bugGNU Development Chain for 68HC11/68HC12 - Bugs: bug #16626, wrong code on 68hcs12


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bug #16626: wrong code on 68hcs12

Submitter:  None
Submitted:  Fri 19 May 2006 08:23:01 AM UTC
Category:  gcc Severity:  3 - Normal
Item Group:  sw-bug Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open

Fri 19 May 2006 08:23:01 AM UTC, original submission:  

I don't know if it is a bug or not.

I have problem with the following short code segment.

After the start of program the tickcount is increased every 10 ms by a timer interrupt. All seems to by ok and DoSoemthing() is called every 50 tickcounts. But if the tickcount goes from 0x7fff to 0x8000 then DoSomething() is called many times (as fast as possible). This iterate on each changing of tickcount from 0x7fff to 0x8000.
The bug occurs only on a 68hcs12 and it runs ok on a 68hc12 processor. (gcc 2.95) The assmbler output is the same for 68hc12 and 68hcs12.

extern void DoSomething();

static short tickCount = 0;

void TriggerEvent(void) {
    static short nextTickTime = 0;

    if (nextTickTime - tickCount <= 0) {
        nextTickTime += 50;
        // to do something

# assembler output
    ldx nextTickTime.0
    tfr x,d
    subd    tickCount
    bgt .L1
    tfr x,d
    addd    #50
    std nextTickTime.0
    bsr DoSomething



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