Apply clang-tidy's modernize-loop-convert to most of lib/Transforms.

Only minor manual fixes. No functionality change intended.

llvm-svn: 273808
diff --git a/llvm/lib/Transforms/IPO/MergeFunctions.cpp b/llvm/lib/Transforms/IPO/MergeFunctions.cpp
index adf0d3f..fe653a7 100644
--- a/llvm/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/llvm/lib/Transforms/IPO/MergeFunctions.cpp
@@ -1578,10 +1578,10 @@
     DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n');
 
     // Insert functions and merge them.
-    for (std::vector<WeakVH>::iterator I = Worklist.begin(),
-           E = Worklist.end(); I != E; ++I) {
-      if (!*I) continue;
-      Function *F = cast<Function>(*I);
+    for (WeakVH &I : Worklist) {
+      if (!I)
+        continue;
+      Function *F = cast<Function>(I);
       if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage()) {
         Changed |= insert(F);
       }