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Assembler working, more testing required

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This commit is contained in:
Ross Wilson 2016-01-30 16:46:49 +07:00
parent f82bb11491
commit eee4670bdc
2 changed files with 99 additions and 126 deletions
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215
pyasm/pyasm
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@ -15,15 +15,12 @@ If <outputfile> is not specified the output filename is the input
"""
"""
The basic structure of the assembler:
0. Read all file lines into memory
1. Create ORG blocks
2. Create CODE blocks from ORG blocks (assemble() function)
3. Check for undefined things in the symbol table
4. Allocate addresses to literal CODE blocks
5. Fix relative addresses in literal blocks
6. Backpatch all code blocks
7. Emit PTP data
This is a classic two pass assembler. The first pass reads all lines and keeps
track of the current location in memory (dot). Labels and EQU values are
remembered in the symbol table.
Pass 2 does pretty much the same thing as pass 1, except that now all labels
must be defined and code is generated.
"""
import sys
@ -47,22 +44,18 @@ ListFileHandle = None # open listing file
OutputFile = None
OutputFileHandle = None # open output file
# the current address during assembly
Dot = None
# the program start address (optional)
StartAddress = None
# the current address in assembled code (dot)
Address = None
# the symbol table(s)
# {<name>: <value>, ... }
SymTable = {}
# {<name>: <line#>, ... }
SymTableLine = {}
# the backpatch list
# [[symname, coderef, offset], [symname, coderef, offset], ... ]
BackpatchList = []
# current line number and the line
CurrentLine = None
CurrentLineNumber = None
@ -71,9 +64,9 @@ CurrentLineNumber = None
Undefined = None
# buffer for blocked code
BlockMaxSize = 255
BlockBuffer = bytearray()
BlockBufferStart = None
BlockMaxSize = 255 # maximum size of buffer (words)
BlockBuffer = bytearray() # actual buffered words
BlockBufferBase = None # base address of the block
######
# Mostly constant stuff
@ -88,17 +81,9 @@ PTPExtension = '.ptp'
# the output listing filename extension
ListFileExtension = '.lst'
# length of a word in bits
WordBits = 16
# number of bytes in the 'zero' leader
ZeroLeaderSize = 32
# address states, AYES = address required,
# ANO = address NOT required
# AOPT = address optional
(AYES, ANO, AOPT) = range(3)
######
# dict mapping opcode to generated word, address opts, address mask & indirect allowed
######
@ -111,6 +96,11 @@ def mask(n):
return value
# address states, AYES = address required,
# ANO = address NOT required
# AOPT = address optional
(AYES, ANO, AOPT) = range(3)
OpcodeData = {
'LAW': ( 0004000, AYES, mask(11), False),
'LWC': ( 0104000, AYES, mask(11), False),
@ -336,6 +326,7 @@ BlockLoader = [
def usage(msg=None):
"""Print usage and optional error message."""
if msg:
print('*'*60)
print(msg)
@ -361,7 +352,6 @@ def write_byte(byte):
Write only the low 8 bits of 'byte'.
"""
print('write_byte: byte=%04o' % byte)
OutputFileHandle.write(chr(byte & 0xFF))
def write_word(word):
@ -373,14 +363,13 @@ def write_word(word):
def write_start(address):
"""Write the start block."""
write_block() # emit any code accumulated
start_block(address)
write_block()
def write_leader():
def write_leader(size=ZeroLeaderSize):
"""Write the papertape leader."""
for _ in range(ZeroLeaderSize):
for _ in range(size):
write_byte(0)
def write_block_loader():
@ -396,11 +385,11 @@ def write_block_loader():
def start_block(addr):
"""Prepare next block to start at 'addr'"""
global BlockBuffer, BlockBufferStart
global BlockBuffer, BlockBufferBase
BlockBuffer = []
BlockBufferStart = addr
print('start_block: BlockBufferStart set to %s' % str(BlockBufferStart))
BlockBufferBase = addr
addr_str = ('%06o' % addr) if addr else str(addr)
def emit_word(word):
"""Put a word into the code block buffer.
@ -418,36 +407,25 @@ def emit_word(word):
def write_block():
"""Write the current code block and reset the buffer."""
global BlockBuffer, BlockBufferStart
global BlockBuffer, BlockBufferBase
code_block_size = len(BlockBuffer)
print('write_block: code_block_size=%d, BlockBufferStart=%s'
% (code_block_size, str(BlockBufferStart)))
if code_block_size == 0:
# block buffer is empty, do nothing
return
# emit the block size and load address
write_byte(code_block_size)
write_word(BlockBufferStart)
write_word(BlockBufferBase)
for word in BlockBuffer:
write_word(word)
# calculate checksum
checksum = 0
for word in BlockBuffer:
checksum += word
if checksum and ~WordMask:
++checksum
checksum &= WordMask
write_word(word)
# emit the block checksum
# calculate and write the checksum
checksum = sum(BlockBuffer) & WordMask
write_word(checksum)
# reset the code buffer
BlockBuffer = []
BlockBufferStart = None
start_block(None)
def write_list(code, addr, lnum, line):
"""Generate one line of listing file.
@ -458,8 +436,8 @@ def write_list(code, addr, lnum, line):
line complete text of the line of assembler
"""
code_str = '%06o' % code if code else ''
addr_str = '%04o' % addr if addr else ''
code_str = '%06o' % code if code is not None else ''
addr_str = '%04o' % addr if addr is not None else ''
lnum_str = '%04d:' % lnum if lnum else ''
line_str = '%s' % line if line else ''
@ -496,10 +474,10 @@ def eval_expr(expr):
Undefined = e.message
if 'is not defined' in e.message:
Undefined = e.message[len("name '"):-len("' is not defined")]
raise NameError("ORG pseudo-opcode expression has '%s' undefined" % Undefined)
# error("ORG pseudo-opcode expression has '%s' undefined" % Undefined)
raise NameError("ORG pseudo-opcode expression has an error")
# error("ORG pseudo-opcode expression has an error")
# raise NameError("ORG pseudo-opcode expression has '%s' undefined" % Undefined)
error("ORG pseudo-opcode expression has '%s' undefined" % Undefined)
# raise NameError("ORG pseudo-opcode expression has an error")
error("ORG pseudo-opcode expression has an error")
return result
@ -579,8 +557,15 @@ def pass_1(lines):
elif opcode == 'ASCII':
# ASCII string, pack two bytes/word, maybe zero byte fill at end
print('ASCII: addr=%' % str(addr))
# TODO worry if string has delimiting quotes
if not addr:
error("ASCII pseudo-op must have a data field")
if addr[0] not in "'\"":
error("ASCII pseudo-op must data field must be a delimited string")
delim = addr[0]
if addr[-1] != delim:
error("ASCII pseudo-op has a badly delimited delimited string")
addr = addr[1:-1]
ascii_len = len(addr)
ascii_words = ascii_len / 2
if ascii_len % 2:
@ -589,7 +574,6 @@ def pass_1(lines):
elif opcode == 'END':
# get the (optional) start address
StartAddress = None
if addr:
StartAddress = eval_expr(addr)
if StartAddress is None:
@ -634,9 +618,6 @@ def pass_2(lines):
# get line fields
(label, opcode, indirect, addr) = split_fields(line)
print('pass_2: label=%s, opcode=%s, indirect=%s, addr=%s'
% (str(label), str(opcode), str(indirect), str(addr)))
if opcode:
# we have an opcode, so code might be generated
if opcode == 'ORG':
@ -648,8 +629,8 @@ def pass_2(lines):
return False
write_block() # write any code accumulated so far
Dot = eval_expr(addr)
print('ORG: Dot set to %06o' % Dot)
start_block(Dot)
write_list(None, Dot, lnum, line)
elif opcode == 'EQU':
# no code, but we must have a label
@ -670,6 +651,8 @@ def pass_2(lines):
except KeyError:
error("EQU label '%s' wasn't defined in first pass!?"
% label)
write_list(None, value, lnum, line)
elif opcode == 'BSS':
# no code, but Dot moves
if not addr or eval_expr(addr) is None:
@ -689,38 +672,59 @@ def pass_2(lines):
write_block() # write any code accumulated so far
Dot += value
start_block(Dot)
write_list(None, None, lnum, line)
elif opcode == 'DATA':
# a single data word
if not addr or eval_expr(addr) is None:
error("BSS pseudo-op has bad value")
error("DATA pseudo-op has a bad value")
return False
value = eval_expr(addr)
if label:
try:
old_value = SymTable[label]
if value != old_value:
error("BSS value has changed, "
"was %06o, is now %06o"
% (old_value, value))
old_dot = SymTable[label]
if Dot != old_dot:
old_dot_str = ('%06o' % old_dot) if old_dot else str(old_dot)
dot_str = ('%06o' % Dot) if Dot else str(Dot)
error("DATA address has changed, "
"was %s, is now %s"
% (old_dot, dot_str))
except KeyError:
error("DATA label '%s' wasn't defined in first pass!?"
% label)
emit_word(value)
write_list(value, Dot, lnum, line)
Dot += 1
elif opcode == 'ASCII':
# 'addr' must exist and be a quote-delimited string
if not addr:
error("ASCII pseudo-op must have a data field")
if addr[0] not in "'\"":
error("ASCII pseudo-op must data field must be a delimited string")
delim = addr[0]
if addr[-1] != delim:
error("ASCII pseudo-op has a badly delimited delimited string")
addr = addr[1:-1]
len_addr = len(addr)
list_lnum = lnum
list_line = line
for i in range(0, len_addr-1, 2):
emit_word(ord((addr[i]) << 8) + ord(addr[i+1]))
word_value = (ord(addr[i]) << 8) + ord(addr[i+1])
emit_word(word_value)
write_list(word_value, Dot, list_lnum, list_line)
list_lnum = ''
list_line = ''
Dot += 1
if len_addr % 2:
emit_word((ord(addr[-1]) << 8))
word_value = (ord(addr[-1]) << 8)
emit_word(word_value)
write_list(word_value, Dot, list_lnum, list_line)
Dot += 1
elif opcode == 'END':
# get optional start address
StartAddress = None
if addr:
# we have the optional start address
start_address = eval_expr(addr)
@ -729,6 +733,7 @@ def pass_2(lines):
"was %06o but now %06o"
% (StartAddress, start_address))
StartAddress = start_address
write_list(None, start_address, lnum, line)
break # end of pass
else:
# actual machine instruction!
@ -741,7 +746,8 @@ def pass_2(lines):
error("Start address has different value in pass 2.\n"
"Was %06o, now %06o"
% (old_dot, Dot))
gen_code(lnum, line, label, label, opcode, indirect, addr)
code = gen_code(lnum, line, label, label, opcode, indirect, addr)
write_list(code, Dot, lnum, line)
Dot += 1
elif label:
@ -751,11 +757,13 @@ def pass_2(lines):
if dot != Dot:
error("Label '%s' has value %06o, was %06o in first pass"
% (label, Dot, dot))
write_list(None, Dot, lnum, line)
else:
write_list(None, None, lnum, line)
# write the final block of code and optional start address
write_block()
if StartAddress is not None:
print('write_start(%06o)' % StartAddress)
write_start(StartAddress)
write_leader()
@ -775,28 +783,21 @@ def gen_code(lnum, line, dot, label, opcode, indirect, addr):
addr address expression, uppercase
Puts the assembled word into the punch buffer.
Also returns the final assembled word.
"""
print('gen_code: lnum=%d, line=%s, label=%s, opcode=%s, addr=%s'
% (lnum, line, str(label), str(opcode), str(addr)))
# get instruction coding details
try:
(word, aok, mask, ind) = OpcodeData[opcode]
except KeyError:
error("%d: %s\nUnrecognized opcode '%s'" % (lnum, line, opcode))
print('word=%06o, aok=%d, mask=%06o, ind=%s' % (word, aok, mask, str(ind)))
value = eval_expr(addr)
if aok in (AYES, AOPT):
print('addr=%s, value=%s' % (str(addr), str(value)))
word_s = format(word, '016b')
mask_s = format(mask, '016b') if mask else ''
value_s = format(value, '016b') if value else ''
print('word=%s, mask=%s, ind=%s, value=%s' % (word_s, mask_s, str(ind), value_s))
# check if 'addr' has overflowed. add in if OK
if value:
if value & mask != value:
@ -811,12 +812,14 @@ def gen_code(lnum, line, dot, label, opcode, indirect, addr):
emit_word(word)
def define_label(label, address, lnum):
return word
def define_label(label, value, lnum):
"""Put 'label' into the symbol tables.
label the label to define
address dot value for he label
lnum ine number the label is defined on
label the label to define
value dot value for the label
lnum line number the label is defined on
It's an error if the label is already defined.
"""
@ -825,37 +828,9 @@ def define_label(label, address, lnum):
prev_lnum = SymTableLine[label]
error("Label '%s' defined twice, at lines %d and %d."
% (label, prev_lnum, lnum))
SymTable[label] = address
SymTable[label] = value
SymTableLine[label] = lnum
def gen_ascii(string, address, lnum, line):
"""Generate data words for ASCII string.
string the string to generate data for
address addres of first generated word (dot)
lnum line number of code
line actual line of code
Returns the updated 'dot' value.
"""
# ensure even number of bytes in string
if len(string) % 2:
string += '\0' # append zero byte as padding
# get 2 bytes at a time and generate words
while string:
ch1 = string[0]
ch2 = string[1]
string = string[2:]
value = (ord(ch1) << 8) + ord(ch2)
write_list(value, address, lnum, line)
address += 1
lnum = None
line = None
return address
def next_symbol(line):
"""Return next symbol and line remainder."""
@ -936,12 +911,9 @@ def assemble_file():
with open(AsmFile, 'rb') as fd:
asm_lines = fd.readlines()
asm_lines = [line.rstrip() for line in asm_lines]
print('asm_lines=\n%s' % '\n'.join(asm_lines))
if pass_1(asm_lines):
print('After pass_1(), SymTable=%s' % str(SymTable))
pass_2(asm_lines)
print('After pass_2(), SymTable=%s' % str(SymTable))
def main():
"""The assembler."""
@ -985,17 +957,14 @@ def main():
if OutputFile is None:
(path, ext) = os.path.splitext(AsmFile)
OutputFile = path + PTPExtension
OutputFileHandle = open(OutputFile, 'wb')
if ListFile is None:
(path, ext) = os.path.splitext(AsmFile)
ListFile = path + ListFileExtension
ListFileHandle = open(ListFile, 'wb')
print('ListFile=%s, OutputFile=%s, AsmFile=%s'
% (str(ListFile), str(OutputFile), str(AsmFile)))
assemble_file()
with open(OutputFile, 'wb') as OutputFileHandle:
assemble_file()
if __name__ == '__main__':
main()

10
pyasm/test2.asm
View File

@ -2,16 +2,20 @@
org 0100
start law 10
lac start2 ; comment
lac *start2 ; comment
lac .-2
hlt
fred equ 2 ; EQU
org . + 010
org 01100
start2
lac start + 2 ; comment
string data 'ascii'
offset data start - 3
ascii 'xxxxxxxx'
ascii 'xxxxxxx'
ascii "xx"
ascii 'x'
end hlt
end start