| 摘要 |
PROBLEM TO BE SOLVED: To minimize additional logic for exception tracking and to eliminate too early wrong notification of an exception by inserting an exception message in an instruction buffer when exceptional conditions are met if an instruction is executed. SOLUTION: An instruction fetch unit 112 after executing a decoded instruction decides whether or not exceptional conditions are met as a result. When the instruction is a latent exception generating instruction, an exception message which indicates, preferably, a specific type of exception and, preferably, an unused instruction code is inserted into the instruction buffer 116. In other cases, the instruction itself is inserted into the instruction buffer 116. A withdrawal unit 122 deletes executed instructions from an instruction buffer 116 in the order of the program, and generates an exception signal if an instruction is a special encoded exception message. An exception is reported only when an exception generating instruction is actually executed, and the problem of too early exception notification is eliminated.
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