[sdcc-devel] Re: regression: promotion to int

[Bernhard H. <sdc...@be...>]

Hi Maarten,

I'm back on the list to tackle this problem.

> Run the mcs51-stack-auto regression test to see bitvars.c fail.
Ok, I see. I commited a fix for this problem. But it's a really ugly story:
bit arithmethic and promotion rules
don't make a good fit.

Given this code (check with build 1123):

    #include <stdbool.h>

    char complement(bool a);

    unsigned char _ff = 0xFF;

    void
    testBits(void)
    {
      complement (~_ff);
    }

In dumpcse the icode is buggy, but after elimination of iTemp0 dumprassgn
looks ok. It's an optimization, which (very luckily) hides a bug. The
optimization doesn't work with stack-auto, and the bug is exposed.

The only clean solution is to introduce promotion for bit variables (this is
the ugly part). It was completely missing up to now. The big disadvantage
are regressions in code size. At the moment I've got no idea how to improve
the code again. But I'll have a 2nd look, hopefully with some new ideas.

Hints are welcome!

Bernhard