Fix creating illegal setcc cond codes.

If GT/UGT or LT/ULT were set to expand, a comparison
with a constant would replace it with the illegal
cond code.

There are several more places later in this function that
will have the same basic problem.

Theoretically R600 should hit this problem for a test,
but for some reason it doesn't.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204727 91177308-0d34-0410-b5e6-96231b3b80d8
ScalarEvolution: Compute exit counts for loops with a power-of-2 step.

If we have a loop of the form
for (unsigned n = 0; n != (k & -32); n += 32) {}
then we know that n is always divisible by 32 and the loop must
terminate. Even if we have a condition where the loop counter will
overflow it'll always hold this invariant.

PR19183. Our loop vectorizer creates this pattern and it's also
occasionally formed by loop counters derived from pointers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204728 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Add failing testcase for <3 x i32> stores.

This is supposed to have the same store size and alignment as <4 x i32>,
but currently is split into a 64-bit and 32-bit store.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204729 91177308-0d34-0410-b5e6-96231b3b80d8