[Clang] call HandleImmediateInvocation before checking for immediate escacalating expressions (reland)

[cor3ntin]

HandleImmediateInvocation can call MarkExpressionAsImmediateEscalating
and should always be called before CheckImmediateEscalatingFunctionDefinition.

However, we were not doing that in ActFunctionBody.

Fixes #119046

[llvmbot]

@llvm/pr-subscribers-clang

Author: cor3ntin (cor3ntin)

Changes

HandleImmediateInvocation can call MarkExpressionAsImmediateEscalating
and should always be called before CheckImmediateEscalatingFunctionDefinition.

However, we were not doing that in ActFunctionBody.

Fixes #119046

---

Full diff: https://github.com/llvm/llvm-project/pull/124708.diff

5 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+1)
• (modified) clang/include/clang/Sema/Sema.h (+2)
• (modified) clang/lib/Sema/SemaDecl.cpp (+3-1)
• (added) clang/test/CodeGenCXX/gh119046.cpp (+32)
• (modified) clang/test/SemaCXX/cxx2b-consteval-propagate.cpp (+16)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index af3632322b8453..29d549efc7382c 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -1008,6 +1008,7 @@ Bug Fixes to C++ Support
 - Fix type of expression when calling a template which returns an ``__array_rank`` querying a type depending on a
   template parameter. Now, such expression can be used with ``static_assert`` and ``constexpr``. (#GH123498)
 - Correctly determine the implicit constexprness of lambdas in dependent contexts. (#GH97958) (#GH114234)
+- Fix that some dependent immediate expressions did not cause immediate escalation (#GH119046)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 528304409b8092..4f399536cc0ed3 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -13139,10 +13139,12 @@ class Sema final : public SemaBase {
     ~SynthesizedFunctionScope() {
       if (PushedCodeSynthesisContext)
         S.popCodeSynthesisContext();
+
       if (auto *FD = dyn_cast<FunctionDecl>(S.CurContext)) {
         FD->setWillHaveBody(false);
         S.CheckImmediateEscalatingFunctionDefinition(FD, S.getCurFunction());
       }
+
       S.PopExpressionEvaluationContext();
       S.PopFunctionScopeInfo();
     }
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index fe68eadc951b5f..a5afafb750e81e 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -16019,7 +16019,6 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
       if (!FD->isDeletedAsWritten())
         FD->setBody(Body);
       FD->setWillHaveBody(false);
-      CheckImmediateEscalatingFunctionDefinition(FD, FSI);
 
       if (getLangOpts().CPlusPlus14) {
         if (!FD->isInvalidDecl() && Body && !FD->isDependentContext() &&
@@ -16397,6 +16396,9 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
     // the declaration context below. Otherwise, we're unable to transform
     // 'this' expressions when transforming immediate context functions.
 
+  if(FD)
+    CheckImmediateEscalatingFunctionDefinition(FD, getCurFunction());
+
   if (!IsInstantiation)
     PopDeclContext();
 
diff --git a/clang/test/CodeGenCXX/gh119046.cpp b/clang/test/CodeGenCXX/gh119046.cpp
new file mode 100644
index 00000000000000..cad76879f08624
--- /dev/null
+++ b/clang/test/CodeGenCXX/gh119046.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -std=c++2a -triple x86_64-elf-gnu %s -emit-llvm -o - | FileCheck %s
+
+struct S {
+    consteval void operator()() {}
+};
+
+template <class Fn>
+constexpr void dispatch(Fn fn) {
+    fn();
+}
+
+template <class Visitor>
+struct value_visitor {
+    constexpr void operator()() { visitor(); }
+    Visitor&& visitor;
+};
+
+template <class Visitor>
+constexpr auto make_dispatch() {
+    return dispatch<value_visitor<S>>;
+}
+
+template <class Visitor>
+constexpr void visit(Visitor&&) {
+    make_dispatch<Visitor>();
+}
+
+void f() { visit(S{}); }
+
+// CHECK: define {{.*}} @_Z1fv
+// CHECK-NOT: define {{.*}} @_Z5visitI1SEvOT_
+// CHECK-NOT: define {{.*}} @_Z13make_dispatchI1SEDav
diff --git a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
index 05904d9ade067f..dd5063cb29c5b7 100644
--- a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
+++ b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
@@ -560,3 +560,19 @@ void foo() {
     S s;
 }
 } // namespace GH118000
+
+namespace GH119046 {
+
+template <typename Cls> constexpr auto tfn(int) {
+  return (unsigned long long)(&Cls::sfn);
+  //expected-note@-1 {{'tfn<GH119046::S>' is an immediate function because its body evaluates the address of a consteval function 'sfn'}}
+};
+struct S { static consteval void sfn() {} };
+
+int f() {
+  int a = 0; // expected-note{{declared here}}
+  return tfn<S>(a);
+  //expected-error@-1 {{call to immediate function 'GH119046::tfn<GH119046::S>' is not a constant expression}}
+  //expected-note@-2 {{read of non-const variable 'a' is not allowed in a constant expression}}
+}
+}

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[cor3ntin]

Much better https://llvm-compile-time-tracker.com/compare_clang.php?from=0e372c3ea31da276ac67c5972e4ef63514577e9c&to=f58459d08ac3eae3b1c77fb4808da60b6e5bb7ec&stat=instructions%3Au&sortBy=interestingness