review: update duplicate attrs warning/error

Author: inbelic

clang/lib/Sema/SemaHLSL.cpp

@@ -958,6 +958,16 @@ void SemaHLSL::handleRootSignatureAttr(Decl *D, const ParsedAttr &AL) {
   }
 
   IdentifierInfo *Ident = AL.getArgAsIdent(0)->getIdentifierInfo();
+  if (auto *RS = D->getAttr<RootSignatureAttr>()) {
+    if (RS->getSignature() != Ident) {
+      Diag(AL.getLoc(), diag::err_disallowed_duplicate_attribute) << RS;
+      return;
+    }
+
+    Diag(AL.getLoc(), diag::warn_duplicate_attribute_exact) << RS;
+    return;
+  }
+
   LookupResult R(SemaRef, Ident, SourceLocation(), Sema::LookupOrdinaryName);
   if (SemaRef.LookupQualifiedName(R, D->getDeclContext()))
     if (auto *SignatureDecl =

clang/test/SemaHLSL/RootSignature-err.hlsl

@@ -9,3 +9,9 @@ void bad_root_signature_0() {}
 // expected-note@+1 {{to match this '('}}
 [RootSignature("", "")]
 void bad_root_signature_1() {}
+
+[RootSignature(""), RootSignature("DescriptorTable()")] // expected-error {{attribute 'RootSignature' cannot appear more than once on a declaration}}
+void bad_root_signature_2() {}
+
+[RootSignature(""), RootSignature("")] // expected-warning {{attribute 'RootSignature' is already applied}}
+void bad_root_signature_3() {}