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
 249         self.respect_pc = respect_pc
 250         if initial_sprs is None:
 251             initial_sprs = {}
 252         if initial_mem is None:
 253             initial_mem = {}
 254         if initial_insns is None:
 255             initial_insns = {}
 256             assert self.respect_pc == False, "instructions required to honor pc"
 257
 258         print ("ISACaller insns", respect_pc, initial_insns, disassembly)
 259
 260         # "fake program counter" mode (for unit testing)
 261         self.fake_pc = 0
 262         if not respect_pc:
 263             if isinstance(initial_mem, tuple):
 264                 self.fake_pc = initial_mem[0]
 265
 266         # disassembly: we need this for now (not given from the decoder)
 267         self.disassembly = {}
 268         if disassembly:
 269             for i, code in enumerate(disassembly):
 270                 self.disassembly[i*4 + self.fake_pc] = code
 271
 272         # set up registers, instruction memory, data memory, PC, SPRs, MSR
 273         self.gpr = GPR(decoder2, regfile)
 274         self.mem = Mem(row_bytes=8, initial_mem=initial_mem)
 275         self.imem = Mem(row_bytes=4, initial_mem=initial_insns)
 276         self.pc = PC()
 277         self.spr = SPR(decoder2, initial_sprs)
 278         self.msr = SelectableInt(initial_msr, 64) # underlying reg
 279
 280         # TODO, needed here:
 281         # FPR (same as GPR except for FP nums)
 282         # 4.2.2 p124 FPSCR (definitely "separate" - not in SPR)
 283         #            note that mffs, mcrfs, mtfsf "manage" this FPSCR
 284         # 2.3.1 CR (and sub-fields CR0..CR6 - CR0 SO comes from XER.SO)
 285         #         note that mfocrf, mfcr, mtcr, mtocrf, mcrxrx "manage" CRs
 286         #         -- Done
 287         # 2.3.2 LR   (actually SPR #8) -- Done
 288         # 2.3.3 CTR  (actually SPR #9) -- Done
 289         # 2.3.4 TAR  (actually SPR #815)
 290         # 3.2.2 p45 XER  (actually SPR #1) -- Done
 291         # 3.2.3 p46 p232 VRSAVE (actually SPR #256)
 292
 293         # create CR then allow portions of it to be "selectable" (below)
 294         self._cr = SelectableInt(initial_cr, 64) # underlying reg
 295         self.cr = FieldSelectableInt(self._cr, list(range(32,64)))
 296
 297         # "undefined", just set to variable-bit-width int (use exts "max")
 298         self.undefined = SelectableInt(0, 256) # TODO, not hard-code 256!
 299
 300         self.namespace = {}
 301         self.namespace.update(self.spr)
 302         self.namespace.update({'GPR': self.gpr,
 303                           'MEM': self.mem,
 304                           'SPR': self.spr,
 305                           'memassign': self.memassign,
 306                           'NIA': self.pc.NIA,
 307                           'CIA': self.pc.CIA,
 308                           'CR': self.cr,
 309                           'MSR': self.msr,
 310                           'undefined': self.undefined,
 311                           'mode_is_64bit': True,
 312                           'SO': XER_bits['SO']
 313                           })
 314
 315
 316         # field-selectable versions of Condition Register TODO check bitranges?
 317         self.crl = []
 318         for i in range(8):
 319             bits = tuple(range(i*4, (i+1)*4))# errr... maybe?
 320             _cr = FieldSelectableInt(self.cr, bits)
 321             self.crl.append(_cr)
 322             self.namespace["CR%d" % i] = _cr
 323
 324         self.decoder = decoder2.dec
 325         self.dec2 = decoder2
 326
 327     def TRAP(self, trap_addr=0x700):
 328         print ("TRAP: TODO")
 329         # store CIA(+4?) in SRR0, set NIA to 0x700
 330         # store MSR in SRR1, set MSR to um errr something, have to check spec
 331         self.spr['SRR0'] = self.pc.CIA
 332         self.spr['SRR1'] = self.namespace['MSR']
 333         self.set_pc(trap_addr)
 334         self.namespace['MSR'][63-PI.TRAP] = 1 # bit 45, "this is a trap"
 335
 336     def memassign(self, ea, sz, val):
 337         self.mem.memassign(ea, sz, val)
 338
 339     def prep_namespace(self, formname, op_fields):
 340         # TODO: get field names from form in decoder*1* (not decoder2)
 341         # decoder2 is hand-created, and decoder1.sigform is auto-generated
 342         # from spec
 343         # then "yield" fields only from op_fields rather than hard-coded
 344         # list, here.
 345         fields = self.decoder.sigforms[formname]
 346         for name in op_fields:
 347             if name == 'spr':
 348                 sig = getattr(fields, name.upper())
 349             else:
 350                 sig = getattr(fields, name)
 351             val = yield sig
 352             if name in ['BF', 'BFA']:
 353                 self.namespace[name] = val
 354             else:
 355                 self.namespace[name] = SelectableInt(val, sig.width)
 356
 357         self.namespace['XER'] = self.spr['XER']
 358         self.namespace['CA'] = self.spr['XER'][XER_bits['CA']].value
 359         self.namespace['CA32'] = self.spr['XER'][XER_bits['CA32']].value
 360
 361     def handle_carry_(self, inputs, outputs, already_done):
 362         inv_a = yield self.dec2.e.invert_a
 363         if inv_a:
 364             inputs[0] = ~inputs[0]
 365
 366         imm_ok = yield self.dec2.e.imm_data.ok
 367         if imm_ok:
 368             imm = yield self.dec2.e.imm_data.data
 369             inputs.append(SelectableInt(imm, 64))
 370         assert len(outputs) >= 1
 371         print ("outputs", repr(outputs))
 372         if isinstance(outputs, list) or isinstance(outputs, tuple):
 373             output = outputs[0]
 374         else:
 375             output = outputs
 376         gts = []
 377         for x in inputs:
 378             print ("gt input", x, output)
 379             gt = (x > output)
 380             gts.append(gt)
 381         print(gts)
 382         cy = 1 if any(gts) else 0
 383         if not (1 & already_done):
 384             self.spr['XER'][XER_bits['CA']] = cy
 385
 386         print ("inputs", inputs)
 387         # 32 bit carry
 388         gts = []
 389         for x in inputs:
 390             print ("input", x, output)
 391             gt = (x[32:64] > output[32:64]) == SelectableInt(1, 1)
 392             gts.append(gt)
 393         cy32 = 1 if any(gts) else 0
 394         if not (2 & already_done):
 395             self.spr['XER'][XER_bits['CA32']] = cy32
 396
 397     def handle_overflow(self, inputs, outputs, div_overflow):
 398         inv_a = yield self.dec2.e.invert_a
 399         if inv_a:
 400             inputs[0] = ~inputs[0]
 401
 402         imm_ok = yield self.dec2.e.imm_data.ok
 403         if imm_ok:
 404             imm = yield self.dec2.e.imm_data.data
 405             inputs.append(SelectableInt(imm, 64))
 406         assert len(outputs) >= 1
 407         print ("handle_overflow", inputs, outputs, div_overflow)
 408         if len(inputs) < 2 and div_overflow != 1:
 409             return
 410
 411         # div overflow is different: it's returned by the pseudo-code
 412         # because it's more complex than can be done by analysing the output
 413         if div_overflow == 1:
 414             ov, ov32 = 1, 1
 415         # arithmetic overflow can be done by analysing the input and output
 416         elif len(inputs) >= 2:
 417             output = outputs[0]
 418
 419             # OV (64-bit)
 420             input_sgn = [exts(x.value, x.bits) < 0 for x in inputs]
 421             output_sgn = exts(output.value, output.bits) < 0
 422             ov = 1 if input_sgn[0] == input_sgn[1] and \
 423                 output_sgn != input_sgn[0] else 0
 424
 425             # OV (32-bit)
 426             input32_sgn = [exts(x.value, 32) < 0 for x in inputs]
 427             output32_sgn = exts(output.value, 32) < 0
 428             ov32 = 1 if input32_sgn[0] == input32_sgn[1] and \
 429                 output32_sgn != input32_sgn[0] else 0
 430
 431         self.spr['XER'][XER_bits['OV']] = ov
 432         self.spr['XER'][XER_bits['OV32']] = ov32
 433         so = self.spr['XER'][XER_bits['SO']]
 434         so = so | ov
 435         self.spr['XER'][XER_bits['SO']] = so
 436
 437     def handle_comparison(self, outputs):
 438         out = outputs[0]
 439         out = exts(out.value, out.bits)
 440         zero = SelectableInt(out == 0, 1)
 441         positive = SelectableInt(out > 0, 1)
 442         negative = SelectableInt(out < 0, 1)
 443         SO = self.spr['XER'][XER_bits['SO']]
 444         cr_field = selectconcat(negative, positive, zero, SO)
 445         self.crl[0].eq(cr_field)
 446
 447     def set_pc(self, pc_val):
 448         self.namespace['NIA'] = SelectableInt(pc_val, 64)
 449         self.pc.update(self.namespace)
 450
 451     def setup_one(self):
 452         """set up one instruction
 453         """
 454         if self.respect_pc:
 455             pc = self.pc.CIA.value
 456         else:
 457             pc = self.fake_pc
 458         self._pc = pc
 459         ins = self.imem.ld(pc, 4, False, True)
 460         if ins is None:
 461             raise KeyError("no instruction at 0x%x" % pc)
 462         print("setup: 0x%x 0x%x %s" % (pc, ins & 0xffffffff, bin(ins)))
 463         print ("NIA, CIA", self.pc.CIA.value, self.pc.NIA.value)
 464
 465         yield self.dec2.dec.raw_opcode_in.eq(ins & 0xffffffff)
 466         yield self.dec2.dec.bigendian.eq(0)  # little / big?
 467
 468     def execute_one(self):
 469         """execute one instruction
 470         """
 471         # get the disassembly code for this instruction
 472         code = self.disassembly[self._pc]
 473         print("sim-execute", hex(self._pc), code)
 474         opname = code.split(' ')[0]
 475         yield from self.call(opname)
 476
 477         if not self.respect_pc:
 478             self.fake_pc += 4
 479         print ("NIA, CIA", self.pc.CIA.value, self.pc.NIA.value)
 480
 481     def get_assembly_name(self):
 482         # TODO, asmregs is from the spec, e.g. add RT,RA,RB
 483         # see http://bugs.libre-riscv.org/show_bug.cgi?id=282
 484         asmcode = yield self.dec2.dec.op.asmcode
 485         asmop = insns.get(asmcode, None)
 486
 487         # sigh reconstruct the assembly instruction name
 488         ov_en = yield self.dec2.e.oe.oe
 489         ov_ok = yield self.dec2.e.oe.ok
 490         if ov_en & ov_ok:
 491             asmop += "."
 492         lk = yield self.dec2.e.lk
 493         if lk:
 494             asmop += "l"
 495         int_op = yield self.dec2.dec.op.internal_op
 496         print ("int_op", int_op)
 497         if int_op in [InternalOp.OP_B.value, InternalOp.OP_BC.value]:
 498             AA = yield self.dec2.dec.fields.FormI.AA[0:-1]
 499             print ("AA", AA)
 500             if AA:
 501                 asmop += "a"
 502         if int_op == InternalOp.OP_MFCR.value:
 503             dec_insn = yield self.dec2.e.insn
 504             if dec_insn & (1<<20) != 0: # sigh
 505                 asmop = 'mfocrf'
 506             else:
 507                 asmop = 'mfcr'
 508         # XXX TODO: for whatever weird reason this doesn't work
 509         # https://bugs.libre-soc.org/show_bug.cgi?id=390
 510         if int_op == InternalOp.OP_MTCRF.value:
 511             dec_insn = yield self.dec2.e.insn
 512             if dec_insn & (1<<20) != 0: # sigh
 513                 asmop = 'mtocrf'
 514             else:
 515                 asmop = 'mtcrf'
 516         return asmop
 517
 518     def call(self, name):
 519         # TODO, asmregs is from the spec, e.g. add RT,RA,RB
 520         # see http://bugs.libre-riscv.org/show_bug.cgi?id=282
 521         asmop = yield from self.get_assembly_name()
 522         print  ("call", name, asmop)
 523         if name not in ['mtcrf', 'mtocrf']:
 524             assert name == asmop, "name %s != %s" % (name, asmop)
 525
 526         info = self.instrs[name]
 527         yield from self.prep_namespace(info.form, info.op_fields)
 528
 529         # preserve order of register names
 530         input_names = create_args(list(info.read_regs) + list(info.uninit_regs))
 531         print(input_names)
 532
 533         # main registers (RT, RA ...)
 534         inputs = []
 535         for name in input_names:
 536             regnum = yield getattr(self.decoder, name)
 537             regname = "_" + name
 538             self.namespace[regname] = regnum
 539             print('reading reg %d' % regnum)
 540             inputs.append(self.gpr(regnum))
 541
 542         # "special" registers
 543         for special in info.special_regs:
 544             if special in special_sprs:
 545                 inputs.append(self.spr[special])
 546             else:
 547                 inputs.append(self.namespace[special])
 548
 549         print(inputs)
 550         results = info.func(self, *inputs)
 551         print(results)
 552
 553         # detect if CA/CA32 already in outputs (sra*, basically)
 554         already_done = 0
 555         if info.write_regs:
 556             output_names = create_args(info.write_regs)
 557             for name in output_names:
 558                 if name == 'CA':
 559                     already_done |= 1
 560                 if name == 'CA32':
 561                     already_done |= 2
 562
 563         print ("carry already done?", bin(already_done))
 564         carry_en = yield self.dec2.e.output_carry
 565         if carry_en:
 566             yield from self.handle_carry_(inputs, results, already_done)
 567
 568         # detect if overflow was in return result
 569         overflow = None
 570         if info.write_regs:
 571             for name, output in zip(output_names, results):
 572                 if name == 'overflow':
 573                     overflow = output
 574
 575         ov_en = yield self.dec2.e.oe.oe
 576         ov_ok = yield self.dec2.e.oe.ok
 577         print ("internal overflow", overflow)
 578         if ov_en & ov_ok:
 579             yield from self.handle_overflow(inputs, results, overflow)
 580
 581         rc_en = yield self.dec2.e.rc.data
 582         if rc_en:
 583             self.handle_comparison(results)
 584
 585         # any modified return results?
 586         if info.write_regs:
 587             for name, output in zip(output_names, results):
 588                 if name == 'overflow': # ignore, done already (above)
 589                     continue
 590                 if isinstance(output, int):
 591                     output = SelectableInt(output, 256)
 592                 if name in ['CA', 'CA32']:
 593                     if carry_en:
 594                         print ("writing %s to XER" % name, output)
 595                         self.spr['XER'][XER_bits[name]] = output.value
 596                     else:
 597                         print ("NOT writing %s to XER" % name, output)
 598                 elif name in info.special_regs:
 599                     print('writing special %s' % name, output, special_sprs)
 600                     if name in special_sprs:
 601                         self.spr[name] = output
 602                     else:
 603                         self.namespace[name].eq(output)
 604                     if name == 'MSR':
 605                         print ('msr written', hex(self.msr.value))
 606                 else:
 607                     regnum = yield getattr(self.decoder, name)
 608                     print('writing reg %d %s' % (regnum, str(output)))
 609                     if output.bits > 64:
 610                         output = SelectableInt(output.value, 64)
 611                     self.gpr[regnum] = output
 612
 613         # update program counter
 614         self.pc.update(self.namespace)
 615
 616
 617 def inject():
 618     """Decorator factory.
 619
 620     this decorator will "inject" variables into the function's namespace,
 621     from the *dictionary* in self.namespace.  it therefore becomes possible
 622     to make it look like a whole stack of variables which would otherwise
 623     need "self." inserted in front of them (*and* for those variables to be
 624     added to the instance) "appear" in the function.
 625
 626     "self.namespace['SI']" for example becomes accessible as just "SI" but
 627     *only* inside the function, when decorated.
 628     """
 629     def variable_injector(func):
 630         @wraps(func)
 631         def decorator(*args, **kwargs):
 632             try:
 633                 func_globals = func.__globals__  # Python 2.6+
 634             except AttributeError:
 635                 func_globals = func.func_globals  # Earlier versions.
 636
 637             context = args[0].namespace # variables to be injected
 638             saved_values = func_globals.copy()  # Shallow copy of dict.
 639             func_globals.update(context)
 640             result = func(*args, **kwargs)
 641             args[0].namespace = func_globals
 642             #exec (func.__code__, func_globals)
 643
 644             #finally:
 645             #    func_globals = saved_values  # Undo changes.
 646
 647             return result
 648
 649         return decorator
 650
 651     return variable_injector
 652