src/soc/decoder/power_decoder2.py

   1 """Power ISA Decoder second stage
   2
   3 based on Anton Blanchard microwatt decode2.vhdl
   4
   5 """
   6 from nmigen import Module, Elaboratable, Signal, Mux, Const, Cat, Repl, Record
   7 from nmigen.cli import rtlil
   8
   9 from nmutil.iocontrol import RecordObject
  10 from nmutil.extend import exts
  11
  12 from soc.decoder.power_decoder import create_pdecode
  13 from soc.decoder.power_enums import (InternalOp, CryIn, Function,
  14                                      CRInSel, CROutSel,
  15                                      LdstLen, In1Sel, In2Sel, In3Sel,
  16                                      OutSel, SPR, RC)
  17
  18
  19 class DecodeA(Elaboratable):
  20     """DecodeA from instruction
  21
  22     decodes register RA, whether immediate-zero, implicit and
  23     explicit CSRs
  24     """
  25
  26     def __init__(self, dec):
  27         self.dec = dec
  28         self.sel_in = Signal(In1Sel, reset_less=True)
  29         self.insn_in = Signal(32, reset_less=True)
  30         self.reg_out = Data(5, name="reg_a")
  31         self.immz_out = Signal(reset_less=True)
  32         self.spr_out = Data(10, "spr_a")
  33
  34     def elaborate(self, platform):
  35         m = Module()
  36         comb = m.d.comb
  37
  38         # select Register A field
  39         ra = Signal(5, reset_less=True)
  40         comb += ra.eq(self.dec.RA)
  41         with m.If((self.sel_in == In1Sel.RA) |
  42                   ((self.sel_in == In1Sel.RA_OR_ZERO) &
  43                    (ra != Const(0, 5)))):
  44             comb += self.reg_out.data.eq(ra)
  45             comb += self.reg_out.ok.eq(1)
  46
  47         # zero immediate requested
  48         with m.If((self.sel_in == In1Sel.RA_OR_ZERO) &
  49                   (self.reg_out.data == Const(0, 5))):
  50             comb += self.immz_out.eq(1)
  51
  52         # decode SPR1 based on instruction type
  53         op = self.dec.op
  54         # BC or BCREG: potential implicit register (CTR)
  55         with m.If((op.internal_op == InternalOp.OP_BC) |
  56                   (op.internal_op == InternalOp.OP_BCREG)):
  57             with m.If(~self.dec.BO[2]): # 3.0B p38 BO2=0, use CTR reg
  58                 comb += self.spr_out.data.eq(SPR.CTR) # constant: CTR
  59                 comb += self.spr_out.ok.eq(1)
  60         # MFSPR or MTSPR: move-from / move-to SPRs
  61         with m.If((op.internal_op == InternalOp.OP_MFSPR) |
  62                   (op.internal_op == InternalOp.OP_MTSPR)):
  63             comb += self.spr_out.data.eq(self.dec.SPR) # SPR field, XFX
  64             comb += self.spr_out.ok.eq(1)
  65
  66         return m
  67
  68
  69 class Data(Record):
  70
  71     def __init__(self, width, name):
  72         name_ok = "%s_ok" % name
  73         layout = ((name, width), (name_ok, 1))
  74         Record.__init__(self, layout)
  75         self.data = getattr(self, name) # convenience
  76         self.ok = getattr(self, name_ok) # convenience
  77         self.data.reset_less = True # grrr
  78         self.reset_less = True # grrr
  79
  80     def ports(self):
  81         return [self.data, self.ok]
  82
  83
  84 class DecodeB(Elaboratable):
  85     """DecodeB from instruction
  86
  87     decodes register RB, different forms of immediate (signed, unsigned),
  88     and implicit SPRs
  89     """
  90
  91     def __init__(self, dec):
  92         self.dec = dec
  93         self.sel_in = Signal(In2Sel, reset_less=True)
  94         self.insn_in = Signal(32, reset_less=True)
  95         self.reg_out = Data(5, "reg_b")
  96         self.imm_out = Data(64, "imm_b")
  97         self.spr_out = Data(10, "spr_b")
  98
  99     def elaborate(self, platform):
 100         m = Module()
 101         comb = m.d.comb
 102
 103         # select Register B field
 104         with m.Switch(self.sel_in):
 105             with m.Case(In2Sel.RB):
 106                 comb += self.reg_out.data.eq(self.dec.RB)
 107                 comb += self.reg_out.ok.eq(1)
 108             with m.Case(In2Sel.CONST_UI):
 109                 comb += self.imm_out.data.eq(self.dec.UI)
 110                 comb += self.imm_out.ok.eq(1)
 111             with m.Case(In2Sel.CONST_SI): # TODO: sign-extend here?
 112                 comb += self.imm_out.data.eq(
 113                     exts(self.dec.SI, 16, 64))
 114                 comb += self.imm_out.ok.eq(1)
 115             with m.Case(In2Sel.CONST_UI_HI):
 116                 comb += self.imm_out.data.eq(self.dec.UI<<16)
 117                 comb += self.imm_out.ok.eq(1)
 118             with m.Case(In2Sel.CONST_SI_HI): # TODO: sign-extend here?
 119                 comb += self.imm_out.data.eq(self.dec.SI<<16)
 120                 comb += self.imm_out.data.eq(
 121                     exts(self.dec.SI << 16, 32, 64))
 122                 comb += self.imm_out.ok.eq(1)
 123             with m.Case(In2Sel.CONST_LI):
 124                 comb += self.imm_out.data.eq(self.dec.LI<<2)
 125                 comb += self.imm_out.ok.eq(1)
 126             with m.Case(In2Sel.CONST_BD):
 127                 comb += self.imm_out.data.eq(self.dec.BD<<2)
 128                 comb += self.imm_out.ok.eq(1)
 129             with m.Case(In2Sel.CONST_DS):
 130                 comb += self.imm_out.data.eq(self.dec.DS<<2)
 131                 comb += self.imm_out.ok.eq(1)
 132             with m.Case(In2Sel.CONST_M1):
 133                 comb += self.imm_out.data.eq(~Const(0, 64)) # all 1s
 134                 comb += self.imm_out.ok.eq(1)
 135             with m.Case(In2Sel.CONST_SH):
 136                 comb += self.imm_out.data.eq(self.dec.sh)
 137                 comb += self.imm_out.ok.eq(1)
 138             with m.Case(In2Sel.CONST_SH32):
 139                 comb += self.imm_out.data.eq(self.dec.SH32)
 140                 comb += self.imm_out.ok.eq(1)
 141
 142         # decode SPR2 based on instruction type
 143         op = self.dec.op
 144         # BCREG implicitly uses CTR or LR for 2nd reg
 145         with m.If(op.internal_op == InternalOp.OP_BCREG):
 146             with m.If(self.dec.FormXL.XO[9]): # 3.0B p38 top bit of XO
 147                 comb += self.spr_out.data.eq(SPR.CTR)
 148             with m.Else():
 149                 comb += self.spr_out.data.eq(SPR.LR)
 150             comb += self.spr_out.ok.eq(1)
 151
 152         return m
 153
 154
 155 class DecodeC(Elaboratable):
 156     """DecodeC from instruction
 157
 158     decodes register RC
 159     """
 160
 161     def __init__(self, dec):
 162         self.dec = dec
 163         self.sel_in = Signal(In3Sel, reset_less=True)
 164         self.insn_in = Signal(32, reset_less=True)
 165         self.reg_out = Data(5, "reg_c")
 166
 167     def elaborate(self, platform):
 168         m = Module()
 169         comb = m.d.comb
 170
 171         # select Register C field
 172         with m.If(self.sel_in == In3Sel.RS):
 173             comb += self.reg_out.data.eq(self.dec.RS)
 174             comb += self.reg_out.ok.eq(1)
 175
 176         return m
 177
 178
 179 class DecodeOut(Elaboratable):
 180     """DecodeOut from instruction
 181
 182     decodes output register RA, RT or SPR
 183     """
 184
 185     def __init__(self, dec):
 186         self.dec = dec
 187         self.sel_in = Signal(OutSel, reset_less=True)
 188         self.insn_in = Signal(32, reset_less=True)
 189         self.reg_out = Data(5, "reg_o")
 190         self.spr_out = Data(10, "spr_o")
 191
 192     def elaborate(self, platform):
 193         m = Module()
 194         comb = m.d.comb
 195
 196         # select Register out field
 197         with m.Switch(self.sel_in):
 198             with m.Case(OutSel.RT):
 199                 comb += self.reg_out.data.eq(self.dec.RT)
 200                 comb += self.reg_out.ok.eq(1)
 201             with m.Case(OutSel.RA):
 202                 comb += self.reg_out.data.eq(self.dec.RA)
 203                 comb += self.reg_out.ok.eq(1)
 204             with m.Case(OutSel.SPR):
 205                 comb += self.spr_out.data.eq(self.dec.SPR) # from XFX
 206                 comb += self.spr_out.ok.eq(1)
 207
 208         return m
 209
 210
 211 class DecodeRC(Elaboratable):
 212     """DecodeRc from instruction
 213
 214     decodes Record bit Rc
 215     """
 216     def __init__(self, dec):
 217         self.dec = dec
 218         self.sel_in = Signal(RC, reset_less=True)
 219         self.insn_in = Signal(32, reset_less=True)
 220         self.rc_out = Data(1, "rc")
 221
 222     def elaborate(self, platform):
 223         m = Module()
 224         comb = m.d.comb
 225
 226         # select Record bit out field
 227         with m.Switch(self.sel_in):
 228             with m.Case(RC.RC):
 229                 comb += self.rc_out.data.eq(self.dec.Rc)
 230                 comb += self.rc_out.ok.eq(1)
 231             with m.Case(RC.ONE):
 232                 comb += self.rc_out.data.eq(1)
 233                 comb += self.rc_out.ok.eq(1)
 234             with m.Case(RC.NONE):
 235                 comb += self.rc_out.data.eq(0)
 236                 comb += self.rc_out.ok.eq(1)
 237
 238         return m
 239
 240
 241 class DecodeOE(Elaboratable):
 242     """DecodeOE from instruction
 243
 244     decodes OE field: uses RC decode detection which might not be good
 245
 246     -- For now, use "rc" in the decode table to decide whether oe exists.
 247     -- This is not entirely correct architecturally: For mulhd and
 248     -- mulhdu, the OE field is reserved. It remains to be seen what an
 249     -- actual POWER9 does if we set it on those instructions, for now we
 250     -- test that further down when assigning to the multiplier oe input.
 251     """
 252     def __init__(self, dec):
 253         self.dec = dec
 254         self.sel_in = Signal(RC, reset_less=True)
 255         self.insn_in = Signal(32, reset_less=True)
 256         self.oe_out = Data(1, "oe")
 257
 258     def elaborate(self, platform):
 259         m = Module()
 260         comb = m.d.comb
 261
 262         # select OE bit out field
 263         with m.Switch(self.sel_in):
 264             with m.Case(RC.RC):
 265                 comb += self.oe_out.data.eq(self.dec.OE)
 266                 comb += self.oe_out.ok.eq(1)
 267
 268         return m
 269
 270 class DecodeCRIn(Elaboratable):
 271     """Decodes input CR from instruction"""
 272
 273     def __init__(self, dec):
 274         self.dec = dec
 275         self.sel_in = Signal(CRInSel, reset_less=True)
 276         self.insn_in = Signal(32, reset_less=True)
 277         self.cr_bitfield = Data(3, "cr_bitfield")
 278         self.cr_bitfield_b = Data(3, "cr_bitfield_b")
 279         self.whole_reg = Signal(reset_less=True)
 280
 281     def elaborate(self, platform):
 282         m = Module()
 283         comb = m.d.comb
 284
 285         comb += self.cr_bitfield.ok.eq(0)
 286         comb += self.cr_bitfield_b.ok.eq(0)
 287         comb += self.whole_reg.eq(0)
 288         with m.Switch(self.sel_in):
 289             with m.Case(CRInSel.NONE):
 290                 pass # No bitfield activated
 291             with m.Case(CRInSel.CR0):
 292                 comb += self.cr_bitfield.data.eq(0)
 293                 comb += self.cr_bitfield.ok.eq(1)
 294             with m.Case(CRInSel.BI):
 295                 comb += self.cr_bitfield.data.eq(self.dec.BI[3:5])
 296                 comb += self.cr_bitfield.ok.eq(1)
 297             with m.Case(CRInSel.BFA):
 298                 comb += self.cr_bitfield.data.eq(self.dec.FormX.BFA[0:-1])
 299                 comb += self.cr_bitfield.ok.eq(1)
 300             with m.Case(CRInSel.BA_BB):
 301                 comb += self.cr_bitfield.data.eq(self.dec.BA[3:5])
 302                 comb += self.cr_bitfield.ok.eq(1)
 303                 comb += self.cr_bitfield_b.data.eq(self.dec.BB[3:5])
 304                 comb += self.cr_bitfield_b.ok.eq(1)
 305             with m.Case(CRInSel.BC):
 306                 comb += self.cr_bitfield.data.eq(self.dec.BC[0:-1])
 307                 comb += self.cr_bitfield.ok.eq(1)
 308             with m.Case(CRInSel.WHOLE_REG):
 309                 comb += self.whole_reg.eq(1)
 310
 311         return m
 312
 313 class DecodeCROut(Elaboratable):
 314     """Decodes input CR from instruction"""
 315
 316     def __init__(self, dec):
 317         self.dec = dec
 318         self.sel_in = Signal(CROutSel, reset_less=True)
 319         self.insn_in = Signal(32, reset_less=True)
 320         self.cr_bitfield = Data(3, "cr_bitfield")
 321         self.whole_reg = Signal(reset_less=True)
 322
 323     def elaborate(self, platform):
 324         m = Module()
 325         comb = m.d.comb
 326
 327         comb += self.cr_bitfield.ok.eq(0)
 328         comb += self.whole_reg.eq(0)
 329         with m.Switch(self.sel_in):
 330             with m.Case(CROutSel.NONE):
 331                 pass # No bitfield activated
 332             with m.Case(CROutSel.CR0):
 333                 comb += self.cr_bitfield.data.eq(0)
 334                 comb += self.cr_bitfield.ok.eq(1)
 335             with m.Case(CROutSel.BF):
 336                 comb += self.cr_bitfield.data.eq(self.dec.FormX.BF[0:-1])
 337                 comb += self.cr_bitfield.ok.eq(1)
 338             with m.Case(CROutSel.BT):
 339                 comb += self.cr_bitfield.data.eq(self.dec.FormXL.BT[3:5])
 340                 comb += self.cr_bitfield.ok.eq(1)
 341             with m.Case(CROutSel.WHOLE_REG):
 342                 comb += self.whole_reg.eq(1)
 343
 344         return m
 345
 346 class XerBits:
 347     def __init__(self):
 348         self.ca = Signal(2, reset_less=True)
 349         self.ov = Signal(2, reset_less=True)
 350         self.so = Signal(reset_less=True)
 351
 352     def ports(self):
 353         return [self.ca, self.ov, self.so]
 354
 355
 356 class Decode2ToExecute1Type(RecordObject):
 357
 358     def __init__(self, name=None):
 359
 360         RecordObject.__init__(self, name=name)
 361
 362         self.valid = Signal(reset_less=True)
 363         self.insn_type = Signal(InternalOp, reset_less=True)
 364         self.fn_unit = Signal(Function, reset_less=True)
 365         self.nia = Signal(64, reset_less=True)
 366         self.write_reg = Data(5, name="rego")
 367         self.read_reg1 = Data(5, name="reg1")
 368         self.read_reg2 = Data(5, name="reg2")
 369         self.read_reg3 = Data(5, name="reg3")
 370         self.imm_data = Data(64, name="imm")
 371         self.write_spr = Data(10, name="spro")
 372         self.read_spr1 = Data(10, name="spr1")
 373         self.read_spr2 = Data(10, name="spr2")
 374
 375         self.read_cr1 = Data(3, name="cr_in1")
 376         self.read_cr2 = Data(3, name="cr_in2")
 377         self.read_cr_whole = Signal(reset_less=True)
 378         self.write_cr = Data(3, name="cr_out")
 379         self.write_cr_whole = Signal(reset_less=True)
 380         #self.read_data1 = Signal(64, reset_less=True)
 381         #self.read_data2 = Signal(64, reset_less=True)
 382         #self.read_data3 = Signal(64, reset_less=True)
 383         #self.cr = Signal(32, reset_less=True) # NO: this is from the CR SPR
 384         #self.xerc = XerBits() # NO: this is from the XER SPR
 385         self.lk = Signal(reset_less=True)
 386         self.rc = Data(1, "rc")
 387         self.oe = Data(1, "oe")
 388         self.invert_a = Signal(reset_less=True)
 389         self.zero_a = Signal(reset_less=True)
 390         self.invert_out = Signal(reset_less=True)
 391         self.input_carry = Signal(CryIn, reset_less=True)
 392         self.output_carry = Signal(reset_less=True)
 393         self.input_cr = Signal(reset_less=True)
 394         self.output_cr = Signal(reset_less=True)
 395         self.is_32bit = Signal(reset_less=True)
 396         self.is_signed = Signal(reset_less=True)
 397         self.insn = Signal(32, reset_less=True)
 398         self.data_len = Signal(4, reset_less=True) # bytes
 399         self.byte_reverse  = Signal(reset_less=True)
 400         self.sign_extend  = Signal(reset_less=True)# do we need this?
 401         self.update  = Signal(reset_less=True) # LD/ST is "update" variant
 402
 403
 404 class PowerDecode2(Elaboratable):
 405
 406     def __init__(self, dec):
 407
 408         self.dec = dec
 409         self.e = Decode2ToExecute1Type()
 410
 411     def ports(self):
 412         return self.dec.ports() + self.e.ports()
 413
 414     def elaborate(self, platform):
 415         m = Module()
 416         comb = m.d.comb
 417
 418         # set up submodule decoders
 419         m.submodules.dec = self.dec
 420         m.submodules.dec_a = dec_a = DecodeA(self.dec)
 421         m.submodules.dec_b = dec_b = DecodeB(self.dec)
 422         m.submodules.dec_c = dec_c = DecodeC(self.dec)
 423         m.submodules.dec_o = dec_o = DecodeOut(self.dec)
 424         m.submodules.dec_rc = dec_rc = DecodeRC(self.dec)
 425         m.submodules.dec_oe = dec_oe = DecodeOE(self.dec)
 426         m.submodules.dec_cr_in = dec_cr_in = DecodeCRIn(self.dec)
 427         m.submodules.dec_cr_out = dec_cr_out = DecodeCROut(self.dec)
 428
 429         # copy instruction through...
 430         for i in [self.e.insn, dec_a.insn_in, dec_b.insn_in,
 431                   dec_c.insn_in, dec_o.insn_in, dec_rc.insn_in,
 432                   dec_oe.insn_in, dec_cr_in.insn_in, dec_cr_out.insn_in]:
 433             comb += i.eq(self.dec.opcode_in)
 434
 435         # ...and subdecoders' input fields
 436         comb += dec_a.sel_in.eq(self.dec.op.in1_sel)
 437         comb += dec_b.sel_in.eq(self.dec.op.in2_sel)
 438         comb += dec_c.sel_in.eq(self.dec.op.in3_sel)
 439         comb += dec_o.sel_in.eq(self.dec.op.out_sel)
 440         comb += dec_rc.sel_in.eq(self.dec.op.rc_sel)
 441         comb += dec_oe.sel_in.eq(self.dec.op.rc_sel) # XXX should be OE sel
 442         comb += dec_cr_in.sel_in.eq(self.dec.op.cr_in)
 443         comb += dec_cr_out.sel_in.eq(self.dec.op.cr_out)
 444
 445         # decode LD/ST length
 446         with m.Switch(self.dec.op.ldst_len):
 447             with m.Case(LdstLen.is1B):
 448                 comb += self.e.data_len.eq(1)
 449             with m.Case(LdstLen.is2B):
 450                 comb += self.e.data_len.eq(2)
 451             with m.Case(LdstLen.is4B):
 452                 comb += self.e.data_len.eq(4)
 453             with m.Case(LdstLen.is8B):
 454                 comb += self.e.data_len.eq(8)
 455
 456         comb += self.e.nia.eq(0)    # XXX TODO
 457         comb += self.e.valid.eq(0)  # XXX TODO
 458         fu = self.dec.op.function_unit
 459         itype = Mux(fu == Function.NONE,
 460                     InternalOp.OP_ILLEGAL,
 461                     self.dec.op.internal_op)
 462         comb += self.e.insn_type.eq(itype)
 463         comb += self.e.fn_unit.eq(fu)
 464
 465         # registers a, b, c and out
 466         comb += self.e.read_reg1.eq(dec_a.reg_out)
 467         comb += self.e.read_reg2.eq(dec_b.reg_out)
 468         comb += self.e.read_reg3.eq(dec_c.reg_out)
 469         comb += self.e.write_reg.eq(dec_o.reg_out)
 470         comb += self.e.imm_data.eq(dec_b.imm_out) # immediate in RB (usually)
 471         comb += self.e.zero_a.eq(dec_a.immz_out)  # RA==0 detected
 472
 473         # rc and oe out
 474         comb += self.e.rc.eq(dec_rc.rc_out)
 475         comb += self.e.oe.eq(dec_oe.oe_out)
 476
 477         # SPRs out
 478         comb += self.e.read_spr1.eq(dec_a.spr_out)
 479         comb += self.e.read_spr2.eq(dec_b.spr_out)
 480         comb += self.e.write_spr.eq(dec_o.spr_out)
 481
 482         comb += self.e.read_cr1.eq(dec_cr_in.cr_bitfield)
 483         comb += self.e.read_cr2.eq(dec_cr_in.cr_bitfield_b)
 484         comb += self.e.read_cr_whole.eq(dec_cr_in.whole_reg)
 485
 486         comb += self.e.write_cr.eq(dec_cr_out.cr_bitfield)
 487         comb += self.e.write_cr_whole.eq(dec_cr_out.whole_reg)
 488
 489         # decoded/selected instruction flags
 490         comb += self.e.invert_a.eq(self.dec.op.inv_a)
 491         comb += self.e.invert_out.eq(self.dec.op.inv_out)
 492         comb += self.e.input_carry.eq(self.dec.op.cry_in)   # carry comes in
 493         comb += self.e.output_carry.eq(self.dec.op.cry_out) # carry goes out
 494         comb += self.e.is_32bit.eq(self.dec.op.is_32b)
 495         comb += self.e.is_signed.eq(self.dec.op.sgn)
 496         with m.If(self.dec.op.lk):
 497             comb += self.e.lk.eq(self.dec.LK) # XXX TODO: accessor
 498
 499         comb += self.e.byte_reverse.eq(self.dec.op.br)
 500         comb += self.e.sign_extend.eq(self.dec.op.sgn_ext)
 501         comb += self.e.update.eq(self.dec.op.upd) # LD/ST "update" mode
 502
 503
 504
 505         # These should be removed eventually
 506         comb += self.e.input_cr.eq(self.dec.op.cr_in)   # condition reg comes in
 507         comb += self.e.output_cr.eq(self.dec.op.cr_out) # condition reg goes in
 508
 509
 510         return m
 511
 512
 513 if __name__ == '__main__':
 514     pdecode = create_pdecode()
 515     dec2 = PowerDecode2(pdecode)
 516     vl = rtlil.convert(dec2, ports=dec2.ports() + pdecode.ports())
 517     with open("dec2.il", "w") as f:
 518         f.write(vl)
 519