[clang] [Sema] Avoid unnecessary copy on MultiLevelTemplateArgumentList. NFC (PR #84459)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 created https://github.com/llvm/llvm-project/pull/84459

We don't modify the MLTAL parameter in `SetupConstraintScope`, and it is better if we don't copy the 120-byte object each time we call the function.

>From 6d51233690d0030e3191198c1a7a330be723b1af Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 8 Mar 2024 18:40:27 +0800
Subject: [PATCH] [Sema] Avoid unnecessary copy on
 MultiLevelTemplateArgumentList. NFC

We don't modify the MLTAL parameter in SetupConstraintScope, and it
is better if we don't copy the 120-byte object each time we call the
function.
---
 clang/include/clang/Sema/Sema.h | 10 ++++++----
 clang/lib/Sema/SemaConcept.cpp  |  3 ++-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 592c7871a4a55d..2cac7e6ca08fad 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -11607,12 +11607,14 @@ class Sema final {
       LocalInstantiationScope &Scope,
       const MultiLevelTemplateArgumentList &TemplateArgs);
 
-  /// used by SetupConstraintCheckingTemplateArgumentsAndScope to recursively(in
+  /// Used by SetupConstraintCheckingTemplateArgumentsAndScope to recursively(in
   /// the case of lambdas) set up the LocalInstantiationScope of the current
   /// function.
-  bool SetupConstraintScope(
-      FunctionDecl *FD, std::optional<ArrayRef<TemplateArgument>> TemplateArgs,
-      MultiLevelTemplateArgumentList MLTAL, LocalInstantiationScope &Scope);
+  bool
+  SetupConstraintScope(FunctionDecl *FD,
+                       std::optional<ArrayRef<TemplateArgument>> TemplateArgs,
+                       const MultiLevelTemplateArgumentList &MLTAL,
+                       LocalInstantiationScope &Scope);
 
   /// Used during constraint checking, sets up the constraint template argument
   /// lists, and calls SetupConstraintScope to set up the
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 2878e4d31ee8fe..a8e387e35fb4c9 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -586,7 +586,8 @@ bool Sema::addInstantiatedCapturesToScope(
 
 bool Sema::SetupConstraintScope(
     FunctionDecl *FD, std::optional<ArrayRef<TemplateArgument>> TemplateArgs,
-    MultiLevelTemplateArgumentList MLTAL, LocalInstantiationScope &Scope) {
+    const MultiLevelTemplateArgumentList &MLTAL,
+    LocalInstantiationScope &Scope) {
   if (FD->isTemplateInstantiation() && FD->getPrimaryTemplate()) {
     FunctionTemplateDecl *PrimaryTemplate = FD->getPrimaryTemplate();
     InstantiatingTemplate Inst(