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avoid needless saving of A register
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Irmen de Jong
parent
afaf8e9beb
commit
a0a561cfb6
@ -6,7 +6,6 @@ Written by Irmen de Jong (irmen@razorvine.net)
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License: GNU GPL 3.0, see LICENSE
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"""
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import sys
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import io
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import math
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import datetime
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@ -435,9 +434,18 @@ class CodeGenerator:
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raise NotImplementedError("decr by > 1") # XXX
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def generate_call(self, stmt: ParseResult.CallStmt) -> None:
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def generate_param_assignments():
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def generate_param_assignments() -> None:
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for assign_stmt in stmt.desugared_call_arguments:
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self.generate_assignment(assign_stmt)
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def params_load_a() -> bool:
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for assign_stmt in stmt.desugared_call_arguments:
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for lv in assign_stmt.leftvalues:
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if isinstance(lv, ParseResult.RegisterValue):
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if lv.register == 'A':
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return True
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return False
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if stmt.target.name:
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symblock, targetdef = self.cur_block.lookup(stmt.target.name)
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else:
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@ -456,7 +464,7 @@ class CodeGenerator:
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if targetdef.clobbered_registers:
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if stmt.preserve_regs:
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clobbered = targetdef.clobbered_registers
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with self.preserving_registers(clobbered):
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with self.preserving_registers(clobbered, loads_a_within=params_load_a()):
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generate_param_assignments()
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self.p("\t\tjsr " + targetstr)
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return
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@ -484,7 +492,7 @@ class CodeGenerator:
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self.p("\t\tjmp ({:s})".format(targetstr))
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else:
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preserve_regs = {'A', 'X', 'Y'} if stmt.preserve_regs else set()
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with self.preserving_registers(preserve_regs):
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with self.preserving_registers(preserve_regs, loads_a_within=params_load_a()):
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generate_param_assignments()
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if targetstr in REGISTER_WORDS:
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if stmt.preserve_regs:
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@ -526,7 +534,7 @@ class CodeGenerator:
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self.p("\t\tjmp " + targetstr)
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else:
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preserve_regs = {'A', 'X', 'Y'} if stmt.preserve_regs else set()
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with self.preserving_registers(preserve_regs):
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with self.preserving_registers(preserve_regs, loads_a_within=params_load_a()):
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generate_param_assignments()
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self.p("\t\tjsr " + targetstr)
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@ -635,7 +643,7 @@ class CodeGenerator:
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elif lv.datatype == DataType.WORD:
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if len(r_register) == 1:
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self.p("\t\tst{:s} {}".format(r_register.lower(), lv_string)) # lsb
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with self.preserving_registers({'A'}):
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with self.preserving_registers({'A'}, loads_a_within=True):
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self.p("\t\tlda #0")
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self.p("\t\tsta {:s}+1".format(lv_string)) # msb
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else:
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@ -657,7 +665,7 @@ class CodeGenerator:
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self.p("\t\tpha\n\t\ttxa\n\t\ttay\n\t\tpla") # X->Y (so we have AY now)
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do_rom_calls()
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else: # XY
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with self.preserving_registers({'A', 'X', 'Y'}):
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with self.preserving_registers({'A', 'X', 'Y'}, loads_a_within=True):
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self.p("\t\ttxa") # X->A (so we have AY now)
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do_rom_calls()
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elif r_register in "AXY":
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@ -673,7 +681,7 @@ class CodeGenerator:
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self.p("\t\ttay")
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do_rom_calls()
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elif r_register == "X":
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with self.preserving_registers({'A', 'X', 'Y'}):
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with self.preserving_registers({'A', 'X', 'Y'}, loads_a_within=True):
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self.p("\t\ttxa")
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self.p("\t\ttay")
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do_rom_calls()
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@ -750,23 +758,24 @@ class CodeGenerator:
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raise CodeError("invalid register " + lv.register)
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@contextlib.contextmanager
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def preserving_registers(self, registers: Set[str]):
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# @todo option to avoid the sta $03/lda$03 when a is loaded anyway
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# this clobbers a ZP scratch register and is therefore safe to use in interrupts
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def preserving_registers(self, registers: Set[str], loads_a_within: bool=False):
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# this clobbers a ZP scratch register and is therefore NOT safe to use in interrupts
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# see http://6502.org/tutorials/register_preservation.html
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if registers == {'A'}:
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self.p("\t\tpha")
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yield
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self.p("\t\tpla")
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elif registers:
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self.p("\t\tsta ${:02x}".format(Zeropage.SCRATCH_B2))
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if not loads_a_within:
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self.p("\t\tsta ${:02x}".format(Zeropage.SCRATCH_B2))
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if 'A' in registers:
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self.p("\t\tpha")
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if 'X' in registers:
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self.p("\t\ttxa\n\t\tpha")
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if 'Y' in registers:
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self.p("\t\ttya\n\t\tpha")
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self.p("\t\tlda ${:02x}".format(Zeropage.SCRATCH_B2))
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if not loads_a_within:
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self.p("\t\tlda ${:02x}".format(Zeropage.SCRATCH_B2))
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yield
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if 'Y' in registers:
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self.p("\t\tpla\n\t\ttay")
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@ -791,13 +800,13 @@ class CodeGenerator:
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if lvdatatype == DataType.BYTE:
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if rvalue.value is not None and not lv.assignable_from(rvalue) or rvalue.datatype != DataType.BYTE:
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raise OverflowError("value doesn't fit in a byte")
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with self.preserving_registers({'A'}):
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with self.preserving_registers({'A'}, loads_a_within=True):
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self.p("\t\tlda #" + r_str)
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self.p("\t\tsta " + assign_target)
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elif lvdatatype == DataType.WORD:
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if rvalue.value is not None and not lv.assignable_from(rvalue):
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raise OverflowError("value doesn't fit in a word")
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with self.preserving_registers({'A'}):
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with self.preserving_registers({'A'}, loads_a_within=True):
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self.p("\t\tlda #<" + r_str)
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self.p("\t\tsta " + assign_target)
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self.p("\t\tlda #>" + r_str)
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@ -831,18 +840,18 @@ class CodeGenerator:
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if lv.datatype == DataType.BYTE:
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if rvalue.datatype != DataType.BYTE:
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raise CodeError("can only assign a byte to a byte", str(rvalue))
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with self.preserving_registers({'A'}):
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with self.preserving_registers({'A'}, loads_a_within=True):
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self.p("\t\tlda " + r_str)
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self.p("\t\tsta " + l_str)
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elif lv.datatype == DataType.WORD:
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if rvalue.datatype == DataType.BYTE:
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with self.preserving_registers({'A'}):
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with self.preserving_registers({'A'}, loads_a_within=True):
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self.p("\t\tlda " + r_str)
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self.p("\t\tsta " + l_str)
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self.p("\t\tlda #0")
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self.p("\t\tsta {:s}+1".format(l_str))
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elif rvalue.datatype == DataType.WORD:
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with self.preserving_registers({'A'}):
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with self.preserving_registers({'A'}, loads_a_within=True):
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self.p("\t\tlda {:s}".format(r_str))
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self.p("\t\tsta {:s}".format(l_str))
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self.p("\t\tlda {:s}+1".format(r_str))
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@ -851,7 +860,7 @@ class CodeGenerator:
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raise CodeError("can only assign a byte or word to a word", str(rvalue))
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elif lv.datatype == DataType.FLOAT:
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if rvalue.datatype == DataType.FLOAT:
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with self.preserving_registers({'A'}):
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with self.preserving_registers({'A'}, loads_a_within=True):
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self.p("\t\tlda " + r_str)
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self.p("\t\tsta " + l_str)
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self.p("\t\tlda {:s}+1".format(r_str))
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@ -870,7 +879,7 @@ class CodeGenerator:
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self.p("\t\tldy #>" + l_str)
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self.p("\t\tjsr c64.FTOMEMXY") # fac1 -> memory XY
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elif rvalue.datatype == DataType.WORD:
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with self.preserving_registers({'A', 'X', 'Y'}):
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with self.preserving_registers({'A', 'X', 'Y'}, loads_a_within=True):
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self.p("\t\tlda " + r_str)
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self.p("\t\tldy {:s}+1".format(r_str))
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self.p("\t\tjsr c64util.GIVUAYF") # uword AY -> fac1
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@ -884,7 +893,7 @@ class CodeGenerator:
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def generate_assign_char_to_memory(self, lv: ParseResult.MemMappedValue, char_str: str) -> None:
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# Memory = Character
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with self.preserving_registers({'A'}):
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with self.preserving_registers({'A'}, loads_a_within=True):
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self.p("\t\tlda #" + char_str)
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if not lv.name:
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self.p("\t\tsta " + Parser.to_hex(lv.address))
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@ -1176,7 +1176,7 @@ class Parser:
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except ParseError:
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pass
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else:
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if symbol:
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if isinstance(symbol, SubroutineDef):
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self.result.sub_used_by(symbol, self.sourceref)
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asmlines.append(line)
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