hakorune/src/mir/join_ir/lowering/mod.rs

//! JoinIR Lowering Functions
//!
//! Phase 27.9: Modular separation of MIR → JoinIR lowering implementations.
//!
//! このモジュールは各種 MIR 関数を JoinIR に変換する lowering 関数を提供します。
//!
//! ## 構成:
//! - `common.rs`: CFG sanity checks と lowering 共通ユーティリティ（Phase 27.10）
//! - `value_id_ranges.rs`: ValueId 範囲管理（Phase 27.13+）
//! - `min_loop.rs`: JoinIrMin.main/0 専用の最小ループ lowering
//! - `skip_ws.rs`: Main.skip/1 の空白スキップ lowering（手書き版＋MIR自動解析版）
//! - `funcscanner_trim.rs`: FuncScannerBox.trim/1 の trim lowering
//! - `stage1_using_resolver.rs`: Stage1UsingResolverBox.resolve_for_source entries loop lowering（Phase 27.12）
//! - `funcscanner_append_defs.rs`: FuncScannerBox._append_defs/2 の配列結合 lowering（Phase 27.14）
//! - `if_select.rs`: Phase 33 If/Else → Select lowering
//! - `if_dry_runner.rs`: Phase 33-10 If lowering dry-run スキャナー（箱化版）

pub mod common;
pub mod exit_args_resolver;
pub mod funcscanner_append_defs;
pub mod funcscanner_trim;
pub mod generic_case_a;
pub mod if_dry_runner; // Phase 33-10.0
pub mod if_merge; // Phase 33-7
pub mod if_select; // Phase 33
pub mod loop_form_intake;
pub mod loop_scope_shape;
pub mod loop_to_join;
pub mod min_loop;
pub mod skip_ws;
pub mod stage1_using_resolver;
pub mod stageb_body;
pub mod stageb_funcscanner;
pub mod value_id_ranges;

// Re-export public lowering functions
pub use funcscanner_append_defs::lower_funcscanner_append_defs_to_joinir;
pub use funcscanner_trim::lower_funcscanner_trim_to_joinir;
// Phase 31: LoopToJoinLowerer 統一箱
pub use loop_to_join::LoopToJoinLowerer;
// Phase 30 F-3: 旧 lower_case_a_loop_to_joinir_for_minimal_skip_ws は _with_scope に置き換え済みのため削除
pub use min_loop::lower_min_loop_to_joinir;
pub use skip_ws::lower_skip_ws_to_joinir;
pub use stage1_using_resolver::lower_stage1_usingresolver_to_joinir;
pub use stageb_body::lower_stageb_body_to_joinir;
pub use stageb_funcscanner::lower_stageb_funcscanner_to_joinir;

// Phase 33: If/Else → Select lowering entry point
use crate::mir::join_ir::JoinInst;
use crate::mir::{BasicBlockId, MirFunction};

/// Phase 33-9.1: Loop lowering対象関数の判定
///
/// これらの関数は Phase 32/33 で LoopToJoinLowerer によって処理されます。
/// If lowering (Select/IfMerge) の対象から除外することで、Loop/If の責務を明確に分離します。
///
/// ## 対象関数（6本）
/// - Main.skip/1: 空白スキップループ
/// - FuncScannerBox.trim/1: 前後空白削除ループ
/// - FuncScannerBox.append_defs/2: 配列結合ループ
/// - Stage1UsingResolverBox.resolve_for_source/5: using解析ループ
/// - StageBBodyExtractorBox.build_body_src/2: Stage-B本体抽出ループ
/// - StageBFuncScannerBox.scan_all_boxes/1: Stage-B Box走査ループ
///
/// ## 将来の拡張
/// NYASH_JOINIR_LOWER_GENERIC=1 で汎用 Case-A ループにも拡張可能
pub(crate) fn is_loop_lowered_function(name: &str) -> bool {
    const LOOP_LOWERED_FUNCTIONS: &[&str] = &[
        "Main.skip/1",
        "FuncScannerBox.trim/1",
        "FuncScannerBox.append_defs/2",
        "Stage1UsingResolverBox.resolve_for_source/5",
        "StageBBodyExtractorBox.build_body_src/2",
        "StageBFuncScannerBox.scan_all_boxes/1",
    ];

    LOOP_LOWERED_FUNCTIONS.contains(&name)
}

/// Phase 33-7: Try to lower if/else to JoinIR Select/IfMerge instruction
///
/// Scope:
/// - Only applies to whitelisted functions:
///   - IfSelectTest.* (Phase 33-2/33-3)
///   - IfMergeTest.* (Phase 33-7)
///   - JsonShapeToMap._read_value_from_pair/1 (Phase 33-4 Stage-1)
///   - Stage1JsonScannerBox.value_start_after_key_pos/2 (Phase 33-4 Stage-B)
/// - Requires NYASH_JOINIR_IF_SELECT=1 environment variable
/// - Falls back to traditional if_phi on pattern mismatch
///
/// Pattern selection:
/// - 1 variable → Select
/// - 2+ variables → IfMerge
///
/// Returns Some(JoinInst::Select) or Some(JoinInst::IfMerge) if pattern matched, None otherwise.
pub fn try_lower_if_to_joinir(
    func: &MirFunction,
    block_id: BasicBlockId,
    debug: bool,
) -> Option<JoinInst> {
    // 1. dev トグルチェック
    if !crate::config::env::joinir_if_select_enabled() {
        return None;
    }

    // Phase 33-9.1: Loop専任関数の除外（Loop/If責務分離）
    // Loop lowering対象関数はIf loweringの対象外にすることで、
    // 1関数につき1 loweringの原則を保証します
    if is_loop_lowered_function(&func.signature.name) {
        return None;
    }

    // Phase 33-8: デバッグログレベル取得（0-3）
    let debug_level = crate::config::env::joinir_debug_level();
    let _debug = debug || debug_level >= 1;

    // 2. Phase 33-8: 関数名ガード拡張（テスト + Stage-1 rollout + 明示承認）
    let is_allowed =
        // Test functions (always enabled)
        func.signature.name.starts_with("IfSelectTest.") ||
        func.signature.name.starts_with("IfSelectLocalTest.") || // Phase 33-10 test
        func.signature.name.starts_with("IfMergeTest.") ||
        func.signature.name.starts_with("Stage1JsonScannerTestBox.") || // Phase 33-5 test

        // Stage-1 rollout (env-controlled)
        (crate::config::env::joinir_stage1_enabled() &&
         func.signature.name.starts_with("Stage1")) ||

        // Explicit approvals (Phase 33-4で検証済み, always on)
        matches!(func.signature.name.as_str(),
            "JsonShapeToMap._read_value_from_pair/1" |
            "Stage1JsonScannerBox.value_start_after_key_pos/2"
        );

    if !is_allowed {
        if debug_level >= 2 {
            eprintln!(
                "[try_lower_if_to_joinir] skipping non-allowed function: {}",
                func.signature.name
            );
        }
        return None;
    }

    if debug_level >= 1 {
        eprintln!("[try_lower_if_to_joinir] trying to lower {}", func.signature.name);
    }

    // 3. Phase 33-7: IfMerge を優先的に試行（複数変数パターン）
    //    IfMerge が成功すればそれを返す、失敗したら Select を試行
    let if_merge_lowerer = if_merge::IfMergeLowerer::new(debug_level);

    if if_merge_lowerer.can_lower_to_if_merge(func, block_id) {
        if let Some(result) = if_merge_lowerer.lower_if_to_if_merge(func, block_id) {
            if debug_level >= 1 {
                eprintln!(
                    "[try_lower_if_to_joinir] ✅ IfMerge lowering used for {}",
                    func.signature.name
                );
            }
            return Some(result);
        }
    }

    // 4. IfMerge が失敗したら Select を試行（単一変数パターン）
    let if_select_lowerer = if_select::IfSelectLowerer::new(debug_level);

    if !if_select_lowerer.can_lower_to_select(func, block_id) {
        if debug_level >= 1 {
            eprintln!(
                "[try_lower_if_to_joinir] pattern not matched for {}",
                func.signature.name
            );
        }
        return None;
    }

    let result = if_select_lowerer.lower_if_to_select(func, block_id);

    if result.is_some() && debug_level >= 1 {
        eprintln!(
            "[try_lower_if_to_joinir] ✅ Select lowering used for {}",
            func.signature.name
        );
    }

    result
}

#[cfg(test)]
mod tests {
    use super::*;

    /// Phase 33-9.1: is_loop_lowered_function() の動作確認
    #[test]
    fn test_is_loop_lowered_function() {
        // Loop 専任関数（6本）は true を返す
        assert!(is_loop_lowered_function("Main.skip/1"));
        assert!(is_loop_lowered_function("FuncScannerBox.trim/1"));
        assert!(is_loop_lowered_function("FuncScannerBox.append_defs/2"));
        assert!(is_loop_lowered_function(
            "Stage1UsingResolverBox.resolve_for_source/5"
        ));
        assert!(is_loop_lowered_function(
            "StageBBodyExtractorBox.build_body_src/2"
        ));
        assert!(is_loop_lowered_function(
            "StageBFuncScannerBox.scan_all_boxes/1"
        ));

        // If lowering 対象関数は false を返す
        assert!(!is_loop_lowered_function("IfSelectTest.simple_return/0"));
        assert!(!is_loop_lowered_function("IfMergeTest.multiple_true/0"));
        assert!(!is_loop_lowered_function(
            "JsonShapeToMap._read_value_from_pair/1"
        ));
        assert!(!is_loop_lowered_function(
            "Stage1JsonScannerBox.value_start_after_key_pos/2"
        ));

        // 一般的な関数も false を返す
        assert!(!is_loop_lowered_function("SomeBox.some_method/3"));
        assert!(!is_loop_lowered_function("Main.main/0"));
    }
}