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
  23 insns_dir = "./riscv/insns"
  24 def list_insns():
  25     res = []
  26     for fname in os.listdir(insns_dir):
  27         if not fname.endswith(".h"):
  28             continue
  29         insn = fname[:-2]
  30         res.append((os.path.join(insns_dir, fname), insn))
  31     return res
  32
  33 patterns = ['WRITE_RD', 'RS1', 'RS2', 'RS3',
  34             'WRITE_FRD', 'FRS1', 'FRS2', 'FRS3']
  35
  36 def find_registers(fname):
  37     res = []
  38     with open(fname) as f:
  39         f = f.read()
  40         for pattern in patterns:
  41             x = f.find(pattern)
  42             if x == -1:
  43                 continue
  44             if pattern.startswith('R') and x != 0 and f[x-1] == 'F':
  45                 # botch-job/hack: RS1 also matches against FRS1 (etc.)
  46                 # check letter before match: if "F", skip it.
  47                 continue
  48             p = pattern
  49             if p.startswith('WRITE_'):
  50                 p = p[6:]
  51             res.append('#define USING_REG_%s' % p)
  52     if len(res) == 0:
  53         return "0"
  54     return '\n'.join(res)
  55
  56 if __name__ == '__main__':
  57     files = list_insns()
  58     for (fname, insn) in files:
  59         regsname = "regs_%s.h" % insn
  60         regsname = os.path.join(insns_dir, regsname)
  61         with open(regsname, "w") as f:
  62             f.write(find_registers(fname))