[Bug 1449119] [NEW] [Ubuntu 15.10] gcc: Optimize swap removal in presence of floating-point vector convert/splat sequence

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On Little Endian systems, GCC performs optimizations to remove
unnecessary element reversals of vectors that are sometimes required to
adjust for behavior of the lxvd2x, etc., instructions.  In one not
uncommon case, such optimizations are defeated when we perform a vector
convert from double-precision to single-precision followed by a vector
splat word.  I have pushed patches upstream to fix this, implemented
using the following revisions:

GCC trunk (6.0):  222351
GCC 5.1:  222394
GCC 4.9:  222420
GCC 4.8:  222427

I would like to see the backported patch applied to the gcc shipped with
the Ubuntu 15.10 release.  We should probably have a conversation about
the next service pack for the 14.04 LTS release as well.

** Affects: gcc-defaults (Ubuntu)
     Importance: Undecided
     Assignee: Matthias Klose (doko)
         Status: In Progress


** Tags: architecture-ppc64le bot-comment bugnameltc-124330 severity-medium targetmilestone-inin1510
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[Ubuntu 15.10] gcc: Optimize swap removal in presence of floating-point vector convert/splat sequence
https://bugs.launchpad.net/bugs/1449119
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