[LegacyPM] Avoid a redundant map lookup in setLastUser. NFC.

As a bonus this makes it (IMO) obvious that the iterator is not
invalidated, so remove the comment explaining that.

1 files changed, 2 insertions, 4 deletions

diff --git a/llvm/lib/IR/LegacyPassManager.cpp b/llvm/lib/IR/LegacyPassManager.cpp
index bb2661d..8fd35ef 100644
--- a/llvm/lib/IR/LegacyPassManager.cpp
+++ b/llvm/lib/IR/LegacyPassManager.cpp
@@ -675,11 +675,9 @@ PMTopLevelManager::setLastUser(ArrayRef<Pass*> AnalysisPasses, Pass *P) {
 
     // If AP is the last user of other passes then make P last user of
     // such passes.
-    for (auto LU : LastUser) {
+    for (auto &LU : LastUser) {
       if (LU.second == AP)
-        // DenseMap iterator is not invalidated here because
-        // this is just updating existing entries.
-        LastUser[LU.first] = P;
+        LU.second = P;
     }
   }
 }