LoopVectorizer: Perform redundancy elimination on induction variables

When the loop vectorizer was part of the SCC inliner pass manager gvn would
run after the loop vectorizer followed by instcombine. This way redundancy
(multiple uses) were removed and instcombine could perform scalarization on the
induction variables. Having moved the loop vectorizer to later we no longer run
any form of redundancy elimination before we perform instcombine. This caused
vectorized induction variables to survive that did not before.

On a recent iMac this helps linpack back from 6000Mflops to 7000Mflops.

This should also help lpbench and paq8p.

I ran a Release (without Asserts) build over the test-suite and did not see any
negative impact on compile time.

radar://15339680

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193891 91177308-0d34-0410-b5e6-96231b3b80d8
DebugInfo: regenerate test case from Clang to adjust for fixes/improvements

I hit some problems with future work due to the member subprogram of
'a_b's type having a subprogram (an implicit default ctor, !52 in the
pre-commit source) with no name. Clang now generates a name for such a
function but in this case doesn't even emit debug info for it as it is
unused (Clang never emits the body of the ctor, instead just emitting
memset if needed).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193892 91177308-0d34-0410-b5e6-96231b3b80d8