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// Copyright 2020 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/msl.h"
#include <unordered_map>
#include <utility>
#include <vector>
#include "src/ast/disable_validation_decoration.h"
#include "src/program_builder.h"
#include "src/sem/call.h"
#include "src/sem/function.h"
#include "src/sem/statement.h"
#include "src/sem/variable.h"
#include "src/transform/canonicalize_entry_point_io.h"
#include "src/transform/external_texture_transform.h"
#include "src/transform/manager.h"
#include "src/transform/promote_initializers_to_const_var.h"
#include "src/transform/wrap_arrays_in_structs.h"
namespace tint {
namespace transform {
Msl::Msl() = default;
Msl::~Msl() = default;
Output Msl::Run(const Program* in, const DataMap&) {
Manager manager;
DataMap data;
manager.Add<CanonicalizeEntryPointIO>();
manager.Add<ExternalTextureTransform>();
manager.Add<PromoteInitializersToConstVar>();
manager.Add<WrapArraysInStructs>();
data.Add<CanonicalizeEntryPointIO::Config>(
CanonicalizeEntryPointIO::BuiltinStyle::kParameter);
auto out = manager.Run(in, data);
if (!out.program.IsValid()) {
return out;
}
ProgramBuilder builder;
CloneContext ctx(&builder, &out.program);
// TODO(jrprice): Consider making this a standalone transform, with target
// storage class(es) as transform options.
HandleModuleScopeVariables(ctx);
ctx.Clone();
return Output{Program(std::move(builder))};
}
void Msl::HandleModuleScopeVariables(CloneContext& ctx) const {
// MSL does not allow private and workgroup variables at module-scope, so we
// push these declarations into the entry point function and then pass them as
// pointer parameters to any function that references them.
// Similarly, texture and sampler types are converted to entry point
// parameters and passed by value to functions that need them.
//
// Since WGSL does not allow function-scope variables to have these storage
// classes, we annotate the new variable declarations with an attribute that
// bypasses that validation rule.
//
// Before:
// ```
// var<private> v : f32 = 2.0;
//
// fn foo() {
// v = v + 1.0;
// }
//
// [[stage(compute)]]
// fn main() {
// foo();
// }
// ```
//
// After:
// ```
// fn foo(v : ptr<private, f32>) {
// *v = *v + 1.0;
// }
//
// [[stage(compute)]]
// fn main() {
// var<private> v : f32 = 2.0;
// foo(&v);
// }
// ```
// Predetermine the list of function calls that need to be replaced.
using CallList = std::vector<const ast::CallExpression*>;
std::unordered_map<const ast::Function*, CallList> calls_to_replace;
std::vector<ast::Function*> functions_to_process;
// Build a list of functions that transitively reference any private or
// workgroup variables, or texture/sampler variables.
for (auto* func_ast : ctx.src->AST().Functions()) {
auto* func_sem = ctx.src->Sem().Get(func_ast);
bool needs_processing = false;
for (auto* var : func_sem->ReferencedModuleVariables()) {
if (var->StorageClass() == ast::StorageClass::kPrivate ||
var->StorageClass() == ast::StorageClass::kWorkgroup ||
var->StorageClass() == ast::StorageClass::kUniformConstant) {
needs_processing = true;
break;
}
}
if (needs_processing) {
functions_to_process.push_back(func_ast);
// Find all of the calls to this function that will need to be replaced.
for (auto* call : func_sem->CallSites()) {
auto* call_sem = ctx.src->Sem().Get(call);
calls_to_replace[call_sem->Stmt()->Function()].push_back(call);
}
}
}
for (auto* func_ast : functions_to_process) {
auto* func_sem = ctx.src->Sem().Get(func_ast);
bool is_entry_point = func_ast->IsEntryPoint();
// Map module-scope variables onto their function-scope replacement.
std::unordered_map<const sem::Variable*, Symbol> var_to_symbol;
for (auto* var : func_sem->ReferencedModuleVariables()) {
if (var->StorageClass() != ast::StorageClass::kPrivate &&
var->StorageClass() != ast::StorageClass::kWorkgroup &&
var->StorageClass() != ast::StorageClass::kUniformConstant) {
continue;
}
// This is the symbol for the variable that replaces the module-scope var.
auto new_var_symbol = ctx.dst->Sym();
auto* store_type = CreateASTTypeFor(&ctx, var->Type()->UnwrapRef());
if (is_entry_point) {
if (store_type->is_handle()) {
// For a texture or sampler variable, redeclare it as an entry point
// parameter. Disable entry point parameter validation.
auto* disable_validation =
ctx.dst->ASTNodes().Create<ast::DisableValidationDecoration>(
ctx.dst->ID(), ast::DisabledValidation::kEntryPointParameter);
auto decos = ctx.Clone(var->Declaration()->decorations());
decos.push_back(disable_validation);
auto* param = ctx.dst->Param(new_var_symbol, store_type, decos);
ctx.InsertFront(func_ast->params(), param);
} else {
// For a private or workgroup variable, redeclare it at function
// scope. Disable storage class validation on this variable.
auto* disable_validation =
ctx.dst->ASTNodes().Create<ast::DisableValidationDecoration>(
ctx.dst->ID(),
ast::DisabledValidation::kFunctionVarStorageClass);
auto* constructor = ctx.Clone(var->Declaration()->constructor());
auto* local_var = ctx.dst->Var(new_var_symbol, store_type,
var->StorageClass(), constructor,
ast::DecorationList{disable_validation});
ctx.InsertFront(func_ast->body()->statements(),
ctx.dst->Decl(local_var));
}
} else {
// For a regular function, redeclare the variable as a parameter.
// Use a pointer for non-handle types.
auto* param_type = store_type;
if (!store_type->is_handle()) {
param_type = ctx.dst->ty.pointer(param_type, var->StorageClass());
}
ctx.InsertBack(func_ast->params(),
ctx.dst->Param(new_var_symbol, param_type));
}
// Replace all uses of the module-scope variable.
// For non-entry points, dereference non-handle pointer parameters.
for (auto* user : var->Users()) {
if (user->Stmt()->Function() == func_ast) {
ast::Expression* expr = ctx.dst->Expr(new_var_symbol);
if (!is_entry_point && !store_type->is_handle()) {
expr = ctx.dst->Deref(expr);
}
ctx.Replace(user->Declaration(), expr);
}
}
var_to_symbol[var] = new_var_symbol;
}
// Pass the variables as pointers to any functions that need them.
for (auto* call : calls_to_replace[func_ast]) {
auto* target = ctx.src->AST().Functions().Find(call->func()->symbol());
auto* target_sem = ctx.src->Sem().Get(target);
// Add new arguments for any variables that are needed by the callee.
// For entry points, pass non-handle types as pointers.
for (auto* target_var : target_sem->ReferencedModuleVariables()) {
if (target_var->StorageClass() == ast::StorageClass::kPrivate ||
target_var->StorageClass() == ast::StorageClass::kWorkgroup ||
target_var->StorageClass() == ast::StorageClass::kUniformConstant) {
ast::Expression* arg = ctx.dst->Expr(var_to_symbol[target_var]);
if (is_entry_point && !target_var->Type()->UnwrapRef()->is_handle()) {
arg = ctx.dst->AddressOf(arg);
}
ctx.InsertBack(call->params(), arg);
}
}
}
}
// Now remove all module-scope variables with these storage classes.
for (auto* var_ast : ctx.src->AST().GlobalVariables()) {
auto* var_sem = ctx.src->Sem().Get(var_ast);
if (var_sem->StorageClass() == ast::StorageClass::kPrivate ||
var_sem->StorageClass() == ast::StorageClass::kWorkgroup ||
var_sem->StorageClass() == ast::StorageClass::kUniformConstant) {
ctx.Remove(ctx.src->AST().GlobalDeclarations(), var_ast);
}
}
}
} // namespace transform
} // namespace tint