On 25.08.2016 14:54, G 3 wrote:
I'm chasing down a bug with QEMU that causes audio to fail on a
Mac OS
guest. In this file:
https://github.com/nixxcode/AppleUSBAudio-273.4.1/blob/master/
AppleUSBAudioClip.cpp
is where a lot of assembly language code is located. I think one
or more
of the PowerPC instructions might be incorrectly implemented so I am
checking each one that the file uses. Starting with lwbrx I made this
program that gives this instruction sample inputs and checks them
with
real outputs. According to the program QEMU implements this
instruction
correctly. Does this program effectively check the lwbrx
instruction or
is it missing something?
...
// Go thru each rA value
for(rA = 0; rA <=12; rA=rA+4)
{
// set the correct answer array for each rA value
if(rA == 0)
answer_array = answer_array0;
else if(rA == 4)
answer_array = answer_array4;
else if(rA == 8)
answer_array = answer_array8;
else
answer_array = answer_array12;
// Go thru each rB value
for(index = 0; index < rB_size; index++)
{
asm volatile("lwbrx %0, %1, %2" : "=r" (result) : "b
%" (rA),
"r" (&(rB[index])));
I think you're not testing the case where rA is r0 here (only where
the
content of rA is 0) ... and rA == r0 is a special case for this
instruction, see the PowerISA for details. So you'd need a separate
asm
volatile statement to test this.
(Also a question: What is the "%" here good for? I did not quite
understand why you're using that here)
Thomas