https://github.com/steffenlarsen updated 
https://github.com/llvm/llvm-project/pull/229008

>From 5fe90f33a2300af0dbbf2ccf2d137c2e7eb2e1a3 Mon Sep 17 00:00:00 2001
From: Steffen Holst Larsen <[email protected]>
Date: Mon, 5 Oct 2026 03:19:41 -0500
Subject: [PATCH 1/7] [Sema][CUDA][HIP] Report deferred diagnostics of
 force-emitted functions

Deferred diagnostics of a __host__ __device__ function are reported once
the function is known to be emitted, which Sema decided from its uses
and external linkage. CodeGen also emits a function regardless of its
uses if it has the used, constructor or destructor attribute, or with
-femit-all-decls, so such inline functions were emitted without their
diagnostics. Treat these functions as emitted, like what
ASTContext::DeclMustBeEmitted does.

Assisted-by: Claude Opus 5.5

Signed-off-by: Steffen Holst Larsen <[email protected]>
---
 clang/lib/Sema/SemaDecl.cpp                   |  8 ++
 .../deferred-diags-forced-emission.cu         | 82 +++++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 clang/test/SemaCUDA/deferred-diags-forced-emission.cu

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 094601a58d508..deaac4178d178 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -21537,6 +21537,14 @@ Sema::FunctionEmissionStatus 
Sema::getEmissionStatus(const FunctionDecl *FD,
 
     if (IsEmittedForExternalSymbol())
       return FunctionEmissionStatus::Emitted;
+
+    // CodeGen also emits a function regardless of its uses if it is forced to,
+    // so its deferred diagnostics must not wait for a use.
+    const FunctionDecl *Def = FD->getDefinition();
+    if (Def && !Def->hasSkippedBody() &&
+        (LangOpts.EmitAllDecls || Def->hasAttr<UsedAttr>() ||
+         Def->hasAttr<ConstructorAttr>() || Def->hasAttr<DestructorAttr>()))
+      return FunctionEmissionStatus::Emitted;
   }
 
   // Otherwise, the function is known-emitted if it's in our set of
diff --git a/clang/test/SemaCUDA/deferred-diags-forced-emission.cu 
b/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
new file mode 100644
index 0000000000000..f588e047b4fe4
--- /dev/null
+++ b/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
@@ -0,0 +1,82 @@
+// RUN: %clang_cc1 -fcxx-exceptions -fcuda-is-device -fsyntax-only 
-verify=dev,dev-used %s
+// RUN: %clang_cc1 -fcxx-exceptions -fsyntax-only -verify=host,host-used %s
+// RUN: %clang_cc1 -fcxx-exceptions -fcuda-is-device -femit-all-decls \
+// RUN:   -fsyntax-only -verify=dev,dev-all %s
+// RUN: %clang_cc1 -fcxx-exceptions -femit-all-decls -fsyntax-only \
+// RUN:   -verify=host,host-all %s
+// RUN: %clang_cc1 -x hip -fcxx-exceptions -fcuda-is-device -fsyntax-only \
+// RUN:   -verify=dev,dev-used %s
+// RUN: %clang_cc1 -x hip -fcxx-exceptions -fsyntax-only 
-verify=host,host-used %s
+
+// The errors are reported in a compilation that emits code too, before the
+// functions are emitted.
+// RUN: %clang_cc1 -fcxx-exceptions -fcuda-is-device -emit-llvm -o /dev/null \
+// RUN:   -verify=dev,dev-used %s
+
+// The deferred diagnostics of a __host__ __device__ function are reported if
+// the function is emitted. Besides the functions that are used, CodeGen emits
+// functions it is forced to emit, whether or not they are used.
+
+#include "Inputs/cuda.h"
+
+__device__ void device_only(); // #device_only
+// host-note@#device_only 4 {{'device_only' declared here}}
+// host-all-note@#device_only {{'device_only' declared here}}
+
+inline __host__ __device__ __attribute__((used)) void used_fn() {
+  throw NULL;
+  // dev-error@-1 {{cannot use 'throw' in __host__ __device__ function}}
+  device_only();
+  // host-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+}
+
+inline __host__ __device__ __attribute__((constructor)) void ctor_fn() {
+  // dev-error@-1 {{CUDA does not support global constructors for __device__ 
functions}}
+  device_only();
+  // host-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+}
+
+inline __host__ __device__ __attribute__((destructor)) void dtor_fn() {
+  // dev-error@-1 {{CUDA does not support global destructors for __device__ 
functions}}
+  device_only();
+  // host-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+}
+
+// Not used, so not emitted unless all declarations are.
+inline __host__ __device__ void unused_fn() {
+  throw NULL;
+  // dev-all-error@-1 {{cannot use 'throw' in __host__ __device__ function}}
+  device_only();
+  // host-all-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+}
+
+// A function used by a forced function is emitted as well.
+inline __host__ __device__ void callee() {
+  throw NULL;
+  // dev-error@-1 {{cannot use 'throw' in __host__ __device__ function}}
+  device_only();
+  // host-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+}
+inline __host__ __device__ __attribute__((used)) void caller() { callee(); }
+// Without -femit-all-decls, callee is only emitted as caller's callee.
+// dev-used-note@-2 {{called by 'caller'}}
+// host-used-note@-3 {{called by 'caller'}}
+
+// The definition inherits the attribute from an earlier declaration.
+__attribute__((used)) inline __host__ __device__ void inherited();
+inline __host__ __device__ void inherited() {
+  throw NULL;
+  // dev-error@-1 {{cannot use 'throw' in __host__ __device__ function}}
+}
+
+// Internal linkage instead of inline.
+static __host__ __device__ __attribute__((used)) void internal() {
+  throw NULL;
+  // dev-error@-1 {{cannot use 'throw' in __host__ __device__ function}}
+}
+
+// An uninstantiated template is not emitted, even with -femit-all-decls.
+template <class T> inline __host__ __device__ void uninstantiated() {
+  throw NULL;
+  device_only();
+}

>From f896b3914b3f62c1ae6af55799269e19ff28aaea Mon Sep 17 00:00:00 2001
From: Steffen Holst Larsen <[email protected]>
Date: Mon, 5 Oct 2026 10:13:26 -0500
Subject: [PATCH 2/7] Add more cases that do not emit

Signed-off-by: Steffen Holst Larsen <[email protected]>
---
 clang/lib/Sema/SemaDecl.cpp                   |  36 ++++-
 .../deferred-diags-forced-emission.cu         | 148 ++++++++++++++++--
 2 files changed, 169 insertions(+), 15 deletions(-)

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index deaac4178d178..f9cc831114413 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -21540,10 +21540,38 @@ Sema::FunctionEmissionStatus 
Sema::getEmissionStatus(const FunctionDecl *FD,
 
     // CodeGen also emits a function regardless of its uses if it is forced to,
     // so its deferred diagnostics must not wait for a use.
-    const FunctionDecl *Def = FD->getDefinition();
-    if (Def && !Def->hasSkippedBody() &&
-        (LangOpts.EmitAllDecls || Def->hasAttr<UsedAttr>() ||
-         Def->hasAttr<ConstructorAttr>() || Def->hasAttr<DestructorAttr>()))
+    auto IsForcedToBeEmitted = [this, FD, Final]() {
+      const FunctionDecl *Def = FD->getDefinition();
+      if (!Def || Def->hasSkippedBody() ||
+          !(LangOpts.EmitAllDecls || getASTContext().DeclMustBeEmitted(Def)))
+        return false;
+      // Immediate functions are never emitted. Whether an immediate-escalating
+      // function is immediate is only known once its body is complete, so
+      // leave that to the check at the end of the translation unit.
+      if (Def->isImmediateFunction() ||
+          (!Final && LangOpts.CPlusPlus20 && Def->isImmediateEscalating()))
+        return false;
+      // Lambdas, implicit functions and functions defaulted on their first
+      // declaration are not handed to CodeGen, so they are only emitted when
+      // used.
+      if (isLambdaMethod(Def) || Def->isImplicit() ||
+          Def->getCanonicalDecl()->isDefaulted())
+        return false;
+      // An available externally definition is only emitted to be inlined into
+      // its callers.
+      if (getASTContext().GetGVALinkageForFunction(Def) ==
+          GVA_AvailableExternally)
+        return false;
+      // Implicit host device templates are only emitted for the device if they
+      // are used on the device.
+      if (LangOpts.CUDAIsDevice &&
+          LangOpts.OffloadImplicitHostDeviceTemplates &&
+          SemaCUDA::isImplicitHostDeviceFunction(Def) && !Def->isConstexpr())
+        return false;
+      return true;
+    };
+
+    if (IsForcedToBeEmitted())
       return FunctionEmissionStatus::Emitted;
   }
 
diff --git a/clang/test/SemaCUDA/deferred-diags-forced-emission.cu 
b/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
index f588e047b4fe4..de1ca6e68f5f5 100644
--- a/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
+++ b/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
@@ -1,17 +1,41 @@
-// RUN: %clang_cc1 -fcxx-exceptions -fcuda-is-device -fsyntax-only 
-verify=dev,dev-used %s
-// RUN: %clang_cc1 -fcxx-exceptions -fsyntax-only -verify=host,host-used %s
-// RUN: %clang_cc1 -fcxx-exceptions -fcuda-is-device -femit-all-decls \
+// RUN: %clang_cc1 -std=c++20 -triple nvptx64-nvidia-cuda \
+// RUN:   -aux-triple x86_64-unknown-linux-gnu -fcxx-exceptions 
-fcuda-is-device \
+// RUN:   -fsyntax-only -verify=dev,dev-used %s
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu 
-fcxx-exceptions \
+// RUN:   -fsyntax-only -verify=host,host-used,host-key %s
+// RUN: %clang_cc1 -std=c++20 -triple nvptx64-nvidia-cuda \
+// RUN:   -aux-triple x86_64-unknown-linux-gnu -fcxx-exceptions 
-fcuda-is-device \
+// RUN:   -femit-all-decls -fsyntax-only -verify=dev,dev-all %s
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu 
-fcxx-exceptions \
+// RUN:   -femit-all-decls -fsyntax-only -verify=host,host-all,host-key %s
+// RUN: %clang_cc1 -std=c++20 -x hip -triple amdgcn-amd-amdhsa \
+// RUN:   -aux-triple x86_64-unknown-linux-gnu -fcxx-exceptions 
-fcuda-is-device \
+// RUN:   -fsyntax-only -verify=dev,dev-used %s
+// RUN: %clang_cc1 -std=c++20 -x hip -triple x86_64-unknown-linux-gnu \
+// RUN:   -fcxx-exceptions -fsyntax-only -verify=host,host-used,host-key %s
+
+// Defaulted functions are immediate-escalating in C++20, which defers their
+// emission status, so check them in C++17 too.
+// RUN: %clang_cc1 -std=c++17 -triple nvptx64-nvidia-cuda \
+// RUN:   -aux-triple x86_64-unknown-linux-gnu -fcxx-exceptions 
-fcuda-is-device \
+// RUN:   -femit-all-decls -fsyntax-only -verify=dev,dev-all,dev-cxx17 %s
+
+// An inline function cannot be a key function in this ABI.
+// RUN: %clang_cc1 -std=c++20 -triple arm64-apple-macosx -fcxx-exceptions \
+// RUN:   -fsyntax-only -verify=host,host-used %s
+
+// Implicit host device templates are only emitted for the device if they are
+// used there, even with -femit-all-decls.
+// RUN: %clang_cc1 -std=c++20 -x hip -triple amdgcn-amd-amdhsa \
+// RUN:   -aux-triple x86_64-unknown-linux-gnu -fcxx-exceptions 
-fcuda-is-device \
+// RUN:   -foffload-implicit-host-device-templates -femit-all-decls \
 // RUN:   -fsyntax-only -verify=dev,dev-all %s
-// RUN: %clang_cc1 -fcxx-exceptions -femit-all-decls -fsyntax-only \
-// RUN:   -verify=host,host-all %s
-// RUN: %clang_cc1 -x hip -fcxx-exceptions -fcuda-is-device -fsyntax-only \
-// RUN:   -verify=dev,dev-used %s
-// RUN: %clang_cc1 -x hip -fcxx-exceptions -fsyntax-only 
-verify=host,host-used %s
 
 // The errors are reported in a compilation that emits code too, before the
 // functions are emitted.
-// RUN: %clang_cc1 -fcxx-exceptions -fcuda-is-device -emit-llvm -o /dev/null \
-// RUN:   -verify=dev,dev-used %s
+// RUN: %clang_cc1 -std=c++20 -triple nvptx64-nvidia-cuda \
+// RUN:   -aux-triple x86_64-unknown-linux-gnu -fcxx-exceptions 
-fcuda-is-device \
+// RUN:   -emit-llvm -o /dev/null -verify=dev,dev-used %s
 
 // The deferred diagnostics of a __host__ __device__ function are reported if
 // the function is emitted. Besides the functions that are used, CodeGen emits
@@ -21,7 +45,9 @@
 
 __device__ void device_only(); // #device_only
 // host-note@#device_only 4 {{'device_only' declared here}}
-// host-all-note@#device_only {{'device_only' declared here}}
+// host-all-note@#device_only 2 {{'device_only' declared here}}
+// host-key-note@#device_only {{'device_only' declared here}}
+__host__ void host_only(); // #host_only
 
 inline __host__ __device__ __attribute__((used)) void used_fn() {
   throw NULL;
@@ -80,3 +106,103 @@ template <class T> inline __host__ __device__ void 
uninstantiated() {
   throw NULL;
   device_only();
 }
+
+// An inline key function is emitted with the vtable.
+struct KeyFunction {
+  virtual __host__ __device__ void key();
+};
+inline __host__ __device__ void KeyFunction::key() {
+  throw NULL;
+  // dev-error@-1 {{cannot use 'throw' in __host__ __device__ function}}
+  device_only();
+  // host-key-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+}
+
+#if __cplusplus >= 202002L
+// dev-all-note@#host_only {{'host_only' declared here}}
+
+// Immediate functions are never emitted, even if forced.
+__attribute__((used)) consteval __host__ __device__ int immediate(int x) {
+  if (x) {
+    (void)&device_only;
+    throw NULL;
+  }
+  return 0;
+}
+
+// Neither is a function that becomes immediate by calling an immediate
+// function, which is only known once its body is complete.
+consteval int id(int x) { return x; }
+template <class T> constexpr __host__ __device__ int escalating(T x) {
+  if (x) {
+    device_only();
+    host_only();
+  }
+  return id(x);
+}
+int escalated = escalating(0);
+
+// Unlike a function that does not become immediate.
+template <class T> constexpr __host__ __device__ int not_escalating(T x) {
+  if (x) {
+    device_only();
+    // host-all-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+    host_only();
+    // dev-all-error@-1 {{reference to __host__ function 'host_only' in 
__host__ __device__ function}}
+  }
+  return x;
+}
+int not_escalated = not_escalating(0);
+#endif
+
+// Lambdas are only emitted if they are used.
+inline auto lambda = [] __attribute__((used)) __host__ __device__ {
+  throw NULL;
+  device_only();
+};
+
+// With -foffload-implicit-host-device-templates, this is an implicit host
+// device function only used on the host.
+template <class T> T implicit_hd(T x) {
+  host_only();
+  return x;
+}
+int host_user() { return implicit_hd(0); }
+
+// An available externally definition is only emitted to be inlined into its
+// callers.
+extern inline __attribute__((gnu_inline, used)) __host__ __device__ void
+available_externally() {
+  throw NULL;
+  device_only();
+}
+
+// Implicit functions and functions defaulted on their first declaration are
+// only emitted when used, here only by host functions.
+struct HostOnly {
+  __host__ HostOnly() {}
+  __host__ ~HostOnly() {} // #host_only_dtor
+  // dev-all-note@#host_only_dtor {{'~HostOnly' declared here}}
+};
+struct Defaulted {
+  HostOnly m;
+  __host__ __device__ ~Defaulted() = default;
+};
+void use_defaulted() { Defaulted d; }
+struct Base {
+  __host__ __device__ Base(int) {}
+};
+struct Inheriting : Base {
+  using Base::Base;
+  HostOnly m;
+};
+void use_inheriting() { Inheriting i(0); }
+
+// Unlike a function defaulted after its first declaration.
+struct DefaultedOutOfLine {
+  HostOnly m;
+  __host__ __device__ ~DefaultedOutOfLine();
+};
+inline __host__ __device__ DefaultedOutOfLine::~DefaultedOutOfLine() = default;
+// dev-all-error@-1 {{reference to __host__ function '~HostOnly' in __host__ 
__device__ function}}
+// dev-cxx17-note@-2 {{in defaulted destructor for 'DefaultedOutOfLine' first 
required here}}

>From c900851dfb7641ab7e80d68b8b51395619e82f0e Mon Sep 17 00:00:00 2001
From: Steffen Holst Larsen <[email protected]>
Date: Tue, 6 Oct 2026 03:31:37 -0500
Subject: [PATCH 3/7] Also consider ctors

Signed-off-by: Steffen Holst Larsen <[email protected]>
---
 clang/lib/Sema/Sema.cpp                       |  5 ++++
 .../SemaCUDA/call-stack-for-deferred-err.cu   | 25 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 29158cfff6231..a3f577b693b46 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -2098,6 +2098,11 @@ class DeferredDiagnosticsEmitter
     if (auto *S = FD->getBody()) {
       this->Visit(S);
     }
+    // A constructor initializes its bases and members, and so calls their
+    // constructors, in its initializer list rather than its body.
+    if (auto *Ctor = dyn_cast<CXXConstructorDecl>(FD))
+      for (CXXCtorInitializer *Init : Ctor->inits())
+        this->Visit(Init->getInit());
     if (CXXDestructorDecl *Dtor = dyn_cast<CXXDestructorDecl>(FD))
       asImpl().VisitCalledDestructors(Dtor);
     UsePath.pop_back();
diff --git a/clang/test/SemaCUDA/call-stack-for-deferred-err.cu 
b/clang/test/SemaCUDA/call-stack-for-deferred-err.cu
index 76bb5116ea283..78bcd744422ed 100644
--- a/clang/test/SemaCUDA/call-stack-for-deferred-err.cu
+++ b/clang/test/SemaCUDA/call-stack-for-deferred-err.cu
@@ -16,3 +16,28 @@ __global__ void kernel() { device_fn2(); } // expected-note 
{{called by 'kernel'
 inline __host__ __device__ void hd_fn(int n) {
   int vla[n]; // expected-error {{variable-length array}}
 }
+
+// A constructor calls the constructors of its bases and members from its
+// initializer list.
+struct Member {
+  __host__ __device__ Member() {
+    int n = 42;
+    int vla[n]; // expected-error {{variable-length array}}
+  }
+};
+struct HasMember { // expected-note {{called by 'HasMember'}}
+  Member m;
+};
+
+struct Base {
+  __host__ __device__ Base() {
+    int n = 42;
+    int vla[n]; // expected-error {{variable-length array}}
+  }
+};
+struct Derived : Base {}; // expected-note {{called by 'Derived'}}
+
+__global__ void ctor_kernel() {
+  HasMember h; // expected-note {{which is called by 'ctor_kernel'}}
+  Derived d;   // expected-note {{which is called by 'ctor_kernel'}}
+}

>From 4b516656ebbf36601b458d4a9d08d2350cec4d14 Mon Sep 17 00:00:00 2001
From: Steffen Holst Larsen <[email protected]>
Date: Fri, 16 Oct 2026 05:19:59 -0500
Subject: [PATCH 4/7] Refactor checks and use common helpers

Signed-off-by: Steffen Holst Larsen <[email protected]>
---
 clang/lib/Sema/SemaDecl.cpp | 73 ++++++++++++++++++-------------------
 1 file changed, 36 insertions(+), 37 deletions(-)

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 0bb4425ae78d8..07cab8a90149e 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -21504,6 +21504,40 @@ void Sema::ActOnPragmaWeakAlias(IdentifierInfo* Name,
   }
 }
 
+/// Whether the definition \p FD is only handed to the ASTConsumer, and thus to
+/// CodeGen, once it is used, so that it is never emitted unless it is used.
+static bool isEmittedOnlyIfUsed(const FunctionDecl *FD) {
+  // Lambda call operators are defined by their lambda expressions, which are
+  // not top-level declarations. Implicit functions and functions defaulted on
+  // their first declaration are defined when they are used.
+  return isLambdaMethod(FD) || FD->isImplicit() ||
+         FD->getCanonicalDecl()->isDefaulted();
+}
+
+/// Whether CodeGen emits \p FD regardless of whether it is used.
+static bool isEmittedRegardlessOfUses(const Sema &S, const FunctionDecl *FD,
+                                      bool Final) {
+  const FunctionDecl *Def = FD->getDefinition();
+  if (!Def || Def->hasSkippedBody())
+    return false;
+  // Immediate functions are never emitted. Whether an immediate-escalating
+  // function is immediate is only known once its body is complete, so leave
+  // that to the check at the end of the translation unit.
+  const LangOptions &LangOpts = S.getLangOpts();
+  if (Def->isImmediateFunction() ||
+      (!Final && LangOpts.CPlusPlus20 && Def->isImmediateEscalating()))
+    return false;
+  if (isEmittedOnlyIfUsed(Def))
+    return false;
+  // An available externally definition is only emitted to be inlined into its
+  // callers.
+  ASTContext &Ctx = S.getASTContext();
+  if (Ctx.GetGVALinkageForFunction(Def) == GVA_AvailableExternally)
+    return false;
+  return Ctx.shouldEmitCUDADecl(Def) &&
+         (LangOpts.EmitAllDecls || Ctx.DeclMustBeEmitted(Def));
+}
+
 Sema::FunctionEmissionStatus Sema::getEmissionStatus(const FunctionDecl *FD,
                                                      bool Final) {
   assert(FD && "Expected non-null FunctionDecl");
@@ -21577,43 +21611,8 @@ Sema::FunctionEmissionStatus 
Sema::getEmissionStatus(const FunctionDecl *FD,
         (T == CUDAFunctionTarget::Device || T == CUDAFunctionTarget::Global))
       return FunctionEmissionStatus::CUDADiscarded;
 
-    if (IsEmittedForExternalSymbol())
-      return FunctionEmissionStatus::Emitted;
-
-    // CodeGen also emits a function regardless of its uses if it is forced to,
-    // so its deferred diagnostics must not wait for a use.
-    auto IsForcedToBeEmitted = [this, FD, Final]() {
-      const FunctionDecl *Def = FD->getDefinition();
-      if (!Def || Def->hasSkippedBody() ||
-          !(LangOpts.EmitAllDecls || getASTContext().DeclMustBeEmitted(Def)))
-        return false;
-      // Immediate functions are never emitted. Whether an immediate-escalating
-      // function is immediate is only known once its body is complete, so
-      // leave that to the check at the end of the translation unit.
-      if (Def->isImmediateFunction() ||
-          (!Final && LangOpts.CPlusPlus20 && Def->isImmediateEscalating()))
-        return false;
-      // Lambdas, implicit functions and functions defaulted on their first
-      // declaration are not handed to CodeGen, so they are only emitted when
-      // used.
-      if (isLambdaMethod(Def) || Def->isImplicit() ||
-          Def->getCanonicalDecl()->isDefaulted())
-        return false;
-      // An available externally definition is only emitted to be inlined into
-      // its callers.
-      if (getASTContext().GetGVALinkageForFunction(Def) ==
-          GVA_AvailableExternally)
-        return false;
-      // Implicit host device templates are only emitted for the device if they
-      // are used on the device.
-      if (LangOpts.CUDAIsDevice &&
-          LangOpts.OffloadImplicitHostDeviceTemplates &&
-          SemaCUDA::isImplicitHostDeviceFunction(Def) && !Def->isConstexpr())
-        return false;
-      return true;
-    };
-
-    if (IsForcedToBeEmitted())
+    if (IsEmittedForExternalSymbol() ||
+        isEmittedRegardlessOfUses(*this, FD, Final))
       return FunctionEmissionStatus::Emitted;
   }
 

>From cae9a2d4ba552f4e327369dcff1292c1af798860 Mon Sep 17 00:00:00 2001
From: Steffen Holst Larsen <[email protected]>
Date: Tue, 20 Oct 2026 03:08:16 -0500
Subject: [PATCH 5/7] Add RTTI test cases

Signed-off-by: Steffen Holst Larsen <[email protected]>
---
 .../deferred-diags-forced-emission.cu         | 41 +++++++++++++++++++
 clang/test/SemaCUDA/device-rtti.cu            | 24 ++++++++++-
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/clang/test/SemaCUDA/deferred-diags-forced-emission.cu 
b/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
index de1ca6e68f5f5..662aac38db288 100644
--- a/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
+++ b/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
@@ -206,3 +206,44 @@ struct DefaultedOutOfLine {
 inline __host__ __device__ DefaultedOutOfLine::~DefaultedOutOfLine() = default;
 // dev-all-error@-1 {{reference to __host__ function '~HostOnly' in __host__ 
__device__ function}}
 // dev-cxx17-note@-2 {{in defaulted destructor for 'DefaultedOutOfLine' first 
required here}}
+
+// Uses of RTTI in device code are diagnosed the same way.
+namespace std {
+class type_info {};
+} // namespace std
+struct Polymorphic {
+  virtual __host__ __device__ ~Polymorphic() {}
+};
+struct DerivedPolymorphic : Polymorphic {};
+
+inline __host__ __device__ __attribute__((used)) void used_rtti(Polymorphic 
*p) {
+  (void)typeid(*p);
+  // dev-error@-1 {{cannot use 'typeid' in __host__ __device__ function as 
RTTI is not available in device code}}
+  (void)dynamic_cast<DerivedPolymorphic *>(p);
+  // dev-error@-1 {{cannot use 'dynamic_cast' in __host__ __device__ function 
as RTTI is not available in device code}}
+}
+
+inline __host__ __device__ void unused_rtti(Polymorphic *p) {
+  (void)typeid(*p);
+  // dev-all-error@-1 {{cannot use 'typeid' in __host__ __device__ function as 
RTTI is not available in device code}}
+}
+
+// A default argument is checked where it is used.
+inline __host__ __device__ void rtti_default_arg(const std::type_info *t = 
&typeid(int)) {}
+// dev-error@-1 {{cannot use 'typeid' in __host__ __device__ function as RTTI 
is not available in device code}}
+inline __host__ __device__ __attribute__((used)) void use_rtti_default_arg() {
+  rtti_default_arg();
+  // dev-note@-1 {{default argument used here}}
+}
+
+// So is a default member initializer, here in the implicit constructor called
+// by a forced function.
+struct RTTIMemberInit { // #rtti_member_init
+  const std::type_info *t = &typeid(int);
+  // dev-error@-1 {{cannot use 'typeid' in __host__ __device__ function as 
RTTI is not available in device code}}
+};
+// dev-note@#rtti_member_init {{default member initializer used here}}
+inline __host__ __device__ __attribute__((used)) void use_rtti_member_init() {
+  RTTIMemberInit m;
+  // dev-note@-1 {{called by 'use_rtti_member_init'}}
+}
diff --git a/clang/test/SemaCUDA/device-rtti.cu 
b/clang/test/SemaCUDA/device-rtti.cu
index c0375dd460ca9..6e508ab7634d0 100644
--- a/clang/test/SemaCUDA/device-rtti.cu
+++ b/clang/test/SemaCUDA/device-rtti.cu
@@ -90,6 +90,12 @@ inline __host__ __device__ void hd3(B *b) {
 __device__ void call_hd3(B *b) { hd3(b); }
 // dev-note@-1 {{called by 'call_hd3'}}
 
+// Error, emitted for device although it is not used there.
+inline __host__ __device__ __attribute__((used)) void hd_used(B *b) {
+  (void)typeid(*b);
+  // dev-error@-1 {{cannot use 'typeid' in __host__ __device__ function as 
RTTI is not available in device code}}
+}
+
 // Templates are checked when they are instantiated.
 template <class T> __device__ T *tmpl_unused(B *b) {
   return dynamic_cast<T *>(b);
@@ -233,13 +239,18 @@ __device__ void use_default_arg() {
   // expected-note@-1 {{default argument used here}}
 }
 
-inline __host__ __device__ void hd_default_arg(const std::type_info *t = 
&typeid(int)) {}
+inline __host__ __device__ void hd_default_arg(const std::type_info *t = 
&typeid(int)) {} // #hd_default_arg
 // expected-error@-1 {{cannot use 'typeid' in __device__ function as RTTI is 
not available in device code}}
 void use_hd_default_arg_host() { hd_default_arg(); }
 __device__ void use_hd_default_arg_device() {
   hd_default_arg();
   // expected-note@-1 {{default argument used here}}
 }
+// dev-error@#hd_default_arg {{cannot use 'typeid' in __host__ __device__ 
function as RTTI is not available in device code}}
+inline __host__ __device__ __attribute__((used)) void 
use_hd_default_arg_used() {
+  hd_default_arg();
+  // dev-note@-1 {{default argument used here}}
+}
 
 // Diagnosed once, at the use, although the default argument is parsed in a
 // __device__ function.
@@ -316,6 +327,17 @@ __device__ void nested_default_arg() {
   (void)n;
 }
 
+// The constructor of a class calls the constructors of its members.
+struct Wrapper { // #wrapper_struct
+  NestedDefaultArg x;
+};
+// dev-note@#wrapper_struct {{called by 'Wrapper'}}
+__device__ void wrapper() {
+  Wrapper n;
+  // dev-note@-1 {{which is called by 'wrapper'}}
+  (void)n;
+}
+
 // A dependent default argument used in a dependent default member initializer.
 template <class T> struct DepNestedDefaultArg { // #dep_nested_struct
   const std::type_info *t = (dep_default_arg<T>(), nullptr);

>From ce0e84e0975f93a795b214274310a3ce9241bb9d Mon Sep 17 00:00:00 2001
From: Steffen Holst Larsen <[email protected]>
Date: Tue, 20 Oct 2026 03:10:47 -0500
Subject: [PATCH 6/7] Remove now redundant change.

Signed-off-by: Steffen Holst Larsen <[email protected]>
---
 clang/lib/Sema/Sema.cpp | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 89a5549544629..bae41a6e6f5cf 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -2104,11 +2104,7 @@ class DeferredDiagnosticsEmitter
       for (auto *Init : Ctor->inits())
         this->Visit(Init->getInit());
     }
-    // A constructor initializes its bases and members, and so calls their
-    // constructors, in its initializer list rather than its body.
-    if (auto *Ctor = dyn_cast<CXXConstructorDecl>(FD))
-      for (CXXCtorInitializer *Init : Ctor->inits())
-        this->Visit(Init->getInit());
+
     if (CXXDestructorDecl *Dtor = dyn_cast<CXXDestructorDecl>(FD))
       asImpl().VisitCalledDestructors(Dtor);
     UsePath.pop_back();

>From fddbf2dea87cc91881a4d332db0d48f4cfa2bfb1 Mon Sep 17 00:00:00 2001
From: Steffen Holst Larsen <[email protected]>
Date: Tue, 20 Oct 2026 03:18:13 -0500
Subject: [PATCH 7/7] Add cases for called lambda and called external def

Signed-off-by: Steffen Holst Larsen <[email protected]>
---
 .../deferred-diags-forced-emission.cu         | 30 ++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/clang/test/SemaCUDA/deferred-diags-forced-emission.cu 
b/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
index 662aac38db288..2176cd53ac0f6 100644
--- a/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
+++ b/clang/test/SemaCUDA/deferred-diags-forced-emission.cu
@@ -44,7 +44,7 @@
 #include "Inputs/cuda.h"
 
 __device__ void device_only(); // #device_only
-// host-note@#device_only 4 {{'device_only' declared here}}
+// host-note@#device_only 6 {{'device_only' declared here}}
 // host-all-note@#device_only 2 {{'device_only' declared here}}
 // host-key-note@#device_only {{'device_only' declared here}}
 __host__ void host_only(); // #host_only
@@ -161,6 +161,19 @@ inline auto lambda = [] __attribute__((used)) __host__ 
__device__ {
   device_only();
 };
 
+// Such as by a forced function.
+inline __host__ __device__ __attribute__((used)) void lambda_caller() {
+  auto lambda = [] {
+    throw NULL;
+    // dev-error@-1 {{cannot use 'throw' in __host__ __device__ function}}
+    device_only();
+    // host-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+  };
+  lambda();
+  // dev-note@-1 {{called by 'lambda_caller'}}
+  // host-note@-2 {{called by 'lambda_caller'}}
+}
+
 // With -foffload-implicit-host-device-templates, this is an implicit host
 // device function only used on the host.
 template <class T> T implicit_hd(T x) {
@@ -177,6 +190,21 @@ available_externally() {
   device_only();
 }
 
+// So it is checked when a forced function calls it.
+extern inline __attribute__((gnu_inline, used)) __host__ __device__ void
+called_available_externally() {
+  throw NULL;
+  // dev-error@-1 {{cannot use 'throw' in __host__ __device__ function}}
+  device_only();
+  // host-error@-1 {{reference to __device__ function 'device_only' in 
__host__ __device__ function}}
+}
+inline __host__ __device__ __attribute__((used)) void
+available_externally_caller() {
+  called_available_externally();
+  // dev-note@-1 {{called by 'available_externally_caller'}}
+  // host-note@-2 {{called by 'available_externally_caller'}}
+}
+
 // Implicit functions and functions defaulted on their first declaration are
 // only emitted when used, here only by host functions.
 struct HostOnly {

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