Intermediate-Code Generation

Jin Tianxing5110309085

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.

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.

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

Example in the Dragon Book

Oprands

Expression

Memory Access

Jump Statement

Examples while () ;

;

for (;;);

Example for jump stmt Maintain stacks of and of loops.

break Jump to the peek of

continue Jump to the peek of

Function Call

Register Use

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.

Stack Frame

Single Static Assignment It is a intuitive approach in intermediate-code

generation.

One can be only assigned once.

Example

Non-SSA Version: always represents (not store in memory)

SSA Version( is stored in memory):