When disabling PRE for a value is directly redundant with itself

(through a loop), don't continue to iterate through the reamining
predecessors.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174994 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/GVN.cpp

@@ -2455,7 +2455,9 @@ bool GVN::performPRE(Function &F) {
           PREPred = P;
           ++NumWithout;
         } else if (predV == CurInst) {
+          /* CurInst dominates this predecessor. */
           NumWithout = 2;
+          break;
         } else {
           predMap[P] = predV;
           ++NumWith;