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Subject: [Bug middle-end/55266] vector expansion: 36 movs for 4 adds
Date: Tue, 13 Nov 2012 10:23:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55266

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> 2012-11-13 10:23:03 UTC ---
The first copy is PR 52436.

The second copy has a patch posted here:
http://gcc.gnu.org/ml/gcc-patches/2012-11/msg00900.html

The last copy would require turning:

  gimple_assign <constructor, _5, {_15, _18}, NULL, NULL>
  gimple_assign <ssa_name, *x_2(D), _5, NULL, NULL>

into:

  gimple_assign <ssa_name, *x_2(D), _15, NULL, NULL>
  gimple_assign <ssa_name, MEM[(vec *)x_2(D) + 16B], _18, NULL, NULL>

(not sure if endianness matters here)

which could maybe more easily be done by splitting the memory write (when the
vector type is not supported) into a suitable number of bit_field_ref
extractions and memory writes and relying on forwprop4 to simplify the
bit_field_refs of the constructor.