[HLSL] Support register binding attribute on global variable

[python3kgae]

Summary

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 https://github.com/llvm/llvm-project/issues/57886.

[python3kgae]

Remove empty line.

[aaron.ballman]

clang/include/clang/Parse/Parser.h

2817–2818

Let's assert we're in HLSL mode here so that we don't accidentally call this from non-HLSL parsing contexts.

clang/test/SemaHLSL/resource_binding_attr_error.hlsl

44

51

Let's add another test for a local extern, like:

void func() {
  extern RWBuffer<float> U : register(u5);
}

[python3kgae]

Ignore local extern decl when check ExternalGlobalVar

clang/test/SemaHLSL/resource_binding_attr_error.hlsl

51

Nice catch.
Never know you could do this.

[aaron.ballman]

clang/include/clang/Parse/Parser.h

2817–2818

Precommit CI finds a way to trigger this assert, so it looks like we caught a case we didn't know about (yay asserts!).

[python3kgae]

Limit MaybeParseHLSLSemantics to HLSL.

[python3kgae]

clang/include/clang/Parse/Parser.h

2817–2818

Yeah. Pre-commit CI is really cool. :)

It would be nice if there's an optional config so we can let it test experimental targets too.

[aaron.ballman]

LGTM!

clang/include/clang/Basic/Attr.td

 
 def SharedVar : SubsetSubject<Var,
                               [{S->hasGlobalStorage() && !S->getTLSKind()}],
                               "global variables">;
 
 def GlobalVar : SubsetSubject<Var,
                              [{S->hasGlobalStorage()}], "global variables">;
 
+def ExternalGlobalVar : SubsetSubject<Var,
+                             [{S->hasGlobalStorage() && S->getStorageClass()!=StorageClass::SC_Static}],
+                             "external global variables">;
+
 def InlineFunction : SubsetSubject<Function,
                              [{S->isInlineSpecified()}], "inline functions">;
 
 def FunctionTmpl
     : SubsetSubject<Function, [{S->getTemplatedKind() ==
                                  FunctionDecl::TK_FunctionTemplate}],
                     "function templates">;
 
def HLSLSV_GroupIndex: HLSLAnnotationAttr {
   let Spellings = [HLSLSemantic<"SV_GroupIndex">];
   let Subjects = SubjectList<[ParmVar, GlobalVar]>;
   let LangOpts = [HLSL];
   let Documentation = [HLSLSV_GroupIndexDocs];
 }
 
 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];
 }
 
 def HLSLShader : InheritableAttr {
   let Spellings = [Microsoft<"shader">];
   let Subjects = SubjectList<[HLSLEntry]>;

clang/include/clang/Parse/Parser.h

bool ParseCXX11AttributeArgs(IdentifierInfo *AttrName,
                                SourceLocation ScopeLoc,
                                CachedTokens &OpenMPTokens);
 
   IdentifierInfo *TryParseCXX11AttributeIdentifier(
       SourceLocation &Loc,
       Sema::AttributeCompletion Completion = Sema::AttributeCompletion::None,
       const IdentifierInfo *EnclosingScope = nullptr);
 
+  void MaybeParseHLSLSemantics(Declarator &D,
+                               SourceLocation *EndLoc = nullptr) {
+    if (Tok.is(tok::colon)) {
+      ParsedAttributes Attrs(AttrFactory);
+      ParseHLSLSemantics(Attrs, EndLoc);
+      D.takeAttributes(Attrs);
+    }
+  }
+
   void MaybeParseHLSLSemantics(ParsedAttributes &Attrs,
                                SourceLocation *EndLoc = nullptr) {
     if (getLangOpts().HLSL && Tok.is(tok::colon))
       ParseHLSLSemantics(Attrs, EndLoc);
   }
 
   void ParseHLSLSemantics(ParsedAttributes &Attrs,
                           SourceLocation *EndLoc = nullptr);

clang/lib/Parse/ParseDecl.cpp

Parser::DeclGroupPtrTy Parser::ParseDeclGroup(ParsingDeclSpec &DS,
   ParseDeclarator(D);
 
   // Bail out if the first declarator didn't seem well-formed.
   if (!D.hasName() && !D.mayOmitIdentifier()) {
     SkipMalformedDecl();
     return nullptr;
   }
 
+  if (getLangOpts().HLSL)
+    MaybeParseHLSLSemantics(D);
+
   if (Tok.is(tok::kw_requires))
     ParseTrailingRequiresClause(D);
 
   // Save late-parsed attributes for now; they need to be parsed in the
   // appropriate function scope after the function Decl has been constructed.
   // These will be parsed in ParseFunctionDefinition or ParseLexedAttrList.
   LateParsedAttrList LateParsedAttrs(true);
   if (D.isFunctionDeclarator()) {
while (TryConsumeToken(tok::comma, CommaLoc)) {
     //    short x, __attribute__((common)) var;    -> declarator
     MaybeParseGNUAttributes(D);
 
     // MSVC parses but ignores qualifiers after the comma as an extension.
     if (getLangOpts().MicrosoftExt)
       DiagnoseAndSkipExtendedMicrosoftTypeAttributes();
 
     ParseDeclarator(D);
+
+    if (getLangOpts().HLSL)
+      MaybeParseHLSLSemantics(D);
+
     if (!D.isInvalidType()) {
       // C++2a [dcl.decl]p1
       //    init-declarator:
       //        declarator initializer[opt]
       //        declarator requires-clause
       if (Tok.is(tok::kw_requires))
         ParseTrailingRequiresClause(D);
       Decl *ThisDecl = ParseDeclarationAfterDeclarator(D);

clang/test/AST/HLSL/resource_binding_attr.hlsl

 float foo() {
 // CHECK: BinaryOperator 0x{{[0-9a-f]+}} <col:10, col:14> 'float' '+'
 // CHECK-NEXT: ImplicitCastExpr 0x{{[0-9a-f]+}} <col:10> 'float' <LValueToRValue>
 // CHECK-NEXT: DeclRefExpr 0x{{[0-9a-f]+}} <col:10> 'float' lvalue Var 0x[[A]] 'a' 'float'
 // CHECK-NEXT: ImplicitCastExpr 0x{{[0-9a-f]+}} <col:14> 'float' <LValueToRValue>
 // 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

 // 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'}}
 cbuffer b : register(i0) {
 
 }
 // expected-error@+1 {{invalid space specifier 's2' used; expected 'space' followed by an integer, like space1}}
 cbuffer c : register(b0, s2) {

 cbuffer B : register(space1) {}
 
 // expected-error@+1 {{wrong argument format for hlsl attribute, use b2 instead}}
 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);
+}
+
+// FIXEME: 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);
+};