Optimization for division by "extern const int"

Question

I am working on a project in which I have the following code:

file1.c

extern const int z;
int x;
do_some_stuff_to_calculate_x();
y = x / z;
do_some_stuff_with_y();

file2.c

const int z = Z_INIT_VALUE; // some value defined in some .h file.

Of interest is dividing by file1.c. Because z- extern, therefore, it is not known at compile time [it will be determined at connection time]. Thus, the compiler cannot optimize the separation.

I know that if the value is zknown at compile time, then the compiler will convert division to multiplication and some other manipulations.

Note that the1.c file will be delivered as a library, so recompiling file1.cwith is file2.cnot a parameter.

Does anyone know to make the linker optimize such things? Or any other trick to avoid this EXPENSIVE division?

:)

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extern const int common_divisor;
extern const int common_addition;

void handleTheDamnInterrupt(void)
{
    int x = *(REG_FOO_1);
    int y = x / common_divisor;
    y += common_addition;
    if( x > some_value )
    {
       y += blah_blah;
    }
    else
    {
       y += foo_bar;
    }

    *(REG_BAR_1) = y;
}

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Answer 1

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Answer 2

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Answer 3

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Answer 4

do_some_stuff .