src/transform/canonicalize_entry_point_io.cc - dawn - Git at Google

 // Copyright 2021 The Tint Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 #include "src/transform/canonicalize_entry_point_io.h"

 #include <algorithm>
 #include <string>
 #include <unordered_set>
 #include <utility>
 #include <vector>

 #include "src/program_builder.h"
 #include "src/sem/function.h"

 TINT_INSTANTIATE_TYPEINFO(tint::transform::CanonicalizeEntryPointIO);
 TINT_INSTANTIATE_TYPEINFO(tint::transform::CanonicalizeEntryPointIO::Config);

 namespace tint {
 namespace transform {

 CanonicalizeEntryPointIO::CanonicalizeEntryPointIO() = default;
 CanonicalizeEntryPointIO::~CanonicalizeEntryPointIO() = default;

 namespace {

 // Comparison function used to reorder struct members such that all members with
 // location attributes appear first (ordered by location slot), followed by
 // those with builtin attributes.
 bool StructMemberComparator(const ast::StructMember* a,
                             const ast::StructMember* b) {
   auto* a_loc = ast::GetDecoration<ast::LocationDecoration>(a->decorations());
   auto* b_loc = ast::GetDecoration<ast::LocationDecoration>(b->decorations());
   auto* a_blt = ast::GetDecoration<ast::BuiltinDecoration>(a->decorations());
   auto* b_blt = ast::GetDecoration<ast::BuiltinDecoration>(b->decorations());
   if (a_loc) {
     if (!b_loc) {
       // `a` has location attribute and `b` does not: `a` goes first.
       return true;
     }
     // Both have location attributes: smallest goes first.
     return a_loc->value() < b_loc->value();
   } else {
     if (b_loc) {
       // `b` has location attribute and `a` does not: `b` goes first.
       return false;
     }
     // Both are builtins: order doesn't matter, just use enum value.
     return a_blt->value() < b_blt->value();
   }
 }

 // Returns true if `deco` is a shader IO decoration.
 bool IsShaderIODecoration(const ast::Decoration* deco) {
   return deco->IsAnyOf<ast::BuiltinDecoration, ast::InterpolateDecoration,
                        ast::InvariantDecoration, ast::LocationDecoration>();
 }

 }  // namespace

 /// State holds the current transform state for a single entry point.
 struct CanonicalizeEntryPointIO::State {
   /// OutputValue represents a shader result that the wrapper function produces.
   struct OutputValue {
     /// The name of the output value.
     std::string name;
     /// The type of the output value.
     ast::Type* type;
     /// The shader IO attributes.
     ast::DecorationList attributes;
     /// The value itself.
     ast::Expression* value;
   };

   /// The clone context.
   CloneContext& ctx;
   /// The transform config.
   CanonicalizeEntryPointIO::Config const cfg;
   /// The entry point function (AST).
   ast::Function* func_ast;
   /// The entry point function (SEM).
   sem::Function const* func_sem;

   /// The new entry point wrapper function's parameters.
   ast::VariableList wrapper_ep_parameters;
   /// The members of the wrapper function's struct parameter.
   ast::StructMemberList wrapper_struct_param_members;
   /// The name of the wrapper function's struct parameter.
   Symbol wrapper_struct_param_name;
   /// The parameters that will be passed to the original function.
   ast::ExpressionList inner_call_parameters;
   /// The members of the wrapper function's struct return type.
   ast::StructMemberList wrapper_struct_output_members;
   /// The wrapper function output values.
   std::vector<OutputValue> wrapper_output_values;
   /// The body of the wrapper function.
   ast::StatementList wrapper_body;

   /// Constructor
   /// @param context the clone context
   /// @param config the transform config
   /// @param function the entry point function
   State(CloneContext& context,
         const CanonicalizeEntryPointIO::Config& config,
         ast::Function* function)
       : ctx(context),
         cfg(config),
         func_ast(function),
         func_sem(ctx.src->Sem().Get(function)) {}

   /// Clones the shader IO decorations from `src`.
   /// @param src the decorations to clone
   /// @return the cloned decorations
   ast::DecorationList CloneShaderIOAttributes(const ast::DecorationList& src) {
     ast::DecorationList new_decorations;
     for (auto* deco : src) {
       if (IsShaderIODecoration(deco)) {
         new_decorations.push_back(ctx.Clone(deco));
       }
     }
     return new_decorations;
   }

   /// Create or return a symbol for the wrapper function's struct parameter.
   /// @returns the symbol for the struct parameter
   Symbol InputStructSymbol() {
     if (!wrapper_struct_param_name.IsValid()) {
       wrapper_struct_param_name = ctx.dst->Sym();
     }
     return wrapper_struct_param_name;
   }

   /// Add a shader input to the entry point.
   /// @param name the name of the shader input
   /// @param type the type of the shader input
   /// @param attributes the attributes to apply to the shader input
   /// @returns an expression which evaluates to the value of the shader input
   ast::Expression* AddInput(std::string name,
                             ast::Type* type,
                             ast::DecorationList attributes) {
     if (cfg.builtin_style == BuiltinStyle::kParameter &&
         ast::HasDecoration<ast::BuiltinDecoration>(attributes)) {
       // If this input is a builtin and we are emitting those as parameters,
       // then add it to the parameter list and pass it directly to the inner
       // function.
       wrapper_ep_parameters.push_back(
           ctx.dst->Param(name, type, std::move(attributes)));
       return ctx.dst->Expr(name);
     } else {
       // Otherwise, move it to the new structure member list.
       wrapper_struct_param_members.push_back(
           ctx.dst->Member(name, type, std::move(attributes)));
       return ctx.dst->MemberAccessor(InputStructSymbol(), name);
     }
   }

   /// Add a shader output to the entry point.
   /// @param name the name of the shader output
   /// @param type the type of the shader output
   /// @param attributes the attributes to apply to the shader output
   /// @param value the value of the shader output
   void AddOutput(std::string name,
                  ast::Type* type,
                  ast::DecorationList attributes,
                  ast::Expression* value) {
     OutputValue output;
     output.name = name;
     output.type = type;
     output.attributes = std::move(attributes);
     output.value = value;
     wrapper_output_values.push_back(output);
   }

   /// Process a non-struct parameter.
   /// This creates a new object for the shader input, moving the shader IO
   /// attributes to it. It also adds an expression to the list of parameters
   /// that will be passed to the original function.
   /// @param param the original function parameter
   void ProcessNonStructParameter(const sem::Parameter* param) {
     // Remove the shader IO attributes from the inner function parameter, and
     // attach them to the new object instead.
     ast::DecorationList attributes;
     for (auto* deco : param->Declaration()->decorations()) {
       if (IsShaderIODecoration(deco)) {
         ctx.Remove(param->Declaration()->decorations(), deco);
         attributes.push_back(ctx.Clone(deco));
       }
     }

     auto name = ctx.src->Symbols().NameFor(param->Declaration()->symbol());
     auto* type = ctx.Clone(param->Declaration()->type());
     auto* input_expr = AddInput(name, type, std::move(attributes));
     inner_call_parameters.push_back(input_expr);
   }

   /// Process a struct parameter.
   /// This creates new objects for each struct member, moving the shader IO
   /// attributes to them. It also creates the structure that will be passed to
   /// the original function.
   /// @param param the original function parameter
   void ProcessStructParameter(const sem::Parameter* param) {
     auto* str = param->Type()->As<sem::Struct>();

     // Recreate struct members in the outer entry point and build an initializer
     // list to pass them through to the inner function.
     ast::ExpressionList inner_struct_values;
     for (auto* member : str->Members()) {
       if (member->Type()->Is<sem::Struct>()) {
         TINT_ICE(Transform, ctx.dst->Diagnostics()) << "nested IO struct";
         continue;
       }

       auto* member_ast = member->Declaration();
       auto name = ctx.src->Symbols().NameFor(member_ast->symbol());
       auto* type = ctx.Clone(member_ast->type());
       auto attributes = CloneShaderIOAttributes(member_ast->decorations());
       auto* input_expr = AddInput(name, type, std::move(attributes));
       inner_struct_values.push_back(input_expr);
     }

     // Construct the original structure using the new shader input objects.
     inner_call_parameters.push_back(ctx.dst->Construct(
         ctx.Clone(param->Declaration()->type()), inner_struct_values));
   }

   /// Process the entry point return type.
   /// This generates a list of output values that are returned by the original
   /// function.
   /// @param inner_ret_type the original function return type
   /// @param original_result the result object produced by the original function
   void ProcessReturnType(const sem::Type* inner_ret_type,
                          Symbol original_result) {
     if (auto* str = inner_ret_type->As<sem::Struct>()) {
       for (auto* member : str->Members()) {
         if (member->Type()->Is<sem::Struct>()) {
           TINT_ICE(Transform, ctx.dst->Diagnostics()) << "nested IO struct";
           continue;
         }

         auto* member_ast = member->Declaration();
         auto name = ctx.src->Symbols().NameFor(member_ast->symbol());
         auto* type = ctx.Clone(member_ast->type());
         auto attributes = CloneShaderIOAttributes(member_ast->decorations());

         // Extract the original structure member.
         AddOutput(name, type, std::move(attributes),
                   ctx.dst->MemberAccessor(original_result, name));
       }
     } else if (!inner_ret_type->Is<sem::Void>()) {
       auto* type = ctx.Clone(func_ast->return_type());
       auto attributes =
           CloneShaderIOAttributes(func_ast->return_type_decorations());

       // Propagate the non-struct return value as is.
       AddOutput("value", type, std::move(attributes),
                 ctx.dst->Expr(original_result));
     }
   }

   /// Add a fixed sample mask to the wrapper function output.
   /// If there is already a sample mask, bitwise-and it with the fixed mask.
   /// Otherwise, create a new output value from the fixed mask.
   void AddFixedSampleMask() {
     // Check the existing output values for a sample mask builtin.
     for (auto& outval : wrapper_output_values) {
       auto* builtin =
           ast::GetDecoration<ast::BuiltinDecoration>(outval.attributes);
       if (builtin && builtin->value() == ast::Builtin::kSampleMask) {
         // Combine the authored sample mask with the fixed mask.
         outval.value = ctx.dst->And(outval.value, cfg.fixed_sample_mask);
         return;
       }
     }

     // No existing sample mask builtin was found, so create a new output value
     // using the fixed sample mask.
     AddOutput("fixed_sample_mask", ctx.dst->ty.u32(),
               {ctx.dst->Builtin(ast::Builtin::kSampleMask)},
               ctx.dst->Expr(cfg.fixed_sample_mask));
   }

   /// Create the wrapper function's struct parameter and type objects.
   void CreateInputStruct() {
     // Sort the struct members to satisfy HLSL interfacing matching rules.
     std::sort(wrapper_struct_param_members.begin(),
               wrapper_struct_param_members.end(), StructMemberComparator);

     // Create the new struct type.
     auto struct_name = ctx.dst->Sym();
     auto* in_struct = ctx.dst->create<ast::Struct>(
         struct_name, wrapper_struct_param_members, ast::DecorationList{});
     ctx.InsertBefore(ctx.src->AST().GlobalDeclarations(), func_ast, in_struct);

     // Create a new function parameter using this struct type.
     auto* param =
         ctx.dst->Param(InputStructSymbol(), ctx.dst->ty.type_name(struct_name));
     wrapper_ep_parameters.push_back(param);
   }

   /// Create and return the wrapper function's struct result object.
   /// @returns the struct type
   ast::Struct* CreateOutputStruct() {
     ast::StatementList assignments;

     auto wrapper_result = ctx.dst->Symbols().New("wrapper_result");

     // Create the struct members and their corresponding assignment statements.
     std::unordered_set<std::string> member_names;
     for (auto& outval : wrapper_output_values) {
       // Use the original output name, unless that is already taken.
       Symbol name;
       if (member_names.count(outval.name)) {
         name = ctx.dst->Symbols().New(outval.name);
       } else {
         name = ctx.dst->Symbols().Register(outval.name);
       }
       member_names.insert(ctx.dst->Symbols().NameFor(name));

       wrapper_struct_output_members.push_back(
           ctx.dst->Member(name, outval.type, std::move(outval.attributes)));
       assignments.push_back(ctx.dst->Assign(
           ctx.dst->MemberAccessor(wrapper_result, name), outval.value));
     }

     // Sort the struct members to satisfy HLSL interfacing matching rules.
     std::sort(wrapper_struct_output_members.begin(),
               wrapper_struct_output_members.end(), StructMemberComparator);

     // Create the new struct type.
     auto* out_struct = ctx.dst->create<ast::Struct>(
         ctx.dst->Sym(), wrapper_struct_output_members, ast::DecorationList{});
     ctx.InsertBefore(ctx.src->AST().GlobalDeclarations(), func_ast, out_struct);

     // Create the output struct object, assign its members, and return it.
     auto* result_object =
         ctx.dst->Var(wrapper_result, ctx.dst->ty.type_name(out_struct->name()));
     wrapper_body.push_back(ctx.dst->Decl(result_object));
     wrapper_body.insert(wrapper_body.end(), assignments.begin(),
                         assignments.end());
     wrapper_body.push_back(ctx.dst->Return(wrapper_result));

     return out_struct;
   }

   // Recreate the original function without entry point attributes and call it.
   /// @returns the inner function call expression
   ast::CallExpression* CallInnerFunction() {
     // Add a suffix to the function name, as the wrapper function will take the
     // original entry point name.
     auto ep_name = ctx.src->Symbols().NameFor(func_ast->symbol());
     auto inner_name = ctx.dst->Symbols().New(ep_name + "_inner");

     // Clone everything, dropping the function and return type attributes.
     // The parameter attributes will have already been stripped during
     // processing.
     auto* inner_function = ctx.dst->create<ast::Function>(
         inner_name, ctx.Clone(func_ast->params()),
         ctx.Clone(func_ast->return_type()), ctx.Clone(func_ast->body()),
         ast::DecorationList{}, ast::DecorationList{});
     ctx.Replace(func_ast, inner_function);

     // Call the function.
     return ctx.dst->Call(inner_function->symbol(), inner_call_parameters);
   }

   /// Process the entry point function.
   void Process() {
     bool needs_fixed_sample_mask = false;
     if (func_ast->pipeline_stage() == ast::PipelineStage::kFragment &&
         cfg.fixed_sample_mask != 0xFFFFFFFF) {
       needs_fixed_sample_mask = true;
     }

     // Exit early if there is no shader IO to handle.
     if (func_sem->Parameters().size() == 0 &&
         func_sem->ReturnType()->Is<sem::Void>() && !needs_fixed_sample_mask) {
       return;
     }

     // Process the entry point parameters, collecting those that need to be
     // aggregated into a single structure.
     if (!func_sem->Parameters().empty()) {
       for (auto* param : func_sem->Parameters()) {
         if (param->Type()->Is<sem::Struct>()) {
           ProcessStructParameter(param);
         } else {
           ProcessNonStructParameter(param);
         }
       }

       // Create a structure parameter for the outer entry point if necessary.
       if (!wrapper_struct_param_members.empty()) {
         CreateInputStruct();
       }
     }

     // Recreate the original function and call it.
     auto* call_inner = CallInnerFunction();

     // Process the return type, and start building the wrapper function body.
     std::function<ast::Type*()> wrapper_ret_type = [&] {
       return ctx.dst->ty.void_();
     };
     if (func_sem->ReturnType()->Is<sem::Void>()) {
       // The function call is just a statement with no result.
       wrapper_body.push_back(ctx.dst->create<ast::CallStatement>(call_inner));
     } else {
       // Capture the result of calling the original function.
       auto* inner_result = ctx.dst->Const(
           ctx.dst->Symbols().New("inner_result"), nullptr, call_inner);
       wrapper_body.push_back(ctx.dst->Decl(inner_result));

       // Process the original return type to determine the outputs that the
       // outer function needs to produce.
       ProcessReturnType(func_sem->ReturnType(), inner_result->symbol());
     }

     // Add a fixed sample mask, if necessary.
     if (needs_fixed_sample_mask) {
       AddFixedSampleMask();
     }

     // Produce the entry point outputs, if necessary.
     if (!wrapper_output_values.empty()) {
       auto* output_struct = CreateOutputStruct();
       wrapper_ret_type = [&, output_struct] {
         return ctx.dst->ty.type_name(output_struct->name());
       };
     }

     // Create the wrapper entry point function.
     // Take the name of the original entry point function.
     auto name = ctx.Clone(func_ast->symbol());
     auto* wrapper_func = ctx.dst->create<ast::Function>(
         name, wrapper_ep_parameters, wrapper_ret_type(),
         ctx.dst->Block(wrapper_body), ctx.Clone(func_ast->decorations()),
         ast::DecorationList{});
     ctx.InsertAfter(ctx.src->AST().GlobalDeclarations(), func_ast,
                     wrapper_func);
   }
 };

 void CanonicalizeEntryPointIO::Run(CloneContext& ctx,
                                    const DataMap& inputs,
                                    DataMap&) {
   auto* cfg = inputs.Get<Config>();
   if (cfg == nullptr) {
     ctx.dst->Diagnostics().add_error(
         diag::System::Transform,
         "missing transform data for " + std::string(TypeInfo().name));
     return;
   }

   // Remove entry point IO attributes from struct declarations.
   // New structures will be created for each entry point, as necessary.
   for (auto* ty : ctx.src->AST().TypeDecls()) {
     if (auto* struct_ty = ty->As<ast::Struct>()) {
       for (auto* member : struct_ty->members()) {
         for (auto* deco : member->decorations()) {
           if (IsShaderIODecoration(deco)) {
             ctx.Remove(member->decorations(), deco);
           }
         }
       }
     }
   }

   for (auto* func_ast : ctx.src->AST().Functions()) {
     if (!func_ast->IsEntryPoint()) {
       continue;
     }

     State state(ctx, *cfg, func_ast);
     state.Process();
   }

   ctx.Clone();
 }

 CanonicalizeEntryPointIO::Config::Config(BuiltinStyle builtins,
                                          uint32_t sample_mask)
     : builtin_style(builtins), fixed_sample_mask(sample_mask) {}

 CanonicalizeEntryPointIO::Config::Config(const Config&) = default;
 CanonicalizeEntryPointIO::Config::~Config() = default;

 }  // namespace transform
 }  // namespace tint
	// Copyright 2021 The Tint Authors.
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	#include "src/transform/canonicalize_entry_point_io.h"

	#include <algorithm>
	#include <string>
	#include <unordered_set>
	#include <utility>
	#include <vector>

	#include "src/program_builder.h"
	#include "src/sem/function.h"

	TINT_INSTANTIATE_TYPEINFO(tint::transform::CanonicalizeEntryPointIO);
	TINT_INSTANTIATE_TYPEINFO(tint::transform::CanonicalizeEntryPointIO::Config);

	namespace tint {
	namespace transform {

	CanonicalizeEntryPointIO::CanonicalizeEntryPointIO() = default;
	CanonicalizeEntryPointIO::~CanonicalizeEntryPointIO() = default;

	namespace {

	// Comparison function used to reorder struct members such that all members with
	// location attributes appear first (ordered by location slot), followed by
	// those with builtin attributes.
	bool StructMemberComparator(const ast::StructMember* a,
	const ast::StructMember* b) {
	auto* a_loc = ast::GetDecoration<ast::LocationDecoration>(a->decorations());
	auto* b_loc = ast::GetDecoration<ast::LocationDecoration>(b->decorations());
	auto* a_blt = ast::GetDecoration<ast::BuiltinDecoration>(a->decorations());
	auto* b_blt = ast::GetDecoration<ast::BuiltinDecoration>(b->decorations());
	if (a_loc) {
	if (!b_loc) {
	// `a` has location attribute and `b` does not: `a` goes first.
	return true;
	}
	// Both have location attributes: smallest goes first.
	return a_loc->value() < b_loc->value();
	} else {
	if (b_loc) {
	// `b` has location attribute and `a` does not: `b` goes first.
	return false;
	}
	// Both are builtins: order doesn't matter, just use enum value.
	return a_blt->value() < b_blt->value();
	}
	}

	// Returns true if `deco` is a shader IO decoration.
	bool IsShaderIODecoration(const ast::Decoration* deco) {
	return deco->IsAnyOf<ast::BuiltinDecoration, ast::InterpolateDecoration,
	ast::InvariantDecoration, ast::LocationDecoration>();
	}

	} // namespace

	/// State holds the current transform state for a single entry point.
	struct CanonicalizeEntryPointIO::State {
	/// OutputValue represents a shader result that the wrapper function produces.
	struct OutputValue {
	/// The name of the output value.
	std::string name;
	/// The type of the output value.
	ast::Type* type;
	/// The shader IO attributes.
	ast::DecorationList attributes;
	/// The value itself.
	ast::Expression* value;
	};

	/// The clone context.
	CloneContext& ctx;
	/// The transform config.
	CanonicalizeEntryPointIO::Config const cfg;
	/// The entry point function (AST).
	ast::Function* func_ast;
	/// The entry point function (SEM).
	sem::Function const* func_sem;

	/// The new entry point wrapper function's parameters.
	ast::VariableList wrapper_ep_parameters;
	/// The members of the wrapper function's struct parameter.
	ast::StructMemberList wrapper_struct_param_members;
	/// The name of the wrapper function's struct parameter.
	Symbol wrapper_struct_param_name;
	/// The parameters that will be passed to the original function.
	ast::ExpressionList inner_call_parameters;
	/// The members of the wrapper function's struct return type.
	ast::StructMemberList wrapper_struct_output_members;
	/// The wrapper function output values.
	std::vector<OutputValue> wrapper_output_values;
	/// The body of the wrapper function.
	ast::StatementList wrapper_body;

	/// Constructor
	/// @param context the clone context
	/// @param config the transform config
	/// @param function the entry point function
	State(CloneContext& context,
	const CanonicalizeEntryPointIO::Config& config,
	ast::Function* function)
	: ctx(context),
	cfg(config),
	func_ast(function),
	func_sem(ctx.src->Sem().Get(function)) {}

	/// Clones the shader IO decorations from `src`.
	/// @param src the decorations to clone
	/// @return the cloned decorations
	ast::DecorationList CloneShaderIOAttributes(const ast::DecorationList& src) {
	ast::DecorationList new_decorations;
	for (auto* deco : src) {
	if (IsShaderIODecoration(deco)) {
	new_decorations.push_back(ctx.Clone(deco));
	}
	}
	return new_decorations;
	}

	/// Create or return a symbol for the wrapper function's struct parameter.
	/// @returns the symbol for the struct parameter
	Symbol InputStructSymbol() {
	if (!wrapper_struct_param_name.IsValid()) {
	wrapper_struct_param_name = ctx.dst->Sym();
	}
	return wrapper_struct_param_name;
	}

	/// Add a shader input to the entry point.
	/// @param name the name of the shader input
	/// @param type the type of the shader input
	/// @param attributes the attributes to apply to the shader input
	/// @returns an expression which evaluates to the value of the shader input
	ast::Expression* AddInput(std::string name,
	ast::Type* type,
	ast::DecorationList attributes) {
	if (cfg.builtin_style == BuiltinStyle::kParameter &&
	ast::HasDecoration<ast::BuiltinDecoration>(attributes)) {
	// If this input is a builtin and we are emitting those as parameters,
	// then add it to the parameter list and pass it directly to the inner
	// function.
	wrapper_ep_parameters.push_back(
	ctx.dst->Param(name, type, std::move(attributes)));
	return ctx.dst->Expr(name);
	} else {
	// Otherwise, move it to the new structure member list.
	wrapper_struct_param_members.push_back(
	ctx.dst->Member(name, type, std::move(attributes)));
	return ctx.dst->MemberAccessor(InputStructSymbol(), name);
	}
	}

	/// Add a shader output to the entry point.
	/// @param name the name of the shader output
	/// @param type the type of the shader output
	/// @param attributes the attributes to apply to the shader output
	/// @param value the value of the shader output
	void AddOutput(std::string name,
	ast::Type* type,
	ast::DecorationList attributes,
	ast::Expression* value) {
	OutputValue output;
	output.name = name;
	output.type = type;
	output.attributes = std::move(attributes);
	output.value = value;
	wrapper_output_values.push_back(output);
	}

	/// Process a non-struct parameter.
	/// This creates a new object for the shader input, moving the shader IO
	/// attributes to it. It also adds an expression to the list of parameters
	/// that will be passed to the original function.
	/// @param param the original function parameter
	void ProcessNonStructParameter(const sem::Parameter* param) {
	// Remove the shader IO attributes from the inner function parameter, and
	// attach them to the new object instead.
	ast::DecorationList attributes;
	for (auto* deco : param->Declaration()->decorations()) {
	if (IsShaderIODecoration(deco)) {
	ctx.Remove(param->Declaration()->decorations(), deco);
	attributes.push_back(ctx.Clone(deco));
	}
	}

	auto name = ctx.src->Symbols().NameFor(param->Declaration()->symbol());
	auto* type = ctx.Clone(param->Declaration()->type());
	auto* input_expr = AddInput(name, type, std::move(attributes));
	inner_call_parameters.push_back(input_expr);
	}

	/// Process a struct parameter.
	/// This creates new objects for each struct member, moving the shader IO
	/// attributes to them. It also creates the structure that will be passed to
	/// the original function.
	/// @param param the original function parameter
	void ProcessStructParameter(const sem::Parameter* param) {
	auto* str = param->Type()->As<sem::Struct>();

	// Recreate struct members in the outer entry point and build an initializer
	// list to pass them through to the inner function.
	ast::ExpressionList inner_struct_values;
	for (auto* member : str->Members()) {
	if (member->Type()->Is<sem::Struct>()) {
	TINT_ICE(Transform, ctx.dst->Diagnostics()) << "nested IO struct";
	continue;
	}

	auto* member_ast = member->Declaration();
	auto name = ctx.src->Symbols().NameFor(member_ast->symbol());
	auto* type = ctx.Clone(member_ast->type());
	auto attributes = CloneShaderIOAttributes(member_ast->decorations());
	auto* input_expr = AddInput(name, type, std::move(attributes));
	inner_struct_values.push_back(input_expr);
	}

	// Construct the original structure using the new shader input objects.
	inner_call_parameters.push_back(ctx.dst->Construct(
	ctx.Clone(param->Declaration()->type()), inner_struct_values));
	}

	/// Process the entry point return type.
	/// This generates a list of output values that are returned by the original
	/// function.
	/// @param inner_ret_type the original function return type
	/// @param original_result the result object produced by the original function
	void ProcessReturnType(const sem::Type* inner_ret_type,
	Symbol original_result) {
	if (auto* str = inner_ret_type->As<sem::Struct>()) {
	for (auto* member : str->Members()) {
	if (member->Type()->Is<sem::Struct>()) {
	TINT_ICE(Transform, ctx.dst->Diagnostics()) << "nested IO struct";
	continue;
	}

	auto* member_ast = member->Declaration();
	auto name = ctx.src->Symbols().NameFor(member_ast->symbol());
	auto* type = ctx.Clone(member_ast->type());
	auto attributes = CloneShaderIOAttributes(member_ast->decorations());

	// Extract the original structure member.
	AddOutput(name, type, std::move(attributes),
	ctx.dst->MemberAccessor(original_result, name));
	}
	} else if (!inner_ret_type->Is<sem::Void>()) {
	auto* type = ctx.Clone(func_ast->return_type());
	auto attributes =
	CloneShaderIOAttributes(func_ast->return_type_decorations());

	// Propagate the non-struct return value as is.
	AddOutput("value", type, std::move(attributes),
	ctx.dst->Expr(original_result));
	}
	}

	/// Add a fixed sample mask to the wrapper function output.
	/// If there is already a sample mask, bitwise-and it with the fixed mask.
	/// Otherwise, create a new output value from the fixed mask.
	void AddFixedSampleMask() {
	// Check the existing output values for a sample mask builtin.
	for (auto& outval : wrapper_output_values) {
	auto* builtin =
	ast::GetDecoration<ast::BuiltinDecoration>(outval.attributes);
	if (builtin && builtin->value() == ast::Builtin::kSampleMask) {
	// Combine the authored sample mask with the fixed mask.
	outval.value = ctx.dst->And(outval.value, cfg.fixed_sample_mask);
	return;
	}
	}

	// No existing sample mask builtin was found, so create a new output value
	// using the fixed sample mask.
	AddOutput("fixed_sample_mask", ctx.dst->ty.u32(),
	{ctx.dst->Builtin(ast::Builtin::kSampleMask)},
	ctx.dst->Expr(cfg.fixed_sample_mask));
	}

	/// Create the wrapper function's struct parameter and type objects.
	void CreateInputStruct() {
	// Sort the struct members to satisfy HLSL interfacing matching rules.
	std::sort(wrapper_struct_param_members.begin(),
	wrapper_struct_param_members.end(), StructMemberComparator);

	// Create the new struct type.
	auto struct_name = ctx.dst->Sym();
	auto* in_struct = ctx.dst->create<ast::Struct>(
	struct_name, wrapper_struct_param_members, ast::DecorationList{});
	ctx.InsertBefore(ctx.src->AST().GlobalDeclarations(), func_ast, in_struct);

	// Create a new function parameter using this struct type.
	auto* param =
	ctx.dst->Param(InputStructSymbol(), ctx.dst->ty.type_name(struct_name));
	wrapper_ep_parameters.push_back(param);
	}

	/// Create and return the wrapper function's struct result object.
	/// @returns the struct type
	ast::Struct* CreateOutputStruct() {
	ast::StatementList assignments;

	auto wrapper_result = ctx.dst->Symbols().New("wrapper_result");

	// Create the struct members and their corresponding assignment statements.
	std::unordered_set<std::string> member_names;
	for (auto& outval : wrapper_output_values) {
	// Use the original output name, unless that is already taken.
	Symbol name;
	if (member_names.count(outval.name)) {
	name = ctx.dst->Symbols().New(outval.name);
	} else {
	name = ctx.dst->Symbols().Register(outval.name);
	}
	member_names.insert(ctx.dst->Symbols().NameFor(name));

	wrapper_struct_output_members.push_back(
	ctx.dst->Member(name, outval.type, std::move(outval.attributes)));
	assignments.push_back(ctx.dst->Assign(
	ctx.dst->MemberAccessor(wrapper_result, name), outval.value));
	}

	// Sort the struct members to satisfy HLSL interfacing matching rules.
	std::sort(wrapper_struct_output_members.begin(),
	wrapper_struct_output_members.end(), StructMemberComparator);

	// Create the new struct type.
	auto* out_struct = ctx.dst->create<ast::Struct>(
	ctx.dst->Sym(), wrapper_struct_output_members, ast::DecorationList{});
	ctx.InsertBefore(ctx.src->AST().GlobalDeclarations(), func_ast, out_struct);

	// Create the output struct object, assign its members, and return it.
	auto* result_object =
	ctx.dst->Var(wrapper_result, ctx.dst->ty.type_name(out_struct->name()));
	wrapper_body.push_back(ctx.dst->Decl(result_object));
	wrapper_body.insert(wrapper_body.end(), assignments.begin(),
	assignments.end());
	wrapper_body.push_back(ctx.dst->Return(wrapper_result));

	return out_struct;
	}

	// Recreate the original function without entry point attributes and call it.
	/// @returns the inner function call expression
	ast::CallExpression* CallInnerFunction() {
	// Add a suffix to the function name, as the wrapper function will take the
	// original entry point name.
	auto ep_name = ctx.src->Symbols().NameFor(func_ast->symbol());
	auto inner_name = ctx.dst->Symbols().New(ep_name + "_inner");

	// Clone everything, dropping the function and return type attributes.
	// The parameter attributes will have already been stripped during
	// processing.
	auto* inner_function = ctx.dst->create<ast::Function>(
	inner_name, ctx.Clone(func_ast->params()),
	ctx.Clone(func_ast->return_type()), ctx.Clone(func_ast->body()),
	ast::DecorationList{}, ast::DecorationList{});
	ctx.Replace(func_ast, inner_function);

	// Call the function.
	return ctx.dst->Call(inner_function->symbol(), inner_call_parameters);
	}

	/// Process the entry point function.
	void Process() {
	bool needs_fixed_sample_mask = false;
	if (func_ast->pipeline_stage() == ast::PipelineStage::kFragment &&
	cfg.fixed_sample_mask != 0xFFFFFFFF) {
	needs_fixed_sample_mask = true;
	}

	// Exit early if there is no shader IO to handle.
	if (func_sem->Parameters().size() == 0 &&
	func_sem->ReturnType()->Is<sem::Void>() && !needs_fixed_sample_mask) {
	return;
	}

	// Process the entry point parameters, collecting those that need to be
	// aggregated into a single structure.
	if (!func_sem->Parameters().empty()) {
	for (auto* param : func_sem->Parameters()) {
	if (param->Type()->Is<sem::Struct>()) {
	ProcessStructParameter(param);
	} else {
	ProcessNonStructParameter(param);
	}
	}

	// Create a structure parameter for the outer entry point if necessary.
	if (!wrapper_struct_param_members.empty()) {
	CreateInputStruct();
	}
	}

	// Recreate the original function and call it.
	auto* call_inner = CallInnerFunction();

	// Process the return type, and start building the wrapper function body.
	std::function<ast::Type*()> wrapper_ret_type = [&] {
	return ctx.dst->ty.void_();
	};
	if (func_sem->ReturnType()->Is<sem::Void>()) {
	// The function call is just a statement with no result.
	wrapper_body.push_back(ctx.dst->create<ast::CallStatement>(call_inner));
	} else {
	// Capture the result of calling the original function.
	auto* inner_result = ctx.dst->Const(
	ctx.dst->Symbols().New("inner_result"), nullptr, call_inner);
	wrapper_body.push_back(ctx.dst->Decl(inner_result));

	// Process the original return type to determine the outputs that the
	// outer function needs to produce.
	ProcessReturnType(func_sem->ReturnType(), inner_result->symbol());
	}

	// Add a fixed sample mask, if necessary.
	if (needs_fixed_sample_mask) {
	AddFixedSampleMask();
	}

	// Produce the entry point outputs, if necessary.
	if (!wrapper_output_values.empty()) {
	auto* output_struct = CreateOutputStruct();
	wrapper_ret_type = [&, output_struct] {
	return ctx.dst->ty.type_name(output_struct->name());
	};
	}

	// Create the wrapper entry point function.
	// Take the name of the original entry point function.
	auto name = ctx.Clone(func_ast->symbol());
	auto* wrapper_func = ctx.dst->create<ast::Function>(
	name, wrapper_ep_parameters, wrapper_ret_type(),
	ctx.dst->Block(wrapper_body), ctx.Clone(func_ast->decorations()),
	ast::DecorationList{});
	ctx.InsertAfter(ctx.src->AST().GlobalDeclarations(), func_ast,
	wrapper_func);
	}
	};

	void CanonicalizeEntryPointIO::Run(CloneContext& ctx,
	const DataMap& inputs,
	DataMap&) {
	auto* cfg = inputs.Get<Config>();
	if (cfg == nullptr) {
	ctx.dst->Diagnostics().add_error(
	diag::System::Transform,
	"missing transform data for " + std::string(TypeInfo().name));
	return;
	}

	// Remove entry point IO attributes from struct declarations.
	// New structures will be created for each entry point, as necessary.
	for (auto* ty : ctx.src->AST().TypeDecls()) {
	if (auto* struct_ty = ty->As<ast::Struct>()) {
	for (auto* member : struct_ty->members()) {
	for (auto* deco : member->decorations()) {
	if (IsShaderIODecoration(deco)) {
	ctx.Remove(member->decorations(), deco);
	}
	}
	}
	}
	}

	for (auto* func_ast : ctx.src->AST().Functions()) {
	if (!func_ast->IsEntryPoint()) {
	continue;
	}

	State state(ctx, *cfg, func_ast);
	state.Process();
	}

	ctx.Clone();
	}

	CanonicalizeEntryPointIO::Config::Config(BuiltinStyle builtins,
	uint32_t sample_mask)
	: builtin_style(builtins), fixed_sample_mask(sample_mask) {}

	CanonicalizeEntryPointIO::Config::Config(const Config&) = default;
	CanonicalizeEntryPointIO::Config::~Config() = default;

	} // namespace transform
	} // namespace tint