91 lines
3.4 KiB
Python
91 lines
3.4 KiB
Python
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"""Insert checks for uninitialized values."""
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from typing import List
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from mypyc.analysis.dataflow import (
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get_cfg,
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cleanup_cfg,
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analyze_must_defined_regs,
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AnalysisDict
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)
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from mypyc.ir.ops import (
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BasicBlock, Op, Branch, Value, RaiseStandardError, Unreachable, Register,
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LoadAddress, Assign, LoadErrorValue
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)
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from mypyc.ir.func_ir import FuncIR, all_values
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def insert_uninit_checks(ir: FuncIR) -> None:
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# Remove dead blocks from the CFG, which helps avoid spurious
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# checks due to unused error handling blocks.
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cleanup_cfg(ir.blocks)
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cfg = get_cfg(ir.blocks)
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must_defined = analyze_must_defined_regs(
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ir.blocks,
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cfg,
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set(ir.arg_regs),
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all_values(ir.arg_regs, ir.blocks))
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ir.blocks = split_blocks_at_uninits(ir.blocks, must_defined.before)
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def split_blocks_at_uninits(blocks: List[BasicBlock],
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pre_must_defined: 'AnalysisDict[Value]') -> List[BasicBlock]:
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new_blocks: List[BasicBlock] = []
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init_registers = []
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init_registers_set = set()
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# First split blocks on ops that may raise.
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for block in blocks:
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ops = block.ops
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block.ops = []
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cur_block = block
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new_blocks.append(cur_block)
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for i, op in enumerate(ops):
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defined = pre_must_defined[block, i]
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for src in op.unique_sources():
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# If a register operand is not guaranteed to be
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# initialized is an operand to something other than a
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# check that it is defined, insert a check.
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# Note that for register operand in a LoadAddress op,
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# we should be able to use it without initialization
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# as we may need to use its address to update itself
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if (isinstance(src, Register) and src not in defined
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and not (isinstance(op, Branch) and op.op == Branch.IS_ERROR)
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and not isinstance(op, LoadAddress)):
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new_block, error_block = BasicBlock(), BasicBlock()
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new_block.error_handler = error_block.error_handler = cur_block.error_handler
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new_blocks += [error_block, new_block]
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if src not in init_registers_set:
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init_registers.append(src)
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init_registers_set.add(src)
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cur_block.ops.append(Branch(src,
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true_label=error_block,
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false_label=new_block,
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op=Branch.IS_ERROR,
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line=op.line))
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raise_std = RaiseStandardError(
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RaiseStandardError.UNBOUND_LOCAL_ERROR,
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f'local variable "{src.name}" referenced before assignment',
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op.line)
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error_block.ops.append(raise_std)
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error_block.ops.append(Unreachable())
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cur_block = new_block
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cur_block.ops.append(op)
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if init_registers:
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new_ops: List[Op] = []
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for reg in init_registers:
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err = LoadErrorValue(reg.type, undefines=True)
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new_ops.append(err)
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new_ops.append(Assign(reg, err))
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new_blocks[0].ops[0:0] = new_ops
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return new_blocks
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