[WebAssembly] Initial support for reference type externref in clang

This patch introduces a new type __externref_t that denotes a WebAssembly opaque
reference type. It also implements builtin __builtin_wasm_ref_null_extern(),
that returns a null value of __externref_t. This lays the ground work
for further builtins and reference types.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D122215

Author: pmatos

clang/include/clang/AST/ASTContext.h

@@ -1127,6 +1127,8 @@ class ASTContext : public RefCountedBase<ASTContext> {
 #define RVV_TYPE(Name, Id, SingletonId) \
   CanQualType SingletonId;
 #include "clang/Basic/RISCVVTypes.def"
+#define WASM_TYPE(Name, Id, SingletonId) CanQualType SingletonId;
+#include "clang/Basic/WebAssemblyReferenceTypes.def"
 
   // Types for deductions in C++0x [stmt.ranged]'s desugaring. Built on demand.
   mutable QualType AutoDeductTy;     // Deduction against 'auto'.
@@ -1475,6 +1477,9 @@ class ASTContext : public RefCountedBase<ASTContext> {
   /// \pre \p EltTy must be a built-in type.
   QualType getScalableVectorType(QualType EltTy, unsigned NumElts) const;
 
+  /// Return a WebAssembly externref type.
+  QualType getWebAssemblyExternrefType() const;
+
   /// Return the unique reference to a vector type of the specified
   /// element type and size.
   ///

clang/include/clang/AST/Type.h

@@ -2029,6 +2029,10 @@ class alignas(8) Type : public ExtQualsTypeCommonBase {
   /// Returns true for SVE scalable vector types.
   bool isSVESizelessBuiltinType() const;
 
+  /// Check if this is a WebAssembly Reference Type.
+  bool isWebAssemblyReferenceType() const;
+  bool isWebAssemblyExternrefType() const;
+
   /// Determines if this is a sizeless type supported by the
   /// 'arm_sve_vector_bits' type attribute, which can be applied to a single
   /// SVE vector or predicate, excluding tuple types such as svint32x4_t.
@@ -2642,6 +2646,9 @@ class BuiltinType : public Type {
 // RVV Types
 #define RVV_TYPE(Name, Id, SingletonId) Id,
 #include "clang/Basic/RISCVVTypes.def"
+// WebAssembly reference types
+#define WASM_TYPE(Name, Id, SingletonId) Id,
+#include "clang/Basic/WebAssemblyReferenceTypes.def"
 // All other builtin types
 #define BUILTIN_TYPE(Id, SingletonId) Id,
 #define LAST_BUILTIN_TYPE(Id) LastKind = Id

clang/include/clang/AST/TypeProperties.td

@@ -813,6 +813,10 @@ let Class = BuiltinType in {
       case BuiltinType::ID: return ctx.SINGLETON_ID;
 #include "clang/Basic/RISCVVTypes.def"
 
+#define WASM_TYPE(NAME, ID, SINGLETON_ID) \
+      case BuiltinType::ID: return ctx.SINGLETON_ID;
+#include "clang/Basic/WebAssemblyReferenceTypes.def"
+
 #define BUILTIN_TYPE(ID, SINGLETON_ID) \
       case BuiltinType::ID: return ctx.SINGLETON_ID;
 #include "clang/AST/BuiltinTypes.def"

clang/include/clang/Basic/BuiltinsWebAssembly.def

@@ -190,5 +190,9 @@ TARGET_BUILTIN(__builtin_wasm_relaxed_dot_i8x16_i7x16_s_i16x8, "V8sV16ScV16Sc",
 TARGET_BUILTIN(__builtin_wasm_relaxed_dot_i8x16_i7x16_add_s_i32x4, "V4iV16ScV16ScV4i", "nc", "relaxed-simd")
 TARGET_BUILTIN(__builtin_wasm_relaxed_dot_bf16x8_add_f32_f32x4, "V4fV8UsV8UsV4f", "nc", "relaxed-simd")
 
+// Reference Types builtins
+
+TARGET_BUILTIN(__builtin_wasm_ref_null_extern, "i", "nct", "reference-types")
+
 #undef BUILTIN
 #undef TARGET_BUILTIN

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -11800,4 +11800,10 @@ def err_loongarch_builtin_requires_la32 : Error<
 def err_builtin_pass_in_regs_non_class : Error<
   "argument %0 is not an unqualified class type">;
 
+
+// WebAssembly reference type and table diagnostics.
+def err_wasm_reference_pr : Error<
+  "%select{pointer|reference}0 to WebAssembly reference type is not allowed">;
+def err_wasm_ca_reference : Error<
+  "cannot %select{capture|take address of}0 WebAssembly reference">;
 } // end of sema component.

clang/include/clang/Basic/WebAssemblyReferenceTypes.def

@@ -0,0 +1,40 @@
+//===-- WebAssemblyReferenceTypes.def - Wasm reference types ----*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines externref_t.  The macros are:
+//
+//    WASM_TYPE(Name, Id, SingletonId)
+//    WASM_REF_TYPE(Name, MangledName, Id, SingletonId, AS)
+//
+// where:
+//
+//  - Name is the name of the builtin type.
+//
+//  - MangledNameBase is the base used for name mangling.
+//
+//  - BuiltinType::Id is the enumerator defining the type.
+//
+//  - Context.SingletonId is the global singleton of this type.
+//
+//  - AS indicates the address space for values of this type.
+//
+// To include this file, define either WASM_REF_TYPE or WASM_TYPE, depending on
+// how much information you want.  The macros will be undefined after inclusion.
+//
+//===----------------------------------------------------------------------===//
+
+
+#ifndef WASM_REF_TYPE
+#define WASM_REF_TYPE(Name, MangledNameBase, Id, SingletonId, AS)           \
+  WASM_TYPE(Name, Id, SingletonId)
+#endif
+
+WASM_REF_TYPE("__externref_t", "externref_t", WasmExternRef, WasmExternRefTy, 10)
+
+#undef WASM_TYPE
+#undef WASM_REF_TYPE

clang/include/clang/Sema/Sema.h

@@ -13496,6 +13496,9 @@ class Sema final {
                                      CallExpr *TheCall);
   bool CheckLoongArchBuiltinFunctionCall(const TargetInfo &TI,
                                          unsigned BuiltinID, CallExpr *TheCall);
+  bool CheckWebAssemblyBuiltinFunctionCall(const TargetInfo &TI,
+                                           unsigned BuiltinID,
+                                           CallExpr *TheCall);
 
   bool SemaBuiltinVAStart(unsigned BuiltinID, CallExpr *TheCall);
   bool SemaBuiltinVAStartARMMicrosoft(CallExpr *Call);
@@ -13561,6 +13564,9 @@ class Sema final {
   ExprResult SemaBuiltinMatrixColumnMajorStore(CallExpr *TheCall,
                                                ExprResult CallResult);
 
+  // WebAssembly builtin handling.
+  bool BuiltinWasmRefNullExtern(CallExpr *TheCall);
+
 public:
   enum FormatStringType {
     FST_Scanf,

clang/include/clang/Serialization/ASTBitCodes.h

@@ -1096,6 +1096,9 @@ enum PredefinedTypeIDs {
 // \brief RISC-V V types with auto numeration
 #define RVV_TYPE(Name, Id, SingletonId) PREDEF_TYPE_##Id##_ID,
 #include "clang/Basic/RISCVVTypes.def"
+// \brief WebAssembly reference types with auto numeration
+#define WASM_TYPE(Name, Id, SingletonId) PREDEF_TYPE_##Id##_ID,
+#include "clang/Basic/WebAssemblyReferenceTypes.def"
 };
 
 /// The number of predefined type IDs that are reserved for

clang/include/clang/module.modulemap

@@ -74,6 +74,8 @@ module Clang_Basic {
   textual header "Basic/Sanitizers.def"
   textual header "Basic/TargetCXXABI.def"
   textual header "Basic/TransformTypeTraits.def"
+  textual header "Basic/TokenKinds.def"
+  textual header "Basic/WebAssemblyReferenceTypes.def"
 
   module * { export * }
 }

clang/lib/AST/ASTContext.cpp

@@ -1507,6 +1507,12 @@ void ASTContext::InitBuiltinTypes(const TargetInfo &Target,
 #include "clang/Basic/RISCVVTypes.def"
   }
 
+  if (Target.getTriple().isWasm() && Target.hasFeature("reference-types")) {
+#define WASM_TYPE(Name, Id, SingletonId)                                       \
+  InitBuiltinType(SingletonId, BuiltinType::Id);
+#include "clang/Basic/WebAssemblyReferenceTypes.def"
+  }
+
   // Builtin type for __objc_yes and __objc_no
   ObjCBuiltinBoolTy = (Target.useSignedCharForObjCBool() ?
                        SignedCharTy : BoolTy);
@@ -2335,6 +2341,12 @@ TypeInfo ASTContext::getTypeInfoImpl(const Type *T) const {
     Align = 8;                                                                 \
     break;
 #include "clang/Basic/RISCVVTypes.def"
+#define WASM_TYPE(Name, Id, SingletonId)                                       \
+  case BuiltinType::Id:                                                        \
+    Width = 0;                                                                 \
+    Align = 8;                                                                 \
+    break;
+#include "clang/Basic/WebAssemblyReferenceTypes.def"
     }
     break;
   case Type::ObjCObjectPointer:
@@ -4072,6 +4084,19 @@ ASTContext::getBuiltinVectorTypeInfo(const BuiltinType *Ty) const {
   }
 }
 
+/// getExternrefType - Return a WebAssembly externref type, which represents an
+/// opaque reference to a host value.
+QualType ASTContext::getWebAssemblyExternrefType() const {
+  if (Target->getTriple().isWasm() && Target->hasFeature("reference-types")) {
+#define WASM_REF_TYPE(Name, MangledName, Id, SingletonId, AS)                  \
+  if (BuiltinType::Id == BuiltinType::WasmExternRef)                           \
+    return SingletonId;
+#include "clang/Basic/WebAssemblyReferenceTypes.def"
+  }
+  assert(false &&
+         "shouldn't try to generate type externref outside WebAssembly target");
+}
+
 /// getScalableVectorType - Return the unique reference to a scalable vector
 /// type of the specified element type and size. VectorType must be a built-in
 /// type.
@@ -8111,6 +8136,8 @@ static char getObjCEncodingForPrimitiveType(const ASTContext *C,
 #include "clang/Basic/AArch64SVEACLETypes.def"
 #define RVV_TYPE(Name, Id, SingletonId) case BuiltinType::Id:
 #include "clang/Basic/RISCVVTypes.def"
+#define WASM_TYPE(Name, Id, SingletonId) case BuiltinType::Id:
+#include "clang/Basic/WebAssemblyReferenceTypes.def"
       {
         DiagnosticsEngine &Diags = C->getDiagnostics();
         unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,