src/soc/decoder/power_decoder2.py

   1 """Power ISA Decoder second stage
   2
   3 based on Anton Blanchard microwatt decode2.vhdl
   4
   5 Note: OP_TRAP is used for exceptions and interrupts (micro-code style) by
   6 over-riding the internal opcode when an exception is needed.
   7 """
   8
   9 from nmigen import Module, Elaboratable, Signal, Mux, Const, Cat, Repl, Record
  10 from nmigen.cli import rtlil
  11 from soc.regfile.regfiles import XERRegs
  12
  13 from nmutil.picker import PriorityPicker
  14 from nmutil.iocontrol import RecordObject
  15 from nmutil.extend import exts
  16
  17 from soc.decoder.power_regspec_map import regspec_decode_read
  18 from soc.decoder.power_regspec_map import regspec_decode_write
  19 from soc.decoder.power_decoder import create_pdecode
  20 from soc.decoder.power_enums import (MicrOp, CryIn, Function,
  21                                      CRInSel, CROutSel,
  22                                      LdstLen, In1Sel, In2Sel, In3Sel,
  23                                      OutSel, SPR, RC, LDSTMode)
  24 from soc.decoder.decode2execute1 import Decode2ToExecute1Type, Data
  25 from soc.consts import MSR
  26
  27 from soc.regfile.regfiles import FastRegs
  28 from soc.consts import TT
  29 from soc.config.state import CoreState
  30 from soc.regfile.util import spr_to_fast
  31
  32
  33 def decode_spr_num(spr):
  34     return Cat(spr[5:10], spr[0:5])
  35
  36
  37 def instr_is_priv(m, op, insn):
  38     """determines if the instruction is privileged or not
  39     """
  40     comb = m.d.comb
  41     is_priv_insn = Signal(reset_less=True)
  42     with m.Switch(op):
  43         with m.Case(MicrOp.OP_ATTN, MicrOp.OP_MFMSR, MicrOp.OP_MTMSRD,
  44                     MicrOp.OP_MTMSR, MicrOp.OP_RFID):
  45             comb += is_priv_insn.eq(1)
  46         # XXX TODO
  47         #with m.Case(MicrOp.OP_TLBIE) : comb += is_priv_insn.eq(1)
  48         with m.Case(MicrOp.OP_MFSPR, MicrOp.OP_MTSPR):
  49             with m.If(insn[20]):  # field XFX.spr[-1] i think
  50                 comb += is_priv_insn.eq(1)
  51     return is_priv_insn
  52
  53
  54 class SPRMap(Elaboratable):
  55     """SPRMap: maps POWER9 SPR numbers to internal enum values, fast and slow
  56     """
  57
  58     def __init__(self):
  59         self.spr_i = Signal(10, reset_less=True)
  60         self.spr_o = Data(SPR, name="spr_o")
  61         self.fast_o = Data(3, name="fast_o")
  62
  63     def elaborate(self, platform):
  64         m = Module()
  65         with m.Switch(self.spr_i):
  66             for i, x in enumerate(SPR):
  67                 with m.Case(x.value):
  68                     m.d.comb += self.spr_o.data.eq(i)
  69                     m.d.comb += self.spr_o.ok.eq(1)
  70             for x, v in spr_to_fast.items():
  71                 with m.Case(x.value):
  72                     m.d.comb += self.fast_o.data.eq(v)
  73                     m.d.comb += self.fast_o.ok.eq(1)
  74         return m
  75
  76
  77 class DecodeA(Elaboratable):
  78     """DecodeA from instruction
  79
  80     decodes register RA, implicit and explicit CSRs
  81     """
  82
  83     def __init__(self, dec):
  84         self.dec = dec
  85         self.sel_in = Signal(In1Sel, reset_less=True)
  86         self.insn_in = Signal(32, reset_less=True)
  87         self.reg_out = Data(5, name="reg_a")
  88         self.spr_out = Data(SPR, "spr_a")
  89         self.fast_out = Data(3, "fast_a")
  90
  91     def elaborate(self, platform):
  92         m = Module()
  93         comb = m.d.comb
  94         m.submodules.sprmap = sprmap = SPRMap()
  95
  96         # select Register A field
  97         ra = Signal(5, reset_less=True)
  98         comb += ra.eq(self.dec.RA)
  99         with m.If((self.sel_in == In1Sel.RA) |
 100                   ((self.sel_in == In1Sel.RA_OR_ZERO) &
 101                    (ra != Const(0, 5)))):
 102             comb += self.reg_out.data.eq(ra)
 103             comb += self.reg_out.ok.eq(1)
 104
 105         # some Logic/ALU ops have RS as the 3rd arg, but no "RA".
 106         with m.If(self.sel_in == In1Sel.RS):
 107             comb += self.reg_out.data.eq(self.dec.RS)
 108             comb += self.reg_out.ok.eq(1)
 109
 110         # decode Fast-SPR based on instruction type
 111         op = self.dec.op
 112         with m.Switch(op.internal_op):
 113
 114             # BC or BCREG: implicit register (CTR) NOTE: same in DecodeOut
 115             with m.Case(MicrOp.OP_BC):
 116                 with m.If(~self.dec.BO[2]):  # 3.0B p38 BO2=0, use CTR reg
 117                     # constant: CTR
 118                     comb += self.fast_out.data.eq(FastRegs.CTR)
 119                     comb += self.fast_out.ok.eq(1)
 120             with m.Case(MicrOp.OP_BCREG):
 121                 xo9 = self.dec.FormXL.XO[9]  # 3.0B p38 top bit of XO
 122                 xo5 = self.dec.FormXL.XO[5]  # 3.0B p38
 123                 with m.If(xo9 & ~xo5):
 124                     # constant: CTR
 125                     comb += self.fast_out.data.eq(FastRegs.CTR)
 126                     comb += self.fast_out.ok.eq(1)
 127
 128             # MFSPR move from SPRs
 129             with m.Case(MicrOp.OP_MFSPR):
 130                 spr = Signal(10, reset_less=True)
 131                 comb += spr.eq(decode_spr_num(self.dec.SPR))  # from XFX
 132                 comb += sprmap.spr_i.eq(spr)
 133                 comb += self.spr_out.eq(sprmap.spr_o)
 134                 comb += self.fast_out.eq(sprmap.fast_o)
 135
 136         return m
 137
 138
 139 class DecodeAImm(Elaboratable):
 140     """DecodeA immediate from instruction
 141
 142     decodes register RA, whether immediate-zero, implicit and
 143     explicit CSRs
 144     """
 145
 146     def __init__(self, dec):
 147         self.dec = dec
 148         self.sel_in = Signal(In1Sel, reset_less=True)
 149         self.immz_out = Signal(reset_less=True)
 150
 151     def elaborate(self, platform):
 152         m = Module()
 153         comb = m.d.comb
 154
 155         # zero immediate requested
 156         ra = Signal(5, reset_less=True)
 157         comb += ra.eq(self.dec.RA)
 158         with m.If((self.sel_in == In1Sel.RA_OR_ZERO) & (ra == Const(0, 5))):
 159             comb += self.immz_out.eq(1)
 160
 161         return m
 162
 163
 164 class DecodeB(Elaboratable):
 165     """DecodeB from instruction
 166
 167     decodes register RB, different forms of immediate (signed, unsigned),
 168     and implicit SPRs.  register B is basically "lane 2" into the CompUnits.
 169     by industry-standard convention, "lane 2" is where fully-decoded
 170     immediates are muxed in.
 171     """
 172
 173     def __init__(self, dec):
 174         self.dec = dec
 175         self.sel_in = Signal(In2Sel, reset_less=True)
 176         self.insn_in = Signal(32, reset_less=True)
 177         self.reg_out = Data(5, "reg_b")
 178         self.fast_out = Data(3, "fast_b")
 179
 180     def elaborate(self, platform):
 181         m = Module()
 182         comb = m.d.comb
 183
 184         # select Register B field
 185         with m.Switch(self.sel_in):
 186             with m.Case(In2Sel.RB):
 187                 comb += self.reg_out.data.eq(self.dec.RB)
 188                 comb += self.reg_out.ok.eq(1)
 189             with m.Case(In2Sel.RS):
 190                 # for M-Form shiftrot
 191                 comb += self.reg_out.data.eq(self.dec.RS)
 192                 comb += self.reg_out.ok.eq(1)
 193
 194         # decode SPR2 based on instruction type
 195         op = self.dec.op
 196         # BCREG implicitly uses LR or TAR for 2nd reg
 197         # CTR however is already in fast_spr1 *not* 2.
 198         with m.If(op.internal_op == MicrOp.OP_BCREG):
 199             xo9 = self.dec.FormXL.XO[9]  # 3.0B p38 top bit of XO
 200             xo5 = self.dec.FormXL.XO[5]  # 3.0B p38
 201             with m.If(~xo9):
 202                 comb += self.fast_out.data.eq(FastRegs.LR)
 203                 comb += self.fast_out.ok.eq(1)
 204             with m.Elif(xo5):
 205                 comb += self.fast_out.data.eq(FastRegs.TAR)
 206                 comb += self.fast_out.ok.eq(1)
 207
 208         return m
 209
 210
 211 class DecodeBImm(Elaboratable):
 212     """DecodeB immediate from instruction
 213     """
 214     def __init__(self, dec):
 215         self.dec = dec
 216         self.sel_in = Signal(In2Sel, reset_less=True)
 217         self.imm_out = Data(64, "imm_b")
 218
 219     def elaborate(self, platform):
 220         m = Module()
 221         comb = m.d.comb
 222
 223         # select Register B Immediate
 224         with m.Switch(self.sel_in):
 225             with m.Case(In2Sel.CONST_UI): # unsigned
 226                 comb += self.imm_out.data.eq(self.dec.UI)
 227                 comb += self.imm_out.ok.eq(1)
 228             with m.Case(In2Sel.CONST_SI):  # sign-extended 16-bit
 229                 si = Signal(16, reset_less=True)
 230                 comb += si.eq(self.dec.SI)
 231                 comb += self.imm_out.data.eq(exts(si, 16, 64))
 232                 comb += self.imm_out.ok.eq(1)
 233             with m.Case(In2Sel.CONST_SI_HI):  # sign-extended 16+16=32 bit
 234                 si_hi = Signal(32, reset_less=True)
 235                 comb += si_hi.eq(self.dec.SI << 16)
 236                 comb += self.imm_out.data.eq(exts(si_hi, 32, 64))
 237                 comb += self.imm_out.ok.eq(1)
 238             with m.Case(In2Sel.CONST_UI_HI): # unsigned
 239                 ui = Signal(16, reset_less=True)
 240                 comb += ui.eq(self.dec.UI)
 241                 comb += self.imm_out.data.eq(ui << 16)
 242                 comb += self.imm_out.ok.eq(1)
 243             with m.Case(In2Sel.CONST_LI): # sign-extend 24+2=26 bit
 244                 li = Signal(26, reset_less=True)
 245                 comb += li.eq(self.dec.LI << 2)
 246                 comb += self.imm_out.data.eq(exts(li, 26, 64))
 247                 comb += self.imm_out.ok.eq(1)
 248             with m.Case(In2Sel.CONST_BD): # sign-extend (14+2)=16 bit
 249                 bd = Signal(16, reset_less=True)
 250                 comb += bd.eq(self.dec.BD << 2)
 251                 comb += self.imm_out.data.eq(exts(bd, 16, 64))
 252                 comb += self.imm_out.ok.eq(1)
 253             with m.Case(In2Sel.CONST_DS): # sign-extended (14+2=16) bit
 254                 ds = Signal(16, reset_less=True)
 255                 comb += ds.eq(self.dec.DS << 2)
 256                 comb += self.imm_out.data.eq(exts(ds, 16, 64))
 257                 comb += self.imm_out.ok.eq(1)
 258             with m.Case(In2Sel.CONST_M1): # signed (-1)
 259                 comb += self.imm_out.data.eq(~Const(0, 64))  # all 1s
 260                 comb += self.imm_out.ok.eq(1)
 261             with m.Case(In2Sel.CONST_SH): # unsigned - for shift
 262                 comb += self.imm_out.data.eq(self.dec.sh)
 263                 comb += self.imm_out.ok.eq(1)
 264             with m.Case(In2Sel.CONST_SH32): # unsigned - for shift
 265                 comb += self.imm_out.data.eq(self.dec.SH32)
 266                 comb += self.imm_out.ok.eq(1)
 267
 268         return m
 269
 270
 271 class DecodeC(Elaboratable):
 272     """DecodeC from instruction
 273
 274     decodes register RC.  this is "lane 3" into some CompUnits (not many)
 275     """
 276
 277     def __init__(self, dec):
 278         self.dec = dec
 279         self.sel_in = Signal(In3Sel, reset_less=True)
 280         self.insn_in = Signal(32, reset_less=True)
 281         self.reg_out = Data(5, "reg_c")
 282
 283     def elaborate(self, platform):
 284         m = Module()
 285         comb = m.d.comb
 286
 287         # select Register C field
 288         with m.Switch(self.sel_in):
 289             with m.Case(In3Sel.RB):
 290                 # for M-Form shiftrot
 291                 comb += self.reg_out.data.eq(self.dec.RB)
 292                 comb += self.reg_out.ok.eq(1)
 293             with m.Case(In3Sel.RS):
 294                 comb += self.reg_out.data.eq(self.dec.RS)
 295                 comb += self.reg_out.ok.eq(1)
 296
 297         return m
 298
 299
 300 class DecodeOut(Elaboratable):
 301     """DecodeOut from instruction
 302
 303     decodes output register RA, RT or SPR
 304     """
 305
 306     def __init__(self, dec):
 307         self.dec = dec
 308         self.sel_in = Signal(OutSel, reset_less=True)
 309         self.insn_in = Signal(32, reset_less=True)
 310         self.reg_out = Data(5, "reg_o")
 311         self.spr_out = Data(SPR, "spr_o")
 312         self.fast_out = Data(3, "fast_o")
 313
 314     def elaborate(self, platform):
 315         m = Module()
 316         comb = m.d.comb
 317         m.submodules.sprmap = sprmap = SPRMap()
 318         op = self.dec.op
 319
 320         # select Register out field
 321         with m.Switch(self.sel_in):
 322             with m.Case(OutSel.RT):
 323                 comb += self.reg_out.data.eq(self.dec.RT)
 324                 comb += self.reg_out.ok.eq(1)
 325             with m.Case(OutSel.RA):
 326                 comb += self.reg_out.data.eq(self.dec.RA)
 327                 comb += self.reg_out.ok.eq(1)
 328             with m.Case(OutSel.SPR):
 329                 spr = Signal(10, reset_less=True)
 330                 comb += spr.eq(decode_spr_num(self.dec.SPR))  # from XFX
 331                 # MFSPR move to SPRs - needs mapping
 332                 with m.If(op.internal_op == MicrOp.OP_MTSPR):
 333                     comb += sprmap.spr_i.eq(spr)
 334                     comb += self.spr_out.eq(sprmap.spr_o)
 335                     comb += self.fast_out.eq(sprmap.fast_o)
 336
 337         with m.Switch(op.internal_op):
 338
 339             # BC or BCREG: implicit register (CTR) NOTE: same in DecodeA
 340             with m.Case(MicrOp.OP_BC, MicrOp.OP_BCREG):
 341                 with m.If(~self.dec.BO[2]):  # 3.0B p38 BO2=0, use CTR reg
 342                     # constant: CTR
 343                     comb += self.fast_out.data.eq(FastRegs.CTR)
 344                     comb += self.fast_out.ok.eq(1)
 345
 346             # RFID 1st spr (fast)
 347             with m.Case(MicrOp.OP_RFID):
 348                 comb += self.fast_out.data.eq(FastRegs.SRR0)  # constant: SRR0
 349                 comb += self.fast_out.ok.eq(1)
 350
 351         return m
 352
 353
 354 class DecodeOut2(Elaboratable):
 355     """DecodeOut2 from instruction
 356
 357     decodes output registers
 358     """
 359
 360     def __init__(self, dec):
 361         self.dec = dec
 362         self.sel_in = Signal(OutSel, reset_less=True)
 363         self.lk = Signal(reset_less=True)
 364         self.insn_in = Signal(32, reset_less=True)
 365         self.reg_out = Data(5, "reg_o")
 366         self.fast_out = Data(3, "fast_o")
 367
 368     def elaborate(self, platform):
 369         m = Module()
 370         comb = m.d.comb
 371
 372         # update mode LD/ST uses read-reg A also as an output
 373         with m.If(self.dec.op.upd == LDSTMode.update):
 374             comb += self.reg_out.eq(self.dec.RA)
 375             comb += self.reg_out.ok.eq(1)
 376
 377         # B, BC or BCREG: potential implicit register (LR) output
 378         # these give bl, bcl, bclrl, etc.
 379         op = self.dec.op
 380         with m.Switch(op.internal_op):
 381
 382             # BC* implicit register (LR)
 383             with m.Case(MicrOp.OP_BC, MicrOp.OP_B, MicrOp.OP_BCREG):
 384                 with m.If(self.lk):  # "link" mode
 385                     comb += self.fast_out.data.eq(FastRegs.LR)  # constant: LR
 386                     comb += self.fast_out.ok.eq(1)
 387
 388             # RFID 2nd spr (fast)
 389             with m.Case(MicrOp.OP_RFID):
 390                 comb += self.fast_out.data.eq(FastRegs.SRR1)  # constant: SRR1
 391                 comb += self.fast_out.ok.eq(1)
 392
 393         return m
 394
 395
 396 class DecodeRC(Elaboratable):
 397     """DecodeRc from instruction
 398
 399     decodes Record bit Rc
 400     """
 401
 402     def __init__(self, dec):
 403         self.dec = dec
 404         self.sel_in = Signal(RC, reset_less=True)
 405         self.insn_in = Signal(32, reset_less=True)
 406         self.rc_out = Data(1, "rc")
 407
 408     def elaborate(self, platform):
 409         m = Module()
 410         comb = m.d.comb
 411
 412         # select Record bit out field
 413         with m.Switch(self.sel_in):
 414             with m.Case(RC.RC):
 415                 comb += self.rc_out.data.eq(self.dec.Rc)
 416                 comb += self.rc_out.ok.eq(1)
 417             with m.Case(RC.ONE):
 418                 comb += self.rc_out.data.eq(1)
 419                 comb += self.rc_out.ok.eq(1)
 420             with m.Case(RC.NONE):
 421                 comb += self.rc_out.data.eq(0)
 422                 comb += self.rc_out.ok.eq(1)
 423
 424         return m
 425
 426
 427 class DecodeOE(Elaboratable):
 428     """DecodeOE from instruction
 429
 430     decodes OE field: uses RC decode detection which might not be good
 431
 432     -- For now, use "rc" in the decode table to decide whether oe exists.
 433     -- This is not entirely correct architecturally: For mulhd and
 434     -- mulhdu, the OE field is reserved. It remains to be seen what an
 435     -- actual POWER9 does if we set it on those instructions, for now we
 436     -- test that further down when assigning to the multiplier oe input.
 437     """
 438
 439     def __init__(self, dec):
 440         self.dec = dec
 441         self.sel_in = Signal(RC, reset_less=True)
 442         self.insn_in = Signal(32, reset_less=True)
 443         self.oe_out = Data(1, "oe")
 444
 445     def elaborate(self, platform):
 446         m = Module()
 447         comb = m.d.comb
 448         op = self.dec.op
 449
 450         with m.Switch(op.internal_op):
 451
 452             # mulhw, mulhwu, mulhd, mulhdu - these *ignore* OE
 453             # also rotate
 454             # XXX ARGH! ignoring OE causes incompatibility with microwatt
 455             # http://lists.libre-soc.org/pipermail/libre-soc-dev/2020-August/000302.html
 456             with m.Case(MicrOp.OP_MUL_H64, MicrOp.OP_MUL_H32,
 457                         MicrOp.OP_EXTS, MicrOp.OP_CNTZ,
 458                         MicrOp.OP_SHL, MicrOp.OP_SHR, MicrOp.OP_RLC,
 459                         MicrOp.OP_LOAD, MicrOp.OP_STORE,
 460                         MicrOp.OP_RLCL, MicrOp.OP_RLCR,
 461                         MicrOp.OP_EXTSWSLI):
 462                 pass
 463
 464             # all other ops decode OE field
 465             with m.Default():
 466                 # select OE bit out field
 467                 with m.Switch(self.sel_in):
 468                     with m.Case(RC.RC):
 469                         comb += self.oe_out.data.eq(self.dec.OE)
 470                         comb += self.oe_out.ok.eq(1)
 471
 472         return m
 473
 474
 475 class DecodeCRIn(Elaboratable):
 476     """Decodes input CR from instruction
 477
 478     CR indices - insn fields - (not the data *in* the CR) require only 3
 479     bits because they refer to CR0-CR7
 480     """
 481
 482     def __init__(self, dec):
 483         self.dec = dec
 484         self.sel_in = Signal(CRInSel, reset_less=True)
 485         self.insn_in = Signal(32, reset_less=True)
 486         self.cr_bitfield = Data(3, "cr_bitfield")
 487         self.cr_bitfield_b = Data(3, "cr_bitfield_b")
 488         self.cr_bitfield_o = Data(3, "cr_bitfield_o")
 489         self.whole_reg = Data(8,  "cr_fxm")
 490
 491     def elaborate(self, platform):
 492         m = Module()
 493         m.submodules.ppick = ppick = PriorityPicker(8, reverse_i=True,
 494                                                        reverse_o=True)
 495
 496         comb = m.d.comb
 497         op = self.dec.op
 498
 499         comb += self.cr_bitfield.ok.eq(0)
 500         comb += self.cr_bitfield_b.ok.eq(0)
 501         comb += self.whole_reg.ok.eq(0)
 502         with m.Switch(self.sel_in):
 503             with m.Case(CRInSel.NONE):
 504                 pass  # No bitfield activated
 505             with m.Case(CRInSel.CR0):
 506                 comb += self.cr_bitfield.data.eq(0) # CR0 (MSB0 numbering)
 507                 comb += self.cr_bitfield.ok.eq(1)
 508             with m.Case(CRInSel.BI):
 509                 comb += self.cr_bitfield.data.eq(self.dec.BI[2:5])
 510                 comb += self.cr_bitfield.ok.eq(1)
 511             with m.Case(CRInSel.BFA):
 512                 comb += self.cr_bitfield.data.eq(self.dec.FormX.BFA)
 513                 comb += self.cr_bitfield.ok.eq(1)
 514             with m.Case(CRInSel.BA_BB):
 515                 comb += self.cr_bitfield.data.eq(self.dec.BA[2:5])
 516                 comb += self.cr_bitfield.ok.eq(1)
 517                 comb += self.cr_bitfield_b.data.eq(self.dec.BB[2:5])
 518                 comb += self.cr_bitfield_b.ok.eq(1)
 519                 comb += self.cr_bitfield_o.data.eq(self.dec.BT[2:5])
 520                 comb += self.cr_bitfield_o.ok.eq(1)
 521             with m.Case(CRInSel.BC):
 522                 comb += self.cr_bitfield.data.eq(self.dec.BC[2:5])
 523                 comb += self.cr_bitfield.ok.eq(1)
 524             with m.Case(CRInSel.WHOLE_REG):
 525                 comb += self.whole_reg.ok.eq(1)
 526                 move_one = Signal(reset_less=True)
 527                 comb += move_one.eq(self.insn_in[20]) # MSB0 bit 11
 528                 with m.If((op.internal_op == MicrOp.OP_MFCR) & move_one):
 529                     # must one-hot the FXM field
 530                     comb += ppick.i.eq(self.dec.FXM)
 531                     comb += self.whole_reg.data.eq(ppick.o)
 532                 with m.Else():
 533                     # otherwise use all of it
 534                     comb += self.whole_reg.data.eq(0xff)
 535
 536         return m
 537
 538
 539 class DecodeCROut(Elaboratable):
 540     """Decodes input CR from instruction
 541
 542     CR indices - insn fields - (not the data *in* the CR) require only 3
 543     bits because they refer to CR0-CR7
 544     """
 545
 546     def __init__(self, dec):
 547         self.dec = dec
 548         self.rc_in = Signal(reset_less=True)
 549         self.sel_in = Signal(CROutSel, reset_less=True)
 550         self.insn_in = Signal(32, reset_less=True)
 551         self.cr_bitfield = Data(3, "cr_bitfield")
 552         self.whole_reg = Data(8,  "cr_fxm")
 553
 554     def elaborate(self, platform):
 555         m = Module()
 556         comb = m.d.comb
 557         op = self.dec.op
 558         m.submodules.ppick = ppick = PriorityPicker(8, reverse_i=True,
 559                                                        reverse_o=True)
 560
 561         comb += self.cr_bitfield.ok.eq(0)
 562         comb += self.whole_reg.ok.eq(0)
 563         with m.Switch(self.sel_in):
 564             with m.Case(CROutSel.NONE):
 565                 pass  # No bitfield activated
 566             with m.Case(CROutSel.CR0):
 567                 comb += self.cr_bitfield.data.eq(0) # CR0 (MSB0 numbering)
 568                 comb += self.cr_bitfield.ok.eq(self.rc_in)  # only when RC=1
 569             with m.Case(CROutSel.BF):
 570                 comb += self.cr_bitfield.data.eq(self.dec.FormX.BF)
 571                 comb += self.cr_bitfield.ok.eq(1)
 572             with m.Case(CROutSel.BT):
 573                 comb += self.cr_bitfield.data.eq(self.dec.FormXL.BT[2:5])
 574                 comb += self.cr_bitfield.ok.eq(1)
 575             with m.Case(CROutSel.WHOLE_REG):
 576                 comb += self.whole_reg.ok.eq(1)
 577                 move_one = Signal(reset_less=True)
 578                 comb += move_one.eq(self.insn_in[20])
 579                 with m.If((op.internal_op == MicrOp.OP_MTCRF)):
 580                     with m.If(move_one):
 581                         # must one-hot the FXM field
 582                         comb += ppick.i.eq(self.dec.FXM)
 583                         with m.If(ppick.en_o):
 584                             comb += self.whole_reg.data.eq(ppick.o)
 585                         with m.Else():
 586                             comb += self.whole_reg.data.eq(0b00000001) # CR7
 587                     with m.Else():
 588                         comb += self.whole_reg.data.eq(self.dec.FXM)
 589                 with m.Else():
 590                     # otherwise use all of it
 591                     comb += self.whole_reg.data.eq(0xff)
 592
 593         return m
 594
 595
 596 class PowerDecodeSubset(Elaboratable):
 597     """PowerDecodeSubset: dynamic subset decoder
 598
 599     """
 600
 601     def __init__(self, dec, opkls=None, fn_name=None, col_subset=None,
 602                             final=False):
 603
 604         self.final = final
 605         if dec is None:
 606             self.opkls = opkls
 607             self.fn_name = fn_name
 608             self.dec = create_pdecode(name=fn_name, col_subset=col_subset,
 609                                       row_subset=self.rowsubsetfn)
 610         else:
 611             self.dec = dec
 612             self.opkls = None
 613             self.fn_name = None
 614         self.e = Decode2ToExecute1Type(name=self.fn_name, opkls=self.opkls)
 615
 616         # state information needed by the Decoder (TODO: this as a Record)
 617         self.state = CoreState("dec2")
 618
 619     def rowsubsetfn(self, opcode, row):
 620         return row['unit'] == self.fn_name
 621
 622     def ports(self):
 623         return self.dec.ports() + self.e.ports()
 624
 625     def needs_field(self, field, op_field):
 626         do = self.e_tmp.do
 627         return hasattr(do, field) and self.op_get(op_field) is not None
 628
 629     def do_copy(self, field, val, final=False):
 630         if final or self.final:
 631             do = self.e.do
 632         else:
 633             do = self.e_tmp.do
 634         if hasattr(do, field) and val is not None:
 635             return getattr(do, field).eq(val)
 636         return []
 637
 638     def op_get(self, op_field):
 639         return getattr(self.dec.op, op_field, None)
 640
 641     def elaborate(self, platform):
 642         m = Module()
 643         comb = m.d.comb
 644         state = self.state
 645         e_out, op, do_out = self.e, self.dec.op, self.e.do
 646         dec_spr, msr, cia, ext_irq = state.dec, state.msr, state.pc, state.eint
 647
 648         # fill in for a normal instruction (not an exception)
 649         # copy over if non-exception, non-privileged etc. is detected
 650         if self.final:
 651             e = self.e
 652         else:
 653             self.e_tmp = e = Decode2ToExecute1Type(name=self.fn_name,
 654                                                    opkls=self.opkls)
 655         do = e.do
 656
 657         # set up submodule decoders
 658         m.submodules.dec = self.dec
 659         m.submodules.dec_rc = dec_rc = DecodeRC(self.dec)
 660         m.submodules.dec_oe = dec_oe = DecodeOE(self.dec)
 661         m.submodules.dec_cr_in = self.dec_cr_in = DecodeCRIn(self.dec)
 662         m.submodules.dec_cr_out = self.dec_cr_out = DecodeCROut(self.dec)
 663
 664         # copy instruction through...
 665         for i in [do.insn,
 666                   dec_rc.insn_in, dec_oe.insn_in,
 667                   self.dec_cr_in.insn_in, self.dec_cr_out.insn_in]:
 668             comb += i.eq(self.dec.opcode_in)
 669
 670         # ...and subdecoders' input fields
 671         comb += dec_rc.sel_in.eq(op.rc_sel)
 672         comb += dec_oe.sel_in.eq(op.rc_sel)  # XXX should be OE sel
 673         comb += self.dec_cr_in.sel_in.eq(op.cr_in)
 674         comb += self.dec_cr_out.sel_in.eq(op.cr_out)
 675         comb += self.dec_cr_out.rc_in.eq(dec_rc.rc_out.data)
 676
 677         # copy "state" over
 678         comb += self.do_copy("msr", msr)
 679         comb += self.do_copy("cia", cia)
 680
 681         # set up instruction, pick fn unit
 682         # no op: defaults to OP_ILLEGAL
 683         comb += self.do_copy("insn_type", self.op_get("internal_op"))
 684         comb += self.do_copy("fn_unit", self.op_get("function_unit"))
 685
 686         # immediates
 687         if self.needs_field("zero_a", "in1_sel"):
 688             m.submodules.dec_ai = dec_ai = DecodeAImm(self.dec)
 689             comb += dec_ai.sel_in.eq(op.in1_sel)
 690             comb += self.do_copy("zero_a", dec_ai.immz_out)  # RA==0 detected
 691         if self.needs_field("imm_data", "in2_sel"):
 692             m.submodules.dec_bi = dec_bi = DecodeBImm(self.dec)
 693             comb += dec_bi.sel_in.eq(op.in2_sel)
 694             comb += self.do_copy("imm_data", dec_bi.imm_out) # imm in RB
 695
 696         # rc and oe out
 697         comb += self.do_copy("rc", dec_rc.rc_out)
 698         comb += self.do_copy("oe", dec_oe.oe_out)
 699
 700         # CR in/out
 701         comb += self.do_copy("read_cr_whole", self.dec_cr_in.whole_reg)
 702         comb += self.do_copy("write_cr_whole", self.dec_cr_out.whole_reg)
 703         comb += self.do_copy("write_cr0", self.dec_cr_out.cr_bitfield.ok)
 704
 705         comb += self.do_copy("input_cr", self.op_get("cr_in"))   # CR in
 706         comb += self.do_copy("output_cr", self.op_get("cr_out"))  # CR out
 707
 708         # decoded/selected instruction flags
 709         comb += self.do_copy("data_len", self.op_get("ldst_len"))
 710         comb += self.do_copy("invert_in", self.op_get("inv_a"))
 711         comb += self.do_copy("invert_out", self.op_get("inv_out"))
 712         comb += self.do_copy("input_carry", self.op_get("cry_in"))
 713         comb += self.do_copy("output_carry", self.op_get("cry_out"))
 714         comb += self.do_copy("is_32bit", self.op_get("is_32b"))
 715         comb += self.do_copy("is_signed", self.op_get("sgn"))
 716         lk = self.op_get("lk")
 717         if lk is not None:
 718             with m.If(lk):
 719                 comb += self.do_copy("lk", self.dec.LK)  # XXX TODO: accessor
 720
 721         comb += self.do_copy("byte_reverse", self.op_get("br"))
 722         comb += self.do_copy("sign_extend", self.op_get("sgn_ext"))
 723         comb += self.do_copy("ldst_mode", self.op_get("upd"))  # LD/ST mode
 724
 725         return m
 726
 727
 728 class PowerDecode2(PowerDecodeSubset):
 729     """PowerDecode2: the main instruction decoder.
 730
 731     whilst PowerDecode is responsible for decoding the actual opcode, this
 732     module encapsulates further specialist, sparse information and
 733     expansion of fields that is inconvenient to have in the CSV files.
 734     for example: the encoding of the immediates, which are detected
 735     and expanded out to their full value from an annotated (enum)
 736     representation.
 737
 738     implicit register usage is also set up, here.  for example: OP_BC
 739     requires implicitly reading CTR, OP_RFID requires implicitly writing
 740     to SRR1 and so on.
 741
 742     in addition, PowerDecoder2 is responsible for detecting whether
 743     instructions are illegal (or privileged) or not, and instead of
 744     just leaving at that, *replacing* the instruction to execute with
 745     a suitable alternative (trap).
 746     """
 747
 748     def elaborate(self, platform):
 749         m = super().elaborate(platform)
 750         comb = m.d.comb
 751         state = self.state
 752         e_out, op, do_out = self.e, self.dec.op, self.e.do
 753         dec_spr, msr, cia, ext_irq = state.dec, state.msr, state.pc, state.eint
 754         e = self.e_tmp
 755         do = e.do
 756
 757         # fill in for a normal instruction (not an exception)
 758         # copy over if non-exception, non-privileged etc. is detected
 759
 760         # set up submodule decoders
 761         m.submodules.dec_a = dec_a = DecodeA(self.dec)
 762         m.submodules.dec_b = dec_b = DecodeB(self.dec)
 763         m.submodules.dec_c = dec_c = DecodeC(self.dec)
 764         m.submodules.dec_o = dec_o = DecodeOut(self.dec)
 765         m.submodules.dec_o2 = dec_o2 = DecodeOut2(self.dec)
 766
 767         # copy instruction through...
 768         for i in [do.insn, dec_a.insn_in, dec_b.insn_in,
 769                   dec_c.insn_in, dec_o.insn_in, dec_o2.insn_in]:
 770             comb += i.eq(self.dec.opcode_in)
 771
 772         # ...and subdecoders' input fields
 773         comb += dec_a.sel_in.eq(op.in1_sel)
 774         comb += dec_b.sel_in.eq(op.in2_sel)
 775         comb += dec_c.sel_in.eq(op.in3_sel)
 776         comb += dec_o.sel_in.eq(op.out_sel)
 777         comb += dec_o2.sel_in.eq(op.out_sel)
 778         if hasattr(do, "lk"):
 779             comb += dec_o2.lk.eq(do.lk)
 780
 781         # registers a, b, c and out and out2 (LD/ST EA)
 782         comb += e.read_reg1.eq(dec_a.reg_out)
 783         comb += e.read_reg2.eq(dec_b.reg_out)
 784         comb += e.read_reg3.eq(dec_c.reg_out)
 785         comb += e.write_reg.eq(dec_o.reg_out)
 786         comb += e.write_ea.eq(dec_o2.reg_out)
 787
 788         # SPRs out
 789         comb += e.read_spr1.eq(dec_a.spr_out)
 790         comb += e.write_spr.eq(dec_o.spr_out)
 791
 792         # Fast regs out
 793         comb += e.read_fast1.eq(dec_a.fast_out)
 794         comb += e.read_fast2.eq(dec_b.fast_out)
 795         comb += e.write_fast1.eq(dec_o.fast_out)
 796         comb += e.write_fast2.eq(dec_o2.fast_out)
 797
 798         # condition registers (CR)
 799         comb += e.read_cr1.eq(self.dec_cr_in.cr_bitfield)
 800         comb += e.read_cr2.eq(self.dec_cr_in.cr_bitfield_b)
 801         comb += e.read_cr3.eq(self.dec_cr_in.cr_bitfield_o)
 802         comb += e.write_cr.eq(self.dec_cr_out.cr_bitfield)
 803
 804         # sigh this is exactly the sort of thing for which the
 805         # decoder is designed to not need.  MTSPR, MFSPR and others need
 806         # access to the XER bits.  however setting e.oe is not appropriate
 807         with m.If(op.internal_op == MicrOp.OP_MFSPR):
 808             comb += e.xer_in.eq(0b111) # SO, CA, OV
 809         with m.If(op.internal_op == MicrOp.OP_CMP):
 810             comb += e.xer_in.eq(1<<XERRegs.SO) # SO
 811         with m.If(op.internal_op == MicrOp.OP_MTSPR):
 812             comb += e.xer_out.eq(1)
 813
 814         # set the trapaddr to 0x700 for a td/tw/tdi/twi operation
 815         with m.If(op.internal_op == MicrOp.OP_TRAP):
 816             # *DO NOT* call self.trap here.  that would reset absolutely
 817             # rverything including destroying read of RA and RB.
 818             comb += self.do_copy("trapaddr", 0x70, True) # strip first nibble
 819
 820         # check if instruction is privileged
 821         is_priv_insn = instr_is_priv(m, op.internal_op, e.do.insn)
 822
 823         # external interrupt? only if MSR.EE set
 824         with m.If(ext_irq & msr[MSR.EE]): # v3.0B p944 (MSR.EE)
 825             self.trap(m, TT.EINT, 0x500)
 826
 827         # decrement counter (v3.0B p1099): TODO 32-bit version (MSR.LPCR)
 828         with m.If(dec_spr[63] & msr[MSR.EE]): # v3.0B 6.5.11 p1076
 829             self.trap(m, TT.DEC, 0x900)   # v3.0B 6.5 p1065
 830
 831         # privileged instruction trap
 832         with m.Elif(is_priv_insn & msr[MSR.PR]):
 833             self.trap(m, TT.PRIV, 0x700)
 834
 835         # illegal instruction must redirect to trap. this is done by
 836         # *overwriting* the decoded instruction and starting again.
 837         # (note: the same goes for interrupts and for privileged operations,
 838         # just with different trapaddr and traptype)
 839         with m.Elif(op.internal_op == MicrOp.OP_ILLEGAL):
 840             # illegal instruction trap
 841             self.trap(m, TT.ILLEG, 0x700)
 842
 843         # no exception, just copy things to the output
 844         with m.Else():
 845             comb += e_out.eq(e)
 846
 847         # trap: (note e.insn_type so this includes OP_ILLEGAL) set up fast regs
 848         # Note: OP_SC could actually be modified to just be a trap
 849         with m.If((do_out.insn_type == MicrOp.OP_TRAP) |
 850                   (do_out.insn_type == MicrOp.OP_SC)):
 851             # TRAP write fast1 = SRR0
 852             comb += e_out.write_fast1.data.eq(FastRegs.SRR0)  # constant: SRR0
 853             comb += e_out.write_fast1.ok.eq(1)
 854             # TRAP write fast2 = SRR1
 855             comb += e_out.write_fast2.data.eq(FastRegs.SRR1)  # constant: SRR1
 856             comb += e_out.write_fast2.ok.eq(1)
 857
 858         # RFID: needs to read SRR0/1
 859         with m.If(do_out.insn_type == MicrOp.OP_RFID):
 860             # TRAP read fast1 = SRR0
 861             comb += e_out.read_fast1.data.eq(FastRegs.SRR0)  # constant: SRR0
 862             comb += e_out.read_fast1.ok.eq(1)
 863             # TRAP read fast2 = SRR1
 864             comb += e_out.read_fast2.data.eq(FastRegs.SRR1)  # constant: SRR1
 865             comb += e_out.read_fast2.ok.eq(1)
 866
 867         return m
 868
 869     def trap(self, m, traptype, trapaddr):
 870         """trap: this basically "rewrites" the decoded instruction as a trap
 871         """
 872         comb = m.d.comb
 873         op, e = self.dec.op, self.e
 874         comb += e.eq(0)  # reset eeeeeverything
 875
 876         # start again
 877         comb += self.do_copy("insn", self.dec.opcode_in, True)
 878         comb += self.do_copy("insn_type", MicrOp.OP_TRAP, True)
 879         comb += self.do_copy("fn_unit", Function.TRAP, True)
 880         comb += self.do_copy("trapaddr", trapaddr >> 4, True) # bottom 4 bits
 881         comb += self.do_copy("traptype", traptype, True)  # request type
 882         comb += self.do_copy("msr", self.state.msr, True) # copy of MSR "state"
 883         comb += self.do_copy("cia", self.state.pc, True)  # copy of PC "state"
 884
 885
 886 def get_rdflags(e, cu):
 887     rdl = []
 888     for idx in range(cu.n_src):
 889         regfile, regname, _ = cu.get_in_spec(idx)
 890         rdflag, read = regspec_decode_read(e, regfile, regname)
 891         rdl.append(rdflag)
 892     print("rdflags", rdl)
 893     return Cat(*rdl)
 894
 895
 896 if __name__ == '__main__':
 897     pdecode = create_pdecode()
 898     dec2 = PowerDecode2(pdecode)
 899     vl = rtlil.convert(dec2, ports=dec2.ports() + pdecode.ports())
 900     with open("dec2.il", "w") as f:
 901         f.write(vl)