[llvm] r245394 - [BasicAA] Revert r221876 because it can produce incorrect aliasing

[Nicholas White via llvm-commits]

Sure - http://reviews.llvm.org/D11847 is the most recent version of my
Sext / Zext handling fixes, and has all the edge cases I've found to
date. It was reverted above due to a bug in it, which I've tracked
down to the below. %arrayidx3 and %ra are MayAlias in 3.6.1 but
NoAlias in my most recent patch.

define void @benchmark_heapsort(i32 %n, double* nocapture %ra) {
  %shr = ashr i32 %n, 1
  %add = add nsw i32 %shr, 1
  %arrayidx3 = getelementptr inbounds double, double* %ra, i64 1
  ret void
}

Also, is there an easy way of measuring code coverage of an llvm-lit
run? Given the number of reversions of this patch I think there are
large coverage gaps, as each iteration has passed all the BasicAA unit
tests :(

Thanks -

Nick