[Clang][Sema] improve sema check of clang::musttail attribute

[jcsxky]

Call function with no-return attribute generates code with unreachable instruction instead of return and if the call statement has clang::musttail attribute, it would crash in VerifyPass. Check this condition in Sema ahead.
Fix issue

[llvmbot]

@llvm/pr-subscribers-hlsl

@llvm/pr-subscribers-clang

Author: Qizhi Hu (jcsxky)

Changes

Call function with no-return attribute generate code with unreachable instruction instead of return and if the call statement has clang::musttail attribute, it would crash in Verify. Check this condition in Sema.

---

Full diff: https://github.com/llvm/llvm-project/pull/77727.diff

3 Files Affected:

• (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+2)
• (modified) clang/lib/Sema/SemaStmt.cpp (+6)
• (added) clang/test/SemaCXX/PR76631.cpp (+7)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 3884dca59e2f3b..b40befc5c1cfb5 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3113,6 +3113,8 @@ def err_musttail_scope : Error<
   "cannot perform a tail call from this return statement">;
 def err_musttail_no_variadic : Error<
   "%0 attribute may not be used with variadic functions">;
+def err_musttail_no_return : Error<
+  "%0 attribute may not be used with no-return-attribute functions">;
 
 def err_nsobject_attribute : Error<
   "'NSObject' attribute is for pointer types only">;
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 21efe25ed84a3d..9e7c8c7e4e8c12 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -786,6 +786,12 @@ bool Sema::checkMustTailAttr(const Stmt *St, const Attr &MTA) {
     return false;
   }
 
+  const auto *CalleeDecl = CE->getCalleeDecl();
+  if (CalleeDecl && CalleeDecl->hasAttr<CXX11NoReturnAttr>()) {
+    Diag(St->getBeginLoc(), diag::err_musttail_no_return) << &MTA;
+    return false;
+  }
+
   // Caller and callee must match in whether they have a "this" parameter.
   if (CallerType.This.isNull() != CalleeType.This.isNull()) {
     if (const auto *ND = dyn_cast_or_null<NamedDecl>(CE->getCalleeDecl())) {
diff --git a/clang/test/SemaCXX/PR76631.cpp b/clang/test/SemaCXX/PR76631.cpp
new file mode 100644
index 00000000000000..df89753bd12580
--- /dev/null
+++ b/clang/test/SemaCXX/PR76631.cpp
@@ -0,0 +1,7 @@
+[[noreturn]] void throw_int() {
+  throw int();
+}
+
+void throw_int_wrapper() {
+  [[clang::musttail]] return throw_int(); // expected-error {{'musttail' attribute may not be used with no-return-attribute functions}}
+}

[erichkeane]

Just needs a release note, else LGTM.

[jcsxky]

Just needs a release note, else LGTM.

Release note has been added.