src/openpower/decoder/power_regspec_map.py

   1 """regspec_decode
   2
   3 functions for the relationship between regspecs and Decode2Execute1Type
   4
   5 these functions encodes the understanding (relationship) between
   6 Regfiles, Computation Units, and the Power ISA Decoder (PowerDecoder2).
   7
   8 based on the regspec, which contains the register file name and register
   9 name, return a tuple of:
  10
  11 * how the decoder should determine whether the Function Unit needs
  12   access to a given Regport or not
  13 * which Regfile number on that port should be read to get that data
  14 * when it comes to writing: likewise, which Regfile num should be written
  15
  16 Note that some of the port numbering encoding is *unary*.  in the case
  17 of "Full Condition Register", it's a full 8-bit mask of read/write-enables.
  18 This actually matches directly with the XFX field in MTCR, and at
  19 some point that 8-bit mask from the instruction could actually be passed
  20 directly through to full_cr (TODO).
  21
  22 For the INT and CR numbering, these are expressed in binary in the
  23 instruction and need to be converted to unary (1<<read_reg1.data).
  24 Note however that XFX in MTCR is unary-masked!
  25
  26 XER regs are implicitly-encoded (hard-coded) based on whether the
  27 operation has carry or overflow.
  28
  29 FAST regfile is, again, implicitly encoded, back in PowerDecode2, based
  30 on the type of operation (see DecodeB for an example, where fast_out
  31 is set, then carried into read_fast2 in PowerDecode2).
  32
  33 The SPR regfile on the other hand is *binary*-encoded, and, furthermore,
  34 has to be "remapped" to internal SPR Enum indices (see SPRMap in PowerDecode2)
  35 see https://libre-so:.org/3d_gpu/architecture/regfile/ section on regspecs
  36 """
  37 from nmigen import Const, Signal
  38 from openpower.consts import XERRegsEnum, FastRegsEnum, StateRegsEnum
  39 from openpower.decoder.power_enums import CryIn
  40 from openpower.util import log
  41 from collections import namedtuple
  42
  43 RegDecodeInfo = namedtuple("RedDecodeInfo", ['okflag', 'regport', 'portlen'])
  44
  45 # XXX TODO: these portlen numbers *must* increase / adapt for SVP64.
  46
  47 def regspec_decode_read(m, e, regfile, name):
  48     """regspec_decode_read
  49     """
  50
  51     rd = None
  52
  53     # INT regfile
  54
  55     if regfile == 'INT':
  56         # Int register numbering is *unary* encoded
  57         if name == 'ra': # RA
  58             rd = RegDecodeInfo(e.read_reg1.ok, e.read_reg1.data, 5)
  59         if name == 'rb': # RB
  60             rd = RegDecodeInfo(e.read_reg2.ok, e.read_reg2.data, 5)
  61         if name == 'rc': # RS
  62             rd = RegDecodeInfo(e.read_reg3.ok, e.read_reg3.data, 5)
  63
  64     # CR regfile
  65
  66     if regfile == 'CR':
  67         # CRRegs register numbering is *unary* encoded
  68         if name == 'full_cr': # full CR (from FXM field)
  69             rd = RegDecodeInfo(e.do.read_cr_whole.ok,
  70                                e.do.read_cr_whole.data, 8)
  71         if name == 'cr_a': # CR A
  72             rd = RegDecodeInfo(e.read_cr1.ok, 1<<(7-e.read_cr1.data), 8)
  73         if name == 'cr_b': # CR B
  74             rd = RegDecodeInfo(e.read_cr2.ok, 1<<(7-e.read_cr2.data), 8)
  75         if name == 'cr_c': # CR C
  76             rd = RegDecodeInfo(e.read_cr3.ok, 1<<(7-e.read_cr3.data), 8)
  77
  78     # XER regfile
  79
  80     if regfile == 'XER':
  81         # XERRegsEnum register numbering is *unary* encoded
  82         SO = 1<<XERRegsEnum.SO
  83         CA = 1<<XERRegsEnum.CA
  84         OV = 1<<XERRegsEnum.OV
  85         if name == 'xer_so':
  86             # SO needs to be read for overflow *and* for creation
  87             # of CR0 and also for MFSPR
  88             rd = RegDecodeInfo(((e.do.oe.oe[0] & e.do.oe.ok) |
  89                                   (e.xer_in & SO == SO)|
  90                                   (e.do.rc.rc & e.do.rc.ok)), SO, 3)
  91         if name == 'xer_ov':
  92             rd = RegDecodeInfo(((e.do.oe.oe[0] & e.do.oe.ok) |
  93                                   (e.xer_in & CA == CA)), OV, 3)
  94         if name == 'xer_ca':
  95             rd = RegDecodeInfo(((e.do.input_carry == CryIn.CA.value) |
  96                                   (e.xer_in & OV == OV)), CA, 3)
  97
  98     # STATE regfile
  99
 100     if regfile == 'STATE':
 101         # STATE register numbering is *unary* encoded
 102         PC = 1<<StateRegsEnum.PC
 103         MSR = 1<<StateRegsEnum.MSR
 104         SVSTATE = 1<<StateRegsEnum.SVSTATE
 105         if name in ['cia', 'nia']:
 106             # TODO: detect read-conditions
 107             rd = RegDecodeInfo(Const(1), PC, 3)
 108         if name == 'msr':
 109             # TODO: detect read-conditions
 110             rd = RegDecodeInfo(Const(1), MSR, 3)
 111         if name == 'svstate':
 112             # TODO: detect read-conditions
 113             rd = RegDecodeInfo(Const(1), SVSTATE, 3)
 114
 115     # FAST regfile
 116
 117     if regfile == 'FAST':
 118         # FAST register numbering is *unary* encoded
 119         if name == 'fast1':
 120             rd = RegDecodeInfo(e.read_fast1.ok, e.read_fast1.data, 4)
 121         if name == 'fast2':
 122             rd = RegDecodeInfo(e.read_fast2.ok, e.read_fast2.data, 4)
 123         if name == 'fast3':
 124             rd = RegDecodeInfo(e.read_fast3.ok, e.read_fast3.data, 4)
 125
 126     # SPR regfile
 127
 128     if regfile == 'SPR':
 129         # SPR register numbering is *binary* encoded
 130         if name == 'spr1':
 131             rd = RegDecodeInfo(e.read_spr1.ok, e.read_spr1.data, 10)
 132
 133     assert rd is not None, "regspec not found %s %s" % (regfile, name)
 134
 135     rname="rd_decode_%s_%s" % (regfile, name)
 136     ok = Signal(name=rname+"_ok", reset_less=True)
 137     data = Signal(rd.portlen, name=rname+"_port", reset_less=True)
 138     m.d.comb += ok.eq(rd.okflag)
 139     m.d.comb += data.eq(rd.regport)
 140
 141     return RegDecodeInfo(ok, data, rd.portlen)
 142
 143
 144 def regspec_decode_write(m, e, regfile, name):
 145     """regspec_decode_write
 146     """
 147
 148     #log("regspec_decode_write", regfile, name, e.__class__.__name__)
 149     wr = None
 150
 151     # INT regfile
 152
 153     if regfile == 'INT':
 154         # Int register numbering is *unary* encoded
 155         if name == 'o': # RT
 156             wr = RegDecodeInfo(e.write_reg.ok, e.write_reg.data, 5)
 157         if name == 'o1': # RA (update mode: LD/ST EA)
 158             wr = RegDecodeInfo(e.write_ea.ok, e.write_ea.data, 5)
 159
 160     # CR regfile
 161
 162     if regfile == 'CR':
 163         # CRRegs register numbering is *unary* encoded
 164         # *sigh*.  numbering inverted on part-CRs.  because POWER.
 165         if name == 'full_cr': # full CR (from FXM field)
 166             wr = RegDecodeInfo(e.do.write_cr_whole.ok,
 167                                  e.do.write_cr_whole.data, 8)
 168         if name == 'cr_a': # CR A
 169             wr = RegDecodeInfo(e.write_cr.ok,
 170                                1<<(7-e.write_cr.data), 8)
 171
 172     # XER regfile
 173
 174     if regfile == 'XER':
 175         # XERRegsEnum register numbering is *unary* encoded
 176         SO = 1<<XERRegsEnum.SO
 177         CA = 1<<XERRegsEnum.CA
 178         OV = 1<<XERRegsEnum.OV
 179         if name == 'xer_so':
 180             wr = RegDecodeInfo(e.xer_out | (e.do.oe.oe[0] & e.do.oe.ok),
 181                                     SO, 3) # hmmm
 182         if name == 'xer_ov':
 183             wr = RegDecodeInfo(e.xer_out | (e.do.oe.oe[0] & e.do.oe.ok),
 184                                     OV, 3) # hmmm
 185         if name == 'xer_ca':
 186             wr = RegDecodeInfo(e.xer_out | (e.do.output_carry),
 187                                     CA, 3) # hmmm
 188
 189     # STATE regfile
 190
 191     if regfile == 'STATE':
 192         # STATE register numbering is *unary* encoded
 193         PC = 1<<StateRegsEnum.PC
 194         MSR = 1<<StateRegsEnum.MSR
 195         SVSTATE = 1<<StateRegsEnum.SVSTATE
 196         if name in ['cia', 'nia']:
 197             wr = RegDecodeInfo(None, PC, 3) # hmmm
 198         if name == 'msr':
 199             wr = RegDecodeInfo(None, MSR, 3) # hmmm
 200         if name == 'svstate':
 201             wr = RegDecodeInfo(None, SVSTATE, 3) # hmmm
 202
 203     # FAST regfile
 204
 205     if regfile == 'FAST':
 206         # FAST register numbering is *unary* encoded
 207         if name == 'fast1':
 208             wr = RegDecodeInfo(e.write_fast1.ok, e.write_fast1.data, 4)
 209         if name == 'fast2':
 210             wr = RegDecodeInfo(e.write_fast2.ok, e.write_fast2.data, 4)
 211         if name == 'fast3':
 212             wr = RegDecodeInfo(e.write_fast3.ok, e.write_fast3.data, 4)
 213
 214     # SPR regfile
 215
 216     if regfile == 'SPR':
 217         # SPR register numbering is *binary* encoded
 218         if name == 'spr1': # SPR1
 219             wr = RegDecodeInfo(e.write_spr.ok, e.write_spr.data, 10)
 220
 221     assert wr is not None, "regspec not found %s %s" % (regfile, name)
 222
 223     rname="wr_decode_%s_%s" % (regfile, name)
 224     if wr.okflag is not None:
 225         ok = Signal(name=rname+"_ok", reset_less=True)
 226         m.d.comb += ok.eq(wr.okflag)
 227     else:
 228         # XXX urrrr, really do have to deal with this some time
 229         ok = None
 230     data = Signal(wr.portlen, name=rname+"_port", reset_less=True)
 231     m.d.comb += data.eq(wr.regport)
 232
 233     return RegDecodeInfo(ok, data, wr.portlen)
 234
 235
 236 def regspec_decode(m, readmode, e, regfile, name):
 237     if readmode:
 238         return regspec_decode_read(m, e, regfile, name)
 239     return regspec_decode_write(m, e, regfile, name)
 240