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[PATCH 0/2] Loop distribution for memset zero


Michael Matz proposed that it would be a good idea for some CPU2006
benchmarks to add a separate heuristic for the loop distribution pass
for the memset zero pattern, and to enable that at -O3 in order to
exercise the loop distribution code.  The following two patches
implement on top of the current loop distribution pass the heuristic,
and enable it at -O3.

The new pass starts by adding to the partitions working list the data
references that are initialized to zero.  These partitions are then
code generated in different loops, and the current loop distribution
detects the memset zero pattern.

Regstrapped on amd64-linux.

SPEC2006 passed with -O3 (except the dealII compile fail that I
haven't fixed in my sources yet...).

Bootstrap failed with BOOT_CFLAGS="-g -O3", but then when I tried also
without these two patches it also failed with the same miscompiled
files, so bootstrap of trunk is broken at -O3, see

Ok for trunk?


  Add pass_loop_distribute_memset_zero.
  Enable flag_tree_loop_distribute_memset_zero at -O3.

 gcc/common.opt               |    4 ++
 gcc/doc/invoke.texi          |   23 ++++++++++++++-
 gcc/opts.c                   |    1 +
 gcc/passes.c                 |    1 +
 gcc/tree-data-ref.c          |   26 +++++++++++++++++
 gcc/tree-data-ref.h          |    1 +
 gcc/tree-loop-distribution.c |   63 ++++++++++++++++++++++++++++++++++++++++++
 gcc/tree-pass.h              |    1 +
 8 files changed, 119 insertions(+), 1 deletions(-)

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