8.1.1 Sub-expression Elimination

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8.1.1 Sub-expression Elimination

The compiler does local and global common subexpression elimination, e.g.:

> `i = x + y + 1;`
> `j = x + y;`

will be translated to

> `iTemp = x + y;`
> `i = iTemp + 1;`
> `j = iTemp;`

Some subexpressions are not as obvious as the above example, e.g.:

> `a->b[i].c = 10;`
> `a->b[i].d = 11;`

In this case the address arithmetic a->b[i] will be computed only once; the equivalent code in C would be.

> `iTemp = a->b[i];`
> `iTemp.c = 10;`
> `iTemp.d = 11;`

The compiler will try to keep these temporary variables in registers.