src/soc/decoder/isa/caller.py

   1 """core of the python-based POWER9 simulator
   2
   3 this is part of a cycle-accurate POWER9 simulator.  its primary purpose is
   4 not speed, it is for both learning and educational purposes, as well as
   5 a method of verifying the HDL.
   6
   7 related bugs:
   8
   9 * https://bugs.libre-soc.org/show_bug.cgi?id=424
  10 """
  11
  12 from functools import wraps
  13 from soc.decoder.orderedset import OrderedSet
  14 from soc.decoder.selectable_int import (FieldSelectableInt, SelectableInt,
  15                                         selectconcat)
  16 from soc.decoder.power_enums import (spr_dict, spr_byname, XER_bits,
  17                                      insns, InternalOp)
  18 from soc.decoder.helpers import exts, trunc_div, trunc_rem
  19 from soc.consts import PI, MSR
  20
  21 from collections import namedtuple
  22 import math
  23 import sys
  24
  25 instruction_info = namedtuple('instruction_info',
  26                               'func read_regs uninit_regs write_regs ' + \
  27                               'special_regs op_fields form asmregs')
  28
  29 special_sprs = {
  30     'LR': 8,
  31     'CTR': 9,
  32     'TAR': 815,
  33     'XER': 1,
  34     'VRSAVE': 256}
  35
  36
  37 def swap_order(x, nbytes):
  38     x = x.to_bytes(nbytes, byteorder='little')
  39     x = int.from_bytes(x, byteorder='big', signed=False)
  40     return x
  41
  42
  43 def create_args(reglist, extra=None):
  44     args = OrderedSet()
  45     for reg in reglist:
  46         args.add(reg)
  47     args = list(args)
  48     if extra:
  49         args = [extra] + args
  50     return args
  51
  52
  53 class Mem:
  54
  55     def __init__(self, row_bytes=8, initial_mem=None):
  56         self.mem = {}
  57         self.bytes_per_word = row_bytes
  58         self.word_log2 = math.ceil(math.log2(row_bytes))
  59         print ("Sim-Mem", initial_mem, self.bytes_per_word, self.word_log2)
  60         if not initial_mem:
  61             return
  62
  63         # different types of memory data structures recognised (for convenience)
  64         if isinstance(initial_mem, list):
  65             initial_mem = (0, initial_mem)
  66         if isinstance(initial_mem, tuple):
  67             startaddr, mem = initial_mem
  68             initial_mem = {}
  69             for i, val in enumerate(mem):
  70                 initial_mem[startaddr + row_bytes*i] = (val, row_bytes)
  71
  72         for addr, (val, width) in initial_mem.items():
  73             #val = swap_order(val, width)
  74             self.st(addr, val, width, swap=False)
  75
  76     def _get_shifter_mask(self, wid, remainder):
  77         shifter = ((self.bytes_per_word - wid) - remainder) * \
  78             8  # bits per byte
  79         # XXX https://bugs.libre-soc.org/show_bug.cgi?id=377
  80         # BE/LE mode?
  81         shifter = remainder * 8
  82         mask = (1 << (wid * 8)) - 1
  83         print ("width,rem,shift,mask", wid, remainder, hex(shifter), hex(mask))
  84         return shifter, mask
  85
  86     # TODO: Implement ld/st of lesser width
  87     def ld(self, address, width=8, swap=True, check_in_mem=False):
  88         print("ld from addr 0x{:x} width {:d}".format(address, width))
  89         remainder = address & (self.bytes_per_word - 1)
  90         address = address >> self.word_log2
  91         assert remainder & (width - 1) == 0, "Unaligned access unsupported!"
  92         if address in self.mem:
  93             val = self.mem[address]
  94         elif check_in_mem:
  95             return None
  96         else:
  97             val = 0
  98         print("mem @ 0x{:x} rem {:d} : 0x{:x}".format(address, remainder, val))
  99
 100         if width != self.bytes_per_word:
 101             shifter, mask = self._get_shifter_mask(width, remainder)
 102             print ("masking", hex(val), hex(mask<<shifter), shifter)
 103             val = val & (mask << shifter)
 104             val >>= shifter
 105         if swap:
 106             val = swap_order(val, width)
 107         print("Read 0x{:x} from addr 0x{:x}".format(val, address))
 108         return val
 109
 110     def st(self, addr, v, width=8, swap=True):
 111         staddr = addr
 112         remainder = addr & (self.bytes_per_word - 1)
 113         addr = addr >> self.word_log2
 114         print("Writing 0x{:x} to ST 0x{:x} memaddr 0x{:x}/{:x}".format(v,
 115                         staddr, addr, remainder, swap))
 116         assert remainder & (width - 1) == 0, "Unaligned access unsupported!"
 117         if swap:
 118             v = swap_order(v, width)
 119         if width != self.bytes_per_word:
 120             if addr in self.mem:
 121                 val = self.mem[addr]
 122             else:
 123                 val = 0
 124             shifter, mask = self._get_shifter_mask(width, remainder)
 125             val &= ~(mask << shifter)
 126             val |= v << shifter
 127             self.mem[addr] = val
 128         else:
 129             self.mem[addr] = v
 130         print("mem @ 0x{:x}: 0x{:x}".format(addr, self.mem[addr]))
 131
 132     def __call__(self, addr, sz):
 133         val = self.ld(addr.value, sz)
 134         print ("memread", addr, sz, val)
 135         return SelectableInt(val, sz*8)
 136
 137     def memassign(self, addr, sz, val):
 138         print ("memassign", addr, sz, val)
 139         self.st(addr.value, val.value, sz)
 140
 141
 142 class GPR(dict):
 143     def __init__(self, decoder, regfile):
 144         dict.__init__(self)
 145         self.sd = decoder
 146         for i in range(32):
 147             self[i] = SelectableInt(regfile[i], 64)
 148
 149     def __call__(self, ridx):
 150         return self[ridx]
 151
 152     def set_form(self, form):
 153         self.form = form
 154
 155     def getz(self, rnum):
 156         #rnum = rnum.value # only SelectableInt allowed
 157         print("GPR getzero", rnum)
 158         if rnum == 0:
 159             return SelectableInt(0, 64)
 160         return self[rnum]
 161
 162     def _get_regnum(self, attr):
 163         getform = self.sd.sigforms[self.form]
 164         rnum = getattr(getform, attr)
 165         return rnum
 166
 167     def ___getitem__(self, attr):
 168         print("GPR getitem", attr)
 169         rnum = self._get_regnum(attr)
 170         return self.regfile[rnum]
 171
 172     def dump(self):
 173         for i in range(0, len(self), 8):
 174             s = []
 175             for j in range(8):
 176                 s.append("%08x" % self[i+j].value)
 177             s = ' '.join(s)
 178             print("reg", "%2d" % i, s)
 179
 180 class PC:
 181     def __init__(self, pc_init=0):
 182         self.CIA = SelectableInt(pc_init, 64)
 183         self.NIA = self.CIA + SelectableInt(4, 64)
 184
 185     def update(self, namespace):
 186         self.CIA = namespace['NIA'].narrow(64)
 187         self.NIA = self.CIA + SelectableInt(4, 64)
 188         namespace['CIA'] = self.CIA
 189         namespace['NIA'] = self.NIA
 190
 191
 192 class SPR(dict):
 193     def __init__(self, dec2, initial_sprs={}):
 194         self.sd = dec2
 195         dict.__init__(self)
 196         for key, v in initial_sprs.items():
 197             if isinstance(key, SelectableInt):
 198                 key = key.value
 199             key = special_sprs.get(key, key)
 200             if isinstance(key, int):
 201                 info = spr_dict[key]
 202             else:
 203                 info = spr_byname[key]
 204             if not isinstance(v, SelectableInt):
 205                 v = SelectableInt(v, info.length)
 206             self[key] = v
 207
 208     def __getitem__(self, key):
 209         print ("get spr", key)
 210         print ("dict", self.items())
 211         # if key in special_sprs get the special spr, otherwise return key
 212         if isinstance(key, SelectableInt):
 213             key = key.value
 214         if isinstance(key, int):
 215             key = spr_dict[key].SPR
 216         key = special_sprs.get(key, key)
 217         if key in self:
 218             res = dict.__getitem__(self, key)
 219         else:
 220             if isinstance(key, int):
 221                 info = spr_dict[key]
 222             else:
 223                 info = spr_byname[key]
 224             dict.__setitem__(self, key, SelectableInt(0, info.length))
 225             res = dict.__getitem__(self, key)
 226         print ("spr returning", key, res)
 227         return res
 228
 229     def __setitem__(self, key, value):
 230         if isinstance(key, SelectableInt):
 231             key = key.value
 232         if isinstance(key, int):
 233             key = spr_dict[key].SPR
 234             print ("spr key", key)
 235         key = special_sprs.get(key, key)
 236         print ("setting spr", key, value)
 237         dict.__setitem__(self, key, value)
 238
 239     def __call__(self, ridx):
 240         return self[ridx]
 241
 242
 243 class ISACaller:
 244     # decoder2 - an instance of power_decoder2
 245     # regfile - a list of initial values for the registers
 246     # initial_{etc} - initial values for SPRs, Condition Register, Mem, MSR
 247     # respect_pc - tracks the program counter.  requires initial_insns
 248     def __init__(self, decoder2, regfile, initial_sprs=None, initial_cr=0,
 249                        initial_mem=None, initial_msr=0,
 250                        initial_insns=None, respect_pc=False,
 251                        disassembly=None,
 252                        initial_pc=0,
 253                        bigendian=True):
 254
 255         self.bigendian = bigendian
 256         self.halted = False
 257         self.respect_pc = respect_pc
 258         if initial_sprs is None:
 259             initial_sprs = {}
 260         if initial_mem is None:
 261             initial_mem = {}
 262         if initial_insns is None:
 263             initial_insns = {}
 264             assert self.respect_pc == False, "instructions required to honor pc"
 265
 266         print ("ISACaller insns", respect_pc, initial_insns, disassembly)
 267
 268         # "fake program counter" mode (for unit testing)
 269         self.fake_pc = 0
 270         disasm_start = 0
 271         if not respect_pc:
 272             if isinstance(initial_mem, tuple):
 273                 self.fake_pc = initial_mem[0]
 274                 disasm_start = self.fake_pc
 275         else:
 276             disasm_start = initial_pc
 277
 278         # disassembly: we need this for now (not given from the decoder)
 279         self.disassembly = {}
 280         if disassembly:
 281             for i, code in enumerate(disassembly):
 282                 self.disassembly[i*4 + disasm_start] = code
 283
 284         # set up registers, instruction memory, data memory, PC, SPRs, MSR
 285         self.gpr = GPR(decoder2, regfile)
 286         self.mem = Mem(row_bytes=8, initial_mem=initial_mem)
 287         self.imem = Mem(row_bytes=4, initial_mem=initial_insns)
 288         self.pc = PC()
 289         self.spr = SPR(decoder2, initial_sprs)
 290         self.msr = SelectableInt(initial_msr, 64) # underlying reg
 291
 292         # TODO, needed here:
 293         # FPR (same as GPR except for FP nums)
 294         # 4.2.2 p124 FPSCR (definitely "separate" - not in SPR)
 295         #            note that mffs, mcrfs, mtfsf "manage" this FPSCR
 296         # 2.3.1 CR (and sub-fields CR0..CR6 - CR0 SO comes from XER.SO)
 297         #         note that mfocrf, mfcr, mtcr, mtocrf, mcrxrx "manage" CRs
 298         #         -- Done
 299         # 2.3.2 LR   (actually SPR #8) -- Done
 300         # 2.3.3 CTR  (actually SPR #9) -- Done
 301         # 2.3.4 TAR  (actually SPR #815)
 302         # 3.2.2 p45 XER  (actually SPR #1) -- Done
 303         # 3.2.3 p46 p232 VRSAVE (actually SPR #256)
 304
 305         # create CR then allow portions of it to be "selectable" (below)
 306         self._cr = SelectableInt(initial_cr, 64) # underlying reg
 307         self.cr = FieldSelectableInt(self._cr, list(range(32,64)))
 308
 309         # "undefined", just set to variable-bit-width int (use exts "max")
 310         self.undefined = SelectableInt(0, 256) # TODO, not hard-code 256!
 311
 312         self.namespace = {}
 313         self.namespace.update(self.spr)
 314         self.namespace.update({'GPR': self.gpr,
 315                           'MEM': self.mem,
 316                           'SPR': self.spr,
 317                           'memassign': self.memassign,
 318                           'NIA': self.pc.NIA,
 319                           'CIA': self.pc.CIA,
 320                           'CR': self.cr,
 321                           'MSR': self.msr,
 322                           'undefined': self.undefined,
 323                           'mode_is_64bit': True,
 324                           'SO': XER_bits['SO']
 325                           })
 326
 327         # update pc to requested start point
 328         self.set_pc(initial_pc)
 329
 330         # field-selectable versions of Condition Register TODO check bitranges?
 331         self.crl = []
 332         for i in range(8):
 333             bits = tuple(range(i*4, (i+1)*4))# errr... maybe?
 334             _cr = FieldSelectableInt(self.cr, bits)
 335             self.crl.append(_cr)
 336             self.namespace["CR%d" % i] = _cr
 337
 338         self.decoder = decoder2.dec
 339         self.dec2 = decoder2
 340
 341     def TRAP(self, trap_addr=0x700, trap_bit=PI.TRAP):
 342         print ("TRAP:", hex(trap_addr))
 343         # store CIA(+4?) in SRR0, set NIA to 0x700
 344         # store MSR in SRR1, set MSR to um errr something, have to check spec
 345         self.spr['SRR0'] = self.pc.CIA
 346         self.spr['SRR1'] = self.namespace['MSR']
 347         self.trap_nia = SelectableInt(trap_addr, 64)
 348         self.namespace['MSR'][63-trap_bit] = 1
 349
 350     def memassign(self, ea, sz, val):
 351         self.mem.memassign(ea, sz, val)
 352
 353     def prep_namespace(self, formname, op_fields):
 354         # TODO: get field names from form in decoder*1* (not decoder2)
 355         # decoder2 is hand-created, and decoder1.sigform is auto-generated
 356         # from spec
 357         # then "yield" fields only from op_fields rather than hard-coded
 358         # list, here.
 359         fields = self.decoder.sigforms[formname]
 360         for name in op_fields:
 361             if name == 'spr':
 362                 sig = getattr(fields, name.upper())
 363             else:
 364                 sig = getattr(fields, name)
 365             val = yield sig
 366             if name in ['BF', 'BFA']:
 367                 self.namespace[name] = val
 368             else:
 369                 self.namespace[name] = SelectableInt(val, sig.width)
 370
 371         self.namespace['XER'] = self.spr['XER']
 372         self.namespace['CA'] = self.spr['XER'][XER_bits['CA']].value
 373         self.namespace['CA32'] = self.spr['XER'][XER_bits['CA32']].value
 374
 375     def handle_carry_(self, inputs, outputs, already_done):
 376         inv_a = yield self.dec2.e.do.invert_a
 377         if inv_a:
 378             inputs[0] = ~inputs[0]
 379
 380         imm_ok = yield self.dec2.e.do.imm_data.ok
 381         if imm_ok:
 382             imm = yield self.dec2.e.do.imm_data.data
 383             inputs.append(SelectableInt(imm, 64))
 384         assert len(outputs) >= 1
 385         print ("outputs", repr(outputs))
 386         if isinstance(outputs, list) or isinstance(outputs, tuple):
 387             output = outputs[0]
 388         else:
 389             output = outputs
 390         gts = []
 391         for x in inputs:
 392             print ("gt input", x, output)
 393             gt = (x > output)
 394             gts.append(gt)
 395         print(gts)
 396         cy = 1 if any(gts) else 0
 397         if not (1 & already_done):
 398             self.spr['XER'][XER_bits['CA']] = cy
 399
 400         print ("inputs", inputs)
 401         # 32 bit carry
 402         gts = []
 403         for x in inputs:
 404             print ("input", x, output)
 405             gt = (x[32:64] > output[32:64]) == SelectableInt(1, 1)
 406             gts.append(gt)
 407         cy32 = 1 if any(gts) else 0
 408         if not (2 & already_done):
 409             self.spr['XER'][XER_bits['CA32']] = cy32
 410
 411     def handle_overflow(self, inputs, outputs, div_overflow):
 412         inv_a = yield self.dec2.e.do.invert_a
 413         if inv_a:
 414             inputs[0] = ~inputs[0]
 415
 416         imm_ok = yield self.dec2.e.do.imm_data.ok
 417         if imm_ok:
 418             imm = yield self.dec2.e.do.imm_data.data
 419             inputs.append(SelectableInt(imm, 64))
 420         assert len(outputs) >= 1
 421         print ("handle_overflow", inputs, outputs, div_overflow)
 422         if len(inputs) < 2 and div_overflow is None:
 423             return
 424
 425         # div overflow is different: it's returned by the pseudo-code
 426         # because it's more complex than can be done by analysing the output
 427         if div_overflow is not None:
 428             ov, ov32 = div_overflow, div_overflow
 429         # arithmetic overflow can be done by analysing the input and output
 430         elif len(inputs) >= 2:
 431             output = outputs[0]
 432
 433             # OV (64-bit)
 434             input_sgn = [exts(x.value, x.bits) < 0 for x in inputs]
 435             output_sgn = exts(output.value, output.bits) < 0
 436             ov = 1 if input_sgn[0] == input_sgn[1] and \
 437                 output_sgn != input_sgn[0] else 0
 438
 439             # OV (32-bit)
 440             input32_sgn = [exts(x.value, 32) < 0 for x in inputs]
 441             output32_sgn = exts(output.value, 32) < 0
 442             ov32 = 1 if input32_sgn[0] == input32_sgn[1] and \
 443                 output32_sgn != input32_sgn[0] else 0
 444
 445         self.spr['XER'][XER_bits['OV']] = ov
 446         self.spr['XER'][XER_bits['OV32']] = ov32
 447         so = self.spr['XER'][XER_bits['SO']]
 448         so = so | ov
 449         self.spr['XER'][XER_bits['SO']] = so
 450
 451     def handle_comparison(self, outputs):
 452         out = outputs[0]
 453         print ("handle_comparison", out.bits, hex(out.value))
 454         # TODO - XXX *processor* in 32-bit mode
 455         # https://bugs.libre-soc.org/show_bug.cgi?id=424
 456         #if is_32bit:
 457         #    o32 = exts(out.value, 32)
 458         #    print ("handle_comparison exts 32 bit", hex(o32))
 459         out = exts(out.value, out.bits)
 460         print ("handle_comparison exts", hex(out))
 461         zero = SelectableInt(out == 0, 1)
 462         positive = SelectableInt(out > 0, 1)
 463         negative = SelectableInt(out < 0, 1)
 464         SO = self.spr['XER'][XER_bits['SO']]
 465         print ("handle_comparison SO", SO)
 466         cr_field = selectconcat(negative, positive, zero, SO)
 467         self.crl[0].eq(cr_field)
 468
 469     def set_pc(self, pc_val):
 470         self.namespace['NIA'] = SelectableInt(pc_val, 64)
 471         self.pc.update(self.namespace)
 472
 473     def setup_one(self):
 474         """set up one instruction
 475         """
 476         if self.respect_pc:
 477             pc = self.pc.CIA.value
 478         else:
 479             pc = self.fake_pc
 480         self._pc = pc
 481         ins = self.imem.ld(pc, 4, False, True)
 482         if ins is None:
 483             raise KeyError("no instruction at 0x%x" % pc)
 484         print("setup: 0x%x 0x%x %s" % (pc, ins & 0xffffffff, bin(ins)))
 485         print ("CIA NIA", self.respect_pc, self.pc.CIA.value, self.pc.NIA.value)
 486
 487         yield self.dec2.dec.raw_opcode_in.eq(ins & 0xffffffff)
 488         yield self.dec2.dec.bigendian.eq(self.bigendian)
 489
 490     def execute_one(self):
 491         """execute one instruction
 492         """
 493         # get the disassembly code for this instruction
 494         code = self.disassembly[self._pc]
 495         print("sim-execute", hex(self._pc), code)
 496         opname = code.split(' ')[0]
 497         yield from self.call(opname)
 498
 499         if not self.respect_pc:
 500             self.fake_pc += 4
 501         print ("execute one, CIA NIA", self.pc.CIA.value, self.pc.NIA.value)
 502
 503     def get_assembly_name(self):
 504         # TODO, asmregs is from the spec, e.g. add RT,RA,RB
 505         # see http://bugs.libre-riscv.org/show_bug.cgi?id=282
 506         asmcode = yield self.dec2.dec.op.asmcode
 507         print ("get assembly name asmcode", asmcode)
 508         asmop = insns.get(asmcode, None)
 509
 510         # sigh reconstruct the assembly instruction name
 511         ov_en = yield self.dec2.e.do.oe.oe
 512         ov_ok = yield self.dec2.e.do.oe.ok
 513         if ov_en & ov_ok:
 514             asmop += "."
 515         lk = yield self.dec2.e.do.lk
 516         if lk:
 517             asmop += "l"
 518         int_op = yield self.dec2.dec.op.internal_op
 519         print ("int_op", int_op)
 520         if int_op in [InternalOp.OP_B.value, InternalOp.OP_BC.value]:
 521             AA = yield self.dec2.dec.fields.FormI.AA[0:-1]
 522             print ("AA", AA)
 523             if AA:
 524                 asmop += "a"
 525         if int_op == InternalOp.OP_MFCR.value:
 526             dec_insn = yield self.dec2.e.do.insn
 527             if dec_insn & (1<<20) != 0: # sigh
 528                 asmop = 'mfocrf'
 529             else:
 530                 asmop = 'mfcr'
 531         # XXX TODO: for whatever weird reason this doesn't work
 532         # https://bugs.libre-soc.org/show_bug.cgi?id=390
 533         if int_op == InternalOp.OP_MTCRF.value:
 534             dec_insn = yield self.dec2.e.do.insn
 535             if dec_insn & (1<<20) != 0: # sigh
 536                 asmop = 'mtocrf'
 537             else:
 538                 asmop = 'mtcrf'
 539         return asmop
 540
 541     def call(self, name):
 542         name = name.strip() # remove spaces if not already done so
 543         if self.halted:
 544             print ("halted - not executing", name)
 545             return
 546
 547         # TODO, asmregs is from the spec, e.g. add RT,RA,RB
 548         # see http://bugs.libre-riscv.org/show_bug.cgi?id=282
 549         asmop = yield from self.get_assembly_name()
 550         print  ("call", name, asmop)
 551
 552         # check halted condition
 553         if name == 'attn':
 554             self.halted = True
 555             return
 556
 557         # check illegal instruction
 558         illegal = False
 559         if name not in ['mtcrf', 'mtocrf']:
 560             illegal = name != asmop
 561
 562         if illegal:
 563             print ("name %s != %s - calling ILLEGAL trap" % (name, asmop))
 564             self.TRAP(0x700, PI.ILLEG)
 565             self.namespace['NIA'] = self.trap_nia
 566             self.pc.update(self.namespace)
 567             return
 568
 569         info = self.instrs[name]
 570         yield from self.prep_namespace(info.form, info.op_fields)
 571
 572         # preserve order of register names
 573         input_names = create_args(list(info.read_regs) +
 574                                   list(info.uninit_regs))
 575         print(input_names)
 576
 577         # main registers (RT, RA ...)
 578         inputs = []
 579         for name in input_names:
 580             regnum = yield getattr(self.decoder, name)
 581             regname = "_" + name
 582             self.namespace[regname] = regnum
 583             print('reading reg %d' % regnum)
 584             inputs.append(self.gpr(regnum))
 585
 586         # "special" registers
 587         for special in info.special_regs:
 588             if special in special_sprs:
 589                 inputs.append(self.spr[special])
 590             else:
 591                 inputs.append(self.namespace[special])
 592
 593         # clear trap (trap) NIA
 594         self.trap_nia = None
 595
 596         print(inputs)
 597         results = info.func(self, *inputs)
 598         print(results)
 599
 600         # "inject" decorator takes namespace from function locals: we need to
 601         # overwrite NIA being overwritten (sigh)
 602         if self.trap_nia is not None:
 603             self.namespace['NIA'] = self.trap_nia
 604
 605         print ("after func", self.namespace['CIA'], self.namespace['NIA'])
 606
 607         # detect if CA/CA32 already in outputs (sra*, basically)
 608         already_done = 0
 609         if info.write_regs:
 610             output_names = create_args(info.write_regs)
 611             for name in output_names:
 612                 if name == 'CA':
 613                     already_done |= 1
 614                 if name == 'CA32':
 615                     already_done |= 2
 616
 617         print ("carry already done?", bin(already_done))
 618         carry_en = yield self.dec2.e.do.output_carry
 619         if carry_en:
 620             yield from self.handle_carry_(inputs, results, already_done)
 621
 622         # detect if overflow was in return result
 623         overflow = None
 624         if info.write_regs:
 625             for name, output in zip(output_names, results):
 626                 if name == 'overflow':
 627                     overflow = output
 628
 629         ov_en = yield self.dec2.e.do.oe.oe
 630         ov_ok = yield self.dec2.e.do.oe.ok
 631         print ("internal overflow", overflow)
 632         if ov_en & ov_ok:
 633             yield from self.handle_overflow(inputs, results, overflow)
 634
 635         rc_en = yield self.dec2.e.do.rc.data
 636         if rc_en:
 637             self.handle_comparison(results)
 638
 639         # any modified return results?
 640         if info.write_regs:
 641             for name, output in zip(output_names, results):
 642                 if name == 'overflow': # ignore, done already (above)
 643                     continue
 644                 if isinstance(output, int):
 645                     output = SelectableInt(output, 256)
 646                 if name in ['CA', 'CA32']:
 647                     if carry_en:
 648                         print ("writing %s to XER" % name, output)
 649                         self.spr['XER'][XER_bits[name]] = output.value
 650                     else:
 651                         print ("NOT writing %s to XER" % name, output)
 652                 elif name in info.special_regs:
 653                     print('writing special %s' % name, output, special_sprs)
 654                     if name in special_sprs:
 655                         self.spr[name] = output
 656                     else:
 657                         self.namespace[name].eq(output)
 658                     if name == 'MSR':
 659                         print ('msr written', hex(self.msr.value))
 660                 else:
 661                     regnum = yield getattr(self.decoder, name)
 662                     print('writing reg %d %s' % (regnum, str(output)))
 663                     if output.bits > 64:
 664                         output = SelectableInt(output.value, 64)
 665                     self.gpr[regnum] = output
 666
 667         print ("end of call", self.namespace['CIA'], self.namespace['NIA'])
 668         # UPDATE program counter
 669         self.pc.update(self.namespace)
 670
 671
 672 def inject():
 673     """Decorator factory.
 674
 675     this decorator will "inject" variables into the function's namespace,
 676     from the *dictionary* in self.namespace.  it therefore becomes possible
 677     to make it look like a whole stack of variables which would otherwise
 678     need "self." inserted in front of them (*and* for those variables to be
 679     added to the instance) "appear" in the function.
 680
 681     "self.namespace['SI']" for example becomes accessible as just "SI" but
 682     *only* inside the function, when decorated.
 683     """
 684     def variable_injector(func):
 685         @wraps(func)
 686         def decorator(*args, **kwargs):
 687             try:
 688                 func_globals = func.__globals__  # Python 2.6+
 689             except AttributeError:
 690                 func_globals = func.func_globals  # Earlier versions.
 691
 692             context = args[0].namespace # variables to be injected
 693             saved_values = func_globals.copy()  # Shallow copy of dict.
 694             func_globals.update(context)
 695             result = func(*args, **kwargs)
 696             print ("globals after", func_globals['CIA'], func_globals['NIA'])
 697             print ("args[0]", args[0].namespace['CIA'],
 698                               args[0].namespace['NIA'])
 699             args[0].namespace = func_globals
 700             #exec (func.__code__, func_globals)
 701
 702             #finally:
 703             #    func_globals = saved_values  # Undo changes.
 704
 705             return result
 706
 707         return decorator
 708
 709     return variable_injector
 710