src/tint/lang/msl/writer/raise/module_scope_vars.cc - dawn - Git at Google

 // Copyright 2024 The Dawn & Tint Authors
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
 //
 // 1. Redistributions of source code must retain the above copyright notice, this
 //    list of conditions and the following disclaimer.
 //
 // 2. Redistributions in binary form must reproduce the above copyright notice,
 //    this list of conditions and the following disclaimer in the documentation
 //    and/or other materials provided with the distribution.
 //
 // 3. Neither the name of the copyright holder nor the names of its
 //    contributors may be used to endorse or promote products derived from
 //    this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #include "src/tint/lang/msl/writer/raise/module_scope_vars.h"

 #include <utility>

 #include "src/tint/lang/core/ir/builder.h"
 #include "src/tint/lang/core/ir/referenced_module_vars.h"
 #include "src/tint/lang/core/ir/validator.h"

 namespace tint::msl::writer::raise {
 namespace {

 using namespace tint::core::fluent_types;  // NOLINT

 /// PIMPL state for the transform.
 struct State {
     /// The IR module.
     core::ir::Module& ir;

     /// The IR builder.
     core::ir::Builder b{ir};

     /// The type manager.
     core::type::Manager& ty{ir.Types()};

     /// The type of the structure that will contain all of the module-scope variables.
     const core::type::Struct* struct_type = nullptr;

     /// The list of module-scope variables.
     Vector<core::ir::Var*, 8> module_vars{};

     /// A map from a function to the value that contains the module-scope variable pointers.
     Hashmap<core::ir::Function*, core::ir::Value*, 8> function_to_struct_value{};

     /// A map from block to its containing function.
     Hashmap<core::ir::Block*, core::ir::Function*, 64> block_to_function{};

     /// The mapping from functions to their transitively referenced workgroup variables.
     core::ir::ReferencedModuleVars<core::ir::Module> referenced_module_vars{ir};

     // The name of the module-scope variables structure.
     static constexpr const char* kModuleVarsName = "tint_module_vars";

     /// Process the module.
     void Process() {
         // Seed the block-to-function map with the function entry blocks.
         // This is used to determine the owning function for any given instruction.
         for (auto& func : ir.functions) {
             block_to_function.Add(func->Block(), func);
         }

         // Create the structure to hold all module-scope variables.
         // This includes all variables declared in the module, even those that are unused by one or
         // more entry points.
         CreateStruct();

         // Process functions in reverse-dependency order (i.e. root to leaves).
         // This is so that when we update the callsites for a function to add the new argument, we
         // will have already added the necessary structure to the callers.
         auto functions = ir.DependencyOrderedFunctions();
         for (auto func = functions.rbegin(); func != functions.rend(); func++) {
             ProcessFunction(*func);
         }

         // Replace uses of each module-scope variable with values extracted from the structure.
         uint32_t index = 0;
         for (auto& var : module_vars) {
             Vector<core::ir::Instruction*, 16> to_destroy;
             auto* ptr = var->Result(0)->Type()->As<core::type::Pointer>();
             var->Result(0)->ForEachUseUnsorted([&](core::ir::Usage use) {  //
                 auto* extracted_variable = GetVariableFromStruct(var, use.instruction, index);

                 // We drop the pointer from handle variables and store them in the struct by value
                 // instead, so remove any load instructions for the handle address space.
                 if (use.instruction->Is<core::ir::Load>() &&
                     ptr->AddressSpace() == core::AddressSpace::kHandle) {
                     use.instruction->Result(0)->ReplaceAllUsesWith(extracted_variable);
                     to_destroy.Push(use.instruction);
                     return;
                 }

                 use.instruction->SetOperand(use.operand_index, extracted_variable);
             });
             var->Destroy();
             index++;

             // Clean up instructions that need to be removed.
             for (auto* inst : to_destroy) {
                 inst->Destroy();
             }
         }
     }

     /// Create the structure type to hold all of the module-scope variables.
     void CreateStruct() {
         // Collect a list of struct members for the variable declarations.
         Vector<core::type::Manager::StructMemberDesc, 8> struct_members;
         for (auto* global : *ir.root_block) {
             if (auto* var = global->As<core::ir::Var>()) {
                 auto* type = var->Result(0)->Type();

                 // Handle types drop the pointer and are passed around by value.
                 auto* ptr = type->As<core::type::Pointer>();
                 if (ptr->AddressSpace() == core::AddressSpace::kHandle) {
                     type = ptr->StoreType();
                 }

                 auto name = ir.NameOf(var);
                 if (!name) {
                     name = ir.symbols.New();
                 }
                 module_vars.Push(var);
                 struct_members.Push(core::type::Manager::StructMemberDesc{name, type});
             }
         }
         if (struct_members.IsEmpty()) {
             return;
         }

         // Create the structure.
         auto name = ir.symbols.New("tint_module_vars_struct");
         struct_type = ty.Struct(name, std::move(struct_members));
     }

     /// Process a function.
     void ProcessFunction(core::ir::Function* func) {
         auto& refs = referenced_module_vars.TransitiveReferences(func);
         if (refs.IsEmpty()) {
             // No module-scope variables are referenced from this function, so no changes needed.
             return;
         }

         // Add the structure the holds the module-scope variable pointers to the function and record
         // it in the map. Entry points will create the structure, other functions will declare it as
         // a parameter.
         if (func->Stage() != core::ir::Function::PipelineStage::kUndefined) {
             function_to_struct_value.Add(func, AddModuleVarsToEntryPoint(func, refs));
         } else {
             function_to_struct_value.Add(func, AddModuleVarsToFunction(func));
         }
     }

     /// Add a module-scope variables structure to an entry point function.
     /// @param func the entry point function to modify
     /// @param referenced_vars the set of variables transitively referenced by the entry point
     /// @returns the structure that holds the module-scope variables
     core::ir::Value* AddModuleVarsToEntryPoint(
         core::ir::Function* func,
         const core::ir::ReferencedModuleVars<core::ir::Module>::VarSet& referenced_vars) {
         core::ir::Value* module_var_struct = nullptr;
         core::ir::FunctionParam* workgroup_allocation_param = nullptr;
         Vector<core::type::Manager::StructMemberDesc, 4> workgroup_struct_members;

         // Add parameters and insert instruction at the top of the entry point to set up the
         // module-scope variables structure.
         b.InsertBefore(func->Block()->Front(), [&] {  //
             Vector<core::ir::Value*, 8> construct_args;
             for (auto var : module_vars) {
                 if (!referenced_vars.Contains(var)) {
                     // The variable isn't used by this entry point, so set the member to unused.
                     construct_args.Push(b.Unused());
                     continue;
                 }

                 // Create a new declaration in the entry point to replace the module-scope variable.
                 // Use either a parameter or a local variable, depending on the address space.
                 core::ir::Value* decl = nullptr;
                 auto* ptr = var->Result(0)->Type()->As<core::type::Pointer>();
                 switch (ptr->AddressSpace()) {
                     case core::AddressSpace::kPrivate: {
                         // Private variables become function-scope variables.
                         auto* local_var = b.Var(ptr);
                         local_var->SetInitializer(var->Initializer());
                         decl = local_var->Result(0);
                         break;
                     }
                     case core::AddressSpace::kStorage:
                     case core::AddressSpace::kUniform: {
                         // Storage and uniform buffers become function parameters.
                         auto* param = b.FunctionParam(ptr);
                         param->SetBindingPoint(var->BindingPoint());
                         func->AppendParam(param);
                         decl = param;
                         break;
                     }
                     case core::AddressSpace::kWorkgroup: {
                         // Workgroup variables are received as a function parameter (to workaround
                         // an MSL compiler bug with threadgroup matrices), and we aggregate all
                         // workgroup variables into a structure to avoid hitting MSL's limit for
                         // threadgroup memory arguments.
                         if (!workgroup_allocation_param) {
                             workgroup_allocation_param = b.FunctionParam(nullptr);
                             func->AppendParam(workgroup_allocation_param);
                         }
                         decl = b.Access(ptr, workgroup_allocation_param,
                                         u32(workgroup_struct_members.Length()))
                                    ->Result(0);
                         workgroup_struct_members.Push(core::type::Manager::StructMemberDesc{
                             ir.symbols.New(),
                             ptr->StoreType(),
                         });
                         break;
                     }
                     case core::AddressSpace::kHandle: {
                         // Handle types become function parameters and drop the pointer.
                         auto* param = b.FunctionParam(ptr->UnwrapPtr());
                         param->SetBindingPoint(var->BindingPoint());
                         func->AppendParam(param);
                         decl = param;
                         break;
                     }
                     default:
                         TINT_UNREACHABLE() << "unhandled address space: " << ptr->AddressSpace();
                 }

                 // Copy an existing name over to the new declaration if present.
                 if (auto name = ir.NameOf(var)) {
                     ir.SetName(decl, name);
                 }
                 construct_args.Push(decl);
             }

             // Construct the structure value and name it with a `let` instruction.
             // The `let` prevents the printer from inlining the constructor, which aids readability.
             auto* construct = b.Construct(struct_type, std::move(construct_args));
             module_var_struct = b.Let(kModuleVarsName, construct)->Result(0);
         });

         // Create the workgroup variable structure if needed.
         if (!workgroup_struct_members.IsEmpty()) {
             auto* workgroup_struct =
                 ty.Struct(ir.symbols.New(), std::move(workgroup_struct_members));
             workgroup_allocation_param->SetType(ty.ptr<workgroup>(workgroup_struct));
         }

         return module_var_struct;
     }

     /// Add a module-scope variables structure to a non-entry-point function.
     /// @param func the function to modify
     /// @returns the parameter that holds the module-scope variables structure
     core::ir::Value* AddModuleVarsToFunction(core::ir::Function* func) {
         // Add a new parameter to receive the module-scope variables structure.
         auto* param = b.FunctionParam(kModuleVarsName, struct_type);
         func->AppendParam(param);

         // Update all callsites to pass the module-scope variables structure as an argument.
         func->ForEachUseUnsorted([&](core::ir::Usage use) {
             if (auto* call = use.instruction->As<core::ir::UserCall>()) {
                 call->AppendArg(*function_to_struct_value.Get(ContainingFunction(call)));
             }
         });

         return param;
     }

     /// Get a variable from the module-scope variable replacement structure, inserting new access
     /// instructions before @p inst.
     /// @param var the variable to get the replacement for
     /// @param inst the instruction that uses the variable
     /// @param index the index of the variable in the structure member list
     /// @returns the variable extracted from the structure
     core::ir::Value* GetVariableFromStruct(core::ir::Var* var,
                                            core::ir::Instruction* inst,
                                            uint32_t index) {
         auto* func = ContainingFunction(inst);
         auto* struct_value = function_to_struct_value.GetOr(func, nullptr);
         auto* type = var->Result(0)->Type();

         // Handle types drop the pointer and are passed around by value.
         auto* ptr = type->As<core::type::Pointer>();
         if (ptr->AddressSpace() == core::AddressSpace::kHandle) {
             type = ptr->StoreType();
         }

         auto* access = b.Access(type, struct_value, u32(index));
         access->InsertBefore(inst);
         return access->Result(0);
     }

     /// Get the function that contains an instruction.
     /// @param inst the instruction
     /// @returns the function
     core::ir::Function* ContainingFunction(core::ir::Instruction* inst) {
         return block_to_function.GetOrAdd(inst->Block(), [&] {  //
             return ContainingFunction(inst->Block()->Parent());
         });
     }
 };

 }  // namespace

 Result<SuccessType> ModuleScopeVars(core::ir::Module& ir) {
     auto result = ValidateAndDumpIfNeeded(ir, "ModuleScopeVars transform");
     if (result != Success) {
         return result.Failure();
     }

     State{ir}.Process();

     return Success;
 }

 }  // namespace tint::msl::writer::raise
	// Copyright 2024 The Dawn & Tint Authors
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// 1. Redistributions of source code must retain the above copyright notice, this
	// list of conditions and the following disclaimer.
	//
	// 2. Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	//
	// 3. Neither the name of the copyright holder nor the names of its
	// contributors may be used to endorse or promote products derived from
	// this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
	// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
	// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#include "src/tint/lang/msl/writer/raise/module_scope_vars.h"

	#include <utility>

	#include "src/tint/lang/core/ir/builder.h"
	#include "src/tint/lang/core/ir/referenced_module_vars.h"
	#include "src/tint/lang/core/ir/validator.h"

	namespace tint::msl::writer::raise {
	namespace {

	using namespace tint::core::fluent_types; // NOLINT

	/// PIMPL state for the transform.
	struct State {
	/// The IR module.
	core::ir::Module& ir;

	/// The IR builder.
	core::ir::Builder b{ir};

	/// The type manager.
	core::type::Manager& ty{ir.Types()};

	/// The type of the structure that will contain all of the module-scope variables.
	const core::type::Struct* struct_type = nullptr;

	/// The list of module-scope variables.
	Vector<core::ir::Var*, 8> module_vars{};

	/// A map from a function to the value that contains the module-scope variable pointers.
	Hashmap<core::ir::Function, core::ir::Value, 8> function_to_struct_value{};

	/// A map from block to its containing function.
	Hashmap<core::ir::Block, core::ir::Function, 64> block_to_function{};

	/// The mapping from functions to their transitively referenced workgroup variables.
	core::ir::ReferencedModuleVars<core::ir::Module> referenced_module_vars{ir};

	// The name of the module-scope variables structure.
	static constexpr const char* kModuleVarsName = "tint_module_vars";

	/// Process the module.
	void Process() {
	// Seed the block-to-function map with the function entry blocks.
	// This is used to determine the owning function for any given instruction.
	for (auto& func : ir.functions) {
	block_to_function.Add(func->Block(), func);
	}

	// Create the structure to hold all module-scope variables.
	// This includes all variables declared in the module, even those that are unused by one or
	// more entry points.
	CreateStruct();

	// Process functions in reverse-dependency order (i.e. root to leaves).
	// This is so that when we update the callsites for a function to add the new argument, we
	// will have already added the necessary structure to the callers.
	auto functions = ir.DependencyOrderedFunctions();
	for (auto func = functions.rbegin(); func != functions.rend(); func++) {
	ProcessFunction(*func);
	}

	// Replace uses of each module-scope variable with values extracted from the structure.
	uint32_t index = 0;
	for (auto& var : module_vars) {
	Vector<core::ir::Instruction*, 16> to_destroy;
	auto* ptr = var->Result(0)->Type()->As<core::type::Pointer>();
	var->Result(0)->ForEachUseUnsorted([&](core::ir::Usage use) { //
	auto* extracted_variable = GetVariableFromStruct(var, use.instruction, index);

	// We drop the pointer from handle variables and store them in the struct by value
	// instead, so remove any load instructions for the handle address space.
	if (use.instruction->Is<core::ir::Load>() &&
	ptr->AddressSpace() == core::AddressSpace::kHandle) {
	use.instruction->Result(0)->ReplaceAllUsesWith(extracted_variable);
	to_destroy.Push(use.instruction);
	return;
	}

	use.instruction->SetOperand(use.operand_index, extracted_variable);
	});
	var->Destroy();
	index++;

	// Clean up instructions that need to be removed.
	for (auto* inst : to_destroy) {
	inst->Destroy();
	}
	}
	}

	/// Create the structure type to hold all of the module-scope variables.
	void CreateStruct() {
	// Collect a list of struct members for the variable declarations.
	Vector<core::type::Manager::StructMemberDesc, 8> struct_members;
	for (auto* global : *ir.root_block) {
	if (auto* var = global->As<core::ir::Var>()) {
	auto* type = var->Result(0)->Type();

	// Handle types drop the pointer and are passed around by value.
	auto* ptr = type->As<core::type::Pointer>();
	if (ptr->AddressSpace() == core::AddressSpace::kHandle) {
	type = ptr->StoreType();
	}

	auto name = ir.NameOf(var);
	if (!name) {
	name = ir.symbols.New();
	}
	module_vars.Push(var);
	struct_members.Push(core::type::Manager::StructMemberDesc{name, type});
	}
	}
	if (struct_members.IsEmpty()) {
	return;
	}

	// Create the structure.
	auto name = ir.symbols.New("tint_module_vars_struct");
	struct_type = ty.Struct(name, std::move(struct_members));
	}

	/// Process a function.
	void ProcessFunction(core::ir::Function* func) {
	auto& refs = referenced_module_vars.TransitiveReferences(func);
	if (refs.IsEmpty()) {
	// No module-scope variables are referenced from this function, so no changes needed.
	return;
	}

	// Add the structure the holds the module-scope variable pointers to the function and record
	// it in the map. Entry points will create the structure, other functions will declare it as
	// a parameter.
	if (func->Stage() != core::ir::Function::PipelineStage::kUndefined) {
	function_to_struct_value.Add(func, AddModuleVarsToEntryPoint(func, refs));
	} else {
	function_to_struct_value.Add(func, AddModuleVarsToFunction(func));
	}
	}

	/// Add a module-scope variables structure to an entry point function.
	/// @param func the entry point function to modify
	/// @param referenced_vars the set of variables transitively referenced by the entry point
	/// @returns the structure that holds the module-scope variables
	core::ir::Value* AddModuleVarsToEntryPoint(
	core::ir::Function* func,
	const core::ir::ReferencedModuleVars<core::ir::Module>::VarSet& referenced_vars) {
	core::ir::Value* module_var_struct = nullptr;
	core::ir::FunctionParam* workgroup_allocation_param = nullptr;
	Vector<core::type::Manager::StructMemberDesc, 4> workgroup_struct_members;

	// Add parameters and insert instruction at the top of the entry point to set up the
	// module-scope variables structure.
	b.InsertBefore(func->Block()->Front(), [&] { //
	Vector<core::ir::Value*, 8> construct_args;
	for (auto var : module_vars) {
	if (!referenced_vars.Contains(var)) {
	// The variable isn't used by this entry point, so set the member to unused.
	construct_args.Push(b.Unused());
	continue;
	}

	// Create a new declaration in the entry point to replace the module-scope variable.
	// Use either a parameter or a local variable, depending on the address space.
	core::ir::Value* decl = nullptr;
	auto* ptr = var->Result(0)->Type()->As<core::type::Pointer>();
	switch (ptr->AddressSpace()) {
	case core::AddressSpace::kPrivate: {
	// Private variables become function-scope variables.
	auto* local_var = b.Var(ptr);
	local_var->SetInitializer(var->Initializer());
	decl = local_var->Result(0);
	break;
	}
	case core::AddressSpace::kStorage:
	case core::AddressSpace::kUniform: {
	// Storage and uniform buffers become function parameters.
	auto* param = b.FunctionParam(ptr);
	param->SetBindingPoint(var->BindingPoint());
	func->AppendParam(param);
	decl = param;
	break;
	}
	case core::AddressSpace::kWorkgroup: {
	// Workgroup variables are received as a function parameter (to workaround
	// an MSL compiler bug with threadgroup matrices), and we aggregate all
	// workgroup variables into a structure to avoid hitting MSL's limit for
	// threadgroup memory arguments.
	if (!workgroup_allocation_param) {
	workgroup_allocation_param = b.FunctionParam(nullptr);
	func->AppendParam(workgroup_allocation_param);
	}
	decl = b.Access(ptr, workgroup_allocation_param,
	u32(workgroup_struct_members.Length()))
	->Result(0);
	workgroup_struct_members.Push(core::type::Manager::StructMemberDesc{
	ir.symbols.New(),
	ptr->StoreType(),
	});
	break;
	}
	case core::AddressSpace::kHandle: {
	// Handle types become function parameters and drop the pointer.
	auto* param = b.FunctionParam(ptr->UnwrapPtr());
	param->SetBindingPoint(var->BindingPoint());
	func->AppendParam(param);
	decl = param;
	break;
	}
	default:
	TINT_UNREACHABLE() << "unhandled address space: " << ptr->AddressSpace();
	}

	// Copy an existing name over to the new declaration if present.
	if (auto name = ir.NameOf(var)) {
	ir.SetName(decl, name);
	}
	construct_args.Push(decl);
	}

	// Construct the structure value and name it with a `let` instruction.
	// The `let` prevents the printer from inlining the constructor, which aids readability.
	auto* construct = b.Construct(struct_type, std::move(construct_args));
	module_var_struct = b.Let(kModuleVarsName, construct)->Result(0);
	});

	// Create the workgroup variable structure if needed.
	if (!workgroup_struct_members.IsEmpty()) {
	auto* workgroup_struct =
	ty.Struct(ir.symbols.New(), std::move(workgroup_struct_members));
	workgroup_allocation_param->SetType(ty.ptr<workgroup>(workgroup_struct));
	}

	return module_var_struct;
	}

	/// Add a module-scope variables structure to a non-entry-point function.
	/// @param func the function to modify
	/// @returns the parameter that holds the module-scope variables structure
	core::ir::Value* AddModuleVarsToFunction(core::ir::Function* func) {
	// Add a new parameter to receive the module-scope variables structure.
	auto* param = b.FunctionParam(kModuleVarsName, struct_type);
	func->AppendParam(param);

	// Update all callsites to pass the module-scope variables structure as an argument.
	func->ForEachUseUnsorted([&](core::ir::Usage use) {
	if (auto* call = use.instruction->As<core::ir::UserCall>()) {
	call->AppendArg(*function_to_struct_value.Get(ContainingFunction(call)));
	}
	});

	return param;
	}

	/// Get a variable from the module-scope variable replacement structure, inserting new access
	/// instructions before @p inst.
	/// @param var the variable to get the replacement for
	/// @param inst the instruction that uses the variable
	/// @param index the index of the variable in the structure member list
	/// @returns the variable extracted from the structure
	core::ir::Value* GetVariableFromStruct(core::ir::Var* var,
	core::ir::Instruction* inst,
	uint32_t index) {
	auto* func = ContainingFunction(inst);
	auto* struct_value = function_to_struct_value.GetOr(func, nullptr);
	auto* type = var->Result(0)->Type();

	// Handle types drop the pointer and are passed around by value.
	auto* ptr = type->As<core::type::Pointer>();
	if (ptr->AddressSpace() == core::AddressSpace::kHandle) {
	type = ptr->StoreType();
	}

	auto* access = b.Access(type, struct_value, u32(index));
	access->InsertBefore(inst);
	return access->Result(0);
	}

	/// Get the function that contains an instruction.
	/// @param inst the instruction
	/// @returns the function
	core::ir::Function* ContainingFunction(core::ir::Instruction* inst) {
	return block_to_function.GetOrAdd(inst->Block(), [&] { //
	return ContainingFunction(inst->Block()->Parent());
	});
	}
	};

	} // namespace

	Result<SuccessType> ModuleScopeVars(core::ir::Module& ir) {
	auto result = ValidateAndDumpIfNeeded(ir, "ModuleScopeVars transform");
	if (result != Success) {
	return result.Failure();
	}

	State{ir}.Process();

	return Success;
	}

	} // namespace tint::msl::writer::raise