[HLSL] Add internal linkage attribute to resources (#166844)

HLSL resources should not be externally visible from the module. We made sure of this by marking them `static` as soon as they were declared. However, this prevents us fixing issue #166458 because there is no way to know if a resource has been explicitly marked `static` by the user, and can therefore be assigned to.

This change moves from making all resources `static` to adding Clang internal linkage attribute to all non-static resource declarations as a global scope.

No explicit test added this change. There is a number of existing HLSL codegen tests that already verify that the resource globals are emitted as `internal global`.

Author: hekota

clang/lib/Sema/SemaHLSL.cpp

@@ -3910,12 +3910,15 @@ void SemaHLSL::ActOnVariableDeclarator(VarDecl *VD) {
     if (VD->getType()->isHLSLIntangibleType())
       collectResourceBindingsOnVarDecl(VD);
 
-    if (isResourceRecordTypeOrArrayOf(VD) ||
-        VD->hasAttr<HLSLVkConstantIdAttr>()) {
-      // Make the variable for resources static. The global externally visible
-      // storage is accessed through the handle, which is a member. The variable
-      // itself is not externally visible.
+    if (VD->hasAttr<HLSLVkConstantIdAttr>())
       VD->setStorageClass(StorageClass::SC_Static);
+
+    if (isResourceRecordTypeOrArrayOf(VD) &&
+        VD->getStorageClass() != SC_Static) {
+      // Add internal linkage attribute to non-static resource variables. The
+      // global externally visible storage is accessed through the handle, which
+      // is a member. The variable itself is not externally visible.
+      VD->addAttr(InternalLinkageAttr::CreateImplicit(getASTContext()));
     }
 
     // process explicit bindings

clang/test/AST/HLSL/cbuffer.hlsl

@@ -153,7 +153,7 @@ cbuffer CB {
   static float SV;
   // CHECK: VarDecl {{.*}} s7 'EmptyStruct' callinit
   EmptyStruct s7;
-  // CHECK: VarDecl {{.*}} Buf 'RWBuffer<float>':'hlsl::RWBuffer<float>' static callinit
+  // CHECK: VarDecl {{.*}} Buf 'RWBuffer<float>':'hlsl::RWBuffer<float>' callinit
   RWBuffer<float> Buf;
   // CHECK: VarDecl {{.*}} ea 'EmptyArrayTypedef':'float[10][0]'
   EmptyArrayTypedef ea;

clang/test/AST/HLSL/private.hlsl

@@ -3,7 +3,7 @@
 // CHECK: VarDecl {{.*}} global_scalar 'hlsl_private int' static cinit
 static int global_scalar = 0;
 
-// CHECK: VarDecl {{.*}} global_buffer 'RWBuffer<float>':'hlsl::RWBuffer<float>' static callinit
+// CHECK: VarDecl {{.*}} global_buffer 'RWBuffer<float>':'hlsl::RWBuffer<float>' callinit
 RWBuffer<float> global_buffer;
 
 class A {