Problem with memcpy on ppc8536

[Fahd Abidi]

Hello, 

I am trying to debug a crash during memcpy while copying data from the
FCM buffer of an mpc8536 to the ddr ram. I debugged memcpy enough
through my BDI3000 to see that the entire contents of the fcm buffer I
want moved are actually moved off to memory location I specify. The
crash comes after it memcpy finishes copying and performs the
instruction "2: cmplwi 0,r5,4": 

memcpy: 
rlwinm. r7,r5,32-3,3,31 /* r0 = r5 >> 3 */ 
addi r6,r3,-4 
addi r4,r4,-4 
beq 2f /* if less than 8 bytes to do */ 
andi. r0,r6,3 /* get dest word aligned */ 
mtctr r7 
bne 5f 
1: lwz r7,4(r4) 
lwzu r8,8(r4) 
stw r7,4(r6) 
stwu r8,8(r6) 
bdnz 1b 
andi. r5,r5,7 
2: cmplwi 0,r5,4 

contents of r5 are 0x0 showing that the entire 0x1000 size transfer I
specified correctly finished. At this point I can check the memory
contents through my BDI and verify all the data is in the ddr as I
expect. Now the strange thing happens, if I execute the "cmplwi 0,r5,4"
the program takes an exception and eventually gets struck at exception
vector 0x700 which I saw from start.S is an "Alignment" exception. I am
not sure what this exception means, can someone help me understand what
is happening? 

Does this exception somehow mean that memcpy did not move all the data?
Does memcpy expect contents of r5 to be 4 and not 0 when it hits the
cmplwi instruction? 


Fahd Abidi
Product Manager - Technical Tools and Development
Ultimate Solutions, Inc.
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Ph: 978-455-3383 x255
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Email: fabidi at ultsol.com
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