From d69d19103fac01b781e4b7f8f138f0d2440b54c1 Mon Sep 17 00:00:00 2001
From: Rouslan Korneychuk <rouslank@msn.com>
Date: Thu, 18 Jan 2024 16:10:54 -0500
Subject: [PATCH] Improve cross-reference resolution performance in the C++
 domain (#11892)

Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>
---
 CHANGES.rst            |  3 +++
 sphinx/domains/c.py    | 16 +++++++++++++---
 sphinx/domains/cpp.py  | 15 ++++++++++++++-
 sphinx/util/cfamily.py | 12 +++++++++++-
 4 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index 9381798d7..f28248a3c 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -24,6 +24,9 @@ Features added
 * #11803: autodoc: Use an overriden ``__repr__()`` function in an enum,
   if defined. Patch by Shengyu Zhang.
 
+* #11892: Improved performance when resolving cross references in cpp domain.
+  Patch by Rouslan Korneychuk.
+
 Bugs fixed
 ----------
 
diff --git a/sphinx/domains/c.py b/sphinx/domains/c.py
index e3570e6fc..4492224b6 100644
--- a/sphinx/domains/c.py
+++ b/sphinx/domains/c.py
@@ -149,8 +149,12 @@ class ASTIdentifier(ASTBaseBase):
         assert len(identifier) != 0
         self.identifier = identifier
 
-    def __eq__(self, other: Any) -> bool:
-        return type(other) is ASTIdentifier and self.identifier == other.identifier
+    # ASTBaseBase already implements this method,
+    # but specialising it here improves performance
+    def __eq__(self, other: object) -> bool:
+        if type(other) is not ASTIdentifier:
+            return NotImplemented
+        return self.identifier == other.identifier
 
     def is_anon(self) -> bool:
         return self.identifier[0] == '@'
@@ -1448,6 +1452,10 @@ class ASTDeclaration(ASTBaseBase):
         # set by CObject._add_enumerator_to_parent
         self.enumeratorScopedSymbol: Symbol | None = None
 
+        # the cache assumes that by the time get_newest_id is called, no
+        # further changes will be made to this object
+        self._newest_id_cache: str | None = None
+
     def clone(self) -> ASTDeclaration:
         return ASTDeclaration(self.objectType, self.directiveType,
                               self.declaration.clone(), self.semicolon)
@@ -1474,7 +1482,9 @@ class ASTDeclaration(ASTBaseBase):
             return id_
 
     def get_newest_id(self) -> str:
-        return self.get_id(_max_id, True)
+        if self._newest_id_cache is None:
+            self._newest_id_cache = self.get_id(_max_id, True)
+        return self._newest_id_cache
 
     def _stringify(self, transform: StringifyTransform) -> str:
         res = transform(self.declaration)
diff --git a/sphinx/domains/cpp.py b/sphinx/domains/cpp.py
index fcadf1f94..9c00d8748 100644
--- a/sphinx/domains/cpp.py
+++ b/sphinx/domains/cpp.py
@@ -615,6 +615,13 @@ class ASTIdentifier(ASTBase):
         assert len(identifier) != 0
         self.identifier = identifier
 
+    # ASTBaseBase already implements this method,
+    # but specialising it here improves performance
+    def __eq__(self, other: object) -> bool:
+        if type(other) is not ASTIdentifier:
+            return NotImplemented
+        return self.identifier == other.identifier
+
     def _stringify(self, transform: StringifyTransform) -> str:
         return transform(self.identifier)
 
@@ -4018,6 +4025,10 @@ class ASTDeclaration(ASTBase):
         # set by CPPObject._add_enumerator_to_parent
         self.enumeratorScopedSymbol: Symbol | None = None
 
+        # the cache assumes that by the time get_newest_id is called, no
+        # further changes will be made to this object
+        self._newest_id_cache: str | None = None
+
     def clone(self) -> ASTDeclaration:
         templatePrefixClone = self.templatePrefix.clone() if self.templatePrefix else None
         trailingRequiresClasueClone = self.trailingRequiresClause.clone() \
@@ -4083,7 +4094,9 @@ class ASTDeclaration(ASTBase):
         return ''.join(res)
 
     def get_newest_id(self) -> str:
-        return self.get_id(_max_id, True)
+        if self._newest_id_cache is None:
+            self._newest_id_cache = self.get_id(_max_id, True)
+        return self._newest_id_cache
 
     def _stringify(self, transform: StringifyTransform) -> str:
         res = []
diff --git a/sphinx/util/cfamily.py b/sphinx/util/cfamily.py
index 644784ff2..8feb82bcc 100644
--- a/sphinx/util/cfamily.py
+++ b/sphinx/util/cfamily.py
@@ -88,7 +88,7 @@ class NoOldIdError(Exception):
 
 
 class ASTBaseBase:
-    def __eq__(self, other: Any) -> bool:
+    def __eq__(self, other: object) -> bool:
         if type(self) is not type(other):
             return False
         try:
@@ -145,6 +145,11 @@ class ASTGnuAttribute(ASTBaseBase):
         self.name = name
         self.args = args
 
+    def __eq__(self, other: object) -> bool:
+        if type(other) is not ASTGnuAttribute:
+            return NotImplemented
+        return self.name == other.name and self.args == other.args
+
     def _stringify(self, transform: StringifyTransform) -> str:
         res = [self.name]
         if self.args:
@@ -204,6 +209,11 @@ class ASTAttributeList(ASTBaseBase):
     def __init__(self, attrs: list[ASTAttribute]) -> None:
         self.attrs = attrs
 
+    def __eq__(self, other: object) -> bool:
+        if type(other) is not ASTAttributeList:
+            return NotImplemented
+        return self.attrs == other.attrs
+
     def __len__(self) -> int:
         return len(self.attrs)