[llvm] [IPO] Avoid repeated hash lookups (NFC) (PR #112821)

[Kazu Hirata via llvm-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/112821

None

>From f32f70575b8c3e0826368300eeeed599e0c78173 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Thu, 17 Oct 2024 07:55:51 -0700
Subject: [PATCH] [IPO] Avoid repeated hash lookups (NFC)

---
 llvm/lib/Transforms/IPO/GlobalDCE.cpp | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/Transforms/IPO/GlobalDCE.cpp b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
index eca36fb31cea0e..9a7447797e723a 100644
--- a/llvm/lib/Transforms/IPO/GlobalDCE.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
@@ -67,16 +67,11 @@ void GlobalDCEPass::ComputeDependencies(Value *V,
     Deps.insert(GV);
   } else if (auto *CE = dyn_cast<Constant>(V)) {
     // Avoid walking the whole tree of a big ConstantExprs multiple times.
-    auto Where = ConstantDependenciesCache.find(CE);
-    if (Where != ConstantDependenciesCache.end()) {
-      auto const &K = Where->second;
-      Deps.insert(K.begin(), K.end());
-    } else {
-      SmallPtrSetImpl<GlobalValue *> &LocalDeps = ConstantDependenciesCache[CE];
+    auto [It, Inserted] = ConstantDependenciesCache.try_emplace(CE);
+    if (Inserted)
       for (User *CEUser : CE->users())
-        ComputeDependencies(CEUser, LocalDeps);
-      Deps.insert(LocalDeps.begin(), LocalDeps.end());
-    }
+        ComputeDependencies(CEUser, It->second);
+    Deps.insert(It->second.begin(), It->second.end());
   }
 }