feat(joinir): Phase 47-A-IMPL - P3 Normalized infrastructure

Implement Pattern3 (if-sum) Normalized infrastructure, extending existing P2
StepSchedule and ShapeGuard systems.

Key changes:

1. StepSchedule generalization (P2 → P2/P3):
   - Renamed: pattern2_step_schedule.rs → step_schedule.rs
   - Extended StepKind enum with P3 variants:
     - IfCond (if condition in body)
     - ThenUpdates (carrier updates in then branch)
     - ElseUpdates (carrier updates in else branch)
   - Added pattern3_if_sum_schedule() function
   - Added unit test: test_pattern3_if_sum_schedule()
   - Updated module references (mod.rs, loop_with_break_minimal.rs)

2. ShapeGuard extension:
   - Added Pattern3IfSumMinimal variant to NormalizedDevShape
   - Added is_pattern3_if_sum_minimal() detector (placeholder)
   - Updated shape detector table
   - Extended capability_for_shape() mapping

3. Bridge integration:
   - bridge.rs: Added P3 shape handling in normalize_for_shape()
   - normalized.rs: Added P3 roundtrip match (uses P2 temporarily)

4. P2/P3 separation:
   - loop_with_break_minimal.rs: Added panic for P3 steps in P2 lowering
   - Clear boundary enforcement (P2 lowerer rejects P3 steps)

5. Documentation:
   - CURRENT_TASK.md: Phase 47-A-IMPL status
   - phase47-norm-p3-design.md: Implementation status section

Benefits:
- Reuses 90% of P2 infrastructure (ConditionEnv, CarrierInfo, ExitLine)
- Clean P2/P3 separation via StepKind
- Pure additive changes (no P2 behavioral changes)
- Ready for Phase 47-A-LOWERING (full P3 Normalized implementation)

Tests: 938/938 PASS (+1 from step_schedule unit test)
- All existing P1/P2 tests pass (no regressions)
- P3 test uses Structured path temporarily (proper lowering in next phase)

Next phase: Implement full P3 Normalized→MIR(direct) lowering

CURRENT_TASK.md

@@ -87,6 +87,13 @@
   - JsonParser P2 ライン（_skip_whitespace/_atoi/_parse_number）全て canonical Normalized 化完了。
   - P3/P4 Normalized 対応は NORM-P3/NORM-P4 フェーズで実施（今回スコープ外）。
   - 937/937 tests PASS。
+- **Phase 47-A-IMPL（実装中 2025-12-12）**:
+  - StepScheduleBox 汎用化: pattern2_step_schedule.rs → step_schedule.rs リネーム
+  - P3 StepKind 追加: IfCond, ThenUpdates, ElseUpdates（P2 lowering との分離完了）
+  - ShapeGuard: Pattern3IfSumMinimal 検出追加（placeholder stub実装）
+  - Normalized bridge: P3 shape handling 追加（P2 normalization 使用）
+  - 938/938 tests PASS（regression なし）
+  - 次ステップ: Phase 47-A-LOWERING で full P3 Normalized lowering 実装
 - **Phase 45-NORM-MODE（実装済み✅ 2025-12-12）**:
   - JoinIR モード一本化: バラバラだったフラグ/feature を `JoinIrMode` enum に集約（StructuredOnly / NormalizedDev / NormalizedCanonical）。
   - `current_joinir_mode()` でモード取得、bridge/runner で `normalized_dev_enabled()` → mode pattern matching に移行。

docs/development/current/main/phase47-norm-p3-design.md

@@ -155,6 +155,27 @@ loop(i < arr.length()) {
 
 Complex P3 patterns from selfhost compiler (deferred to later phase).
 
+## Implementation Status
+
+**Phase 47-A-PREP** (✅ Complete, commit 42ecd7a7):
+- Fixture added: `pattern3_if_sum_minimal` in `normalized/fixtures.rs`
+- Test stub added: `test_normalized_pattern3_if_sum_minimal_runner_dev_switch_matches_structured`
+- Basic infrastructure for P3 development mode testing
+
+**Phase 47-A-IMPL** (✅ Complete, 2025-12-12):
+- ✅ StepSchedule renamed and extended: `pattern2_step_schedule.rs` → `step_schedule.rs`
+- ✅ P3 StepKind added: `IfCond`, `ThenUpdates`, `ElseUpdates`
+- ✅ Pattern2 lowering separation: P3 steps panic in P2 lowering (clean boundary)
+- ✅ ShapeGuard: `Pattern3IfSumMinimal` detection added (placeholder stub)
+- ✅ Normalized bridge: P3 shape handling in `normalize_for_shape()` and roundtrip
+- ✅ 938/938 tests PASS (no regressions)
+- ⏳ TODO: Full P3 Normalized lowering (Phase 47-A-LOWERING)
+
+**Next Phase** (Phase 47-A-LOWERING):
+- Implement `lower_pattern3_if_sum_minimal()` fully
+- Generate Normalized JpInst for P3 structure (If branching, conditional updates)
+- Test VM output comparison (Normalized vs Structured)
+
 ## Implementation Strategy
 
 ### Phase 47-A: Minimal sum_count (dev-only)

src/mir/join_ir/lowering/loop_with_break_minimal.rs

@@ -70,7 +70,7 @@ use crate::mir::join_ir::lowering::join_value_space::JoinValueSpace;
 use crate::mir::join_ir::lowering::loop_body_local_env::LoopBodyLocalEnv;
 use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
 use crate::mir::join_ir::lowering::loop_update_analyzer::UpdateExpr;
-use crate::mir::join_ir::lowering::pattern2_step_schedule::{
+use crate::mir::join_ir::lowering::step_schedule::{
     build_pattern2_schedule, Pattern2ScheduleContext, Pattern2StepKind,
 };
 use crate::mir::join_ir::lowering::update_env::UpdateEnv;
@@ -667,6 +667,10 @@ pub(crate) fn lower_loop_with_break_minimal(
             Pattern2StepKind::BreakCheck => loop_step_func.body.append(&mut break_block),
             Pattern2StepKind::Updates => loop_step_func.body.append(&mut carrier_update_block),
             Pattern2StepKind::Tail => loop_step_func.body.append(&mut tail_block),
+            // Phase 47-A: P3 steps not used in P2 lowering (handled in Pattern3 lowerer)
+            Pattern2StepKind::IfCond | Pattern2StepKind::ThenUpdates | Pattern2StepKind::ElseUpdates => {
+                panic!("Pattern3 step kinds should not appear in Pattern2 lowering");
+            }
         }
     }
 

src/mir/join_ir/lowering/mod.rs

@@ -61,7 +61,7 @@ pub(crate) mod loop_view_builder; // Phase 33-23: Loop lowering dispatch
 pub mod loop_with_break_minimal; // Phase 188-Impl-2: Pattern 2 minimal lowerer
 pub mod loop_with_continue_minimal;
 pub mod method_call_lowerer; // Phase 224-B: MethodCall lowering (metadata-driven)
-pub(crate) mod pattern2_step_schedule; // Phase 39: Pattern2 evaluation order scheduler
+pub(crate) mod step_schedule; // Phase 47-A: Generic step scheduler for P2/P3 (renamed from pattern2_step_schedule)
 pub mod method_return_hint; // Phase 83: P3-D 既知メソッド戻り値型推論箱
 pub mod scope_manager; // Phase 231: Unified variable scope management // Phase 195: Pattern 4 minimal lowerer
                        // Phase 242-EX-A: loop_with_if_phi_minimal removed - replaced by loop_with_if_phi_if_sum

src/mir/join_ir/lowering/step_schedule.rs

@@ -1,9 +1,11 @@
-//! Pattern 2 step scheduler (StepScheduleBox).
+//! Phase 47-A: Generic step scheduling for Pattern2/Pattern3 loops
 //!
-//! Decides the evaluation order for Pattern 2 lowering without hardcoding it
+//! Determines evaluation order for loop steps (header cond, body init, break check, etc).
-//! inside the lowerer. This keeps the lowerer focused on emitting fragments,
+//! Used by both P2 (break) and P3 (if-sum) patterns.
-//! while this box decides how to interleave them (e.g., body-local init before
+//!
-//! break checks when the break depends on body-local values).
+//! This keeps the lowerer focused on emitting fragments, while this box decides
+//! how to interleave them (e.g., body-local init before break checks when the
+//! break depends on body-local values).
 
 use crate::config::env;
 use crate::config::env::joinir_dev::joinir_test_debug_enabled;
@@ -13,11 +15,17 @@ use crate::mir::join_ir::lowering::loop_body_local_env::LoopBodyLocalEnv;
 /// Steps that can be reordered by the scheduler.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub(crate) enum Pattern2StepKind {
-    HeaderCond,
+    // P2 (Pattern2 Break) steps
-    BodyInit,
+    HeaderCond,   // loop(cond)
-    BreakCheck,
+    BodyInit,     // local ch = ...
-    Updates,
+    BreakCheck,   // if (cond) break
-    Tail,
+    Updates,      // sum = sum + 1
+    Tail,         // i = i + 1
+
+    // Phase 47-A: P3 (Pattern3 If-Sum) steps
+    IfCond,       // if (cond) in body
+    ThenUpdates,  // carrier updates in then branch
+    ElseUpdates,  // carrier updates in else branch (if any)
 }
 
 impl Pattern2StepKind {
@@ -28,6 +36,10 @@ impl Pattern2StepKind {
             Pattern2StepKind::BreakCheck => "break",
             Pattern2StepKind::Updates => "updates",
             Pattern2StepKind::Tail => "tail",
+            // Phase 47-A: P3 steps
+            Pattern2StepKind::IfCond => "if-cond",
+            Pattern2StepKind::ThenUpdates => "then-updates",
+            Pattern2StepKind::ElseUpdates => "else-updates",
         }
     }
 }
@@ -136,6 +148,17 @@ fn log_schedule(ctx: &Pattern2ScheduleContext, schedule: &Pattern2StepSchedule)
     );
 }
 
+/// Phase 47-A: Generate step schedule for Pattern3 (if-sum) loops
+pub(crate) fn pattern3_if_sum_schedule() -> Vec<Pattern2StepKind> {
+    vec![
+        Pattern2StepKind::HeaderCond,   // loop(i < n)
+        Pattern2StepKind::IfCond,       // if (i > 0)
+        Pattern2StepKind::ThenUpdates,  // sum = sum + i
+        // ElseUpdates omitted for minimal (no else branch)
+        Pattern2StepKind::Tail,         // i = i + 1
+    ]
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -221,4 +244,14 @@ mod tests {
         );
         assert_eq!(schedule.reason(), "body-local break dependency");
     }
+
+    #[test]
+    fn test_pattern3_if_sum_schedule() {
+        let schedule = pattern3_if_sum_schedule();
+        assert_eq!(schedule.len(), 4);
+        assert_eq!(schedule[0], Pattern2StepKind::HeaderCond);
+        assert_eq!(schedule[1], Pattern2StepKind::IfCond);
+        assert_eq!(schedule[2], Pattern2StepKind::ThenUpdates);
+        assert_eq!(schedule[3], Pattern2StepKind::Tail);
+    }
 }

src/mir/join_ir/normalized.rs

@@ -905,6 +905,11 @@ pub(crate) fn normalized_dev_roundtrip_structured(
                 let norm = normalize_pattern2_minimal(module);
                 normalized_pattern2_to_structured(&norm)
             })),
+            // Phase 47-A: P3 minimal uses P2 normalization for now
+            NormalizedDevShape::Pattern3IfSumMinimal => catch_unwind(AssertUnwindSafe(|| {
+                let norm = normalize_pattern2_minimal(module);
+                normalized_pattern2_to_structured(&norm)
+            })),
         };
 
         match attempt {

src/mir/join_ir/normalized/shape_guard.rs

@@ -50,6 +50,8 @@ pub enum NormalizedDevShape {
     JsonparserAtoiMini,
     JsonparserAtoiReal,
     JsonparserParseNumberReal,
+    // Phase 47-A: Pattern3 (if-sum) minimal
+    Pattern3IfSumMinimal,
 }
 
 type Detector = fn(&JoinModule) -> bool;
@@ -77,6 +79,11 @@ const SHAPE_DETECTORS: &[(NormalizedDevShape, Detector)] = &[
         NormalizedDevShape::JsonparserParseNumberReal,
         detectors::is_jsonparser_parse_number_real,
     ),
+    // Phase 47-A: Pattern3 if-sum minimal
+    (
+        NormalizedDevShape::Pattern3IfSumMinimal,
+        detectors::is_pattern3_if_sum_minimal,
+    ),
 ];
 
 /// direct ブリッジで扱う shape（dev 限定）。
@@ -104,6 +111,8 @@ pub fn capability_for_shape(shape: &NormalizedDevShape) -> ShapeCapability {
         JsonparserAtoiMini | JsonparserAtoiReal => P2CoreAtoi,
         JsonparserParseNumberReal => P2MidParseNumber,
         Pattern1Mini => P2CoreSimple, // Also core simple pattern
+        // Phase 47-A: P3 minimal maps to P2CoreSimple for now (future: P3CoreSimple)
+        Pattern3IfSumMinimal => P2CoreSimple,
     };
 
     ShapeCapability::new(kind)
@@ -338,6 +347,18 @@ mod detectors {
                 .any(|f| f.name == "jsonparser_parse_number_real")
     }
 
+    /// Phase 47-A: Check if module matches Pattern3 if-sum minimal shape
+    pub(crate) fn is_pattern3_if_sum_minimal(module: &JoinModule) -> bool {
+        // For now, simple heuristic:
+        // - Has Pattern3 structure (if-sum)
+        // - Single carrier (sum)
+        // - Simple loop condition
+
+        // TODO: Implement proper detection based on fixture
+        // For Phase 47-A, this will be called explicitly in tests
+        false  // Placeholder - will be refined in later commits
+    }
+
     pub(super) fn find_loop_step(module: &JoinModule) -> Option<&JoinFunction> {
         module
             .functions

src/mir/join_ir_vm_bridge/bridge.rs

@@ -72,6 +72,10 @@ fn normalize_for_shape(
         | NormalizedDevShape::JsonparserParseNumberReal => {
             catch_unwind(AssertUnwindSafe(|| normalize_pattern2_minimal(module)))
         }
+        // Phase 47-A: P3 minimal normalization (stub - will use P2 for now)
+        NormalizedDevShape::Pattern3IfSumMinimal => {
+            catch_unwind(AssertUnwindSafe(|| normalize_pattern2_minimal(module)))
+        }
     };
 
     match result {