feat(joinir): Phase 184 If lowering mainline & JOINIR_IF_TARGETS

Establish If lowering infrastructure with dedicated JOINIR_IF_TARGETS
table, separate from loop lowering (JOINIR_TARGETS).

Implementation:
- Add JOINIR_IF_TARGETS table with 6 representative functions
- Add is_if_lowered_function() for table-based lookup
- Update is_if_mainline_target() to use table (SSOT)
- Update is_joinir_if_toplevel_target() with table-first lookup
- Export via join_ir_vm_bridge_dispatch public API

Representative functions:
- IfSelectTest.test/1 (simple return pattern)
- IfSelectLocalTest.main/0 (local variable pattern)
- IfMergeTest.simple_true/0, simple_false/0 (multiple variables)
- JsonShapeToMap._read_value_from_pair/1 (Stage-1 production)
- Stage1JsonScannerBox.value_start_after_key_pos/2 (Stage-B production)

Architecture: Loop/If separation complete (1関数につき1 lowering)

Verification: All representative paths pass with NYASH_JOINIR_DEBUG=1

Phase 184 complete → Phase 185+ ready

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/mir/join_ir_vm_bridge_dispatch/mod.rs

@@ -20,7 +20,9 @@ use lower_only_routes::{
     try_run_stage1_usingresolver, try_run_stageb_body, try_run_stageb_funcscanner,
 };
 use targets::find_joinir_target;
-pub use targets::{JoinIrBridgeKind, JoinIrTargetDesc, JOINIR_TARGETS};
+pub use targets::{
+    is_if_lowered_function, JoinIrBridgeKind, JoinIrTargetDesc, JOINIR_IF_TARGETS, JOINIR_TARGETS,
+};
 
 use crate::mir::MirModule;
 

src/mir/join_ir_vm_bridge_dispatch/targets.rs

@@ -25,15 +25,16 @@ pub struct JoinIrTargetDesc {
     pub default_enabled: bool,
 }
 
-/// JoinIR ブリッジ対象テーブル（SSOT）
+/// JoinIR ループ lowering 対象テーブル（SSOT）
 ///
 /// Phase 32 L-4: 全対象関数を一覧化し、Exec/LowerOnly の区分を明示する。
 /// Phase 82: このテーブルが唯一の SSOT。is_loop_lowered_function() はここから参照。
 /// Phase 182: representative paths 対応（3 upgrades - LOOP ONLY）
+/// Phase 184: Loop/If 分離を明文化（If は JOINIR_IF_TARGETS へ）
 ///
 /// **重要**: このテーブルは LOOP lowering 専用です。
 /// If lowering の関数を追加すると、is_loop_lowered_function() で除外され、
-/// if-lowering が機能しなくなります。If 関数は is_joinir_if_toplevel_target() で管理。
+/// if-lowering が機能しなくなります。If 関数は JOINIR_IF_TARGETS で管理。
 ///
 /// | 関数 | Kind | デフォルト有効 | 備考 |
 /// |-----|------|---------------|------|
@@ -89,3 +90,81 @@ pub(crate) fn find_joinir_target(module: &MirModule) -> Option<&'static JoinIrTa
         .iter()
         .find(|target| module.functions.contains_key(target.func_name))
 }
+
+// ============================================================================
+// Phase 184: JoinIR If Lowering Targets (Separate from Loop Targets)
+// ============================================================================
+
+/// JoinIR If lowering 対象テーブル（SSOT）
+///
+/// Phase 184: Loop lowering（JOINIR_TARGETS）と分離した If lowering 専用テーブル。
+/// Phase 182 で判明した設計制約（JOINIR_TARGETS は Loop 専用）に基づく責務分離。
+///
+/// **責務**:
+/// - If/Else → Select/IfMerge lowering の対象関数を一覧化
+/// - Loop lowering と独立して管理（1関数につき1 lowering の原則）
+///
+/// **使用箇所**:
+/// - `is_if_mainline_target()`: Core ON 時の本線化判定
+/// - `try_lower_if_to_joinir()`: If lowering 試行時のホワイトリスト
+///
+/// | 関数 | Kind | デフォルト有効 | 備考 |
+/// |-----|------|---------------|------|
+/// | IfSelectTest.test/1 | Exec | Yes | Phase 33-2/33-3 simple return pattern |
+/// | IfSelectLocalTest.main/0 | Exec | Yes | Phase 33-10 local variable pattern |
+/// | IfMergeTest.simple_true/0 | Exec | Yes | Phase 33-7 multiple variables (IfMerge) |
+/// | IfMergeTest.simple_false/0 | Exec | Yes | Phase 33-7 multiple variables (IfMerge) |
+/// | JsonShapeToMap._read_value_from_pair/1 | Exec | Yes | Phase 33-4 Stage-1 実用関数 |
+/// | Stage1JsonScannerBox.value_start_after_key_pos/2 | Exec | Yes | Phase 33-4 Stage-B 実用関数 |
+///
+/// Phase 184 設計ドキュメント:
+/// - docs/private/roadmap2/phases/phase-184/if_lowering_inventory.md
+/// - docs/private/roadmap2/phases/phase-184/README.md
+pub const JOINIR_IF_TARGETS: &[JoinIrTargetDesc] = &[
+    // Test functions (Phase 33 series)
+    JoinIrTargetDesc {
+        func_name: "IfSelectTest.test/1",
+        kind: JoinIrBridgeKind::Exec,
+        default_enabled: true, // Simple return pattern (Phase 33-2/33-3)
+    },
+    JoinIrTargetDesc {
+        func_name: "IfSelectLocalTest.main/0",
+        kind: JoinIrBridgeKind::Exec,
+        default_enabled: true, // Local variable pattern (Phase 33-10)
+    },
+    JoinIrTargetDesc {
+        func_name: "IfMergeTest.simple_true/0",
+        kind: JoinIrBridgeKind::Exec,
+        default_enabled: true, // Multiple variables (Phase 33-7)
+    },
+    JoinIrTargetDesc {
+        func_name: "IfMergeTest.simple_false/0",
+        kind: JoinIrBridgeKind::Exec,
+        default_enabled: true, // Multiple variables (Phase 33-7)
+    },
+    // Selfhost/Production functions (Phase 33-4 explicit approvals)
+    JoinIrTargetDesc {
+        func_name: "JsonShapeToMap._read_value_from_pair/1",
+        kind: JoinIrBridgeKind::Exec,
+        default_enabled: true, // Stage-1 実用関数
+    },
+    JoinIrTargetDesc {
+        func_name: "Stage1JsonScannerBox.value_start_after_key_pos/2",
+        kind: JoinIrBridgeKind::Exec,
+        default_enabled: true, // Stage-B 実用関数
+    },
+];
+
+/// Phase 184: If lowering 対象関数の判定
+///
+/// JOINIR_IF_TARGETS テーブルから対象関数を検索し、
+/// default_enabled が true の関数のみを本線対象とする。
+///
+/// **用途**:
+/// - `is_if_mainline_target()`: Core ON 時の本線化判定
+/// - `should_try_joinir_mainline(func_name, is_loop=false)` 経由で使用
+pub fn is_if_lowered_function(name: &str) -> bool {
+    JOINIR_IF_TARGETS
+        .iter()
+        .any(|t| t.func_name == name && t.default_enabled)
+}