Difference: ProjectHome (28 vs. 29)

Revision 292008-02-17 - ChenDing

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META TOPICPARENT name="CS255Spring08"
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Part 2: Weird Control Flow (10%)

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  • Reverse all printf, scanf, and __builtin_puts statements in a basic block. If there are k such statements in a basic block, the first statement will be switched with the last statement, the second statement will be switched with the (k-1)th statement, and so on. At a function call such as scanf and printf, Gcc copies the arguments to a temporary variable. For the project, you need to move these copy statements with the call. A recent question and answer discusses some ambiguity and its recommended resolution.
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  • Reverse all printf, scanf, and __builtin_puts statements in a basic block. If there are k such statements in a basic block, the first statement will be switched with the last statement, the second statement will be switched with the (k-1)th statement, and so on. At a call to printf, Gcc copies the arguments to a temporary variable. For the project, you need to move these copy statements with the call. A recent question and answer discusses some ambiguity and its recommended resolution.
 
  • If the statement is a conditional branch in the form of if cond goto L1; else goto L2, change it to if (not cond) goto L1; else goto L2. You only need to deal with >, >=, <, <=, ==, =!.
  • If the statement is a self increment (or decrement) by 1, change it to the opposite, that is, to decrement (or increment) by 1. For example, change i=i+1 to i=i-1 and vice versa.
  • Try all our test cases to make sure that your compiler generates code with no error, even though the generated code may not run correctly.
 
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