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