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// 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