We only used to add the edge from the cloned loop to PHIs that
corresponded to values defined by the loop. We need to do this for all
PHIs obviously since we need a PHI operand for each incoming edge.
This includes things like PHIs with a constant value or with values
defined before the original loop (see the testcases).
After the patch the PHIs are added to the exit block in two passes.
In the first pass we ensure there is a single-operand (LCSSA) PHI for
each value defined by the loop.
In the second pass we loop through each (single-operand) PHI and add the
value for the edge from the cloned loop. If the value is defined in the
loop we'll use the cloned instruction from the cloned loop.
Fixes PR28037
llvm-svn: 272649
Adam Nemet