id_regs.py

   1 #!/usr/bin/env python
   2 # Copyright (C) 2018 Luke Kenneth Casson Leighton <lkcl@lkcl.net>
   3
   4 """ identify registers used in riscv/insns/*.h and create code
   5     that can be used in spike at runtime
   6
   7     the design of spike assumes that once an opcode is identified,
   8     the role of decoding the instruction is implicitly rolled into
   9     and included inside the function that emulates that opcode.
  10
  11     however there may be circumstances where the behaviour of an
  12     instruction has to change depending on "tags" associated with
  13     the registers (security extensions, simple-v extension).
  14
  15     therefore this code walks the instruction implementations
  16     in riscv/insns/*.h looking for register usage patterns.
  17     the resultant table can be used *prior* to the emulation,
  18     without having to manually maintain such a table.
  19 """
  20
  21 import os
  22 import sys
  23
  24 insns_dir = "./riscv/insns"
  25 def list_insns():
  26     if len(sys.argv) == 2:
  27         fullfname = sys.argv[1]
  28         pth, fname = os.path.split(fullfname)
  29         insn = fname[:-2]
  30         return [(fullfname, insn)]
  31
  32     res = []
  33     for fname in os.listdir(insns_dir):
  34         if not fname.endswith(".h"):
  35             continue
  36         if fname.startswith("regs_"):
  37             continue
  38         insn = fname[:-2]
  39         res.append((os.path.join(insns_dir, fname), insn))
  40     return res
  41
  42 cintpatterns = [ 'WRITE_RVC_RS1S', 'WRITE_RVC_RS2S',
  43                  'RVC_RS1', 'RVC_RS2', 'RVC_RS1S', 'RVC_RS2S', ]
  44 cfloatpatterns = [ 'WRITE_RVC_FRS2S', 'RVC_FRS2 ', 'RVC_FRS2S ']
  45 intpatterns   = ['WRITE_RD' , 'RS1', 'RS2', 'RS3']
  46 floatpatterns = ['WRITE_FRD', 'FRS1', 'FRS2', 'FRS3']
  47 patterns = intpatterns + floatpatterns
  48 patterns += cintpatterns
  49 patterns += cfloatpatterns
  50
  51 allfloats = floatpatterns + cfloatpatterns
  52 floatmask = (1<<len(allfloats)-1)
  53 allints = intpatterns + cintpatterns[2:]
  54
  55 skip = '#define USING_NOREGS\n' \
  56        '#define REGS_PATTERN 0x0\n'
  57 def find_registers(fname):
  58     # HACK! macro-skipping csr* instructions too painful
  59     if 'csr' in fname:
  60         return skip
  61     res = []
  62     isintfloat = 0x0 + floatmask << len(allints)
  63     with open(fname) as f:
  64         f = f.read()
  65         for pattern in patterns:
  66             x = f.find(pattern)
  67             if x == -1:
  68                 continue
  69             if pattern.startswith('R') and x != 0 and f[x-1] == 'F':
  70                 # botch-job/hack: RS1 also matches against FRS1 (etc.)
  71                 # check letter before match: if "F", skip it.
  72                 continue
  73             if pattern.startswith('R') and x != 0 and f[x-1] == '_':
  74                 # RS1 also matches against RVC_RS1 (etc.)
  75                 # check letter before match: if "_", skip it.
  76                 continue
  77             if pattern.startswith('FR') and x != 0 and f[x-1] == '_':
  78                 # RS1 also matches against RVC_FRS1 (etc.)
  79                 # check letter before match: if "_", skip it.
  80                 continue
  81             if 'RVC_' in pattern and f[x+len(pattern)] == 'S':
  82                 # RVC_RS2S also matches against RVC_RS2 (etc.)
  83                 # check letter at end of match: if "S", skip it.
  84                 continue
  85             p = pattern
  86             if p.startswith('WRITE_'):
  87                 p = p[6:]
  88             if pattern in allints:
  89                 idx = allints.index(pattern)
  90                 isintfloat += 1 << idx
  91             if pattern in allfloats:
  92                 idx = allfloats.index(pattern)
  93                 isintfloat &= ~(1 << (idx+len(allints)))
  94             res.append('#define USING_REG_%s' % p)
  95     if not res:
  96         return skip
  97     res.append('#define REGS_PATTERN 0x%x' % isintfloat)
  98     return '\n'.join(res)
  99
 100 if __name__ == '__main__':
 101     files = list_insns()
 102     for (fname, insn) in files:
 103         regsname = "regs_%s.h" % insn
 104         regsname = os.path.join(insns_dir, regsname)
 105         with open(regsname, "w") as f:
 106             f.write(find_registers(fname))