[parisc-linux] parisc asm questions

[parisc-linux] parisc asm questions

[Randolph Chung]

would someone please enlighten me about why this is happening?

i have a simple fetch-add asm loop:

/* arg0 is a pointer to a buffer, %arg1 is the length, %r4 == %arg1>>2 */
$loop:
	ldws,ma		4(%arg0), %r3
	addc		%ret0, %r3, %ret0
	addib,<>	-1, %r4, $loop
	addi		-4, %arg1, %arg1

i notice that the sum returned is sometimes off by a certain amount from
what i was expecting.  while i was tracing this down, i added a line to 
the loop so that it's:

$loop:
	add		%r0, %r3, %r3	/* isn't this equivalent to a nop? */
	ldws,ma		4(%arg0), %r3
	addc		%ret0, %r3, %ret0
	addib,<>	-1, %r4, $loop
	addi		-4, %arg1, %arg1

and i get fairly different behavior. I think I'm not understanding how
the carry bit gets updated or something. any hints will be much appreciated.

randolph
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