src/transform/zero_init_workgroup_memory.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/zero_init_workgroup_memory.h"

 #include <unordered_map>
 #include <utility>

 #include "src/program_builder.h"
 #include "src/sem/atomic_type.h"
 #include "src/sem/function.h"
 #include "src/sem/variable.h"
 #include "src/utils/get_or_create.h"

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

 namespace tint {
 namespace transform {

 /// PIMPL state for the ZeroInitWorkgroupMemory transform
 struct ZeroInitWorkgroupMemory::State {
   /// The clone context
   CloneContext& ctx;
   /// The config
   Config cfg;

   /// Zero() generates the statements required to zero initialize the workgroup
   /// storage expression of type `ty`.
   /// @param ty the expression type
   /// @param stmts the built statements
   /// @param get_expr a function that builds the AST nodes for the expression
   void Zero(const sem::Type* ty,
             ast::StatementList& stmts,
             const std::function<ast::Expression*()>& get_expr) {
     if (CanZero(ty)) {
       auto* var = get_expr();
       auto* zero_init = ctx.dst->Construct(CreateASTTypeFor(&ctx, ty));
       stmts.emplace_back(
           ctx.dst->create<ast::AssignmentStatement>(var, zero_init));
       return;
     }

     if (auto* atomic = ty->As<sem::Atomic>()) {
       auto* zero_init =
           ctx.dst->Construct(CreateASTTypeFor(&ctx, atomic->Type()));
       auto* store = ctx.dst->Call("atomicStore", ctx.dst->AddressOf(get_expr()),
                                   zero_init);
       stmts.emplace_back(ctx.dst->create<ast::CallStatement>(store));
       return;
     }

     if (auto* str = ty->As<sem::Struct>()) {
       for (auto* member : str->Members()) {
         auto name = ctx.Clone(member->Declaration()->symbol());
         Zero(member->Type(), stmts,
              [&] { return ctx.dst->MemberAccessor(get_expr(), name); });
       }
       return;
     }

     if (auto* arr = ty->As<sem::Array>()) {
       if (ShouldEmitForLoop(arr)) {
         auto i = ctx.dst->Symbols().New("i");
         auto* i_decl = ctx.dst->Decl(ctx.dst->Var(i, ctx.dst->ty.i32()));
         auto* cond = ctx.dst->create<ast::BinaryExpression>(
             ast::BinaryOp::kLessThan, ctx.dst->Expr(i),
             ctx.dst->Expr(static_cast<int>(arr->Count())));
         auto* inc = ctx.dst->Assign(i, ctx.dst->Add(i, 1));
         ast::StatementList for_stmts;
         Zero(arr->ElemType(), for_stmts,
              [&] { return ctx.dst->IndexAccessor(get_expr(), i); });
         auto* body = ctx.dst->Block(for_stmts);
         stmts.emplace_back(ctx.dst->For(i_decl, cond, inc, body));
       } else {
         for (size_t i = 0; i < arr->Count(); i++) {
           Zero(arr->ElemType(), stmts, [&] {
             return ctx.dst->IndexAccessor(get_expr(),
                                           static_cast<ProgramBuilder::u32>(i));
           });
         }
       }
       return;
     }

     TINT_UNREACHABLE(Transform, ctx.dst->Diagnostics())
         << "could not zero workgroup type: " << ty->type_name();
   }

   /// @returns true if the type `ty` can be zeroed with a simple zero-value
   /// expression in the form of a type constructor without operands. If
   /// CanZero() returns false, then the type needs to be initialized by
   /// decomposing the initialization into multiple sub-initializations.
   /// @param ty the type to inspect
   bool CanZero(const sem::Type* ty) {
     if (ty->Is<sem::Atomic>()) {
       return false;
     }
     if (auto* str = ty->As<sem::Struct>()) {
       for (auto* member : str->Members()) {
         if (!CanZero(member->Type())) {
           return false;
         }
       }
     }
     if (auto* arr = ty->As<sem::Array>()) {
       if (ShouldEmitForLoop(arr) || !CanZero(arr->ElemType())) {
         return false;
       }
     }
     return true;
   }

   /// @returns true if the array should be emitted as a for-loop instead of
   /// using zero-initializer statements.
   /// @param array the array
   bool ShouldEmitForLoop(const sem::Array* array) {
     // TODO(bclayton): If array sizes become pipeline-overridable then this
     // we need to return true for these arrays.
     // See https://github.com/gpuweb/gpuweb/pull/1792
     return (cfg.init_arrays_with_loop_size_threshold != 0) &&
            (array->SizeInBytes() >= cfg.init_arrays_with_loop_size_threshold);
   }
 };

 ZeroInitWorkgroupMemory::ZeroInitWorkgroupMemory() = default;

 ZeroInitWorkgroupMemory::~ZeroInitWorkgroupMemory() = default;

 void ZeroInitWorkgroupMemory::Run(CloneContext& ctx,
                                   const DataMap& inputs,
                                   DataMap&) {
   auto& sem = ctx.src->Sem();

   Config cfg;
   if (auto* c = inputs.Get<Config>()) {
     cfg = *c;
   }

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

     // Generate a list of statements to zero initialize each of the workgroup
     // storage variables.
     ast::StatementList stmts;
     auto* func = sem.Get(ast_func);
     for (auto* var : func->ReferencedModuleVariables()) {
       if (var->StorageClass() != ast::StorageClass::kWorkgroup) {
         continue;
       }
       State{ctx, cfg}.Zero(var->Type()->UnwrapRef(), stmts, [&] {
         auto var_name = ctx.Clone(var->Declaration()->symbol());
         return ctx.dst->Expr(var_name);
       });
     }

     if (stmts.empty()) {
       continue;  // No workgroup variables to initialize.
     }

     // Scan the entry point for an existing local_invocation_index builtin
     // parameter
     ast::Expression* local_index = nullptr;
     for (auto* param : ast_func->params()) {
       if (auto* builtin = ast::GetDecoration<ast::BuiltinDecoration>(
               param->decorations())) {
         if (builtin->value() == ast::Builtin::kLocalInvocationIndex) {
           local_index = ctx.dst->Expr(ctx.Clone(param->symbol()));
           break;
         }
       }

       if (auto* str = sem.Get(param)->Type()->As<sem::Struct>()) {
         for (auto* member : str->Members()) {
           if (auto* builtin = ast::GetDecoration<ast::BuiltinDecoration>(
                   member->Declaration()->decorations())) {
             if (builtin->value() == ast::Builtin::kLocalInvocationIndex) {
               auto* param_expr = ctx.dst->Expr(ctx.Clone(param->symbol()));
               auto member_name = ctx.Clone(member->Declaration()->symbol());
               local_index = ctx.dst->MemberAccessor(param_expr, member_name);
               break;
             }
           }
         }
       }
     }
     if (!local_index) {
       // No existing local index parameter. Append one to the entry point.
       auto* param = ctx.dst->Param(
           ctx.dst->Symbols().New("local_invocation_index"), ctx.dst->ty.u32(),
           {ctx.dst->Builtin(ast::Builtin::kLocalInvocationIndex)});
       ctx.InsertBack(ast_func->params(), param);
       local_index = ctx.dst->Expr(param->symbol());
     }

     // We only want to zero-initialize the workgroup memory with the first
     // shader invocation. Construct an if statement that holds stmts.
     // TODO(crbug.com/tint/910): We should attempt to optimize this for arrays.
     auto* if_zero_local_index = ctx.dst->create<ast::BinaryExpression>(
         ast::BinaryOp::kEqual, local_index, ctx.dst->Expr(0u));
     auto* if_stmt = ctx.dst->If(if_zero_local_index, ctx.dst->Block(stmts));

     // Insert this if-statement at the top of the entry point.
     ctx.InsertFront(ast_func->body()->statements(), if_stmt);

     // Append a single workgroup barrier after the if statement.
     ctx.InsertFront(
         ast_func->body()->statements(),
         ctx.dst->create<ast::CallStatement>(ctx.dst->Call("workgroupBarrier")));
   }

   ctx.Clone();
 }

 ZeroInitWorkgroupMemory::Config::Config() = default;
 ZeroInitWorkgroupMemory::Config::Config(const Config&) = default;
 ZeroInitWorkgroupMemory::Config::~Config() = default;
 ZeroInitWorkgroupMemory::Config& ZeroInitWorkgroupMemory::Config::operator=(
     const 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/zero_init_workgroup_memory.h"

	#include <unordered_map>
	#include <utility>

	#include "src/program_builder.h"
	#include "src/sem/atomic_type.h"
	#include "src/sem/function.h"
	#include "src/sem/variable.h"
	#include "src/utils/get_or_create.h"

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

	namespace tint {
	namespace transform {

	/// PIMPL state for the ZeroInitWorkgroupMemory transform
	struct ZeroInitWorkgroupMemory::State {
	/// The clone context
	CloneContext& ctx;
	/// The config
	Config cfg;

	/// Zero() generates the statements required to zero initialize the workgroup
	/// storage expression of type `ty`.
	/// @param ty the expression type
	/// @param stmts the built statements
	/// @param get_expr a function that builds the AST nodes for the expression
	void Zero(const sem::Type* ty,
	ast::StatementList& stmts,
	const std::function<ast::Expression*()>& get_expr) {
	if (CanZero(ty)) {
	auto* var = get_expr();
	auto* zero_init = ctx.dst->Construct(CreateASTTypeFor(&ctx, ty));
	stmts.emplace_back(
	ctx.dst->create<ast::AssignmentStatement>(var, zero_init));
	return;
	}

	if (auto* atomic = ty->As<sem::Atomic>()) {
	auto* zero_init =
	ctx.dst->Construct(CreateASTTypeFor(&ctx, atomic->Type()));
	auto* store = ctx.dst->Call("atomicStore", ctx.dst->AddressOf(get_expr()),
	zero_init);
	stmts.emplace_back(ctx.dst->create<ast::CallStatement>(store));
	return;
	}

	if (auto* str = ty->As<sem::Struct>()) {
	for (auto* member : str->Members()) {
	auto name = ctx.Clone(member->Declaration()->symbol());
	Zero(member->Type(), stmts,
	[&] { return ctx.dst->MemberAccessor(get_expr(), name); });
	}
	return;
	}

	if (auto* arr = ty->As<sem::Array>()) {
	if (ShouldEmitForLoop(arr)) {
	auto i = ctx.dst->Symbols().New("i");
	auto* i_decl = ctx.dst->Decl(ctx.dst->Var(i, ctx.dst->ty.i32()));
	auto* cond = ctx.dst->create<ast::BinaryExpression>(
	ast::BinaryOp::kLessThan, ctx.dst->Expr(i),
	ctx.dst->Expr(static_cast<int>(arr->Count())));
	auto* inc = ctx.dst->Assign(i, ctx.dst->Add(i, 1));
	ast::StatementList for_stmts;
	Zero(arr->ElemType(), for_stmts,
	[&] { return ctx.dst->IndexAccessor(get_expr(), i); });
	auto* body = ctx.dst->Block(for_stmts);
	stmts.emplace_back(ctx.dst->For(i_decl, cond, inc, body));
	} else {
	for (size_t i = 0; i < arr->Count(); i++) {
	Zero(arr->ElemType(), stmts, [&] {
	return ctx.dst->IndexAccessor(get_expr(),
	static_cast<ProgramBuilder::u32>(i));
	});
	}
	}
	return;
	}

	TINT_UNREACHABLE(Transform, ctx.dst->Diagnostics())
	<< "could not zero workgroup type: " << ty->type_name();
	}

	/// @returns true if the type `ty` can be zeroed with a simple zero-value
	/// expression in the form of a type constructor without operands. If
	/// CanZero() returns false, then the type needs to be initialized by
	/// decomposing the initialization into multiple sub-initializations.
	/// @param ty the type to inspect
	bool CanZero(const sem::Type* ty) {
	if (ty->Is<sem::Atomic>()) {
	return false;
	}
	if (auto* str = ty->As<sem::Struct>()) {
	for (auto* member : str->Members()) {
	if (!CanZero(member->Type())) {
	return false;
	}
	}
	}
	if (auto* arr = ty->As<sem::Array>()) {
	if (ShouldEmitForLoop(arr) \|\| !CanZero(arr->ElemType())) {
	return false;
	}
	}
	return true;
	}

	/// @returns true if the array should be emitted as a for-loop instead of
	/// using zero-initializer statements.
	/// @param array the array
	bool ShouldEmitForLoop(const sem::Array* array) {
	// TODO(bclayton): If array sizes become pipeline-overridable then this
	// we need to return true for these arrays.
	// See https://github.com/gpuweb/gpuweb/pull/1792
	return (cfg.init_arrays_with_loop_size_threshold != 0) &&
	(array->SizeInBytes() >= cfg.init_arrays_with_loop_size_threshold);
	}
	};

	ZeroInitWorkgroupMemory::ZeroInitWorkgroupMemory() = default;

	ZeroInitWorkgroupMemory::~ZeroInitWorkgroupMemory() = default;

	void ZeroInitWorkgroupMemory::Run(CloneContext& ctx,
	const DataMap& inputs,
	DataMap&) {
	auto& sem = ctx.src->Sem();

	Config cfg;
	if (auto* c = inputs.Get<Config>()) {
	cfg = *c;
	}

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

	// Generate a list of statements to zero initialize each of the workgroup
	// storage variables.
	ast::StatementList stmts;
	auto* func = sem.Get(ast_func);
	for (auto* var : func->ReferencedModuleVariables()) {
	if (var->StorageClass() != ast::StorageClass::kWorkgroup) {
	continue;
	}
	State{ctx, cfg}.Zero(var->Type()->UnwrapRef(), stmts, [&] {
	auto var_name = ctx.Clone(var->Declaration()->symbol());
	return ctx.dst->Expr(var_name);
	});
	}

	if (stmts.empty()) {
	continue; // No workgroup variables to initialize.
	}

	// Scan the entry point for an existing local_invocation_index builtin
	// parameter
	ast::Expression* local_index = nullptr;
	for (auto* param : ast_func->params()) {
	if (auto* builtin = ast::GetDecoration<ast::BuiltinDecoration>(
	param->decorations())) {
	if (builtin->value() == ast::Builtin::kLocalInvocationIndex) {
	local_index = ctx.dst->Expr(ctx.Clone(param->symbol()));
	break;
	}
	}

	if (auto* str = sem.Get(param)->Type()->As<sem::Struct>()) {
	for (auto* member : str->Members()) {
	if (auto* builtin = ast::GetDecoration<ast::BuiltinDecoration>(
	member->Declaration()->decorations())) {
	if (builtin->value() == ast::Builtin::kLocalInvocationIndex) {
	auto* param_expr = ctx.dst->Expr(ctx.Clone(param->symbol()));
	auto member_name = ctx.Clone(member->Declaration()->symbol());
	local_index = ctx.dst->MemberAccessor(param_expr, member_name);
	break;
	}
	}
	}
	}
	}
	if (!local_index) {
	// No existing local index parameter. Append one to the entry point.
	auto* param = ctx.dst->Param(
	ctx.dst->Symbols().New("local_invocation_index"), ctx.dst->ty.u32(),
	{ctx.dst->Builtin(ast::Builtin::kLocalInvocationIndex)});
	ctx.InsertBack(ast_func->params(), param);
	local_index = ctx.dst->Expr(param->symbol());
	}

	// We only want to zero-initialize the workgroup memory with the first
	// shader invocation. Construct an if statement that holds stmts.
	// TODO(crbug.com/tint/910): We should attempt to optimize this for arrays.
	auto* if_zero_local_index = ctx.dst->create<ast::BinaryExpression>(
	ast::BinaryOp::kEqual, local_index, ctx.dst->Expr(0u));
	auto* if_stmt = ctx.dst->If(if_zero_local_index, ctx.dst->Block(stmts));

	// Insert this if-statement at the top of the entry point.
	ctx.InsertFront(ast_func->body()->statements(), if_stmt);

	// Append a single workgroup barrier after the if statement.
	ctx.InsertFront(
	ast_func->body()->statements(),
	ctx.dst->create<ast::CallStatement>(ctx.dst->Call("workgroupBarrier")));
	}

	ctx.Clone();
	}

	ZeroInitWorkgroupMemory::Config::Config() = default;
	ZeroInitWorkgroupMemory::Config::Config(const Config&) = default;
	ZeroInitWorkgroupMemory::Config::~Config() = default;
	ZeroInitWorkgroupMemory::Config& ZeroInitWorkgroupMemory::Config::operator=(
	const Config&) = default;

	} // namespace transform
	} // namespace tint