BitTest and While or IF statement

[bignand]

Dear Friends,

I'm try to develop my first C application on PIC 16F676. Normally I use MPASM from microchip.
I'm using the Uregistred version of the compiler.

I'm usually check the assembler generated by the compiler to check the quality of code due the uC used have so little RAM/FLASH.

I have found two strange behavoiur:

FIRST:

check this piece of code

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do {
  // Make SomeThing
} while (1);

The compiler generate all the code to check if 1 is 1 !!!!
Normally all the compiler substitute the while with a unconditioned jump.

SECOND:

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while (!INTCON.T0IF);

The compiler make this code:

Cast bit to short integer
(Make an bittest and load STACK1 with the value 1 if bit asserted)
Load STACK2 with the value 0
Make a test beetwen short integer.

It's better make a bit-test like

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REP          BTFSC  INTCON,T0IF
               GOTO   REP

Can Anyone observed this?
There's any work-around to do the compiler uses bit-tests?

[pizon]

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do {
  // Make SomeThing
} while (1);

The compiler generate all the code to check if 1 is 1 !!!!
Normally all the compiler substitute the while with a unconditioned jump.

I checked this on mikroC v2.1.0.0 and it generates optimal code (unconditional jump). If you have an older version, please upgrade to this one.

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while (!INTCON.T0IF);

...There's any work-around to do the compiler uses bit-tests?

At the present moment,

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while (INTCON.T0IF == 0) 

will produce somewhat less code for bit testing. You can do it like this as well:

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void main() {
...
  asm  {
    BTFSC     INTCON,T0IF
    GOTO      ___main_Usr_Lbl_01
  }
    //do something
    goto Usr_Lbl_02;
  Usr_Lbl_01:
    //do something else
  Usr_Lbl_02:
    //continue program
}

The program memory page settings are then up to you.

MikroC is a work in progress; it is being constantly improved and will continue to do so. Unfortunately, the advanced code optimization issues must come last, due to the nature of work.

[gambrose]

I tend to write something like this if i am looking for performance. good idea get compiler to generate the labels.

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//do something

do
{

    //do something else

asm BTFSC     INTCON,T0IF
}while(1);

//continue program

[gblair]

You need a simple goto:

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Loop:
  ...
  goto Loop;

[gambrose]

the

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do{
}while(1) 

provide the simple goto loop but the compiler provides the loop label names which is a much better situation else you find your code jumping to a point in another function because you forgot you used that name already.