When GVN needs to split critical edges for load PRE, check all of the

When GVN needs to split critical edges for load PRE, check all of the
predecessors before returning.  Otherwise, if multiple predecessor edges need
splitting, we only get one of them per iteration.  This makes a small but
measurable compile time improvement with -enable-full-load-pre.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97521 91177308-0d34-0410-b5e6-96231b3b80d8