[SPIRV] Add diagnostic for boolean bitfields (#7822)

Adds a diagnostic to flag the use of boolean bitfields in structs when
targeting SPIR-V. This is not supported for variables that are not
externally visible.

This change introduces a new error message in SemaHLSL to detect and
report this unsupported usage for:
- Local variables
- Function parameters
- Static global variables

A new test file is added to verify the diagnostic is triggered in these
cases and not for externally visible global variables.

Avoid the segfault reported in
#7790.

Author: s-perron

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

@@ -1303,6 +1303,10 @@ def err_not_integral_type_bitfield : Error<
   "bit-field %0 has non-integral type %1">;
 def err_not_integral_type_anon_bitfield : Error<
   "anonymous bit-field has non-integral type %0">;
+def err_spirv_boolean_bitfield_in_type
+    : Error<"type %0 contains a boolean bitfield which is not supported for "
+            "variables that are not externally visible when "
+            "targeting SPIR-V">;
 def err_member_function_initialization : Error<
   "initializer on function does not look like a pure-specifier">;
 def err_non_virtual_pure : Error<

tools/clang/lib/Sema/SemaHLSL.cpp

@@ -16072,6 +16072,33 @@ bool Sema::DiagnoseHLSLDecl(Declarator &D, DeclContext *DC, Expr *BitWidth,
       result = false;
     }
   }
+  if (getLangOpts().SPIRV) {
+    // See https://github.com/microsoft/DirectXShaderCompiler/issues/7790.
+    // Booleans are an abstract type in SPIR-V and cannot be used as a
+    // bitfield container. In variables that are externally visible, the
+    // boolean is turned into an integer, so this is not a problem.
+    if (isLocalVar || isParameter || (isGlobal && isStatic)) {
+      QualType T = qt;
+      if (!T->isDependentType()) {
+        if (const auto *AT = T->getAsArrayTypeUnsafe())
+          T = AT->getElementType();
+
+        if (const RecordType *RT = T->getAs<RecordType>()) {
+          const RecordDecl *RD = RT->getDecl();
+          for (const FieldDecl *FD : RD->fields()) {
+            if (FD->isBitField() && FD->getType()->isBooleanType()) {
+              Diag(D.getIdentifierLoc(),
+                   diag::err_spirv_boolean_bitfield_in_type)
+                  << T;
+              D.setInvalidType();
+              return false;
+            }
+          }
+        }
+      }
+    }
+  }
+
 #endif // ENABLE_SPIRV_CODEGEN
   // SPIRV change ends
 

tools/clang/test/SemaHLSL/spirv-boolean-bitfield.hlsl

@@ -0,0 +1,29 @@
+// RUN: %dxc -T cs_6_0 -E main -spirv -verify %s
+
+struct Test {
+    bool a: 1;
+    int b;
+};
+
+// This should not have an error because it is externally visible.
+RWStructuredBuffer<Test> buffer;
+Test g_non_static_global;
+
+// Global static variable
+static Test g_t; // expected-error {{type 'Test' contains a boolean bitfield which is not supported for variables that are not externally visible when targeting SPIR-V}}
+
+// Global static array
+static Test g_t_arr[2]; // expected-error {{type 'Test' contains a boolean bitfield which is not supported for variables that are not externally visible when targeting SPIR-V}}
+
+void foo(Test p) {} // expected-error {{type 'Test' contains a boolean bitfield which is not supported for variables that are not externally visible when targeting SPIR-V}}
+
+void bar(Test p[2]) {} // expected-error {{type 'Test' contains a boolean bitfield which is not supported for variables that are not externally visible when targeting SPIR-V}}
+
+[numthreads(1, 1, 1)]
+void main() {
+    // Local variable
+    Test t; // expected-error {{type 'Test' contains a boolean bitfield which is not supported for variables that are not externally visible when targeting SPIR-V}}
+
+    // Local array
+    Test t_arr[2]; // expected-error {{type 'Test' contains a boolean bitfield which is not supported for variables that are not externally visible when targeting SPIR-V}}
+}