220 lines
7.7 KiB
Python
220 lines
7.7 KiB
Python
# MIT License
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#
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# Copyright (c) 2023 Neil Webber
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# FUNCTIONALITY DISCLAIMER:
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# This is NOT meant to recreate the entire idea of a PDP-11 assembler.
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# Rather, it is meant as an ad-hoc assistance for creating and
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# debugging small test programs, of the sort that are found in pdptest.
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# As such, the methods here are written on an "as-needed" basis and
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# are focused around helping to create hand-constructed test code.
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#
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class PDP11InstructionAssembler:
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B6MODES = {}
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_rnames = [(f"R{_i}", _i) for _i in range(8)] + [("SP", 6), ("PC", 7)]
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for _rn, _i in _rnames:
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B6MODES[f"{_rn}"] = _i # register direct
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B6MODES[f"({_rn})"] = 0o10 | _i # register indirect
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B6MODES[f"({_rn})+"] = 0o20 | _i # autoincrement
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B6MODES[f"@({_rn})+"] = 0o30 | _i # autoincr deferred
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B6MODES[f"-({_rn})"] = 0o40 | _i # autodecrement
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B6MODES[f"@-({_rn})"] = 0o50 | _i # autodecr deferred
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del _i, _rn, _rnames
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def __init__(self):
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self.activeblock = None
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def startblock(self):
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self.activeblock = []
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def addtoblock(self, insts):
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if self.activeblock is not None:
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self.activeblock += insts
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return insts
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def endblock(self):
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insts, self.activeblock = self.activeblock, None
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return insts
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def immediate_value(self, s):
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base = 8
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if s[-1] == '.':
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base = 10
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s = s[:-1]
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val = int(s, base)
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# as a convenience, allow negative values and convert them
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if val < 0 and val >= -32768:
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val += 65536
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if val > 65535 or val < 0:
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raise ValueError(f"illegal value '{s}' = {val}")
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return val
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# this is a notational convenience to create a f'*${i].' string
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# for an operand that is an immediate deferred (i.e., numeric pointer)
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def ptr(self, i):
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return f'*${i}.'
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def operand_parser(self, operand_string, /):
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"""Parse operand_string ('r1', '-(sp)', '4(r5)', $177776, etc).
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Returns: sequence: [6 bit code, additional words ...]
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Raises ValueError for syntax errors.
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Literals that should become (pc)+ (mode 0o27) must start with '$'
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They will be octal unless they end with a '.'
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Literals that are pointers and should become @(pc)+ must
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start with '*$' and will be octal unless they end with a '.'
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An integer, i, can be passed in directly; it is becomes f"${i}."
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"""
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# NOTE: Not all forms implemented yet. See FUNCTIONALITY DISCLAIMER.
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# for convenience
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def valerr():
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return ValueError(f"cannot parse '{operand_string}'")
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# normalize the operand, upper case for strings, turn ints back
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# into their corresponding string (roundabout, but easiest)
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try:
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operand = operand_string.upper()
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except AttributeError:
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operand = f"${operand_string}."
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# bail out if spaces in middle, and remove spaces at ends
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s = operand.split()
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if len(s) > 1:
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raise valerr()
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operand = s[0]
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# operand now fully normalized: upper case, no spaces.
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# the first/easiest to try is to see if it is an immediate.
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# It will (must) start with either '$', or '*$' if so.
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try:
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if operand[0] == '$':
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return [0o27, self.immediate_value(operand[1:])]
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elif operand.startswith('*$'):
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return [0o37, self.immediate_value(operand[2:])]
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except ValueError:
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raise valerr() from None
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# wasn't immediate, see if it matches the precomputed modes
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try:
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return [self.B6MODES[operand]]
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except KeyError:
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pass
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# last chance: X(Rn) and @X(rn)
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# see if X(Rn) or @X(Rn)...
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if operand[0] == '@':
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mode = 0o70
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operand = operand[1:]
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else:
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mode = 0o60
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# for starters, it must contain one '(' so should split to 2
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s = operand.split('(')
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if len(s) != 2:
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raise valerr()
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idxval = self.immediate_value(s[0])
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# the back end of this, with the '(' put back on,
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# must end with ')' and must parse
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if s[1][-1] != ')':
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raise valerr()
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try:
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b6 = self.B6MODES['(' + s[1]]
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except KeyError:
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raise valerr() from None
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return [mode | (b6 & 0o07), idxval]
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def _2op(self, operation, src, dst):
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src6, *src_i = self.operand_parser(src)
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dst6, *dst_i = self.operand_parser(dst)
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return [ operation | src6 << 6 | dst6, *src_i, *dst_i ]
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def _1op(self, operation, dst):
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dst6, *dst_i = self.operand_parser(dst)
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return [ operation | dst6, *dst_i ]
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def mov(self, src, dst):
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return self.addtoblock(self._2op(0o010000, src, dst))
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def clr(self, dst):
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return self.addtoblock(self._1op(0o005000, dst))
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def inc(self, dst):
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return self.addtoblock(self._1op(0o005200, dst))
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def halt(self):
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return self.addtoblock([0])
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xxx = """
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0o012706, 0o20000, # put system stack at 8k and works down
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0o012737, 0o22222, 0o20000,
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0o012737, 0o33333, 0o20002,
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0o012737, 0o44444, 0o40000,
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# point both kernel seg 0 PARs to physical zero
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0o005037, cn.KISA0, # CLR $KISA0
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0o005037, cn.KDSA0, # CLR $KDSA0
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# kernel seg 7 D space PAR to I/O page (at 22-bit location)
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0o012737, 0o017760000 >> 6, cn.KDSA0 + (7 * 2),
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# user I seg 0 to 0o20000, user D seg 0 to 0o40000
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0o012737, 0o20000 >> 6, cn.UISA0,
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0o012737, 0o40000 >> 6, cn.UDSA0,
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# set the PDRs for segment zero
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0o012703, 0o077406, # MOV #77406,R3
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# 77406 = PDR<2:0> = ACF = 0o110 = read/write
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# PLF<14:8> =0o0774 = full length (128*64 bytes = 8K)
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0o010337, cn.KISD0, # MOV R3,KISD0 ...
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0o010337, cn.KDSD0,
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0o010337, cn.UISD0,
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0o010337, cn.UDSD0,
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# PDR for segment 7
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0o010337, cn.KDSD0 + (7 * 2),
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# set previous mode to USER, keeping current mode KERNEL, pri 7
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0o012737, (p.KERNEL << 14) | (p.USER << 12) | (7 << 5),
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self.ioaddr(p, p.PS_OFFS),
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# turn on 22-bit mode, unibus mapping, and I/D sep for k & u
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0o012737, 0o000065, self.ioaddr(p, p.mmu.MMR3_OFFS),
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# turn on relocation mode ... yeehah! (MMR0 known zero here)
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0o005237, self.ioaddr(p, p.mmu.MMR0_OFFS), # INC MMR0
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)
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"""
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