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Basic Blocks refactoring #112

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27 changes: 13 additions & 14 deletions dncil/cil/body/__init__.py
Original file line number Diff line number Diff line change
@@ -216,16 +216,13 @@ def parse_basic_blocks(self):
# 3. Instructions that immediately follow unconditional or conditional jump/goto statements are considered leaders
# https://www.geeksforgeeks.org/basic-blocks-in-compiler-design/

leaders: Set[int] = set()
# add #1: first instruction is a leader
leaders: Set[int] = set(self.instructions[:1]) if self.instructions else set()
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for idx, insn in enumerate(self.instructions):
if idx == 0:
# add #1
leaders.add(insn.offset)

if any((insn.is_br(), insn.is_cond_br(), insn.is_leave())):
# add #2
# add #2: targets of branches are leaders
leaders.add(cast(int, insn.operand))
# add #3
# add #3: instructions immediately following unconditional or conditional branches are leaders
try:
leaders.add(self.instructions[idx + 1].offset)
except IndexError:
@@ -239,10 +236,9 @@ def parse_basic_blocks(self):
# new leader, new basic block
bb_curr = BasicBlock(instructions=[insn])
self.basic_blocks.append(bb_curr)
continue

assert bb_curr is not None
bb_curr.instructions.append(insn)
else:
assert bb_curr is not None
bb_curr.instructions.append(insn)
Comment on lines +241 to +243
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Can you provide context for this change? What is it addressing?

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This change was made in accordance to: mandiant/capa#1326 (comment)


# create mapping of first instruction to basic block
bb_map: Dict[int, BasicBlock] = {}
@@ -265,11 +261,14 @@ def parse_basic_blocks(self):
# no fallthrough
continue

# connect fallthrough
# connect fallthrough:
# if a basic block has a fallthrough successor, it will be the next basic block in our list
# since instructions, leaders, and basic blocks are processed sequentially
try:
bb_next: BasicBlock = self.basic_blocks[idx + 1]
bb.succs.append(bb_next)
bb_next.preds.append(bb)
except IndexError:
# end of method
continue
else:
bb.succs.append(bb_next)
bb_next.preds.append(bb)
Comment on lines +274 to +276
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Can you provide context for this change? What is it addressing?

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This change was made in accordance to:
mandiant/capa#1326 (comment)