Description:
A non-optimal code sequence is illustrated.  There exists an opportunity to reuse a value loaded in a loop and avoid reloading it on a subsequent iteration of the loop.  Duplicate using gcc 3.5 and command line:

gcc -O3 -m64 -c test.c

Testcase:
typedef struct {
    unsigned int e;
} str;
char *q;

void foo (char *p) {

  while (1) {
    q = p - ((str *)p)->e;
    if (((str *)q)->e) break;
    p = q;
  }

}

Assembly:
 On entry to the loop body, the first "lwz 0,0(9)" is reloading the value already loaded into gpr0 by the peeled iteration of the loop.  On subsequent iterations of the loop, the value has already been loaded by the second lwz on the previous iteration.  Thus, the first lwz is unnecessary.

.foo:
	lwz 0,0(3)
	ld 11,.LC0@toc(2)
	subf 3,0,3
	std 3,0(11)
	lwz 0,0(3)
	cmpwi 7,0,0
	bnelr- 7
	mr 9,3
.L4:
	lwz 0,0(9)  <-- Unnecessary, value is already in gpr 0.
	subf 9,0,9
	std 9,0(11)
	lwz 0,0(9)
	cmpwi 7,0,0
	beq+ 7,.L4
	blr