Extended Description

In this example code:

#include <stdlib.h>
#include <string.h>
#define TESTSTRING2 "Dot. date. datum. 123. Some more doubtful demonstration dummy data."
int stringSearch_Clib (long count) {
int i, c = 0;long j;char * p;
char b[sizeof(TESTSTRING2)];

strcpy (b, TESTSTRING2);
for (j=0; j < count; j++) {
for (c=i=0; i < 250; i++) {
if (NULL != (p = strstr (b, "ummy"))) c += (int) (p - b);
if (NULL != (p = strstr (b, " data"))) c += (int) (p - b);
c += (int) strcspn (b, "by");
}
}
return c;
}

The calls to strstr and strcspn are loop invariant and should be hoisted. They aren't though, because
the inner loop isn't getting rotated. This can easily be seen with:

$ llvm-gcc t.c -emit-llvm -O3 -o - -S | llvm-as | opt -print-cfg

and then viewing cfg.stringSearch_Clib.dot.

-Chris