🚀 go-pugleaf

strauch@emmy.mathematik.uni-dortmund.de (Michael Strauch) writes:

>jzh@abb-sc.abb-sc.com (Jason Huang) writes:


>>Anybody like to point me out on assembler instruction
>>using 'asm' please? For I/O instructions, IN AL,DX; OUT DX,AL.

>Try this one: asm("inb %dx,%al");
>              asm("outb %al,%dx");
Better not try it. It might produce the wanted code (not TOO sure about
it, though), but will not inform the compiler about what registers
it clobbers. Try something like
asm volatile("inb %1,%0"  : "a" (char-variable) : "d" (word-expression))
the volatile tells gnu not to significantly move this template,
the d and a tell it only that registers satisfy the register constraints
(will more registers/addressing modes work with i386?)
resp. First group are output parameters, second input.
asm volatile("outb %0,%1" : : "a" (char-exp), "d" (word-exp))
-- 
 David Kastrup        dak@pool.informatik.rwth-aachen.de          
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