[IndVar] Don't widen loop compare unless IV user is sign extended.
PR21030

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218539 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Fix a moderately terrifying bug in the new 128-bit shuffle logic
that managed to elude all of my fuzz testing historically. =/

Something changed to allow this code path to actually be exercised and
it was doing bad things. It is especially heavily exercised by the
patterns that emerge when doing AVX shuffles that end up lowered through
the 128-bit code path.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218540 91177308-0d34-0410-b5e6-96231b3b80d8