64 lines
2.1 KiB
Python
64 lines
2.1 KiB
Python
"""
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Classes for φ nodes in a RiscV CFG :py:class:`CFG <Lib.CFG.CFG>` under SSA Form:
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:py:class:`PhiNode` for a statement of the form temp_x = φ(temp_0, ..., temp_n).
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These particular kinds of statements are expected to be in the field
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b._phis for a :py:class:`Block <Lib.CFG.Block>` b.
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"""
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from dataclasses import dataclass
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from typing import List, Dict
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from Lib.Operands import Operand, Temporary, DataLocation, Renamer
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from Lib.Statement import Statement, Label
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@dataclass
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class PhiNode(Statement):
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"""
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A φ node is a renaming in the CFG, of the form temp_x = φ(temp_0, ..., temp_n).
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The field var contains the variable temp_x.
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The field srcs links each corresponding predecessor in the CFG
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---identified by its label---, to the variable temp_i of the φ
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node.
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"""
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var: DataLocation
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srcs: Dict[Label, Operand]
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def defined(self) -> List[Operand]:
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"""Return the variable defined by the φ node."""
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return [self.var]
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def get_srcs(self) -> Dict[Label, Operand]:
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"""
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Return the dictionnary associating for each previous block the corresponding variable.
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"""
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return self.srcs
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def used(self) -> List[Operand]:
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"""Return the variables used by the statement."""
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return list(self.srcs.values())
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def rename(self, renamer: Renamer) -> None:
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"""Rename the variable defined by the φ node with a fresh name."""
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if isinstance(self.var, Temporary):
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self.var = renamer.fresh(self.var)
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def rename_from(self, renamer: Renamer, label: Label) -> None:
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"""Rename the variable associated to the block identified by `label`."""
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if label in self.srcs:
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t = self.srcs[label]
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if isinstance(t, Temporary):
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if renamer.defined(t):
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self.srcs[label] = renamer.replace(t)
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else:
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del self.srcs[label]
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def __str__(self):
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return "{} = φ({})".format(self.var, self.srcs)
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def __hash__(self):
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return hash((self.var, *self.srcs.items()))
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def printIns(self, stream):
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print(' # ' + str(self), file=stream)
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