blob: 906132c6916c0fde5d936b0c8b2c9524c3870de5 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
|
/* { dg-do compile } */
/* { dg-options "-O2 -Wunsafe-loop-optimizations" } */
extern void g(void);
void
f (unsigned n)
{
unsigned k;
for(k = 0;k <= n;k++) /* { dg-warning "cannot optimize.*infinite loops" } */
g();
for(k = 0;k <= n;k += 4) /* { dg-warning "cannot optimize.*overflow" } */
g();
/* 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.
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
here, the previous loop exited, thus there exists k > n. */
for(k = 5;k <= n;k += 5)
g();
/* So we need the following loop, instead. */
for(k = 4;k <= n;k += 5) /* { dg-warning "cannot optimize.*overflow" } */
g();
for(k = 15;k >= n;k--) /* { dg-warning "cannot optimize.*infinite" } */
g();
}
|
