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

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kazutakahirata
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@kazutakahirata kazutakahirata requested a review from nikic February 9, 2025 19:38
@llvmbot llvmbot added clang Clang issues not falling into any other category clang:modules C++20 modules and Clang Header Modules labels Feb 9, 2025
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llvmbot commented Feb 9, 2025

@llvm/pr-subscribers-clang

Author: Kazu Hirata (kazutakahirata)

Changes

Full diff: https://github.com/llvm/llvm-project/pull/126429.diff

1 Files Affected:

  • (modified) clang/lib/Serialization/ASTReader.cpp (+6-4)
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);
   }
 }
 

@llvmbot
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llvmbot commented Feb 9, 2025

@llvm/pr-subscribers-clang-modules

Author: Kazu Hirata (kazutakahirata)

Changes

Full diff: https://github.com/llvm/llvm-project/pull/126429.diff

1 Files Affected:

  • (modified) clang/lib/Serialization/ASTReader.cpp (+6-4)
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);
   }
 }
 

@kazutakahirata kazutakahirata merged commit b48b422 into llvm:main Feb 9, 2025
11 checks passed
@kazutakahirata kazutakahirata deleted the cleanup_001_repeated_hash_lookups_clang_Serialization branch February 9, 2025 21:33
Icohedron pushed a commit to Icohedron/llvm-project that referenced this pull request Feb 11, 2025
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3 participants