Re: [avr-gcc-list] How to control the optimizer from the C source?

[Anton Erasmus]

On 13 Aug 2004 at 10:50, Bernard Fouché wrote:

> I met an optimization problem: while porting code from icc to gcc, I had the
> following routine:
[routine etc snipped]

Hi,

Try the following - It produces to concecutive writes to the CLKPR register.
It also allows you to keep your critical section much shorter.

 void set_clkdiv(int mode)
{
    unsigned char tmp1,tmp2;

    switch(mode)
    {
       case 0:
       case 1:
          tmp1=0x80;
          tmp2=0x00;
          break;
       case 2:
          tmp1=0x80;
          tmp2=0x01;
          break;
       case 4:
          tmp1=0x80;
          tmp2=0x02;
          break;
       case 8:
          tmp1=0x80;
          tmp2=0x03;
          break;
       case 16:
          tmp1=0x80;
          tmp2=0x04;
          break;
       case 32:
          tmp1=0x80;
          tmp2=0x05;
          break;
       case 64:
          tmp1=0x80;
          tmp2=0x06;
          break;
       case 128:
          tmp1=0x80;
          tmp2=0x07;
          break;
       case 256:
          tmp1=0x80;
          tmp2=0x08;
          break;
    }
    cli();
    CLKPR=tmp1;
    CLKPR=tmp2;
    sei(); //re-enable interrupts
}

Regards
  Anton Erasmus
--
A J Erasmus