Revert "use range loop, try to make comments more meaningful; NFCI"

This reverts commit r266541 since it introduces a use-after-free:
  http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/11471

llvm-svn: 266550

1 files changed, 10 insertions, 7 deletions

diff --git a/llvm/lib/IR/AutoUpgrade.cpp b/llvm/lib/IR/AutoUpgrade.cpp
index 9ddfc91978e..121b43b7964 100644
--- a/llvm/lib/IR/AutoUpgrade.cpp
+++ b/llvm/lib/IR/AutoUpgrade.cpp
@@ -802,18 +802,21 @@ void llvm::UpgradeIntrinsicCall(CallInst *CI, Function *NewFn) {
   }
 }
 
-void llvm::UpgradeCallsToIntrinsic(Function *F) {
+// 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) {
   assert(F && "Illegal attempt to upgrade a non-existent intrinsic.");
 
-  // Check if this function should be upgraded and get the replacement function
-  // if there is one.
+  // Upgrade the function and check if it is a totaly new function.
   Function *NewFn;
   if (UpgradeIntrinsicFunction(F, NewFn)) {
-    // Replace all users of the old function with the new function or new IR.
-    for (User *U : F->users())
-      if (CallInst *CI = dyn_cast<CallInst>(U))
+    // 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;) {
+      if (CallInst *CI = dyn_cast<CallInst>(*UI++))
         UpgradeIntrinsicCall(CI, NewFn);
-
+    }
     // Remove old function, no longer used, from the module.
     F->eraseFromParent();
   }