[HLSL2021] Disallow bitfields and annotations (microsoft#4711)

This change makes mixing bitfields and HLSL annotations an error. Since
the syntax for HLSL annotations and bitfields are ambiguous, this change
works around some issues with the ambiguity by disallowing mixing the
two on the same declaration.

Fixes microsoft#4686

Author: llvm-beanz

tools/clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -7457,6 +7457,8 @@ def err_hlsl_attribute_valid_on_function_only: Error<
   "attribute is valid only on functions">;
 def err_hlsl_bitfields: Error<
   "bitfields are not supported in HLSL">;
+def err_hlsl_bitfields_with_annotation: Error<
+  "bitfields are not allowed with HLSL annotations">;
 def err_hlsl_cannot_convert: Error<
   "cannot %select{implicitly |}0convert %select{|output parameter }1from %2 to %3">;
 def err_hlsl_half_load_store: Error<

tools/clang/lib/Sema/SemaHLSL.cpp

@@ -13389,9 +13389,15 @@ bool Sema::DiagnoseHLSLDecl(Declarator &D, DeclContext *DC, Expr *BitWidth,
   // SPIRV change ends
 
   // Disallow bitfields where not enabled explicitly or by HV
-  if (BitWidth && !getLangOpts().EnableBitfields) {
-    Diag(BitWidth->getExprLoc(), diag::err_hlsl_bitfields);
-    result = false;
+  if (BitWidth) {
+    if (!getLangOpts().EnableBitfields) {
+      Diag(BitWidth->getExprLoc(), diag::err_hlsl_bitfields);
+      result = false;
+    } else if (!D.UnusualAnnotations.empty()) {
+      Diag(BitWidth->getExprLoc(),
+           diag::err_hlsl_bitfields_with_annotation);
+      result = false;
+    }
   }
 
   // Validate unusual annotations.

tools/clang/test/HLSL/bitfields-and-annotations.hlsl

@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -HV 2021 -verify %s
+
+struct [raypayload] Payload {
+    int a : 1            : write(caller) : read(anyhit); // expected-error {{bitfields are not allowed with HLSL annotations}}
+    int b : 17           : write(miss)   : read(caller); // expected-error {{bitfields are not allowed with HLSL annotations}}
+    int c  : write(miss) : 13            : read(caller); // expected-error {{bitfields are not allowed with HLSL annotations}}
+    int d  : write(miss) : read(caller);
+};
+
+struct Inputs {
+    int a : 16 : SV_GroupIndex; // expected-error {{bitfields are not allowed with HLSL annotations}}
+    int b : SV_Position : 16;  // expected-error {{bitfields are not allowed with HLSL annotations}}
+};

tools/clang/unittests/HLSL/VerifierTest.cpp

@@ -100,6 +100,7 @@ class VerifierTest TEST_CLASS_DERIVATION {
   TEST_METHOD(RunWriteConstArrays)
   TEST_METHOD(RunAtomicsOnBitfields)
   TEST_METHOD(RunUnboundedResourceArrays)
+  TEST_METHOD(RunBitFieldAnnotations)
   void CheckVerifies(const wchar_t* path) {
     WEX::TestExecution::SetVerifyOutput verifySettings(WEX::TestExecution::VerifyOutputSettings::LogOnlyFailures);
     const char startMarker[] = "%clang_cc1";
@@ -433,3 +434,7 @@ TEST_F(VerifierTest, RunAtomicsOnBitfields) {
 TEST_F(VerifierTest, RunUnboundedResourceArrays) {
   CheckVerifiesHLSL(L"invalid-unbounded-resource-arrays.hlsl");
 }
+
+TEST_F(VerifierTest, RunBitFieldAnnotations) {
+  CheckVerifiesHLSL(L"bitfields-and-annotations.hlsl");
+}