http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55334
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |rguenth at gcc dot gnu.org
--- Comment #23 from Richard Biener <rguenth at gcc dot gnu.org> 2012-12-21
14:27:18 UTC ---
In fact there are a few dependences we can solve:
191: versioning for alias required: can't determine dependence between
MEM[(real(kind=8)[0:D.1986] *)&x + 20247552B][_20] and
MEM[(real(kind=8)[0:D.1989] *)&x + 37823552B][_20]
from
Creating dr for MEM[(real(kind=8)[0:D.1986] *)&x + 20247552B][_20]
analyze_innermost: success.
base_address: &x
offset from base address: (ssizetype) ((sizetype) (((_7 - stride.11_6)
+ pretmp_791) + pretmp_813) * 8)
constant offset from base address: 20247568
step: 8
aligned to: 8
base_object: MEM[(real(kind=8)[0:D.1986] *)&x + 20247552B]
Access function 0: {{(stride.9_4 * 2 + pretmp_792) + 2, +,
stride.9_4}_2, +, 1}_3
and
Creating dr for MEM[(real(kind=8)[0:D.1983] *)&x][_20]
analyze_innermost: success.
base_address: &x
offset from base address: (ssizetype) ((sizetype) (((_7 - stride.11_6)
+ pretmp_791) + pretmp_813) * 8)
constant offset from base address: 16
step: 8
aligned to: 8
base_object: MEM[(real(kind=8)[0:D.1983] *)&x]
Access function 0: {{(stride.9_4 * 2 + pretmp_792) + 2, +,
stride.9_4}_2, +, 1}_3
we hit:
/* If the references do not access the same object, we do not know
whether they alias or not. */
if (!operand_equal_p (DR_BASE_OBJECT (a), DR_BASE_OBJECT (b), 0))
{
DDR_ARE_DEPENDENT (res) = chrec_dont_know;
return res;
}
but for the case the access functions are the same we can conclude the
accesses cannot alias if the base_objects cannot alias (danger! data-ref
does not record an "access size", so with the same access function
but only 1-byte offset in base_object this can lead to false disambiguations,
so it might in the end not be that easy ...) This size issue is also
why we cannot translate the base_object internal offset into an access
function (see testcases I added for bugs we had there)
