lsw.c

The Valgrind distribution has multiple tools. The most popular is the memory checking tool (called M

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Apparently the "b" register constraint is like "r" except that it
   disallows the use of r0, which means it is safe to use in places
   where the appearance of r0 would cause a problem due to it being
   read as zero. */

static void announce ( char* str )
{
   printf("------ %s ------\n", str);
}

int main ( void )
{
  int i;
  char* a1 = malloc(100);
  char* a2 = malloc(100);
  strcpy(a1,"here is a stringHERE IS A STRING");

  announce("lswi n == 8 (fe special cased)");
  asm volatile("li 5,0\n\t"
               "lswi 3,%0, 8\n\t" 
               "stw 3,0(%1)\n\t"
               "stw 4,4(%1)\n\t"
               "stw 5,8(%1)\n\t"
               : : "b"(a1), "b"(a2) : "r3", "r4", "r5", 
                                      "cc", "memory" );
  printf("%s\n", a2);
  for (i = 0; i < 12; i++)
    printf("%d = 0x%2x\n", i, a2[i]);
  printf("\n");


  announce("lswi n /= 8");
  asm volatile("lswi 3,%0, 9\n\t" 
               "stw 3,0(%1)\n\t"
               "stw 4,4(%1)\n\t"
               "stw 5,8(%1)\n\t"
               : : "b"(a1), "b"(a2) : "r3", "r4", "r5", 
                                      "cc", "memory" );
  printf("%s\n", a2);
  for (i = 0; i < 12; i++)
    printf("%d = 0x%2x\n", i, a2[i]);
  printf("\n");


  announce("lswx");
  free(a2);
  a2 = malloc(100);
  asm volatile("li  8, 11\n\t"
               "mtxer 8\n\t"
               "lswx 3,%0,%2\n\t" 
               "stw 3,0(%1)\n\t"
               "stw 4,4(%1)\n\t"
               "stw 5,8(%1)\n\t"
               : : "b"(a1), "b"(a2), "b"(16) : "r3", "r4", "r5", "r8", 
                                               "cc", "memory" );
  printf("%s\n", a2);
  for (i = 0; i < 12; i++)
     printf("%d = 0x%2x\n", i, a2[i]);
  printf("\n");


  announce("stswi n == 8 (fe special cased)");
  free(a2);
  a2 = calloc(100,1);
  asm volatile("lswi 3,%0, 19\n\t"
               "stswi 3,%1, 8\n"
	       : : "b"(a1), "b"(a2) : "r3","r4","r5","r6","r7",
                                      "cc", "memory" );
  printf("%s\n", a2);
  printf("\n");


  announce("stswi n /= 8");
  free(a2);
  a2 = calloc(100,1);
  asm volatile("lswi 3,%0, 19\n\t"
               "stswi 3,%1, 17\n"
	       : : "b"(a1), "b"(a2) : "r3","r4","r5","r6","r7",
                                      "cc", "memory" );
  printf("%s\n", a2);
  printf("\n");


  announce("stswx");
  free(a2);
  a2 = calloc(100,1);
  asm volatile("li  8, 11\n\t"
               "mtxer 8\n\t"
               "lswx  3,%0,%2\n\t" 
               "stswx 3,%1,%2\n\t" 
               : : "b"(a1), "b"(a2), "b"(16) : "r3", "r4", "r5", "r8", 
                                               "cc", "memory" );
  printf("%s\n", a2+16);
  printf("\n");

  return 0;
}