[HLSL] Resource initialization by constructors (#135120)

- Adds resource constructor that takes explicit binding for all resource
classes.
- Updates implementation of default resource constructor to initialize
resource handle to `poison`.
- Removes initialization of resource classes from Codegen.
- Initialization of `cbuffer` still needs to happen in `CGHLSLRuntime`
because it does not have a corresponding resource class type.
- Adds `ImplicitCastExpr` for builtin function calls. Sema adds these
automatically when a method of a template class is instantiated, but
some resource classes like `ByteAddressBuffer` are not templates so they
need to have this added explicitly.

Design proposal: llvm/wg-hlsl#197

Closes #134154

Author: hekota

clang/include/clang/Basic/Builtins.td

@@ -4801,6 +4801,18 @@ def HLSLResourceGetPointer : LangBuiltin<"HLSL_LANG"> {
   let Prototype = "void(...)";
 }
 
+def HLSLResourceUninitializedHandle : LangBuiltin<"HLSL_LANG"> {
+  let Spellings = ["__builtin_hlsl_resource_uninitializedhandle"];
+  let Attributes = [NoThrow];
+  let Prototype = "void(...)";
+}
+
+def HLSLResourceHandleFromBinding : LangBuiltin<"HLSL_LANG"> {
+  let Spellings = ["__builtin_hlsl_resource_handlefrombinding"];
+  let Attributes = [NoThrow];
+  let Prototype = "void(...)";
+}
+
 def HLSLAll : LangBuiltin<"HLSL_LANG"> {
   let Spellings = ["__builtin_hlsl_all"];
   let Attributes = [NoThrow, Const];

clang/include/clang/Sema/SemaHLSL.h

@@ -105,6 +105,7 @@ class SemaHLSL : public SemaBase {
                          HLSLParamModifierAttr::Spelling Spelling);
   void ActOnTopLevelFunction(FunctionDecl *FD);
   void ActOnVariableDeclarator(VarDecl *VD);
+  bool ActOnUninitializedVarDecl(VarDecl *D);
   void ActOnEndOfTranslationUnit(TranslationUnitDecl *TU);
   void CheckEntryPoint(FunctionDecl *FD);
   void CheckSemanticAnnotation(FunctionDecl *EntryPoint, const Decl *Param,

clang/lib/CodeGen/CGHLSLBuiltins.cpp

@@ -285,6 +285,24 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
         RetTy, CGM.getHLSLRuntime().getCreateResourceGetPointerIntrinsic(),
         ArrayRef<Value *>{HandleOp, IndexOp});
   }
+  case Builtin::BI__builtin_hlsl_resource_uninitializedhandle: {
+    llvm::Type *HandleTy = CGM.getTypes().ConvertType(E->getType());
+    return llvm::PoisonValue::get(HandleTy);
+  }
+  case Builtin::BI__builtin_hlsl_resource_handlefrombinding: {
+    llvm::Type *HandleTy = CGM.getTypes().ConvertType(E->getType());
+    Value *RegisterOp = EmitScalarExpr(E->getArg(1));
+    Value *SpaceOp = EmitScalarExpr(E->getArg(2));
+    Value *RangeOp = EmitScalarExpr(E->getArg(3));
+    Value *IndexOp = EmitScalarExpr(E->getArg(4));
+    // FIXME: NonUniformResourceIndex bit is not yet implemented
+    // (llvm/llvm-project#135452)
+    Value *NonUniform =
+        llvm::ConstantInt::get(llvm::Type::getInt1Ty(getLLVMContext()), false);
+    return Builder.CreateIntrinsic(
+        HandleTy, CGM.getHLSLRuntime().getCreateHandleFromBindingIntrinsic(),
+        ArrayRef<Value *>{SpaceOp, RegisterOp, RangeOp, IndexOp, NonUniform});
+  }
   case Builtin::BI__builtin_hlsl_all: {
     Value *Op0 = EmitScalarExpr(E->getArg(0));
     return Builder.CreateIntrinsic(

clang/lib/CodeGen/CGHLSLRuntime.cpp

@@ -41,8 +41,9 @@ using namespace llvm;
 
 using llvm::hlsl::CBufferRowSizeInBytes;
 
-static void createResourceInitFn(CodeGenModule &CGM, llvm::GlobalVariable *GV,
-                                 unsigned Slot, unsigned Space);
+static void initializeBufferFromBinding(CodeGenModule &CGM,
+                                        llvm::GlobalVariable *GV, unsigned Slot,
+                                        unsigned Space);
 
 namespace {
 
@@ -255,14 +256,14 @@ void CGHLSLRuntime::addBuffer(const HLSLBufferDecl *BufDecl) {
   // Add globals for constant buffer elements and create metadata nodes
   emitBufferGlobalsAndMetadata(BufDecl, BufGV);
 
-  // Resource initialization
+  // Initialize cbuffer from binding (implicit or explicit)
   const HLSLResourceBindingAttr *RBA =
       BufDecl->getAttr<HLSLResourceBindingAttr>();
   // FIXME: handle implicit binding if no binding attribute is found
   // (llvm/llvm-project#110722)
   if (RBA)
-    createResourceInitFn(CGM, BufGV, RBA->getSlotNumber(),
-                         RBA->getSpaceNumber());
+    initializeBufferFromBinding(CGM, BufGV, RBA->getSlotNumber(),
+                                RBA->getSpaceNumber());
 }
 
 llvm::TargetExtType *
@@ -505,15 +506,15 @@ void CGHLSLRuntime::generateGlobalCtorDtorCalls() {
   }
 }
 
-static void createResourceInitFn(CodeGenModule &CGM, llvm::GlobalVariable *GV,
-                                 unsigned Slot, unsigned Space) {
-  LLVMContext &Ctx = CGM.getLLVMContext();
-  llvm::Type *Int1Ty = llvm::Type::getInt1Ty(Ctx);
+static void initializeBuffer(CodeGenModule &CGM, llvm::GlobalVariable *GV,
+                             Intrinsic::ID IntrID,
+                             ArrayRef<llvm::Value *> Args) {
 
+  LLVMContext &Ctx = CGM.getLLVMContext();
   llvm::Function *InitResFunc = llvm::Function::Create(
       llvm::FunctionType::get(CGM.VoidTy, false),
       llvm::GlobalValue::InternalLinkage,
-      ("_init_resource_" + GV->getName()).str(), CGM.getModule());
+      ("_init_buffer_" + GV->getName()).str(), CGM.getModule());
   InitResFunc->addFnAttr(llvm::Attribute::AlwaysInline);
 
   llvm::BasicBlock *EntryBB =
@@ -522,28 +523,12 @@ static void createResourceInitFn(CodeGenModule &CGM, llvm::GlobalVariable *GV,
   const DataLayout &DL = CGM.getModule().getDataLayout();
   Builder.SetInsertPoint(EntryBB);
 
-  // Make sure the global variable is resource handle (cbuffer) or
-  // resource class (=class where the first element is a resource handle).
+  // Make sure the global variable is buffer resource handle
   llvm::Type *HandleTy = GV->getValueType();
-  assert((HandleTy->isTargetExtTy() ||
-          (HandleTy->isStructTy() &&
-           HandleTy->getStructElementType(0)->isTargetExtTy())) &&
-         "unexpected type of the global");
-  if (!HandleTy->isTargetExtTy())
-    HandleTy = HandleTy->getStructElementType(0);
+  assert(HandleTy->isTargetExtTy() && "unexpected type of the buffer global");
 
-  llvm::Value *Args[] = {
-      llvm::ConstantInt::get(CGM.IntTy, Space), /* reg_space */
-      llvm::ConstantInt::get(CGM.IntTy, Slot),  /* lower_bound */
-      // FIXME: resource arrays are not yet implemented
-      llvm::ConstantInt::get(CGM.IntTy, 1), /* range_size */
-      llvm::ConstantInt::get(CGM.IntTy, 0), /* index */
-      // FIXME: NonUniformResourceIndex bit is not yet implemented
-      llvm::ConstantInt::get(Int1Ty, false) /* non-uniform */
-  };
   llvm::Value *CreateHandle = Builder.CreateIntrinsic(
-      /*ReturnType=*/HandleTy,
-      CGM.getHLSLRuntime().getCreateHandleFromBindingIntrinsic(), Args, nullptr,
+      /*ReturnType=*/HandleTy, IntrID, Args, nullptr,
       Twine(GV->getName()).concat("_h"));
 
   llvm::Value *HandleRef = Builder.CreateStructGEP(GV->getValueType(), GV, 0);
@@ -554,24 +539,20 @@ static void createResourceInitFn(CodeGenModule &CGM, llvm::GlobalVariable *GV,
   CGM.AddCXXGlobalInit(InitResFunc);
 }
 
-void CGHLSLRuntime::handleGlobalVarDefinition(const VarDecl *VD,
-                                              llvm::GlobalVariable *GV) {
-
-  // If the global variable has resource binding, create an init function
-  // for the resource
-  const HLSLResourceBindingAttr *RBA = VD->getAttr<HLSLResourceBindingAttr>();
-  if (!RBA)
-    // FIXME: collect unbound resources for implicit binding resolution later
-    // on?
-    return;
-
-  if (!VD->getType().getTypePtr()->isHLSLResourceRecord())
-    // FIXME: Only simple declarations of resources are supported for now.
-    // Arrays of resources or resources in user defined classes are
-    // not implemented yet.
-    return;
-
-  createResourceInitFn(CGM, GV, RBA->getSlotNumber(), RBA->getSpaceNumber());
+static void initializeBufferFromBinding(CodeGenModule &CGM,
+                                        llvm::GlobalVariable *GV, unsigned Slot,
+                                        unsigned Space) {
+  llvm::Type *Int1Ty = llvm::Type::getInt1Ty(CGM.getLLVMContext());
+  llvm::Value *Args[] = {
+      llvm::ConstantInt::get(CGM.IntTy, Space), /* reg_space */
+      llvm::ConstantInt::get(CGM.IntTy, Slot),  /* lower_bound */
+      llvm::ConstantInt::get(CGM.IntTy, 1),     /* range_size */
+      llvm::ConstantInt::get(CGM.IntTy, 0),     /* index */
+      llvm::ConstantInt::get(Int1Ty, false)     /* non-uniform */
+  };
+  initializeBuffer(CGM, GV,
+                   CGM.getHLSLRuntime().getCreateHandleFromBindingIntrinsic(),
+                   Args);
 }
 
 llvm::Instruction *CGHLSLRuntime::getConvergenceToken(BasicBlock &BB) {

clang/lib/CodeGen/CGHLSLRuntime.h

@@ -150,7 +150,6 @@ class CGHLSLRuntime {
 
   void emitEntryFunction(const FunctionDecl *FD, llvm::Function *Fn);
   void setHLSLFunctionAttributes(const FunctionDecl *FD, llvm::Function *Fn);
-  void handleGlobalVarDefinition(const VarDecl *VD, llvm::GlobalVariable *Var);
 
   llvm::Instruction *getConvergenceToken(llvm::BasicBlock &BB);
 

clang/lib/CodeGen/CodeGenModule.cpp

@@ -5760,9 +5760,6 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
     getCUDARuntime().handleVarRegistration(D, *GV);
   }
 
-  if (LangOpts.HLSL)
-    getHLSLRuntime().handleGlobalVarDefinition(D, GV);
-
   GV->setInitializer(Init);
   if (emitter)
     emitter->finalize(GV);

clang/lib/Sema/HLSLBuiltinTypeDeclBuilder.cpp

@@ -400,6 +400,7 @@ void BuiltinTypeMethodBuilder::createDecl() {
 
   // create params & set them to the function prototype
   SmallVector<ParmVarDecl *> ParmDecls;
+  unsigned CurScopeDepth = DeclBuilder.SemaRef.getCurScope()->getDepth();
   auto FnProtoLoc =
       Method->getTypeSourceInfo()->getTypeLoc().getAs<FunctionProtoTypeLoc>();
   for (int I = 0, E = Params.size(); I != E; I++) {
@@ -414,6 +415,7 @@ void BuiltinTypeMethodBuilder::createDecl() {
           HLSLParamModifierAttr::Create(AST, SourceRange(), MP.Modifier);
       Parm->addAttr(Mod);
     }
+    Parm->setScopeInfo(CurScopeDepth, I);
     ParmDecls.push_back(Parm);
     FnProtoLoc.setParam(I, Parm);
   }
@@ -447,10 +449,14 @@ BuiltinTypeMethodBuilder::callBuiltin(StringRef BuiltinName,
       AST, NestedNameSpecifierLoc(), SourceLocation(), FD, false,
       FD->getNameInfo(), AST.BuiltinFnTy, VK_PRValue);
 
+  auto *ImpCast = ImplicitCastExpr::Create(
+      AST, AST.getPointerType(FD->getType()), CK_BuiltinFnToFnPtr, DRE, nullptr,
+      VK_PRValue, FPOptionsOverride());
+
   if (ReturnType.isNull())
     ReturnType = FD->getReturnType();
 
-  Expr *Call = CallExpr::Create(AST, DRE, Args, ReturnType, VK_PRValue,
+  Expr *Call = CallExpr::Create(AST, ImpCast, Args, ReturnType, VK_PRValue,
                                 SourceLocation(), FPOptionsOverride());
   StmtsList.push_back(Call);
   return *this;
@@ -632,11 +638,33 @@ BuiltinTypeDeclBuilder &BuiltinTypeDeclBuilder::addDefaultHandleConstructor() {
   if (Record->isCompleteDefinition())
     return *this;
 
-  // FIXME: initialize handle to poison value; this can be added after
-  // resource constructor from binding is implemented, otherwise the handle
-  // value will get overwritten.
+  using PH = BuiltinTypeMethodBuilder::PlaceHolder;
+  QualType HandleType = getResourceHandleField()->getType();
   return BuiltinTypeMethodBuilder(*this, "", SemaRef.getASTContext().VoidTy,
                                   false, true)
+      .callBuiltin("__builtin_hlsl_resource_uninitializedhandle", HandleType,
+                   PH::Handle)
+      .assign(PH::Handle, PH::LastStmt)
+      .finalize();
+}
+
+BuiltinTypeDeclBuilder &
+BuiltinTypeDeclBuilder::addHandleConstructorFromBinding() {
+  if (Record->isCompleteDefinition())
+    return *this;
+
+  using PH = BuiltinTypeMethodBuilder::PlaceHolder;
+  ASTContext &AST = SemaRef.getASTContext();
+  QualType HandleType = getResourceHandleField()->getType();
+
+  return BuiltinTypeMethodBuilder(*this, "", AST.VoidTy, false, true)
+      .addParam("registerNo", AST.UnsignedIntTy)
+      .addParam("spaceNo", AST.UnsignedIntTy)
+      .addParam("range", AST.IntTy)
+      .addParam("index", AST.UnsignedIntTy)
+      .callBuiltin("__builtin_hlsl_resource_handlefrombinding", HandleType,
+                   PH::Handle, PH::_0, PH::_1, PH::_2, PH::_3)
+      .assign(PH::Handle, PH::LastStmt)
       .finalize();
 }
 

clang/lib/Sema/HLSLBuiltinTypeDeclBuilder.h

@@ -78,6 +78,7 @@ class BuiltinTypeDeclBuilder {
 
   // Builtin types methods
   BuiltinTypeDeclBuilder &addDefaultHandleConstructor();
+  BuiltinTypeDeclBuilder &addHandleConstructorFromBinding();
 
   // Builtin types methods
   BuiltinTypeDeclBuilder &addLoadMethods();

clang/lib/Sema/HLSLExternalSemaSource.cpp

@@ -131,7 +131,8 @@ static BuiltinTypeDeclBuilder setupBufferType(CXXRecordDecl *Decl, Sema &S,
                                               bool RawBuffer) {
   return BuiltinTypeDeclBuilder(S, Decl)
       .addHandleMember(RC, IsROV, RawBuffer)
-      .addDefaultHandleConstructor();
+      .addDefaultHandleConstructor()
+      .addHandleConstructorFromBinding();
 }
 
 // This function is responsible for constructing the constraint expression for

clang/lib/Sema/SemaDecl.cpp

@@ -14378,10 +14378,8 @@ void Sema::ActOnUninitializedDecl(Decl *RealDecl) {
         Var->getType().getAddressSpace() == LangAS::opencl_local)
       return;
 
-    // In HLSL, objects in the hlsl_constant address space are initialized
-    // externally, so don't synthesize an implicit initializer.
-    if (getLangOpts().HLSL &&
-        Var->getType().getAddressSpace() == LangAS::hlsl_constant)
+    // Handle HLSL uninitialized decls
+    if (getLangOpts().HLSL && HLSL().ActOnUninitializedVarDecl(Var))
       return;
 
     // C++03 [dcl.init]p9: