/* { dg-do compile } */
|
/* { dg-do compile } */
|
/* { dg-options "-O2 -Wunsafe-loop-optimizations" } */
|
/* { dg-options "-O2 -Wunsafe-loop-optimizations" } */
|
extern void g(void);
|
extern void g(void);
|
|
|
void
|
void
|
f (unsigned n)
|
f (unsigned n)
|
{
|
{
|
unsigned k;
|
unsigned k;
|
for(k = 0;k <= n;k++) /* { dg-warning "cannot optimize.*infinite loops" } */
|
for(k = 0;k <= n;k++) /* { dg-warning "cannot optimize.*infinite loops" } */
|
g();
|
g();
|
|
|
for(k = 0;k <= n;k += 4) /* { dg-warning "cannot optimize.*overflow" } */
|
for(k = 0;k <= n;k += 4) /* { dg-warning "cannot optimize.*overflow" } */
|
g();
|
g();
|
|
|
/* We used to get warning for this loop. However, since then # of iterations
|
/* We used to get warning for this loop. However, since then # of iterations
|
analysis improved, and we can now prove that this loop does not verflow.
|
analysis improved, and we can now prove that this loop does not verflow.
|
This is because the only case when it would overflow is if n = ~0 (since
|
This is because the only case when it would overflow is if n = ~0 (since
|
~0 is divisible by 5), and this cannot be the case, since when we got
|
~0 is divisible by 5), and this cannot be the case, since when we got
|
here, the previous loop exited, thus there exists k > n. */
|
here, the previous loop exited, thus there exists k > n. */
|
for(k = 5;k <= n;k += 5)
|
for(k = 5;k <= n;k += 5)
|
g();
|
g();
|
|
|
/* So we need the following loop, instead. */
|
/* So we need the following loop, instead. */
|
for(k = 4;k <= n;k += 5) /* { dg-warning "cannot optimize.*overflow" } */
|
for(k = 4;k <= n;k += 5) /* { dg-warning "cannot optimize.*overflow" } */
|
g();
|
g();
|
|
|
for(k = 15;k >= n;k--) /* { dg-warning "cannot optimize.*infinite" } */
|
for(k = 15;k >= n;k--) /* { dg-warning "cannot optimize.*infinite" } */
|
g();
|
g();
|
}
|
}
|
|
|
