以下是一个简单的 Python 代码示例,演示了如何使用四元式将代码划分为基本块:
```python
# 定义四元式列表
quadruples = [
("+", "a", "b", "t1"),
("*", "t1", "c", "t2"),
("-", "t2", "d", "t3"),
("=", "t3", "", "e"),
("if", "e", "", "L1"),
("+", "f", "g", "t4"),
("*", "t4", "h", "t5"),
("-", "t5", "i", "t6"),
("=", "t6", "", "j"),
("goto", "", "", "L2"),
("label", "", "", "L1"),
("print", "k", "", ""),
("label", "", "", "L2")
]
# 划分基本块
basic_blocks = []
current_block = []
for quadruple in quadruples:
current_block.append(quadruple)
if quadruple[0] == "if" or quadruple[0] == "goto" or quadruple[0] == "label":
basic_blocks.append(current_block)
current_block = []
# 打印基本块
for i, block in enumerate(basic_blocks):
print("Basic Block", i+1)
for quadruple in block:
print(quadruple)
```
在这个示例中,我们首先定义了一个包含四元式的列表。然后,我们遍历每个四元式,并将其添加到当前基本块中。如果当前四元式是控制流语句(如 `if`、`goto` 或 `label`),则我们认为该基本块已经结束,并将其添加到基本块列表中。然后,我们创建一个新的空基本块,并继续遍历四元式。
最后,我们打印出所有的基本块,以便检查它们是否正确划分。在这个示例中,我们有三个基本块:第一个包含前两个四