[Bug tree-optimization/37573] [4.4 Regression] gcc-4.4 regression: incorrect code generation with -O1 -ftree-vectorize
irar at il dot ibm dot com
gcc-bugzilla@gcc.gnu.org
Sun Sep 21 07:56:00 GMT 2008
------- Comment #6 from irar at il dot ibm dot com 2008-09-21 07:54 -------
(In reply to comment #5)
> The data dependence on the previous loop is clearly not considered, the loop is
> vectorized as if c on the rhs and c on the lhs were different non-overlapping
> arrays.
>
The data dependence analysis returns chrec_known for that ddr (probably getting
confused by *&s.c[0] and *&s.c[1] base objects), so the vectorizer thinks they
are independent and vectorizes the loop.
*D.1659_13
base_address: &s.c[0]
offset from base address: 0
constant offset from base address: 0
step: 4
aligned to: 128
base_object: *&s.c[0]
symbol tag: SMT.62
*D.1655_9
base_address: &s.c[1]
offset from base address: 0
constant offset from base address: 0
step: 4
aligned to: 128
base_object: *&s.c[1]
symbol tag: SMT.62
(compute_affine_dependence
(stmt_a =
D.1660_14 = *D.1659_13;
)
(stmt_b =
*D.1655_9 = D.1664_23;
)
)
--
irar at il dot ibm dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rakdver at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37573
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