[llvm] 1b42be6 - [Utils] Avoid repeated hash lookups (NFC) (#131267)

[via llvm-commits]

Author: Kazu Hirata
Date: 2025-03-14T07:22:17-07:00
New Revision: 1b42be6fe8b850703e0f8e807234e3cb3332ebe0

URL: https://github.com/llvm/llvm-project/commit/1b42be6fe8b850703e0f8e807234e3cb3332ebe0
DIFF: https://github.com/llvm/llvm-project/commit/1b42be6fe8b850703e0f8e807234e3cb3332ebe0.diff

LOG: [Utils] Avoid repeated hash lookups (NFC) (#131267)

It's safe to use try_emplace instead of operator[] here because:

- PhiPredIVs is empty at the beginning of the loop, and

- The elements we are inserting into PhiPredIVs are unique.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 09bf2c7daf06a..17c5fa6503f20 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -7555,10 +7555,10 @@ bool SimplifyCFGOpt::simplifyDuplicateSwitchArms(SwitchInst *SI,
   // SwitchSuccWrapper.
   PhiPredIVs.reserve(Phis.size());
   for (PHINode *Phi : Phis) {
-    PhiPredIVs[Phi] =
-        SmallDenseMap<BasicBlock *, Value *, 8>(Phi->getNumIncomingValues());
+    auto &IVs =
+        PhiPredIVs.try_emplace(Phi, Phi->getNumIncomingValues()).first->second;
     for (auto &IV : Phi->incoming_values())
-      PhiPredIVs[Phi].insert({Phi->getIncomingBlock(IV), IV.get()});
+      IVs.insert({Phi->getIncomingBlock(IV), IV.get()});
   }
 
   // Build a set such that if the SwitchSuccWrapper exists in the set and