try to make comments more meaningful; NFC

Retry r266541 without the range-based-for-loop-change that was wrong.

llvm-svn: 266658

diff --git a/llvm/lib/IR/AutoUpgrade.cpp b/llvm/lib/IR/AutoUpgrade.cpp
index 121b43b..12e269a 100644 (file)
--- a/llvm/lib/IR/AutoUpgrade.cpp
+++ b/llvm/lib/IR/AutoUpgrade.cpp
@@ -802,21 +802,19 @@ void llvm::UpgradeIntrinsicCall(CallInst *CI, Function *NewFn) {
   }
 }
 
-// This tests each Function to determine if it needs upgrading. When we find
-// one we are interested in, we then upgrade all calls to reflect the new
-// function.
-void llvm::UpgradeCallsToIntrinsic(Function* F) {
+void llvm::UpgradeCallsToIntrinsic(Function *F) {
   assert(F && "Illegal attempt to upgrade a non-existent intrinsic.");
 
-  // Upgrade the function and check if it is a totaly new function.
+  // Check if this function should be upgraded and get the replacement function
+  // if there is one.
   Function *NewFn;
   if (UpgradeIntrinsicFunction(F, NewFn)) {
-    // Replace all uses to the old function with the new one if necessary.
-    for (Value::user_iterator UI = F->user_begin(), UE = F->user_end();
-         UI != UE;) {
+    // Replace all users of the old function with the new function or new
+    // instructions. This is not a range loop because the call is deleted.
+    for (auto UI = F->user_begin(), UE = F->user_end(); UI != UE; )
       if (CallInst *CI = dyn_cast<CallInst>(*UI++))
         UpgradeIntrinsicCall(CI, NewFn);
-    }
+
     // Remove old function, no longer used, from the module.
     F->eraseFromParent();
   }