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Intermediate-Code Generation

Intermediate-Code Generation. Jin Tianxing 5110309085. Purpose. Theoretically, we can directly generate the MIPS assemble code after semantic analysis. Intermediate-code give us opportunities to register allocation, code optimization and easiness when debugging.

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Intermediate-Code Generation

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  1. Intermediate-Code Generation Jin Tianxing 5110309085

  2. Purpose • Theoretically, we can directly generate the MIPS assemble code after semantic analysis. • Intermediate-code give us opportunities to register allocation, code optimization and easiness when debugging. • After this, the input code and AST can be thrown away.

  3. Where is the data? • There are only two possible place containing data: and . • That means the intermediate-code get data only with and • For simplicity, we assume the number of is unlimited.

  4. Quadruple • A quadruple consists of an , which can possibly be null. • You should design your own IR package. • Here is a viable example.

  5. Example in the Dragon Book

  6. Oprands

  7. Expression

  8. Memory Access

  9. Jump Statement

  10. Examples • while () ; • ; • for (;;);

  11. Example for jump stmt • Maintain stacks of and of loops. • break • Jump to the peek of • continue • Jump to the peek of

  12. Function Call

  13. Register Use

  14. What to do when calling a function? • Save in memory. • Change , • (jump and link) to the of the function. • When from a function: • address(value) stores in a . • (jump register) • Restore from memory.

  15. Stack Frame

  16. Single Static Assignment • It is a intuitive approach in intermediate-code generation. • One can be only assigned once.

  17. Example • Non-SSA Version: • always represents (not store in memory) • SSA Version( is stored in memory):

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