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[Bug tree-optimization/34265] Missed optimizations
- From: "dominiq at lps dot ens dot fr" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 3 Dec 2007 18:58:59 -0000
- Subject: [Bug tree-optimization/34265] Missed optimizations
- References: <bug-34265-12313@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #31 from dominiq at lps dot ens dot fr 2007-12-03 18:58 -------
> If there are no loops, then "straight-line parallelization" [SLP] should vectorize
> your manually unrolled sequence in comment #24.
Yes it should, but if does not after patch #5. The unanswered question so far
is why it does not, then how to change the patch so that it does it. Anyhow,
the "good" vectorization should be along the k loop (length 9 instead of 3). My
understanding of my tests is first that 5/9<2/3 and, more important, the
packing/unpacking overhead is a smaller penalty if it is shared as in the k
vectorization.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34265