == 24'hffffff) begin
 245             z_e <=z_e + 1;
 246           end
 247         end
 248         state <= pack;
 249       end
 250
 251       pack:
 252       begin
 253         z[22 : 0] <= z_m[22:0];
 254         z[30 : 23] <= z_e[7:0] + 127;
 255         z[31] <= z_s;
 256         if ($signed(z_e) == -126 && z_m[23] == 0) begin
 257           z[30 : 23] <= 0;
 258         end
 259         //if overflow occurs, return inf
 260         if ($signed(z_e) > 127) begin
 261           z[22 : 0] <= 0;
 262           z[30 : 23] <= 255;
 263           z[31] <= z_s;
 264         end
 265         state <= put_z;
 266       end
 267
 268       put_z:
 269       begin
 270         s_output_z_stb <= 1;
 271         s_output_z <= z;
 272         if (s_output_z_stb && output_z_ack) begin
 273           s_output_z_stb <= 0;
 274           state <= get_a;
 275         end
 276 end
 277
 278 """