[HLSL] Implement RWBuffer::operator[] via __builtin_hlsl_resource_getpointer

This introduces `__builtin_hlsl_resource_getpointer`, which lowers to
`llvm.dx.resource.getpointer` and is used to implement indexing into resources.

This will only work through the backend for typed buffers at this point, but
the changes to structured buffers should be correct as far as the frontend is
concerned.

Note: We probably want this to return a reference in the HLSL device address
space, but for now we're just using address space 0. Creating a device address
space and updating this code can be done later as necessary.

Fixes llvm#95956

Author: bogner

clang/include/clang/Basic/Builtins.td

@@ -4738,6 +4738,12 @@ def GetDeviceSideMangledName : LangBuiltin<"CUDA_LANG"> {
 }
 
 // HLSL
+def HLSLTypedBufferPointer : LangBuiltin<"HLSL_LANG"> {
+  let Spellings = ["__builtin_hlsl_resource_getpointer"];
+  let Attributes = [NoThrow];
+  let Prototype = "void(...)";
+}
+
 def HLSLAll : LangBuiltin<"HLSL_LANG"> {
   let Spellings = ["__builtin_hlsl_all"];
   let Attributes = [NoThrow, Const];

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -12496,6 +12496,7 @@ def err_hlsl_pointers_unsupported : Error<
   "%select{pointers|references}0 are unsupported in HLSL">;
 def err_hlsl_missing_resource_class : Error<"HLSL resource needs to have [[hlsl::resource_class()]] attribute">;
 def err_hlsl_attribute_needs_intangible_type: Error<"attribute %0 can be used only on HLSL intangible type %1">;
+def err_hlsl_builtin_requires_resource: Error<"operand must be of __hlsl_resource_t type">;
 
 def err_hlsl_operator_unsupported : Error<
   "the '%select{&|*|->}0' operator is unsupported in HLSL">;

clang/lib/AST/Type.cpp

@@ -4723,7 +4723,9 @@ LinkageInfo LinkageComputer::computeTypeLinkageInfo(const Type *T) {
   case Type::Pipe:
     return computeTypeLinkageInfo(cast<PipeType>(T)->getElementType());
   case Type::HLSLAttributedResource:
-    llvm_unreachable("not yet implemented");
+    return computeTypeLinkageInfo(cast<HLSLAttributedResourceType>(T)
+                                      ->getContainedType()
+                                      ->getCanonicalTypeInternal());
   }
 
   llvm_unreachable("unhandled type class");

clang/lib/CodeGen/CGBuiltin.cpp

@@ -19044,6 +19044,16 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
     return nullptr;
 
   switch (BuiltinID) {
+  case Builtin::BI__builtin_hlsl_resource_getpointer: {
+    Value *HandleOp = EmitScalarExpr(E->getArg(0));
+    Value *IndexOp = EmitScalarExpr(E->getArg(1));
+
+    // TODO: Map to an hlsl_device address space.
+    llvm::Type *RetTy = llvm::PointerType::getUnqual(getLLVMContext());
+
+    return Builder.CreateIntrinsic(RetTy, Intrinsic::dx_resource_getpointer,
+                                   ArrayRef<Value *>{HandleOp, IndexOp});
+  }
   case Builtin::BI__builtin_hlsl_all: {
     Value *Op0 = EmitScalarExpr(E->getArg(0));
     return Builder.CreateIntrinsic(

clang/lib/Sema/HLSLExternalSemaSource.cpp

@@ -218,23 +218,33 @@ struct BuiltinTypeDeclBuilder {
     auto FnProtoLoc = TSInfo->getTypeLoc().getAs<FunctionProtoTypeLoc>();
     FnProtoLoc.setParam(0, IdxParam);
 
-    // FIXME: Placeholder to make sure we return the correct type - create
-    // field of element_type and return reference to it. This field will go
-    // away once indexing into resources is properly implemented in
-    // llvm/llvm-project#95956.
-    if (Fields.count("e") == 0) {
-      addMemberVariable("e", ElemTy, {});
-    }
-    FieldDecl *ElemFieldDecl = Fields["e"];
-
     auto *This =
         CXXThisExpr::Create(AST, SourceLocation(),
                             MethodDecl->getFunctionObjectParameterType(), true);
-    Expr *ElemField = MemberExpr::CreateImplicit(
-        AST, This, false, ElemFieldDecl, ElemFieldDecl->getType(), VK_LValue,
-        OK_Ordinary);
-    auto *Return =
-        ReturnStmt::Create(AST, SourceLocation(), ElemField, nullptr);
+    FieldDecl *Handle = Fields["__handle"];
+    auto *HandleExpr = MemberExpr::CreateImplicit(
+        AST, This, false, Handle, Handle->getType(), VK_LValue, OK_Ordinary);
+
+    auto *IndexExpr = DeclRefExpr::Create(
+        AST, NestedNameSpecifierLoc(), SourceLocation(), IdxParam, false,
+        DeclarationNameInfo(IdxParam->getDeclName(), SourceLocation()),
+        AST.UnsignedIntTy, VK_PRValue);
+
+    FunctionDecl *FD =
+        lookupBuiltinFunction(SemaRef, "__builtin_hlsl_resource_getpointer");
+    DeclRefExpr *Builtin = DeclRefExpr::Create(
+        AST, NestedNameSpecifierLoc(), SourceLocation(), FD, false,
+        FD->getNameInfo(), AST.BuiltinFnTy, VK_PRValue);
+
+    // TODO: Map to an hlsl_device address space.
+    QualType ElemPtrTy = AST.getPointerType(ElemTy);
+    Expr *Call = CallExpr::Create(AST, Builtin, {HandleExpr, IndexExpr},
+                                  ElemPtrTy, VK_PRValue,
+                                  SourceLocation(), FPOptionsOverride());
+    Expr *Deref = UnaryOperator::Create(
+        AST, Call, UO_Deref, ElemTy, VK_PRValue, OK_Ordinary, SourceLocation(),
+        /*CanOverflow=*/false, FPOptionsOverride());
+    auto *Return = ReturnStmt::Create(AST, SourceLocation(), Deref, nullptr);
 
     MethodDecl->setBody(CompoundStmt::Create(AST, {Return}, FPOptionsOverride(),
                                              SourceLocation(),

clang/lib/Sema/SemaExpr.cpp

@@ -980,6 +980,9 @@ Sema::VarArgKind Sema::isValidVarArgType(const QualType &Ty) {
   if (Ty->isObjCObjectType())
     return VAK_Invalid;
 
+  if (getLangOpts().HLSL && Ty->getAs<HLSLAttributedResourceType>())
+    return VAK_Valid;
+
   if (getLangOpts().MSVCCompat)
     return VAK_MSVCUndefined;
 

clang/lib/Sema/SemaHLSL.cpp

@@ -1926,6 +1926,25 @@ static bool CheckResourceHandle(
 // returning an ExprError
 bool SemaHLSL::CheckBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
   switch (BuiltinID) {
+  case Builtin::BI__builtin_hlsl_resource_getpointer: {
+    if (SemaRef.checkArgCount(TheCall, 2))
+      return true;
+    auto *ResourceTy =
+        TheCall->getArg(0)->getType()->getAs<HLSLAttributedResourceType>();
+    if (!ResourceTy) {
+      SemaRef.Diag(TheCall->getBeginLoc(),
+                   diag::err_hlsl_builtin_requires_resource)
+          << TheCall->getArg(0)->getSourceRange();
+      return true;
+    }
+
+    QualType ContainedTy = ResourceTy->getContainedType();
+    // TODO: Map to an hlsl_device address space.
+    TheCall->setType(getASTContext().getPointerType(ContainedTy));
+    TheCall->setValueKind(VK_LValue);
+
+    break;
+  }
   case Builtin::BI__builtin_hlsl_all:
   case Builtin::BI__builtin_hlsl_any: {
     if (SemaRef.checkArgCount(TheCall, 1))

clang/test/AST/HLSL/StructuredBuffers-AST.hlsl

@@ -78,16 +78,32 @@ RESOURCE<float> Buffer;
 // CHECK-SUBSCRIPT-NEXT: ParmVarDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> Idx 'unsigned int'
 // CHECK-SUBSCRIPT-NEXT: CompoundStmt 0x{{[0-9A-Fa-f]+}} <<invalid sloc>>
 // CHECK-SUBSCRIPT-NEXT: ReturnStmt 0x{{[0-9A-Fa-f]+}} <<invalid sloc>>
-// CHECK-SUBSCRIPT-NEXT: MemberExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type' lvalue .e 0x{{[0-9A-Fa-f]+}}
+// CHECK-SUBSCRIPT-NEXT: UnaryOperator 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type' prefix '*' cannot overflow
+// CHECK-SUBSCRIPT-NEXT: CallExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type *'
+// CHECK-SUBSCRIPT-NEXT: DeclRefExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '<builtin fn type>' Function 0x{{[0-9A-Fa-f]+}} '__builtin_hlsl_resource_getpointer' 'void (...) noexcept'
+// CHECK-SUBSCRIPT-NEXT: MemberExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '__hlsl_resource_t
+// CHECK-SUBSCRIPT-SAME{LITERAL}: [[hlsl::resource_class(
+// CHECK-SUBSCRIPT-SAME{LITERAL}: [[hlsl::raw_buffer]]
+// CHECK-SUBSCRIPT-SAME{LITERAL}: [[hlsl::contained_type(element_type)]]
+// CHECK-SUBSCRIPT-SAME: ' lvalue .__handle 0x{{[0-9A-Fa-f]+}}
 // CHECK-SUBSCRIPT-NEXT: CXXThisExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'const [[RESOURCE]]<element_type>' lvalue implicit this
+// CHECK-SUBSCRIPT-NEXT: DeclRefExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'unsigned int' ParmVar 0x{{[0-9A-Fa-f]+}} 'Idx' 'unsigned int'
 // CHECK-SUBSCRIPT-NEXT: AlwaysInlineAttr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> Implicit always_inline
 
 // CHECK-SUBSCRIPT-NEXT: CXXMethodDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> operator[] 'element_type &(unsigned int)'
 // CHECK-SUBSCRIPT-NEXT: ParmVarDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> Idx 'unsigned int'
 // CHECK-SUBSCRIPT-NEXT: CompoundStmt 0x{{[0-9A-Fa-f]+}} <<invalid sloc>>
 // CHECK-SUBSCRIPT-NEXT: ReturnStmt 0x{{[0-9A-Fa-f]+}} <<invalid sloc>>
-// CHECK-SUBSCRIPT-NEXT: MemberExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type' lvalue .e 0x{{[0-9A-Fa-f]+}}
+// CHECK-SUBSCRIPT-NEXT: UnaryOperator 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type' prefix '*' cannot overflow
+// CHECK-SUBSCRIPT-NEXT: CallExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type *'
+// CHECK-SUBSCRIPT-NEXT: DeclRefExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '<builtin fn type>' Function 0x{{[0-9A-Fa-f]+}} '__builtin_hlsl_resource_getpointer' 'void (...) noexcept'
+// CHECK-SUBSCRIPT-NEXT: MemberExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '__hlsl_resource_t
+// CHECK-SUBSCRIPT-SAME{LITERAL}: [[hlsl::resource_class(
+// CHECK-SUBSCRIPT-SAME{LITERAL}: [[hlsl::raw_buffer]]
+// CHECK-SUBSCRIPT-SAME{LITERAL}: [[hlsl::contained_type(element_type)]]
+// CHECK-SUBSCRIPT-SAME: ' lvalue .__handle 0x{{[0-9A-Fa-f]+}}
 // CHECK-SUBSCRIPT-NEXT: CXXThisExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '[[RESOURCE]]<element_type>' lvalue implicit this
+// CHECK-SUBSCRIPT-NEXT: DeclRefExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'unsigned int' ParmVar 0x{{[0-9A-Fa-f]+}} 'Idx' 'unsigned int'
 // CHECK-SUBSCRIPT-NEXT: AlwaysInlineAttr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> Implicit always_inline
 
 // CHECK-NOSUBSCRIPT-NOT: CXXMethodDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> operator[] 'const element_type &(unsigned int) const'

clang/test/AST/HLSL/TypedBuffers-AST.hlsl

@@ -61,16 +61,30 @@ RESOURCE<float> Buffer;
 // CHECK-NEXT: ParmVarDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> Idx 'unsigned int'
 // CHECK-NEXT: CompoundStmt 0x{{[0-9A-Fa-f]+}} <<invalid sloc>>
 // CHECK-NEXT: ReturnStmt 0x{{[0-9A-Fa-f]+}} <<invalid sloc>>
-// CHECK-NEXT: MemberExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type' lvalue .e 0x{{[0-9A-Fa-f]+}}
+// CHECK-NEXT: UnaryOperator 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type' prefix '*' cannot overflow
+// CHECK-NEXT: CallExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type *'
+// CHECK-NEXT: DeclRefExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '<builtin fn type>' Function 0x{{[0-9A-Fa-f]+}} '__builtin_hlsl_resource_getpointer' 'void (...) noexcept'
+// CHECK-NEXT: MemberExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '__hlsl_resource_t
+// CHECK-SAME{LITERAL}: [[hlsl::resource_class(UAV)]]
+// CHECK-SAME{LITERAL}: [[hlsl::contained_type(element_type)]]
+// CHECK-SAME: ' lvalue .__handle 0x{{[0-9A-Fa-f]+}}
 // CHECK-NEXT: CXXThisExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'const [[RESOURCE]]<element_type>' lvalue implicit this
+// CHECK-NEXT: DeclRefExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'unsigned int' ParmVar 0x{{[0-9A-Fa-f]+}} 'Idx' 'unsigned int'
 // CHECK-NEXT: AlwaysInlineAttr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> Implicit always_inline
 
 // CHECK-NEXT: CXXMethodDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> operator[] 'element_type &(unsigned int)'
 // CHECK-NEXT: ParmVarDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> Idx 'unsigned int'
 // CHECK-NEXT: CompoundStmt 0x{{[0-9A-Fa-f]+}} <<invalid sloc>>
 // CHECK-NEXT: ReturnStmt 0x{{[0-9A-Fa-f]+}} <<invalid sloc>>
-// CHECK-NEXT: MemberExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type' lvalue .e 0x{{[0-9A-Fa-f]+}}
+// CHECK-NEXT: UnaryOperator 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type' prefix '*' cannot overflow
+// CHECK-NEXT: CallExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'element_type *'
+// CHECK-NEXT: DeclRefExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '<builtin fn type>' Function 0x{{[0-9A-Fa-f]+}} '__builtin_hlsl_resource_getpointer' 'void (...) noexcept'
+// CHECK-NEXT: MemberExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '__hlsl_resource_t
+// CHECK-SAME{LITERAL}: [[hlsl::resource_class(UAV)]]
+// CHECK-SAME{LITERAL}: [[hlsl::contained_type(element_type)]]
+// CHECK-SAME: ' lvalue .__handle 0x{{[0-9A-Fa-f]+}}
 // CHECK-NEXT: CXXThisExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> '[[RESOURCE]]<element_type>' lvalue implicit this
+// CHECK-NEXT: DeclRefExpr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> 'unsigned int' ParmVar 0x{{[0-9A-Fa-f]+}} 'Idx' 'unsigned int'
 // CHECK-NEXT: AlwaysInlineAttr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> Implicit always_inline
 
 // CHECK: ClassTemplateSpecializationDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> class [[RESOURCE]] definition

clang/test/CodeGenHLSL/builtins/RWBuffer-constructor.hlsl

@@ -6,10 +6,10 @@
 
 RWBuffer<float> Buf : register(u5, space3);
 
-// CHECK: %"class.hlsl::RWBuffer" = type { target("dx.TypedBuffer", float, 1, 0, 0), float }
+// CHECK: %"class.hlsl::RWBuffer" = type { target("dx.TypedBuffer", float, 1, 0, 0) }
 // CHECK: @Buf = global %"class.hlsl::RWBuffer" zeroinitializer, align 4
 
-// CHECK: define linkonce_odr void @_ZN4hlsl8RWBufferIfEC2Ev(ptr noundef nonnull align 4 dereferenceable(8) %this)
+// CHECK: define linkonce_odr void @_ZN4hlsl8RWBufferIfEC2Ev(ptr noundef nonnull align 4 dereferenceable(4) %this)
 // CHECK-NEXT: entry:
 
 // CHECK: define internal void @_GLOBAL__sub_I_RWBuffer_constructor.hlsl()