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// Copyright 2022 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/tint/transform/utils/hoist_to_decl_before.h"
#include <utility>
#include "src/tint/program_builder.h"
#include "src/tint/sem/block_statement.h"
#include "src/tint/sem/for_loop_statement.h"
#include "src/tint/sem/if_statement.h"
#include "src/tint/sem/reference.h"
#include "src/tint/sem/variable.h"
#include "src/tint/sem/while_statement.h"
#include "src/tint/utils/hashmap.h"
#include "src/tint/utils/reverse.h"
#include "src/tint/utils/transform.h"
namespace tint::transform {
/// Private implementation of HoistToDeclBefore transform
struct HoistToDeclBefore::State {
/// Constructor
/// @param ctx_in the clone context
explicit State(CloneContext& ctx_in) : ctx(ctx_in), b(*ctx_in.dst) {}
/// @copydoc HoistToDeclBefore::Add()
bool Add(const sem::Expression* before_expr,
const ast::Expression* expr,
VariableKind kind,
const char* decl_name) {
auto name = b.Symbols().New(decl_name);
switch (kind) {
case VariableKind::kLet: {
auto builder = [this, expr, name] {
return b.Decl(b.Let(name, ctx.CloneWithoutTransform(expr)));
};
if (!InsertBeforeImpl(before_expr->Stmt(), std::move(builder))) {
return false;
}
break;
}
case VariableKind::kVar: {
auto builder = [this, expr, name] {
return b.Decl(b.Var(name, ctx.CloneWithoutTransform(expr)));
};
if (!InsertBeforeImpl(before_expr->Stmt(), std::move(builder))) {
return false;
}
break;
}
case VariableKind::kConst: {
auto builder = [this, expr, name] {
return b.Decl(b.Const(name, ctx.CloneWithoutTransform(expr)));
};
if (!InsertBeforeImpl(before_expr->Stmt(), std::move(builder))) {
return false;
}
break;
}
}
// Replace the initializer expression with a reference to the let
ctx.Replace(expr, b.Expr(name));
return true;
}
/// @copydoc HoistToDeclBefore::InsertBefore(const sem::Statement*, const ast::Statement*)
bool InsertBefore(const sem::Statement* before_stmt, const ast::Statement* stmt) {
if (stmt) {
auto builder = [stmt] { return stmt; };
return InsertBeforeImpl(before_stmt, std::move(builder));
}
return InsertBeforeImpl(before_stmt, Decompose{});
}
/// @copydoc HoistToDeclBefore::InsertBefore(const sem::Statement*, const StmtBuilder&)
bool InsertBefore(const sem::Statement* before_stmt, const StmtBuilder& builder) {
return InsertBeforeImpl(before_stmt, std::move(builder));
}
/// @copydoc HoistToDeclBefore::Prepare()
bool Prepare(const sem::Expression* before_expr) {
return InsertBefore(before_expr->Stmt(), nullptr);
}
private:
CloneContext& ctx;
ProgramBuilder& b;
/// Holds information about a for-loop that needs to be decomposed into a
/// loop, so that declaration statements can be inserted before the
/// condition expression or continuing statement.
struct LoopInfo {
utils::Vector<StmtBuilder, 8> cond_decls;
utils::Vector<StmtBuilder, 8> cont_decls;
};
/// Info for each else-if that needs decomposing
struct ElseIfInfo {
/// Decls to insert before condition
utils::Vector<StmtBuilder, 8> cond_decls;
};
/// For-loops that need to be decomposed to loops.
utils::Hashmap<const sem::ForLoopStatement*, LoopInfo, 4> for_loops;
/// Whiles that need to be decomposed to loops.
utils::Hashmap<const sem::WhileStatement*, LoopInfo, 4> while_loops;
/// 'else if' statements that need to be decomposed to 'else {if}'
utils::Hashmap<const ast::IfStatement*, ElseIfInfo, 4> else_ifs;
template <size_t N>
static auto Build(const utils::Vector<StmtBuilder, N>& builders) {
return utils::Transform(builders, [&](auto& builder) { return builder(); });
}
/// @returns a new LoopInfo reference for the given @p for_loop.
/// @note if this is the first call to this method, then RegisterForLoopTransform() is
/// automatically called.
/// @warning the returned reference is invalid if this is called a second time, or the
/// #for_loops map is mutated.
auto ForLoop(const sem::ForLoopStatement* for_loop) {
if (for_loops.IsEmpty()) {
RegisterForLoopTransform();
}
return for_loops.GetOrZero(for_loop);
}
/// @returns a new LoopInfo reference for the given @p while_loop.
/// @note if this is the first call to this method, then RegisterWhileLoopTransform() is
/// automatically called.
/// @warning the returned reference is invalid if this is called a second time, or the
/// #for_loops map is mutated.
auto WhileLoop(const sem::WhileStatement* while_loop) {
if (while_loops.IsEmpty()) {
RegisterWhileLoopTransform();
}
return while_loops.GetOrZero(while_loop);
}
/// @returns a new ElseIfInfo reference for the given @p else_if.
/// @note if this is the first call to this method, then RegisterElseIfTransform() is
/// automatically called.
/// @warning the returned reference is invalid if this is called a second time, or the
/// #else_ifs map is mutated.
auto ElseIf(const ast::IfStatement* else_if) {
if (else_ifs.IsEmpty()) {
RegisterElseIfTransform();
}
return else_ifs.GetOrZero(else_if);
}
/// Registers the handler for transforming for-loops based on the content of the #for_loops map.
void RegisterForLoopTransform() const {
ctx.ReplaceAll([&](const ast::ForLoopStatement* stmt) -> const ast::Statement* {
auto& sem = ctx.src->Sem();
if (auto* fl = sem.Get(stmt)) {
if (auto info = for_loops.Find(fl)) {
auto* for_loop = fl->Declaration();
// For-loop needs to be decomposed to a loop.
// Build the loop body's statements.
// Start with any let declarations for the conditional expression.
auto body_stmts = Build(info->cond_decls);
// If the for-loop has a condition, emit this next as:
// if (!cond) { break; }
if (auto* cond = for_loop->condition) {
// !condition
auto* not_cond =
b.create<ast::UnaryOpExpression>(ast::UnaryOp::kNot, ctx.Clone(cond));
// { break; }
auto* break_body = b.Block(b.create<ast::BreakStatement>());
// if (!condition) { break; }
body_stmts.Push(b.If(not_cond, break_body));
}
// Next emit the for-loop body
body_stmts.Push(ctx.Clone(for_loop->body));
// Finally create the continuing block if there was one.
const ast::BlockStatement* continuing = nullptr;
if (auto* cont = for_loop->continuing) {
// Continuing block starts with any let declarations used by
// the continuing.
auto cont_stmts = Build(info->cont_decls);
cont_stmts.Push(ctx.Clone(cont));
continuing = b.Block(cont_stmts);
}
auto* body = b.Block(body_stmts);
auto* loop = b.Loop(body, continuing);
if (auto* init = for_loop->initializer) {
return b.Block(ctx.Clone(init), loop);
}
return loop;
}
}
return nullptr;
});
}
/// Registers the handler for transforming while-loops based on the content of the #while_loops
/// map.
void RegisterWhileLoopTransform() const {
// At least one while needs to be transformed into a loop.
ctx.ReplaceAll([&](const ast::WhileStatement* stmt) -> const ast::Statement* {
auto& sem = ctx.src->Sem();
if (auto* w = sem.Get(stmt)) {
if (auto info = while_loops.Find(w)) {
auto* while_loop = w->Declaration();
// While needs to be decomposed to a loop.
// Build the loop body's statements.
// Start with any let declarations for the conditional
// expression.
auto body_stmts = utils::Transform(info->cond_decls,
[&](auto& builder) { return builder(); });
// Emit the condition as:
// if (!cond) { break; }
auto* cond = while_loop->condition;
// !condition
auto* not_cond = b.Not(ctx.Clone(cond));
// { break; }
auto* break_body = b.Block(b.Break());
// if (!condition) { break; }
body_stmts.Push(b.If(not_cond, break_body));
// Next emit the body
body_stmts.Push(ctx.Clone(while_loop->body));
const ast::BlockStatement* continuing = nullptr;
auto* body = b.Block(body_stmts);
auto* loop = b.Loop(body, continuing);
return loop;
}
}
return nullptr;
});
}
/// Registers the handler for transforming if-statements based on the content of the #else_ifs
/// map.
void RegisterElseIfTransform() const {
// Decompose 'else-if' statements into 'else { if }' blocks.
ctx.ReplaceAll([&](const ast::IfStatement* stmt) -> const ast::Statement* {
if (auto info = else_ifs.Find(stmt)) {
// Build the else block's body statements, starting with let decls for the
// conditional expression.
auto body_stmts = Build(info->cond_decls);
// Move the 'else-if' into the new `else` block as a plain 'if'.
auto* cond = ctx.Clone(stmt->condition);
auto* body = ctx.Clone(stmt->body);
auto* new_if = b.If(cond, body, b.Else(ctx.Clone(stmt->else_statement)));
body_stmts.Push(new_if);
// Replace the 'else-if' with the new 'else' block.
return b.Block(body_stmts);
}
return nullptr;
});
}
/// A type used to signal to InsertBeforeImpl that no insertion should take place - instead flow
/// control statements should just be decomposed.
struct Decompose {};
template <typename BUILDER>
bool InsertBeforeImpl(const sem::Statement* before_stmt, BUILDER&& builder) {
(void)builder; // Avoid 'unused parameter' warning due to 'if constexpr'
auto* ip = before_stmt->Declaration();
auto* else_if = before_stmt->As<sem::IfStatement>();
if (else_if && else_if->Parent()->Is<sem::IfStatement>()) {
// Insertion point is an 'else if' condition.
// Need to convert 'else if' to 'else { if }'.
auto else_if_info = ElseIf(else_if->Declaration());
// Index the map to convert this else if, even if `stmt` is nullptr.
auto& decls = else_if_info->cond_decls;
if constexpr (!std::is_same_v<BUILDER, Decompose>) {
decls.Push(std::forward<BUILDER>(builder));
}
return true;
}
if (auto* fl = before_stmt->As<sem::ForLoopStatement>()) {
// Insertion point is a for-loop condition.
// For-loop needs to be decomposed to a loop.
// Index the map to convert this for-loop, even if `stmt` is nullptr.
auto& decls = ForLoop(fl)->cond_decls;
if constexpr (!std::is_same_v<BUILDER, Decompose>) {
decls.Push(std::forward<BUILDER>(builder));
}
return true;
}
if (auto* w = before_stmt->As<sem::WhileStatement>()) {
// Insertion point is a while condition.
// While needs to be decomposed to a loop.
// Index the map to convert this while, even if `stmt` is nullptr.
auto& decls = WhileLoop(w)->cond_decls;
if constexpr (!std::is_same_v<BUILDER, Decompose>) {
decls.Push(std::forward<BUILDER>(builder));
}
return true;
}
auto* parent = before_stmt->Parent(); // The statement's parent
if (auto* block = parent->As<sem::BlockStatement>()) {
// Insert point sits in a block. Simple case.
// Insert the stmt before the parent statement.
if constexpr (!std::is_same_v<BUILDER, Decompose>) {
ctx.InsertBefore(block->Declaration()->statements, ip,
std::forward<BUILDER>(builder));
}
return true;
}
if (auto* fl = parent->As<sem::ForLoopStatement>()) {
// Insertion point is a for-loop initializer or continuing statement.
// These require special care.
if (fl->Declaration()->initializer == ip) {
// Insertion point is a for-loop initializer.
// Insert the new statement above the for-loop.
if constexpr (!std::is_same_v<BUILDER, Decompose>) {
ctx.InsertBefore(fl->Block()->Declaration()->statements, fl->Declaration(),
std::forward<BUILDER>(builder));
}
return true;
}
if (fl->Declaration()->continuing == ip) {
// Insertion point is a for-loop continuing statement.
// For-loop needs to be decomposed to a loop.
// Index the map to convert this for-loop, even if `stmt` is nullptr.
auto& decls = ForLoop(fl)->cont_decls;
if constexpr (!std::is_same_v<BUILDER, Decompose>) {
decls.Push(std::forward<BUILDER>(builder));
}
return true;
}
TINT_ICE(Transform, b.Diagnostics()) << "unhandled use of expression in for-loop";
return false;
}
TINT_ICE(Transform, b.Diagnostics())
<< "unhandled expression parent statement type: " << parent->TypeInfo().name;
return false;
}
};
HoistToDeclBefore::HoistToDeclBefore(CloneContext& ctx) : state_(std::make_unique<State>(ctx)) {}
HoistToDeclBefore::~HoistToDeclBefore() {}
bool HoistToDeclBefore::Add(const sem::Expression* before_expr,
const ast::Expression* expr,
VariableKind kind,
const char* decl_name) {
return state_->Add(before_expr, expr, kind, decl_name);
}
bool HoistToDeclBefore::InsertBefore(const sem::Statement* before_stmt,
const ast::Statement* stmt) {
return state_->InsertBefore(before_stmt, stmt);
}
bool HoistToDeclBefore::InsertBefore(const sem::Statement* before_stmt,
const StmtBuilder& builder) {
return state_->InsertBefore(before_stmt, builder);
}
bool HoistToDeclBefore::Prepare(const sem::Expression* before_expr) {
return state_->Prepare(before_expr);
}
} // namespace tint::transform