On 25.08.2016 18:55, G 3 wrote:
On Aug 25, 2016, at 6:03 PM, Thomas Huth wrote:
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
Thank you very much for commenting. For the case where rA is r0,
are you
saying something like this:
asm volatile("lwbrx %0, 0, %1" : "=r" (result) : "r" (&(rB
[index])));
Yes, this is what I had in mind.
Didn't find the text 'r0' here, but it did mention this:
"If GPR RA is 0, then the EA is the contents of GPR RB". Is that the
same thing?
Yes, I am normally using "r0" instead of "0" so that it can not be
confused that easily with an immediate value.
By the way, if you don't know it yet, you can get the official
Power ISA
here:
https://www.power.org/wp-content/uploads/2013/05/
PowerISA_V2.07_PUBLIC.pdf
The percent is for me to quickly see if any of the test failed.
QEMU is
at 100% for this test.
I didn't mean the printf statement, but the % character in the "b%"
part
of the asm volatile statement.