[Bug 1353142] Re: subversion tests fail on ppc64el when built with -O3

[William J. Schmidt]

Agree that the code is wrong, and the vectorizer appears to be out of
line.  Out of curiosity, does anything change if the "const" is taken
off of const char* source?  It shouldn't make a difference without
__restrict__, but I'm grasping at straws for why the vectorizer thinks
source and target can be dealiased.  In any case there shouldn't be
anything target-specific about this bug, so opening a GCC tree-
optimization bug is called for...  If you toss me a reduced test case I
can also take a look at the vect-details dump to narrow it down a bit,
but there have been a lot of changes to the vectorizer since I last
poked my nose in there.  (-fvect-cost-model=dynamic didn't even exist,
so I don't know what that is.)

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https://bugs.launchpad.net/bugs/1353142

Title:
  subversion tests fail on ppc64el when built with -O3

Status in “gcc-4.9” package in Ubuntu:
  New
Status in “subversion” package in Ubuntu:
  New

Bug description:
  subversion tests fail on ppc64el when built with -O3, seen in

  https://launchpad.net/ubuntu/+source/subversion/1.8.9-2ubuntu1

  building with -O2 lets the tests succeed
  https://launchpad.net/ubuntu/+source/subversion/1.8.9-2ubuntu2

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