src/tint/lang/spirv/writer/ast_raise/while_to_loop.cc

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#include "src/tint/lang/spirv/writer/ast_raise/while_to_loop.h"

#include <utility>

#include "src/tint/lang/wgsl/ast/break_statement.h"
#include "src/tint/lang/wgsl/program/clone_context.h"
#include "src/tint/lang/wgsl/program/program_builder.h"
#include "src/tint/lang/wgsl/resolver/resolve.h"

TINT_INSTANTIATE_TYPEINFO(tint::spirv::writer::WhileToLoop);

namespace tint::spirv::writer {
namespace {

bool ShouldRun(const Program& program) {
    for (auto* node : program.ASTNodes().Objects()) {
        if (node->Is<ast::WhileStatement>()) {
            return true;
        }
    }
    return false;
}

}  // namespace

WhileToLoop::WhileToLoop() = default;

WhileToLoop::~WhileToLoop() = default;

ast::transform::Transform::ApplyResult WhileToLoop::Apply(const Program& src,
                                                          const ast::transform::DataMap&,
                                                          ast::transform::DataMap&) const {
    if (!ShouldRun(src)) {
        return SkipTransform;
    }

    ProgramBuilder b;
    program::CloneContext ctx{&b, &src, /* auto_clone_symbols */ true};

    ctx.ReplaceAll([&](const ast::WhileStatement* w) -> const ast::Statement* {
        tint::Vector<const ast::Statement*, 16> stmts;
        auto* cond = w->condition;

        // !condition
        auto* not_cond = b.Not(ctx.Clone(cond));

        // { break; }
        auto* break_body = b.Block(b.Break());

        // if (!condition) { break; }
        stmts.Push(b.If(not_cond, break_body));

        for (auto* stmt : w->body->statements) {
            stmts.Push(ctx.Clone(stmt));
        }

        const ast::BlockStatement* continuing = nullptr;

        auto* body = b.Block(stmts);
        auto* loop = b.Loop(body, continuing);

        return loop;
    });

    ctx.Clone();
    return resolver::Resolve(b);
}

}  // namespace tint::spirv::writer