[clang] [Clang] Optimize some `getBeginLoc` implementations (PR #141058)

[Erich Keane via cfe-commits]

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@@ -1510,41 +1519,41 @@ CallExpr *CallExpr::Create(const ASTContext &Ctx, Expr *Fn,
   unsigned NumArgs = std::max<unsigned>(Args.size(), MinNumArgs);
   unsigned SizeOfTrailingObjects = CallExpr::sizeOfTrailingObjects(
       /*NumPreArgs=*/0, NumArgs, FPFeatures.requiresTrailingStorage());
-  void *Mem =
-      Ctx.Allocate(sizeof(CallExpr) + SizeOfTrailingObjects, alignof(CallExpr));
-  return new (Mem) CallExpr(CallExprClass, Fn, /*PreArgs=*/{}, Args, Ty, VK,
-                            RParenLoc, FPFeatures, MinNumArgs, UsesADL);
+  void *Mem = Ctx.Allocate(
+      sizeToAllocateForCallExprSubclass<CallExpr>(SizeOfTrailingObjects),
+      alignof(CallExpr));
+  CallExpr *E =
+      new (Mem) CallExpr(CallExprClass, Fn, /*PreArgs=*/{}, Args, Ty, VK,
+                         RParenLoc, FPFeatures, MinNumArgs, UsesADL);
+  E->updateTrailingSourceLoc();
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erichkeane wrote:

Same concern here.  We're doing an immediate update, but I wonder if there is value to delaying this call until we are in a 'getBeginLoc`.

https://github.com/llvm/llvm-project/pull/141058