[HLSL] Support register binding attribute on global variable

Allow register binding attribute on variables.

Report warning when register binding attribute applies to local variable or static variable.
It will be ignored in this case.

Type check for register binding is tracked with #57886.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D134617

clang/include/clang/Basic/Attr.td

@@ -133,6 +133,12 @@ def SharedVar : SubsetSubject<Var,
 def GlobalVar : SubsetSubject<Var,
                              [{S->hasGlobalStorage()}], "global variables">;
 
+def ExternalGlobalVar : SubsetSubject<Var,
+                             [{S->hasGlobalStorage() &&
+                               S->getStorageClass()!=StorageClass::SC_Static &&
+                               !S->isLocalExternDecl()}],
+                             "external global variables">;
+
 def InlineFunction : SubsetSubject<Function,
                              [{S->isInlineSpecified()}], "inline functions">;
 
@@ -3992,7 +3998,7 @@ def HLSLSV_GroupIndex: HLSLAnnotationAttr {
 
 def HLSLResourceBinding: InheritableAttr {
   let Spellings = [HLSLSemantic<"register">];
-  let Subjects = SubjectList<[HLSLBufferObj, GlobalVar]>;
+  let Subjects = SubjectList<[HLSLBufferObj, ExternalGlobalVar]>;
   let LangOpts = [HLSL];
   let Args = [StringArgument<"Slot">, StringArgument<"Space", 1>];
   let Documentation = [HLSLResourceBindingDocs];

clang/include/clang/Parse/Parser.h

@@ -2881,8 +2881,19 @@ class Parser : public CodeCompletionHandler {
       Sema::AttributeCompletion Completion = Sema::AttributeCompletion::None,
       const IdentifierInfo *EnclosingScope = nullptr);
 
+  void MaybeParseHLSLSemantics(Declarator &D,
+                               SourceLocation *EndLoc = nullptr) {
+    assert(getLangOpts().HLSL && "MaybeParseHLSLSemantics is for HLSL only");
+    if (Tok.is(tok::colon)) {
+      ParsedAttributes Attrs(AttrFactory);
+      ParseHLSLSemantics(Attrs, EndLoc);
+      D.takeAttributes(Attrs);
+    }
+  }
+
   void MaybeParseHLSLSemantics(ParsedAttributes &Attrs,
                                SourceLocation *EndLoc = nullptr) {
+    assert(getLangOpts().HLSL && "MaybeParseHLSLSemantics is for HLSL only");
     if (getLangOpts().HLSL && Tok.is(tok::colon))
       ParseHLSLSemantics(Attrs, EndLoc);
   }

clang/lib/Parse/ParseDecl.cpp

@@ -2054,6 +2054,9 @@ Parser::DeclGroupPtrTy Parser::ParseDeclGroup(ParsingDeclSpec &DS,
     return nullptr;
   }
 
+  if (getLangOpts().HLSL)
+    MaybeParseHLSLSemantics(D);
+
   if (Tok.is(tok::kw_requires))
     ParseTrailingRequiresClause(D);
 
@@ -2223,6 +2226,10 @@ Parser::DeclGroupPtrTy Parser::ParseDeclGroup(ParsingDeclSpec &DS,
       DiagnoseAndSkipExtendedMicrosoftTypeAttributes();
 
     ParseDeclarator(D);
+
+    if (getLangOpts().HLSL)
+      MaybeParseHLSLSemantics(D);
+
     if (!D.isInvalidType()) {
       // C++2a [dcl.decl]p1
       //    init-declarator:
@@ -7165,7 +7172,8 @@ void Parser::ParseParameterDeclarationClause(
 
     // Parse GNU attributes, if present.
     MaybeParseGNUAttributes(ParmDeclarator);
-    MaybeParseHLSLSemantics(DS.getAttributes());
+    if (getLangOpts().HLSL)
+      MaybeParseHLSLSemantics(DS.getAttributes());
 
     if (Tok.is(tok::kw_requires)) {
       // User tried to define a requires clause in a parameter declaration,

clang/test/AST/HLSL/resource_binding_attr.hlsl

@@ -22,3 +22,16 @@ float foo() {
 // CHECK-NEXT: DeclRefExpr 0x{{[0-9a-f]+}} <col:14> 'float' lvalue Var 0x[[B]] 'b' 'float'
   return a + b;
 }
+
+// CHECK: VarDecl 0x{{[0-9a-f]+}} <{{.*}}> col:17 UAV 'RWBuffer<float>':'hlsl::RWBuffer<>' callinit
+// CHECK-NEXT:-CXXConstructExpr 0x{{[0-9a-f]+}} <col:17> 'RWBuffer<float>':'hlsl::RWBuffer<>' 'void ()'
+// CHECK-NEXT:-HLSLResourceBindingAttr 0x{{[0-9a-f]+}} <col:23> "u3" "space0"
+RWBuffer<float> UAV : register(u3);
+
+// CHECK: -VarDecl 0x{{[0-9a-f]+}} <{{.*}}> col:17 UAV1 'RWBuffer<float>':'hlsl::RWBuffer<>' callinit
+// CHECK-NEXT:-CXXConstructExpr 0x{{[0-9a-f]+}} <col:17> 'RWBuffer<float>':'hlsl::RWBuffer<>' 'void ()'
+// CHECK-NEXT:-HLSLResourceBindingAttr 0x{{[0-9a-f]+}} <col:24> "u2" "space0"
+// CHECK-NEXT:-VarDecl 0x{{[0-9a-f]+}} <col:1, col:38> col:38 UAV2 'RWBuffer<float>':'hlsl::RWBuffer<>' callinit
+// CHECK-NEXT:-CXXConstructExpr 0x{{[0-9a-f]+}} <col:38> 'RWBuffer<float>':'hlsl::RWBuffer<>' 'void ()'
+// CHECK-NEXT:-HLSLResourceBindingAttr 0x{{[0-9a-f]+}} <col:45> "u4" "space0"
+RWBuffer<float> UAV1 : register(u2), UAV2 : register(u4);

clang/test/SemaHLSL/resource_binding_attr_error.hlsl

@@ -1,10 +1,6 @@
 // RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-library -x hlsl -o - -fsyntax-only %s -verify
 
-// expected-error@+5 {{expected ';' after top level declarator}}
-// expected-error@+4 {{expected ')'}}
-// expected-note@+3 {{to match this '('}}
-// expected-error@+2 {{a type specifier is required for all declarations}}
-// expected-error@+1 {{illegal storage class on file-scoped variable}}
+// expected-error@+1 {{invalid resource class specifier 'c' used; expected 'b', 's', 't', or 'u'}}
 float a : register(c0, space1);
 
 // expected-error@+1 {{invalid resource class specifier 'i' used; expected 'b', 's', 't', or 'u'}}
@@ -36,3 +32,29 @@ cbuffer C : register(b 2) {}
 // expected-error@+2 {{wrong argument format for hlsl attribute, use b2 instead}}
 // expected-error@+1 {{wrong argument format for hlsl attribute, use space3 instead}}
 cbuffer D : register(b 2, space 3) {}
+
+// expected-warning@+1 {{'register' attribute only applies to cbuffer/tbuffer and external global variables}}
+static RWBuffer<float> U : register(u5);
+
+void foo() {
+  // expected-warning@+1 {{'register' attribute only applies to cbuffer/tbuffer and external global variables}}
+  RWBuffer<float> U : register(u3);
+}
+void foo2() {
+  // expected-warning@+1 {{'register' attribute only applies to cbuffer/tbuffer and external global variables}}
+  extern RWBuffer<float> U2 : register(u5);
+}
+// FIXME: expect-error once fix https://github.com/llvm/llvm-project/issues/57886.
+float b : register(u0, space1);
+
+// expected-warning@+1 {{'register' attribute only applies to cbuffer/tbuffer and external global variables}}
+void bar(RWBuffer<float> U : register(u3)) {
+
+}
+
+struct S {
+  // FIXME: generate better error when support semantic on struct field.
+  // See https://github.com/llvm/llvm-project/issues/57889.
+  // expected-error@+1 {{expected expression}}
+  RWBuffer<float> U : register(u3);
+};