[clang] [Serialization] Avoid repeated hash lookups (NFC) (PR #126429)

[Kazu Hirata via cfe-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/126429

None

>From becef8506667f2434f5e5cbbeee493870cff799c Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Sun, 9 Feb 2025 11:18:38 -0800
Subject: [PATCH] [Serialization] Avoid repeated hash lookups (NFC)

---
 clang/lib/Serialization/ASTReader.cpp | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index b74bd586e74d7a9..3c64b67503195c3 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -645,10 +645,11 @@ collectMacroDefinitions(const PreprocessorOptions &PPOpts,
 
     // For an #undef'd macro, we only care about the name.
     if (IsUndef) {
-      if (MacroNames && !Macros.count(MacroName))
+      auto [It, Inserted] = Macros.try_emplace(MacroName);
+      if (MacroNames && Inserted)
         MacroNames->push_back(MacroName);
 
-      Macros[MacroName] = std::make_pair("", true);
+      It->second = std::make_pair("", true);
       continue;
     }
 
@@ -661,9 +662,10 @@ collectMacroDefinitions(const PreprocessorOptions &PPOpts,
       MacroBody = MacroBody.substr(0, End);
     }
 
-    if (MacroNames && !Macros.count(MacroName))
+    auto [It, Inserted] = Macros.try_emplace(MacroName);
+    if (MacroNames && Inserted)
       MacroNames->push_back(MacroName);
-    Macros[MacroName] = std::make_pair(MacroBody, false);
+    It->second = std::make_pair(MacroBody, false);
   }
 }