[Clang][AArch64] Add diagnostic for calls from non-ZA to shared-ZA functions.

The caller is required to have ZA state if it wants to share it with a callee.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D157270

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -3629,6 +3629,8 @@ def err_sme_attr_mismatch : Error<
   "function declared %0 was previously declared %1, which has different SME function attributes">;
 def err_sme_call_in_non_sme_target : Error<
   "call to a streaming function requires 'sme'">;
+def err_sme_za_call_no_za_state : Error<
+  "call to a shared ZA function requires the caller to have ZA state">;
 def err_sme_definition_using_sm_in_non_sme_target : Error<
   "function executed in streaming-SVE mode requires 'sme'">;
 def err_sme_definition_using_za_in_non_sme_target : Error<

clang/lib/Sema/SemaChecking.cpp

@@ -6811,6 +6811,22 @@ void Sema::checkCall(NamedDecl *FDecl, const FunctionProtoType *Proto,
         Diag(Loc, diag::err_sme_call_in_non_sme_target);
       }
     }
+
+    // If the callee uses AArch64 SME ZA state but the caller doesn't define
+    // any, then this is an error.
+    if (ExtInfo.AArch64SMEAttributes & FunctionType::SME_PStateZASharedMask) {
+      bool CallerHasZAState = false;
+      if (const auto *CallerFD = dyn_cast<FunctionDecl>(CurContext)) {
+        if (CallerFD->hasAttr<ArmNewZAAttr>())
+          CallerHasZAState = true;
+        else if (const auto *FPT = CallerFD->getType()->getAs<FunctionProtoType>())
+          CallerHasZAState = FPT->getExtProtoInfo().AArch64SMEAttributes &
+                             FunctionType::SME_PStateZASharedMask;
+      }
+
+      if (!CallerHasZAState)
+        Diag(Loc, diag::err_sme_za_call_no_za_state);
+    }
   }
 
   if (FDecl && FDecl->hasAttr<AllocAlignAttr>()) {

clang/test/CodeGen/aarch64-sme-intrinsics/aarch64-sme-attrs.cpp

@@ -255,7 +255,7 @@ int call() { return 0; }
 
 template <typename T, typename... Other>
 __attribute__((always_inline))
-int call(T f, Other... other) {
+int call(T f, Other... other) __arm_shared_za {
     return f() + call(other...);
 }
 
@@ -270,7 +270,7 @@ int call(T f, Other... other) {
 // CHECK-NEXT: add nsw
 // CHECK-NEXT: add nsw
 // CHECK-NEXT: ret
-int test_variadic_template() {
+int test_variadic_template() __arm_shared_za {
   return call(normal_callee,
               streaming_decl,
               streaming_compatible_decl,

clang/test/Sema/aarch64-sme-func-attrs.c

@@ -178,7 +178,31 @@ void redecl_preserve_za(void) __arm_shared_za {}
 void redecl_nopreserve_za(void) __arm_shared_za;
 void redecl_nopreserve_za(void) __arm_shared_za __arm_preserves_za {}
 
+void non_za_definition(void (*shared_za_fn_ptr)(void) __arm_shared_za) {
+  sme_arm_new_za(); // OK
+  // expected-error@+2 {{call to a shared ZA function requires the caller to have ZA state}}
+  // expected-cpp-error@+1 {{call to a shared ZA function requires the caller to have ZA state}}
+  sme_arm_shared_za();
+  // expected-error@+2 {{call to a shared ZA function requires the caller to have ZA state}}
+  // expected-cpp-error@+1 {{call to a shared ZA function requires the caller to have ZA state}}
+  shared_za_fn_ptr();
+}
+
+void shared_za_definition(void (*shared_za_fn_ptr)(void) __arm_shared_za) __arm_shared_za {
+  sme_arm_shared_za(); // OK
+  shared_za_fn_ptr(); // OK
+}
+
+__arm_new_za void new_za_definition(void (*shared_za_fn_ptr)(void) __arm_shared_za) {
+  sme_arm_shared_za(); // OK
+  shared_za_fn_ptr(); // OK
+}
+
 #ifdef __cplusplus
+int shared_za_initializer(void) __arm_shared_za;
+// expected-cpp-error@+1 {{call to a shared ZA function requires the caller to have ZA state}}
+int global = shared_za_initializer();
+
 struct S {
   virtual void shared_za_memberfn(void) __arm_shared_za;
 };