[avr-libc-dev] Re: [avr-libc-commit] [2158] Submitted by Jan Waclawek:

[Wouter van Gulik]

Joerg Wunsch schreef:
> +
> +\code
> +#define cli() __asm volatile( "cli" ::: "memory" )
> +#define sei() __asm volatile( "sei" ::: "memory" )
> +
> +unsigned int ivar;
> +
> +void test2( unsigned int val )
> +{
> +  val = 65535U / val;
> +
> +  cli();
> +
> +  ivar = val;
> +
> +  sei();
> +}
> +\endcode
> +
> +compiles with optimisations switched on (-Os) to
> +
> +\verbatim
> +00000112 <test2>:
> + 112:  bc 01           movw    r22, r24
> + 114:  f8 94           cli
> + 116:  8f ef           ldi     r24, 0xFF       ; 255
> + 118:  9f ef           ldi     r25, 0xFF       ; 255
> + 11a:  0e 94 96 00     call    0x12c   ; 0x12c <__udivmodhi4>
> + 11e:  70 93 01 02     sts     0x0201, r23
> + 122:  60 93 00 02     sts     0x0200, r22
> + 126:  78 94           sei
> + 128:  08 95           ret
> +\endverbatim
> +
> +where the potentially slow multiplication is moved across cli(),
> +resulting in interrupts to be disabled longer than intended.
There is "typo", the texts talks about multiplication instead of divide.

HTH,

Wouter