refactor(phi): Phase 59 PhiInputCollector inline in loopform_builder

Phase 59: PhiBuilderBox / PhiInputCollector JoinIR統合（部分完了）

## 変更内容

- loopform_builder.rs: PhiInputCollector使用を完全にインライン化
  - seal_pinned_phis (L455): インライン化
  - seal_carrier_phis (L528): インライン化
  - build_exit_phis (L746): インライン化
- PhiInputCollector import を削除

## インライン化されたロジック

1. 入力収集: Vec<(BasicBlockId, ValueId)>
2. sanitize: BTreeMapで重複削除＆ソート
3. optimize_same_value: 全同値ならPHI不要
4. finalize: Vec返却

## 残存callsite

- loop_builder.rs:524 (continue merge) - JoinIRに概念なし、現状維持

## テスト結果

- loopform: 14 passed / 0 failed
- JoinIR: 56 passed / 0 failed

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

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

src/mir/phi_core/loopform_builder.rs

@@ -9,7 +9,8 @@
  */
 
 use crate::mir::phi_core::loop_snapshot_merge::LoopSnapshotMergeBox;
-use crate::mir::phi_core::phi_input_collector::PhiInputCollector;
+// Phase 59: PhiInputCollector使用廃止（インライン化完了）
+// use crate::mir::phi_core::phi_input_collector::PhiInputCollector;
 use crate::mir::{BasicBlockId, ValueId};
 use std::collections::BTreeMap;
 
@@ -452,32 +453,56 @@ impl LoopFormBuilder {
                 continue;
             }
 
-            let mut collector = PhiInputCollector::new();
+            // ========================================
-            collector.add_preheader(self.preheader_id, pinned.preheader_copy);
+            // Phase 59: PhiInputCollector インライン化
+            // ========================================
+            // Step 1: 入力収集
+            let mut raw_inputs: Vec<(BasicBlockId, ValueId)> = Vec::new();
+            raw_inputs.push((self.preheader_id, pinned.preheader_copy));
 
             for (cid, snapshot) in continue_snapshots {
                 if let Some(&value) = snapshot.get(&pinned.name) {
-                    collector.add_snapshot(&[(*cid, value)]);
+                    raw_inputs.push((*cid, value));
                 }
             }
 
             let latch_value = ops
                 .get_variable_at_block(&pinned.name, latch_id)
                 .unwrap_or(pinned.header_phi);
-            collector.add_latch(latch_id, latch_value);
+            raw_inputs.push((latch_id, latch_value));
-            collector.sanitize();
 
-            if let Some(same_value) = collector.optimize_same_value() {
+            // Step 2: sanitize (BTreeMapで重複削除＆ソート)
+            let mut sanitized: std::collections::BTreeMap<BasicBlockId, ValueId> =
+                std::collections::BTreeMap::new();
+            for (bb, val) in &raw_inputs {
+                sanitized.insert(*bb, *val);
+            }
+            let inputs: Vec<(BasicBlockId, ValueId)> = sanitized.into_iter().collect();
+
+            // Step 3: optimize_same_value
+            let same_value = if inputs.is_empty() {
+                None
+            } else if inputs.len() == 1 {
+                Some(inputs[0].1)
+            } else {
+                let first_val = inputs[0].1;
+                if inputs.iter().all(|(_, val)| *val == first_val) {
+                    Some(first_val)
+                } else {
+                    None
+                }
+            };
+
+            if let Some(same_val) = same_value {
                 if debug {
                     eprintln!(
                         "[loopform/seal_phis] OPTIMIZED pinned '{}': phi={:?} → same_value={:?} (loop-invariant)",
-                        pinned.name, pinned.header_phi, same_value
+                        pinned.name, pinned.header_phi, same_val
                     );
                 }
                 continue;
             }
 
-            let inputs = collector.finalize();
             if debug {
                 eprintln!(
                     "[loopform/seal_phis] pinned '{}' phi={:?} inputs={:?}",
@@ -525,29 +550,53 @@ impl LoopFormBuilder {
                     )
                 })?;
 
-            let mut collector = PhiInputCollector::new();
+            // ========================================
-            collector.add_preheader(self.preheader_id, carrier.preheader_copy);
+            // Phase 59: PhiInputCollector インライン化
+            // ========================================
+            // Step 1: 入力収集
+            let mut raw_inputs: Vec<(BasicBlockId, ValueId)> = Vec::new();
+            raw_inputs.push((self.preheader_id, carrier.preheader_copy));
 
             for (cid, snapshot) in continue_snapshots {
                 if let Some(&value) = snapshot.get(&carrier.name) {
-                    collector.add_snapshot(&[(*cid, value)]);
+                    raw_inputs.push((*cid, value));
                 }
             }
 
-            collector.add_latch(latch_id, carrier.latch_value);
+            raw_inputs.push((latch_id, carrier.latch_value));
-            collector.sanitize();
 
-            if let Some(same_value) = collector.optimize_same_value() {
+            // Step 2: sanitize (BTreeMapで重複削除＆ソート)
+            let mut sanitized: std::collections::BTreeMap<BasicBlockId, ValueId> =
+                std::collections::BTreeMap::new();
+            for (bb, val) in &raw_inputs {
+                sanitized.insert(*bb, *val);
+            }
+            let inputs: Vec<(BasicBlockId, ValueId)> = sanitized.into_iter().collect();
+
+            // Step 3: optimize_same_value
+            let same_value = if inputs.is_empty() {
+                None
+            } else if inputs.len() == 1 {
+                Some(inputs[0].1)
+            } else {
+                let first_val = inputs[0].1;
+                if inputs.iter().all(|(_, val)| *val == first_val) {
+                    Some(first_val)
+                } else {
+                    None
+                }
+            };
+
+            if let Some(same_val) = same_value {
                 if debug {
                     eprintln!(
                         "[loopform/seal_phis] OPTIMIZED carrier '{}': phi={:?} → same_value={:?} (misclassified as carrier, actually loop-invariant)",
-                        carrier.name, carrier.header_phi, same_value
+                        carrier.name, carrier.header_phi, same_val
                     );
                 }
                 continue;
             }
 
-            let inputs = collector.finalize();
             if debug {
                 eprintln!(
                     "[loopform/seal_phis] carrier '{}' phi={:?} inputs={:?}",
@@ -740,23 +789,44 @@ impl LoopFormBuilder {
             inspector,
         )?;
 
-        // 4. PHI 生成（Phase 26-B-3: PhiInputCollectorを使用）
+        // ========================================
+        // Phase 59: PHI生成（PhiInputCollectorインライン化）
+        // ========================================
+        // 旧: PhiInputCollector::new() + add_snapshot + sanitize + optimize_same_value
+        // 新: BTreeMapで直接処理（同等のロジックをインライン展開）
         for (var_name, inputs) in all_vars {
-            // Phase 26-B-3: Use PhiInputCollector for unified PHI input handling
+            // Step 1: sanitize - BTreeMapで重複削除＆ソート
-            let mut collector = PhiInputCollector::new();
+            let mut sanitized: std::collections::BTreeMap<BasicBlockId, ValueId> =
-            collector.add_snapshot(&inputs);
+                std::collections::BTreeMap::new();
-            collector.sanitize();
+            for (bb, val) in &inputs {
+                sanitized.insert(*bb, *val);
+            }
+            let final_inputs: Vec<(BasicBlockId, ValueId)> = sanitized.into_iter().collect();
 
             if debug {
                 eprintln!(
                     "[DEBUG/exit_phi] Variable '{}': {} inputs",
                     var_name,
-                    collector.len()
+                    final_inputs.len()
                 );
             }
 
-            // Phase 25.2: optimize_same_value() で最適化判定
+            // Step 2: optimize_same_value - 全て同じ値ならPHI不要
-            if let Some(same_val) = collector.optimize_same_value() {
+            let same_value = if final_inputs.is_empty() {
+                None
+            } else if final_inputs.len() == 1 {
+                Some(final_inputs[0].1)
+            } else {
+                let first_val = final_inputs[0].1;
+                if final_inputs.iter().all(|(_, val)| *val == first_val) {
+                    Some(first_val)
+                } else {
+                    None
+                }
+            };
+
+            // Step 3: PHI生成 or 直接バインド
+            if let Some(same_val) = same_value {
                 // 全て同じ値 or 単一入力 → PHI 不要
                 if debug {
                     eprintln!(
@@ -767,8 +837,6 @@ impl LoopFormBuilder {
                 ops.update_var(var_name, same_val);
             } else {
                 // 異なる値を持つ場合は PHI ノードを生成
-                let final_inputs = collector.finalize();
-
                 let phi_id = ops.new_value();
                 if debug {
                     eprintln!(