Use empty() instead of comparing size() with zero.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46514 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/IPO/SimplifyLibCalls.cpp

@@ -740,7 +740,7 @@ public:
     
     // If the constant string's length is zero we can optimize this by just
     // doing a store of 0 at the first byte of the destination
-    if (SrcStr.size() == 0) {
+    if (SrcStr.empty()) {
       new StoreInst(ConstantInt::get(Type::Int8Ty, 0), Dst, CI);
       return ReplaceCallWith(CI, Dst);
     }