Constify method.  NFC

llvm-svn: 237167
diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 0b98f6c..b692866 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -490,7 +490,7 @@
 /// This is true when all incoming values are that instruction.
 /// This pattern occurs most often with LCSSA PHI nodes.
 ///
-static bool isTriviallyReplacablePHI(PHINode &PN, Instruction &I) {
+static bool isTriviallyReplacablePHI(const PHINode &PN, const Instruction &I) {
   for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
     if (PN.getIncomingValue(i) != &I)
       return false;