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import re
from analyzer import StackItem, Instruction, Uop
from dataclasses import dataclass
from cwriter import CWriter
UNUSED = {"unused"}
def maybe_parenthesize(sym: str) -> str:
"""Add parentheses around a string if it contains an operator
and is not already parenthesized.
An exception is made for '*' which is common and harmless
in the context where the symbolic size is used.
"""
if sym.startswith("(") and sym.endswith(")"):
return sym
if re.match(r"^[\s\w*]+$", sym):
return sym
else:
return f"({sym})"
def var_size(var: StackItem) -> str:
if var.condition:
# Special case simplifications
if var.condition == "0":
return "0"
elif var.condition == "1":
return var.size
elif var.condition == "oparg & 1" and var.size == "1":
return f"({var.condition})"
else:
return f"(({var.condition}) ? {var.size} : 0)"
else:
return var.size
@dataclass
class StackOffset:
"The stack offset of the virtual base of the stack from the physical stack pointer"
popped: list[str]
pushed: list[str]
@staticmethod
def empty() -> "StackOffset":
return StackOffset([], [])
def pop(self, item: StackItem) -> None:
self.popped.append(var_size(item))
def push(self, item: StackItem) -> None:
self.pushed.append(var_size(item))
def __sub__(self, other: "StackOffset") -> "StackOffset":
return StackOffset(self.popped + other.pushed, self.pushed + other.popped)
def __neg__(self) -> "StackOffset":
return StackOffset(self.pushed, self.popped)
def simplify(self) -> None:
"Remove matching values from both the popped and pushed list"
if not self.popped or not self.pushed:
return
# Sort the list so the lexically largest element is last.
popped = sorted(self.popped)
pushed = sorted(self.pushed)
self.popped = []
self.pushed = []
while popped and pushed:
pop = popped.pop()
push = pushed.pop()
if pop == push:
pass
elif pop > push:
# if pop > push, there can be no element in pushed matching pop.
self.popped.append(pop)
pushed.append(push)
else:
self.pushed.append(push)
popped.append(pop)
self.popped.extend(popped)
self.pushed.extend(pushed)
def to_c(self) -> str:
self.simplify()
int_offset = 0
symbol_offset = ""
for item in self.popped:
try:
int_offset -= int(item)
except ValueError:
symbol_offset += f" - {maybe_parenthesize(item)}"
for item in self.pushed:
try:
int_offset += int(item)
except ValueError:
symbol_offset += f" + {maybe_parenthesize(item)}"
if symbol_offset and not int_offset:
res = symbol_offset
else:
res = f"{int_offset}{symbol_offset}"
if res.startswith(" + "):
res = res[3:]
if res.startswith(" - "):
res = "-" + res[3:]
return res
def clear(self) -> None:
self.popped = []
self.pushed = []
class SizeMismatch(Exception):
pass
class Stack:
def __init__(self) -> None:
self.top_offset = StackOffset.empty()
self.base_offset = StackOffset.empty()
self.peek_offset = StackOffset.empty()
self.variables: list[StackItem] = []
self.defined: set[str] = set()
def pop(self, var: StackItem) -> str:
self.top_offset.pop(var)
if not var.peek:
self.peek_offset.pop(var)
indirect = "&" if var.is_array() else ""
if self.variables:
popped = self.variables.pop()
if popped.size != var.size:
raise SizeMismatch(
f"Size mismatch when popping '{popped.name}' from stack to assign to {var.name}. "
f"Expected {var.size} got {popped.size}"
)
if popped.name == var.name:
return ""
elif popped.name in UNUSED:
self.defined.add(var.name)
return (
f"{var.name} = {indirect}stack_pointer[{self.top_offset.to_c()}];\n"
)
elif var.name in UNUSED:
return ""
else:
self.defined.add(var.name)
return f"{var.name} = {popped.name};\n"
self.base_offset.pop(var)
if var.name in UNUSED:
return ""
else:
self.defined.add(var.name)
cast = f"({var.type})" if (not indirect and var.type) else ""
assign = (
f"{var.name} = {cast}{indirect}stack_pointer[{self.base_offset.to_c()}];"
)
if var.condition:
if var.condition == "1":
return f"{assign}\n"
elif var.condition == "0":
return ""
else:
return f"if ({var.condition}) {{ {assign} }}\n"
return f"{assign}\n"
def push(self, var: StackItem) -> str:
self.variables.append(var)
if var.is_array() and var.name not in self.defined and var.name not in UNUSED:
c_offset = self.top_offset.to_c()
self.top_offset.push(var)
self.defined.add(var.name)
return f"{var.name} = &stack_pointer[{c_offset}];\n"
else:
self.top_offset.push(var)
return ""
def flush(self, out: CWriter, cast_type: str = "PyObject *") -> None:
out.start_line()
for var in self.variables:
if not var.peek:
cast = f"({cast_type})" if var.type else ""
if var.name not in UNUSED and not var.is_array():
if var.condition:
if var.condition == "0":
continue
elif var.condition != "1":
out.emit(f"if ({var.condition}) ")
out.emit(
f"stack_pointer[{self.base_offset.to_c()}] = {cast}{var.name};\n"
)
self.base_offset.push(var)
if self.base_offset.to_c() != self.top_offset.to_c():
print("base", self.base_offset.to_c(), "top", self.top_offset.to_c())
assert False
number = self.base_offset.to_c()
if number != "0":
out.emit(f"stack_pointer += {number};\n")
self.variables = []
self.base_offset.clear()
self.top_offset.clear()
self.peek_offset.clear()
out.start_line()
def as_comment(self) -> str:
return f"/* Variables: {[v.name for v in self.variables]}. Base offset: {self.base_offset.to_c()}. Top offset: {self.top_offset.to_c()} */"
def get_stack_effect(inst: Instruction) -> Stack:
stack = Stack()
for uop in inst.parts:
if not isinstance(uop, Uop):
continue
for var in reversed(uop.stack.inputs):
stack.pop(var)
for i, var in enumerate(uop.stack.outputs):
stack.push(var)
return stack
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