[Bug tree-optimization/65310] New: vectorizer uses wrong alignment
rguenth at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Wed Mar 4 11:28:00 GMT 2015
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65310
Bug ID: 65310
Summary: vectorizer uses wrong alignment
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
Noticed by Jan Hubicka in PR65270:
Hi,
while looking for a testcase that would trigger with tree-tail-merge (because
gimple-fold seems to also miss MEM_REF merging) I noticed following oddity:
struct a
{
int a[100000];
};
typedef struct a b __attribute__ ((aligned (32)));
typedef struct a c __attribute__ ((aligned (8)));
typedef struct a d __attribute__ ((aligned (32)));
__attribute__ ((used))
t(b *a, int aligned, b *d)
{
int i,v;
c *ptr = a;
for (i=0;i<100000;i++)
{
ptr->a[i]++;
}
}
main()
{
}
here the loop gets vectorized with assumed alignmen 32.
Changing declaretion to:
t(c *a, int aligned, b *d)
produces correct 8 byte alignment loop.
Alignment of the type of variable A shall not be used.
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