On Wed, Jun 13, 2001 at 07:21:41AM -0700, David S. Miller wrote:
> I can't believe there is no reliable way to get rid of that
> pesky "$" gcc is adding to the symbol. Oh well...
GCC on ARM does a similar thing - all constants in the assembler are
prefixed with '#' or '@'. Using the 'i' constraint adds this. This
behaviour is actually useful when you want to pass a constant or a
register - it allows GCC to make the decision for you, and do the
right thing in the assembler fragment. Eg, the following code used
to be in the kernel until 2.3:
extern __inline__ void __outb (unsigned int value, unsigned int port)
{
unsigned long temp;
__asm__ __volatile__(
"tst %2, #0x80000000\n\t"
"mov %0, %4\n\t"
"addeq %0, %0, %3\n\t"
"strb %1, [%0, %2, lsl #2] @ outb"
: "=&r" (temp)
: "r" (value), "r" (port), "Ir" (PCIO_BASE - IO_BASE), "Ir" (IO_BASE)
: "cc");
}
%3 and %4 might be a constant:
mov r5, #0x03000000
or a real register if the constant can't be loaded in one instruction:
mov r5, r1
'I' in this case means "a constant suitable for use with the arithmetic
instructions".
--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html
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This archive was generated by hypermail 2b29 : Fri Jun 15 2001 - 21:00:18 EST