[PATCH] D136633: [clang][AST] avoid unnecessary FunctionProtoTypes.FindNodeOrInsertPos call

[Troy Johnson via Phabricator via cfe-commits]

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getFunctionTypeInternal forms a FoldingSetNodeID and then calls FunctionProtoTypes.FindNodeOrInsertPos(). Later, upon returning from recursion, it calls FunctionProtoTypes.FindNodeOrInsertPos() again with the same ID. This second call will yield the same InsertPos unless the recursion caused FunctionProtoTypes to rebucket. The rebucketing can be detected by comparing the capacity of the set before and after the recursion, which allows us to skip the redundant call.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D136633

Files:
  clang/lib/AST/ASTContext.cpp


Index: clang/lib/AST/ASTContext.cpp
===================================================================
--- clang/lib/AST/ASTContext.cpp
+++ clang/lib/AST/ASTContext.cpp
@@ -4514,13 +4514,17 @@
 
     // Adjust the canonical function result type.
     CanQualType CanResultTy = getCanonicalFunctionResultType(ResultTy);
+    const auto OrigCapacity = FunctionProtoTypes.capacity();
     Canonical =
         getFunctionTypeInternal(CanResultTy, CanonicalArgs, CanonicalEPI, true);
 
-    // Get the new insert position for the node we care about.
-    FunctionProtoType *NewIP =
-      FunctionProtoTypes.FindNodeOrInsertPos(ID, InsertPos);
-    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
+    // Get the new insert position for the node we care about, if the recursive
+    // call invalidated InsertPos.
+    if (FunctionProtoTypes.capacity() != OrigCapacity) {
+      FunctionProtoType *NewIP =
+        FunctionProtoTypes.FindNodeOrInsertPos(ID, InsertPos);
+      assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
+    }
   }
 
   // Compute the needed size to hold this FunctionProtoType and the


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