[HLSL] Add RWBuffer default constructor

[beanz]

Summary

This fills out the default constructor for RWBuffer to assign the
handle with the result of __builtin_hlsl_create_handle which we can
then treat as a pointer to the resource data through the mid-level of
the compiler.

Depends on D130016

[bogner]

Is it worth adding a test that calls this constructor / checks that we end up with a call to the builtin?

clang/lib/Sema/HLSLExternalSemaSource.cpp

155

In this case it just creates a literal so it's technically fine, but in general seeing these "emit" functions in argument lists can lead to things like the generated IR being in a different order depending on the compiler. Better to store the Expr in a variable as a matter of style.

clang/include/clang/Basic/HLSLRuntime.h

+//===- HLSLRuntime.h - HLSL Runtime -----------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Defines the clang::IdentifierInfo, clang::IdentifierTable, and
+/// clang::Selector interfaces.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CLANG_BASIC_HLSLRUNTIME_H
+#define CLANG_BASIC_HLSLRUNTIME_H
+
+#include <cstdint>
+
+namespace clang {
+namespace hlsl {
+
+enum class ResourceClass : uint8_t {
+  SRV = 0,
+  UAV,
+  CBuffer,
+  Sampler,
+  NumClasses
+};
+
+} // namespace hlsl
+} // namespace clang
+
+#endif // CLANG_BASIC_HLSLRUNTIME_H

clang/lib/Sema/HLSLExternalSemaSource.cpp

 //===--- HLSLExternalSemaSource.cpp - HLSL Sema Source --------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 //
 //===----------------------------------------------------------------------===//
 
 #include "clang/Sema/HLSLExternalSemaSource.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/Attr.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/Basic/AttrKinds.h"
+#include "clang/Basic/HLSLRuntime.h"
+#include "clang/Sema/Lookup.h"
 #include "clang/Sema/Sema.h"
 
 #include <functional>
 
 using namespace clang;
+using namespace hlsl;
 
 namespace {
 
 struct TemplateParameterListBuilder;
 
 struct BuiltinTypeDeclBuilder {
   CXXRecordDecl *Record = nullptr;
   ClassTemplateDecl *Template = nullptr;
   NamespaceDecl *HLSLNamespace = nullptr;
+  llvm::StringMap<FieldDecl *> Fields;
 
   BuiltinTypeDeclBuilder(CXXRecordDecl *R) : Record(R) {
     Record->startDefinition();
     Template = Record->getDescribedClassTemplate();
   }
 
   BuiltinTypeDeclBuilder(Sema &S, NamespaceDecl *Namespace, StringRef Name)
       : HLSLNamespace(Namespace) {
addMemberVariable(StringRef Name, QualType Type,
     TypeSourceInfo *MemTySource =
         AST.getTrivialTypeSourceInfo(Type, SourceLocation());
     auto *Field = FieldDecl::Create(
         AST, Record, SourceLocation(), SourceLocation(), &II, Type, MemTySource,
         nullptr, false, InClassInitStyle::ICIS_NoInit);
     Field->setAccess(Access);
     Field->setImplicit(true);
     Record->addDecl(Field);
+    Fields[Name] = Field;
     return *this;
   }
 
   BuiltinTypeDeclBuilder &
   addHandleMember(AccessSpecifier Access = AccessSpecifier::AS_private) {
     return addMemberVariable("h", Record->getASTContext().VoidPtrTy, Access);
   }
 
+  static DeclRefExpr *lookupBuiltinFunction(ASTContext &AST, Sema &S,
+                                            StringRef Name) {
+    CXXScopeSpec SS;
+    IdentifierInfo &II = AST.Idents.get(Name, tok::TokenKind::identifier);
+    DeclarationNameInfo NameInfo =
+        DeclarationNameInfo(DeclarationName(&II), SourceLocation());
+    LookupResult R(S, NameInfo, Sema::LookupOrdinaryName);
+    S.LookupParsedName(R, S.getCurScope(), &SS, false);
+    assert(R.isSingleResult() &&
+           "Since this is a builtin it should always resolve!");
+    auto *VD = cast<ValueDecl>(R.getFoundDecl());
+    QualType Ty = VD->getType();
+    return DeclRefExpr::Create(AST, NestedNameSpecifierLoc(), SourceLocation(),
+                               VD, false, NameInfo, Ty, VK_PRValue);
+  }
+
+  static Expr *emitResourceClassExpr(ASTContext &AST, ResourceClass RC) {
+    return IntegerLiteral::Create(
+        AST,
+        llvm::APInt(AST.getIntWidth(AST.UnsignedCharTy),
+                    static_cast<uint8_t>(RC)),
+        AST.UnsignedCharTy, SourceLocation());
+  }
+
+  BuiltinTypeDeclBuilder &addDefaultHandleConstructor(Sema &S,
+                                                      ResourceClass RC) {
+    ASTContext &AST = Record->getASTContext();
+
+    QualType ConstructorType =
+        AST.getFunctionType(AST.VoidTy, {}, FunctionProtoType::ExtProtoInfo());
+
+    CanQualType CanTy = Record->getTypeForDecl()->getCanonicalTypeUnqualified();
+    DeclarationName Name = AST.DeclarationNames.getCXXConstructorName(CanTy);
+    CXXConstructorDecl *Constructor = CXXConstructorDecl::Create(
+        AST, Record, SourceLocation(),
+        DeclarationNameInfo(Name, SourceLocation()), ConstructorType,
+        AST.getTrivialTypeSourceInfo(ConstructorType, SourceLocation()),
+        ExplicitSpecifier(), false, true, false,
+        ConstexprSpecKind::Unspecified);
+
+    DeclRefExpr *Fn =
+        lookupBuiltinFunction(AST, S, "__builtin_hlsl_create_handle");
+
+    Expr *RCExpr = emitResourceClassExpr(AST, RC);
+    CallExpr *Call =
+        CallExpr::Create(AST, Fn, {RCExpr}, AST.VoidPtrTy, VK_PRValue,
+                         SourceLocation(), FPOptionsOverride());
+
+    CXXThisExpr *This = new (AST)
+        CXXThisExpr(SourceLocation(), Constructor->getThisType(), true);
+    MemberExpr *Handle = MemberExpr::CreateImplicit(
+        AST, This, true, Fields["h"], Fields["h"]->getType(), VK_LValue,
+        OK_Ordinary);
+    BinaryOperator *Assign = BinaryOperator::Create(
+        AST, Handle, Call, BO_Assign, Handle->getType(), VK_LValue, OK_Ordinary,
+        SourceLocation(), FPOptionsOverride());
+
+    Constructor->setBody(
+        CompoundStmt::Create(AST, {Assign}, FPOptionsOverride(),
+                             SourceLocation(), SourceLocation()));
+    Constructor->setAccess(AccessSpecifier::AS_public);
+    Record->addDecl(Constructor);
+    return *this;
+  }
+
   BuiltinTypeDeclBuilder &startDefinition() {
     Record->startDefinition();
     return *this;
   }
 
   BuiltinTypeDeclBuilder &completeDefinition() {
     assert(Record->isBeingDefined() &&
            "Definition must be started before completing it.");
if (auto TDecl = dyn_cast<ClassTemplateSpecializationDecl>(Record))
     Record = TDecl->getSpecializedTemplate()->getTemplatedDecl();
   auto It = Completions.find(Record);
   if (It == Completions.end())
     return;
   It->second(Record);
 }
 
 void HLSLExternalSemaSource::completeBufferType(CXXRecordDecl *Record) {
-  BuiltinTypeDeclBuilder(Record).addHandleMember().completeDefinition();
+  BuiltinTypeDeclBuilder(Record)
+      .addHandleMember()
+      .addDefaultHandleConstructor(*SemaPtr, ResourceClass::UAV)
+      .completeDefinition();
 }

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

 
 // CHECK: FinalAttr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> Implicit final
 // CHECK-NEXT: FieldDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> implicit h 'void *'
 // CHECK: ClassTemplateSpecializationDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> class RWBuffer definition
 
 // CHECK: TemplateArgument type 'float'
 // CHECK-NEXT: BuiltinType 0x{{[0-9A-Fa-f]+}} 'float'
 // CHECK-NEXT: FinalAttr 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> Implicit final
-// CHECK-NEXT: FieldDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc>  implicit h 'void *'
+// CHECK-NEXT: FieldDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc>  implicit referenced h 'void *'

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

+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-library -x hlsl -emit-llvm -disable-llvm-passes -o - %s | FileCheck %s
+
+RWBuffer<float> Buf;
+
+// CHECK: define linkonce_odr noundef ptr @"??0?$RWBuffer@M@hlsl@@QAA@XZ"
+// CHECK-NEXT: entry:
+
+// CHECK: %[[HandleRes:[0-9]+]] = call ptr @llvm.dx.create.handle(i8 1)
+// CHECK: store ptr %[[HandleRes]], ptr %h, align 4