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327 lines
18 KiB
Python
327 lines
18 KiB
Python
"""
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Programming Language for 6502/6510 microprocessors, codename 'Sick'
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This is the optimizer that applies various optimizations to the parse tree,
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eliminates statements that have no effect, optimizes calculations etc.
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Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
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"""
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from typing import List, no_type_check, Union
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from .datatypes import DataType, VarType
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from .plyparse import *
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from .plylex import print_warning, print_bold
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from .constantfold import ConstantFold
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class Optimizer:
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def __init__(self, mod: Module) -> None:
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self.num_warnings = 0
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self.module = mod
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self.optimizations_performed = False
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self.constant_folder = ConstantFold(self.module)
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def optimize(self) -> None:
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self.num_warnings = 0
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self.optimizations_performed = True
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# keep optimizing as long as there were changes made
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while self.optimizations_performed:
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self.optimizations_performed = False
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self._optimize()
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# remaining optimizations that have to be done just once:
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self.remove_unused_subroutines()
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self.remove_empty_blocks()
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def _optimize(self) -> None:
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self.constant_folder.fold_constants(True) # perform constant folding and simple expression optimization
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# @todo expression optimization: reduce expression nesting / flattening of parenthesis
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# @todo expression optimization: simplify logical expression when a term makes it always true or false
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# @todo expression optimization: optimize some simple multiplications into shifts (A*=8 -> A<<3)
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# @todo expression optimization: create augmented assignment from assignment that only refers to its lvalue (A=A+10, A=4*A, ...)
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self.optimize_assignments()
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self.remove_superfluous_assignments()
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# @todo optimize addition with self into shift 1 (A+=A -> A<<=1)
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self.optimize_goto_compare_with_zero()
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self.join_incrdecrs()
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# @todo remove gotos with conditions that are always false
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# @todo remove loops with conditions that are always empty/false
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# @todo analyse for unreachable code and remove that (f.i. code after goto or return that has no label so can never be jumped to)
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def join_incrdecrs(self) -> None:
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def combine(incrdecrs: List[IncrDecr], scope: Scope) -> None:
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# combine the separate incrdecrs
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replaced = False
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total = 0
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for i in incrdecrs:
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if i.operator == "++":
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total += i.howmuch
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else:
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total -= i.howmuch
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if total == 0:
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replaced = True
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for x in incrdecrs:
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scope.remove_node(x)
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else:
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is_float = False
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if isinstance(target, SymbolName):
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symdef = target.my_scope().lookup(target.name)
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is_float = isinstance(symdef, VarDef) and symdef.datatype == DataType.FLOAT
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elif isinstance(target, Dereference):
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is_float = target.datatype == DataType.FLOAT
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if is_float or -255 <= total <= 255:
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replaced = True
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for x in incrdecrs[1:]:
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scope.remove_node(x)
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incrdecr = self._make_incrdecr(incrdecrs[0], target, abs(total), "++" if total >= 0 else "--")
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scope.replace_node(incrdecrs[0], incrdecr)
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else:
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# total is > 255 or < -255, make an augmented assignment out of it instead of an incrdecr
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aug_assign = AugAssignment(operator="-=" if total < 0 else "+=", sourceref=incrdecrs[0].sourceref) # type: ignore
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left = incrdecrs[0].target
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right = LiteralValue(value=abs(total), sourceref=incrdecrs[0].sourceref) # type: ignore
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left.parent = aug_assign
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right.parent = aug_assign
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aug_assign.nodes.append(left)
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aug_assign.nodes.append(right)
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aug_assign.mark_lhs()
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replaced = True
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for x in incrdecrs[1:]:
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scope.remove_node(x)
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scope.replace_node(incrdecrs[0], aug_assign)
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if replaced:
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self.optimizations_performed = True
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self.num_warnings += 1
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print_warning("{}: merged a sequence of incr/decrs or augmented assignments".format(incrdecrs[0].sourceref))
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for scope in self.module.all_nodes(Scope):
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target = None
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incrdecrs = [] # type: List[IncrDecr]
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for node in list(scope.nodes):
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if isinstance(node, IncrDecr):
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if target is None:
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target = node.target
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incrdecrs.append(node)
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continue
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if self._same_target(target, node.target):
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incrdecrs.append(node)
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continue
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if len(incrdecrs) > 1:
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combine(incrdecrs, scope) # type: ignore
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incrdecrs.clear()
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target = None
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if isinstance(node, IncrDecr):
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# it was an incrdecr with a different target than what we had gathered so far.
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if target is None:
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target = node.target
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incrdecrs.append(node)
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if len(incrdecrs) > 1:
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# combine remaining incrdecrs at the bottom of the block
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combine(incrdecrs, scope) # type: ignore
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def _same_target(self, node1: Union[Register, SymbolName, Dereference],
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node2: Union[Register, SymbolName, Dereference]) -> bool:
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if isinstance(node1, Register) and isinstance(node2, Register) and node1.name == node2.name:
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return True
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if isinstance(node1, SymbolName) and isinstance(node2, SymbolName) and node1.name == node2.name:
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return True
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if isinstance(node1, Dereference) and isinstance(node2, Dereference):
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if type(node1.operand) is not type(node2.operand):
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return False
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if isinstance(node1.operand, (SymbolName, LiteralValue, Register)):
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return node1.operand == node2.operand
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if not isinstance(node1, AstNode) or not isinstance(node2, AstNode):
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raise TypeError("same_target called with invalid type(s)", node1, node2)
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return False
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def remove_superfluous_assignments(self) -> None:
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# remove consecutive assignment statements to the same target, only keep the last value (only if its a constant!)
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# this is NOT done for memory mapped variables because these often represent a volatile register of some sort!
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for scope in self.module.all_nodes(Scope):
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prev_node = None # type: AstNode
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for node in list(scope.nodes):
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if isinstance(node, Assignment) and isinstance(prev_node, Assignment):
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if isinstance(node.right, (LiteralValue, Register)) and self._same_target(node.left, prev_node.left):
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if isinstance(node.left, SymbolName):
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# only optimize if the symbol is not a memory mapped address (volatile memory!)
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symdef = node.left.my_scope().lookup(node.left.name)
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if isinstance(symdef, VarDef) and symdef.vartype == VarType.MEMORY:
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continue
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scope.remove_node(prev_node)
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self.optimizations_performed = True
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self.num_warnings += 1
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print_warning("{}: removed superfluous assignment".format(prev_node.sourceref))
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prev_node = node
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@no_type_check
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def optimize_assignments(self) -> None:
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# remove assignment statements that do nothing (A=A)
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# remove augmented assignments that have no effect (x+=0, x-=0, x/=1, x//=1, x*=1)
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# convert augmented assignments to simple incr/decr if value allows it (A+=10 => incr A by 10)
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# simplify some calculations (x*=0, x**=0) to simple constant value assignment
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# @todo remove or simplify logical aug assigns like A |= 0, A |= true, A |= false (or perhaps turn them into byte values first?)
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for assignment in self.module.all_nodes():
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if isinstance(assignment, Assignment):
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if self._same_target(assignment.left, assignment.right):
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assignment.my_scope().remove_node(assignment)
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self.optimizations_performed = True
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self.num_warnings += 1
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print_warning("{}: removed statement that has no effect (left=right)".format(assignment.sourceref))
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elif isinstance(assignment, AugAssignment):
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if isinstance(assignment.right, LiteralValue) and isinstance(assignment.right.value, (int, float)):
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if assignment.right.value == 0:
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if assignment.operator in ("+=", "-=", "|=", "<<=", ">>=", "^="):
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self.num_warnings += 1
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print_warning("{}: removed statement that has no effect (aug.assign zero)".format(assignment.sourceref))
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assignment.my_scope().remove_node(assignment)
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self.optimizations_performed = True
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elif assignment.operator == "*=":
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self.num_warnings += 1
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print_warning("{}: statement replaced by = 0".format(assignment.sourceref))
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new_assignment = self._make_new_assignment(assignment, 0)
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assignment.my_scope().replace_node(assignment, new_assignment)
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self.optimizations_performed = True
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elif assignment.operator == "**=":
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self.num_warnings += 1
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print_warning("{}: statement replaced by = 1".format(assignment.sourceref))
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new_assignment = self._make_new_assignment(assignment, 1)
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assignment.my_scope().replace_node(assignment, new_assignment)
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self.optimizations_performed = True
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elif assignment.right.value >= 8 and assignment.operator in ("<<=", ">>="):
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print("{}: shifting result is always zero".format(assignment.sourceref))
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new_stmt = Assignment(sourceref=assignment.sourceref)
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new_stmt.nodes.append(assignment.left)
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new_stmt.nodes.append(LiteralValue(value=0, sourceref=assignment.sourceref))
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assignment.my_scope().replace_node(assignment, new_stmt)
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assignment.mark_lhs()
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self.optimizations_performed = True
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elif assignment.operator in ("+=", "-=") and 0 < assignment.right.value < 256:
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howmuch = assignment.right
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if howmuch.value not in (0, 1):
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_, howmuch = coerce_constant_value(datatype_of(assignment.left, assignment.my_scope()),
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howmuch, assignment.sourceref)
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new_stmt = IncrDecr(operator="++" if assignment.operator == "+=" else "--",
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howmuch=howmuch.value, sourceref=assignment.sourceref)
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new_stmt.target = assignment.left
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new_stmt.target.parent = new_stmt
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assignment.my_scope().replace_node(assignment, new_stmt)
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self.optimizations_performed = True
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elif assignment.right.value == 1 and assignment.operator in ("/=", "//=", "*="):
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self.num_warnings += 1
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print_warning("{}: removed statement that has no effect (aug.assign identity)".format(assignment.sourceref))
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assignment.my_scope().remove_node(assignment)
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self.optimizations_performed = True
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@no_type_check
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def _make_new_assignment(self, old_aug_assignment: AugAssignment, constantvalue: int) -> Assignment:
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new_assignment = Assignment(sourceref=old_aug_assignment.sourceref)
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new_assignment.parent = old_aug_assignment.parent
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left = old_aug_assignment.left
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left.parent = new_assignment
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new_assignment.nodes.append(left)
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value = LiteralValue(value=constantvalue, sourceref=old_aug_assignment.sourceref)
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value.parent = new_assignment
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new_assignment.nodes.append(value)
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new_assignment.mark_lhs()
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return new_assignment
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@no_type_check
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def _make_aug_assign(self, old_assign: Assignment, target: Union[Register, SymbolName, Dereference],
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value: Union[int, float], operator: str) -> AugAssignment:
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assert isinstance(target, (Register, SymbolName, Dereference))
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a = AugAssignment(operator=operator, sourceref=old_assign.sourceref)
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a.nodes.append(target)
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target.parent = a
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lv = LiteralValue(value=value, sourceref=old_assign.sourceref)
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a.nodes.append(lv)
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lv.parent = a
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a.parent = old_assign.parent
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a.mark_lhs()
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return a
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@no_type_check
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def _make_incrdecr(self, old_stmt: AstNode, target: Union[Register, SymbolName, Dereference],
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howmuch: Union[int, float], operator: str) -> IncrDecr:
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assert isinstance(target, (Register, SymbolName, Dereference))
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a = IncrDecr(operator=operator, howmuch=howmuch, sourceref=old_stmt.sourceref)
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a.nodes.append(target)
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target.parent = a
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a.parent = old_stmt.parent
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return a
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@no_type_check
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def remove_unused_subroutines(self) -> None:
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# some symbols are used by the emitted assembly code from the code generator,
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# and should never be removed or the assembler will fail
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never_remove = {"c64.FREADUY", "c64.FTOMEMXY", "c64.FADD", "c64.FSUB",
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"c64flt.GIVUAYF", "c64flt.copy_mflt", "c64flt.float_add_one", "c64flt.float_sub_one",
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"c64flt.float_add_SW1_to_XY", "c64flt.float_sub_SW1_from_XY"}
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num_discarded = 0
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for sub in self.module.all_nodes(Subroutine):
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usages = self.module.subroutine_usage[(sub.parent.name, sub.name)]
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if not usages and sub.parent.name + '.' + sub.name not in never_remove:
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sub.parent.remove_node(sub)
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num_discarded += 1
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# if num_discarded:
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# print("discarded {:d} unused subroutines".format(num_discarded))
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@no_type_check
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def optimize_goto_compare_with_zero(self) -> None:
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# a conditional goto that compares a value with zero will be simplified
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# the comparison operator and rvalue (0) will be removed and the if-status changed accordingly
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for goto in self.module.all_nodes(Goto):
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if isinstance(goto.condition, Expression):
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pass # @todo optimize goto conditionals
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# if cond and isinstance(cond.rvalue, (int, float)) and cond.rvalue.value == 0:
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# simplified = False
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# if cond.ifstatus in ("true", "ne"):
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# if cond.comparison_op == "==":
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# # if_true something == 0 -> if_not something
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# cond.ifstatus = "not"
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# cond.comparison_op, cond.rvalue = "", None
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# simplified = True
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# elif cond.comparison_op == "!=":
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# # if_true something != 0 -> if_true something
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# cond.comparison_op, cond.rvalue = "", None
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# simplified = True
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# elif cond.ifstatus in ("not", "eq"):
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# if cond.comparison_op == "==":
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# # if_not something == 0 -> if_true something
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# cond.ifstatus = "true"
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# cond.comparison_op, cond.rvalue = "", None
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# simplified = True
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# elif cond.comparison_op == "!=":
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# # if_not something != 0 -> if_not something
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# cond.comparison_op, cond.rvalue = "", None
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# simplified = True
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# if simplified:
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# print("{}: simplified comparison with zero".format(stmt.sourceref))
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def remove_empty_blocks(self) -> None:
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# remove blocks without name and without address, or that are empty
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for node in self.module.all_nodes():
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if isinstance(node, (Subroutine, Block)):
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if not node.scope:
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continue
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if all(isinstance(n, Directive) for n in node.scope.nodes):
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empty = True
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for n in node.scope.nodes:
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empty = empty and n.name not in {"asmbinary", "asminclude"}
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if empty:
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self.num_warnings += 1
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print_warning("ignoring empty block or subroutine", node.sourceref)
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assert isinstance(node.parent, (Block, Module))
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node.my_scope().nodes.remove(node)
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if isinstance(node, Block):
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if not node.name and node.address is None:
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self.num_warnings += 1
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print_warning("ignoring block without name and address", node.sourceref)
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assert isinstance(node.parent, Module)
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node.my_scope().nodes.remove(node)
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def optimize(mod: Module) -> None:
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opt = Optimizer(mod)
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opt.optimize()
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if opt.num_warnings:
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print_bold("There are {:d} optimization warnings.".format(opt.num_warnings))
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