[clang] [AArch64][SME] Add diagnostics to CheckConstexprFunctionDefinition (PR #121777)

[Benjamin Maxwell via cfe-commits]

================
@@ -1328,4 +1328,57 @@ void SemaARM::handleInterruptAttr(Decl *D, const ParsedAttr &AL) {
                  ARMInterruptAttr(getASTContext(), AL, Kind));
 }
 
+// Check if the function definition uses any AArch64 SME features without
+// having the '+sme' feature enabled and warn user if sme locally streaming
+// function returns or uses arguments with VL-based types.
+void SemaARM::CheckSMEFunctionDefAttributes(const FunctionDecl *FD) {
+  const auto *Attr = FD->getAttr<ArmNewAttr>();
+  bool UsesSM = FD->hasAttr<ArmLocallyStreamingAttr>();
+  bool UsesZA = Attr && Attr->isNewZA();
+  bool UsesZT0 = Attr && Attr->isNewZT0();
+
+  if (FD->hasAttr<ArmLocallyStreamingAttr>()) {
+    if (FD->getReturnType()->isSizelessVectorType())
+      Diag(FD->getLocation(),
+           diag::warn_sme_locally_streaming_has_vl_args_returns)
+          << /*IsArg=*/false;
+    if (llvm::any_of(FD->parameters(), [](ParmVarDecl *P) {
+          return P->getOriginalType()->isSizelessVectorType();
+        }))
+      Diag(FD->getLocation(),
+           diag::warn_sme_locally_streaming_has_vl_args_returns)
+          << /*IsArg=*/true;
+  }
+  if (const auto *FPT = FD->getType()->getAs<FunctionProtoType>()) {
+    FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
+    UsesSM |= EPI.AArch64SMEAttributes & FunctionType::SME_PStateSMEnabledMask;
+    UsesZA |= FunctionType::getArmZAState(EPI.AArch64SMEAttributes) !=
+              FunctionType::ARM_None;
+    UsesZT0 |= FunctionType::getArmZT0State(EPI.AArch64SMEAttributes) !=
+               FunctionType::ARM_None;
+  }
+
+  ASTContext &Context = getASTContext();
+  if (UsesSM || UsesZA) {
+    llvm::StringMap<bool> FeatureMap;
+    Context.getFunctionFeatureMap(FeatureMap, FD);
+    if (!FeatureMap.contains("sme")) {
+      if (UsesSM)
+        Diag(FD->getLocation(),
+             diag::err_sme_definition_using_sm_in_non_sme_target);
+      else
+        Diag(FD->getLocation(),
+             diag::err_sme_definition_using_za_in_non_sme_target);
+    }
+  }
+  if (UsesZT0) {
+    llvm::StringMap<bool> FeatureMap;
+    Context.getFunctionFeatureMap(FeatureMap, FD);
+    if (!FeatureMap.contains("sme2")) {
+      Diag(FD->getLocation(),
+           diag::err_sme_definition_using_zt0_in_non_sme2_target);
+    }
+  }
+}
----------------
MacDue wrote:

```suggestion
  if (UsesSM || UsesZA || UsesZT0) {
    llvm::StringMap<bool> FeatureMap;
    Context.getFunctionFeatureMap(FeatureMap, FD);
    if (!FeatureMap.contains("sme")) {
      if (UsesSM)
        Diag(FD->getLocation(),
             diag::err_sme_definition_using_sm_in_non_sme_target);
      else
        Diag(FD->getLocation(),
             diag::err_sme_definition_using_za_in_non_sme_target);
    }
    if (!FeatureMap.contains("sme2")) {
      Diag(FD->getLocation(),
           diag::err_sme_definition_using_zt0_in_non_sme2_target);
    }    
  }
}
```

https://github.com/llvm/llvm-project/pull/121777