[Qemu-devel] Effective way to test PowerPC lwbrx instruction

[G 3 <programmingkidx@gmail.com>]

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?

#include <stdio.h>

// instructions to test
// lwbrx, lhbrx, rlwimi, stwbrx, stfiwx, fctiw, fmadd, sthbrx, mffs,
// mtfsf

void test_lwbrx()
{
     // http://www.ds.ewi.tudelft.nl/vakken/in1006/instruction-set/ 
lwbrx.html
     // rA can be 0, 4, 8, 12
     long index, result, rA;
     const int rB_size = 32;
     long rB[rB_size];
     long *answer_array;
     float total, correct;

     // answers with rA = 0
     long answer_array0[] = {0x0, 0x78563412, 0xf0ac6824, 0x68039d36,  
0xe059d148,
     0x58b0055b, 0xd0063a6d, 0x485d6e7f, 0xc0b3a291, 0x380ad7a3,  
0xb0600bb6,
     0x28b73fc8, 0xa00d74da, 0x1864a8ec, 0x90badcfe, 0x8111111,  
0x80674523,
     0xf8bd7935, 0x7014ae47, 0xe86ae259, 0x60c1166c, 0xd8174b7e,  
0x506e7f90,
     0xc8c4b3a2, 0x401be8b4, 0xb8711cc7, 0x30c850d9, 0xa81e85eb,  
0x2075b9fd,
     0x98cbed0f, 0x10222222, 0x88785634};

     // answers with rA = 4
     long answer_array4[] = {0x78563412, 0xf0ac6824, 0x68039d36,  
0xe059d148,
     0x58b0055b, 0xd0063a6d, 0x485d6e7f, 0xc0b3a291, 0x380ad7a3,  
0xb0600bb6,
     0x28b73fc8, 0xa00d74da, 0x1864a8ec, 0x90badcfe, 0x8111111,  
0x80674523,
     0xf8bd7935, 0x7014ae47, 0xe86ae259, 0x60c1166c, 0xd8174b7e,  
0x506e7f90,
     0xc8c4b3a2, 0x401be8b4, 0xb8711cc7, 0x30c850d9, 0xa81e85eb,  
0x2075b9fd,
     0x98cbed0f, 0x10222222, 0x88785634, 0x0};

     // answers with rA = 8
     long answer_array8[] = {0xf0ac6824, 0x68039d36, 0xe059d148,  
0x58b0055b,
     0xd0063a6d, 0x485d6e7f, 0xc0b3a291, 0x380ad7a3, 0xb0600bb6,  
0x28b73fc8,
     0xa00d74da, 0x1864a8ec, 0x90badcfe, 0x8111111, 0x80674523,  
0xf8bd7935,
     0x7014ae47, 0xe86ae259, 0x60c1166c, 0xd8174b7e, 0x506e7f90,  
0xc8c4b3a2,
     0x401be8b4, 0xb8711cc7, 0x30c850d9, 0xa81e85eb, 0x2075b9fd,  
0x98cbed0f,
     0x10222222, 0x88785634, 0x0, 0x0};

     // answers with rA = 12
     long answer_array12[] = {0x68039d36, 0xe059d148, 0x58b0055b,  
0xd0063a6d,
     0x485d6e7f, 0xc0b3a291, 0x380ad7a3, 0xb0600bb6, 0x28b73fc8,  
0xa00d74da,
     0x1864a8ec, 0x90badcfe, 0x8111111, 0x80674523, 0xf8bd7935,  
0x7014ae47,
     0xe86ae259, 0x60c1166c, 0xd8174b7e, 0x506e7f90, 0xc8c4b3a2,  
0x401be8b4,
     0xb8711cc7, 0x30c850d9, 0xa81e85eb, 0x2075b9fd, 0x98cbed0f,  
0x10222222,
     0x88785634, 0x0, 0x0, 0x0};

     // Fill up rB array
     for(index = 0; index < rB_size; index++)
     {
         rB[index] = 0x12345678 * index;
     }

     total = 0;
     correct = 0;

     // 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])));
             printf("lwbrx rA: %d  rB: 0x%x  result: 0x%x", rA, rB 
[index], result);
             //printf("0x%x, ", result); // used to make answers

             total++;

             // check recorded answer with calculated answer
             if(result == answer_array[index]) {
                 printf(" correct\n");
                 correct++;
             } else {
                 printf(" WRONG! should be 0x%x\n", answer_array 
[index]);
             }
         }
     }

     printf("Percent correct: %.2f%c\n", correct/total*100, '%');
}

int main (int argc, const char * argv[]) {
     test_lwbrx();
     return 0;
}


This program was tested on a real PowerPC G3 and G5. The results were  
100% when ran in QEMU in a Mac OS 10.4 guest.