Viewing file:  prefetch-5.c (1.28 KB) -rw-r--r--
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/* { dg-do compile { target { i?86-*-* x86_64-*-* } } } */
/* { dg-options "-O2 -fprefetch-loop-arrays -march=amdfam10 --param min-insn-to-prefetch-ratio=5 -fdump-tree-aprefetch-details" } */
/* These are common idioms for writing variable-length arrays at the end
of structures. We should not deduce anything about the number of iterations
of the loops from them. */
struct tail0
{
int xxx;
int yyy[0];
};
int loop0 (int n, struct tail0 *x)
{
int i, s = 0;
for (i = 0; i < n; i++)
s += x->yyy[i];
return s;
}
struct tail1
{
int xxx;
int yyy[1];
};
int loop1 (int n, struct tail1 *x)
{
int i, s = 0;
for (i = 0; i < n; i++)
s += x->yyy[i];
return s;
}
/* It is unlikely that this should be a tail array. We may deduce that most
likely, the loop iterates about 5 times, and the array is not worth prefetching. */
struct tail5
{
int xxx;
int yyy[5];
};
int loop5 (int n, struct tail5 *x)
{
int i, s = 0;
for (i = 0; i < n; i++)
s += x->yyy[i];
return s;
}
/* Until we are able to track likely upper bounds, we can't really work out that
small trailing arrays should not be prefetched. */
/* { dg-final { scan-tree-dump-times "Issued prefetch" 2 "aprefetch" } } */
/* { dg-final { scan-tree-dump-times "Not prefetching" 1 "aprefetch" } } */
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