feat(joinir): Phase 33-8 Stage-1 rollout infrastructure

Add environment variable controls and debug logging for JoinIR lowering rollout.

Changes:
- Add HAKO_JOINIR_STAGE1 env var for Stage-1 function rollout control
- Add HAKO_JOINIR_DEBUG (0-3) for granular debug logging
  - Level 0: Silent (default)
  - Level 1: Basic lowering info
  - Level 2: Pattern matching details
  - Level 3: Full variable/instruction dump
- Implement 3-tier whitelist system:
  - Tier 1: Test functions (always enabled)
  - Tier 2: Stage-1 rollout (env-controlled)
  - Tier 3: Explicit approvals (validated in Phase 33-4)
- Add A/B test automation script (tools/joinir_ab_test.sh)
- Update if_merge.rs and if_select.rs with debug_level support

Environment variables (with NYASH_* fallback for compatibility):
- HAKO_JOINIR_IF_SELECT: Enable JoinIR lowering
- HAKO_JOINIR_STAGE1: Enable Stage-1 function rollout
- HAKO_JOINIR_DEBUG: Debug log level (0-3)

A/B test verification: PASSED on joinir_if_merge_{simple,multiple}.hako

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

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

src/config/env.rs

@@ -218,9 +218,51 @@ pub fn joinir_llvm_experiment_enabled() -> bool {
 }
 
 /// Phase 33: JoinIR If Select 実験の有効化
-/// Set NYASH_JOINIR_IF_SELECT=1 to enable experimental If/Else → Select lowering.
+/// Primary: HAKO_JOINIR_IF_SELECT (Phase 33-8+). Fallback: NYASH_JOINIR_IF_SELECT (deprecated).
 pub fn joinir_if_select_enabled() -> bool {
-    env_bool("NYASH_JOINIR_IF_SELECT")
+    // Primary: HAKO_JOINIR_IF_SELECT
+    if let Some(v) = env_flag("HAKO_JOINIR_IF_SELECT") {
+        return v;
+    }
+    // Fallback: NYASH_JOINIR_IF_SELECT (deprecated)
+    if env_bool("NYASH_JOINIR_IF_SELECT") {
+        warn_alias_once("NYASH_JOINIR_IF_SELECT", "HAKO_JOINIR_IF_SELECT");
+        return true;
+    }
+    false
+}
+
+/// Phase 33-8: JoinIR Stage-1 rollout toggle
+/// Set HAKO_JOINIR_STAGE1=1 to enable JoinIR lowering for Stage-1 functions.
+pub fn joinir_stage1_enabled() -> bool {
+    // Primary: HAKO_JOINIR_STAGE1
+    if let Some(v) = env_flag("HAKO_JOINIR_STAGE1") {
+        return v;
+    }
+    // Fallback: NYASH_JOINIR_STAGE1 (deprecated)
+    if env_bool("NYASH_JOINIR_STAGE1") {
+        warn_alias_once("NYASH_JOINIR_STAGE1", "HAKO_JOINIR_STAGE1");
+        return true;
+    }
+    false
+}
+
+/// Phase 33-8: JoinIR debug log level (0-3)
+/// - 0: No logs (default)
+/// - 1: Basic logs (which functions were lowered)
+/// - 2: Pattern matching details (CFG analysis)
+/// - 3: Full dump (all variables, all instructions)
+pub fn joinir_debug_level() -> u8 {
+    // Primary: HAKO_JOINIR_DEBUG
+    if let Ok(v) = std::env::var("HAKO_JOINIR_DEBUG") {
+        return v.parse().unwrap_or(0);
+    }
+    // Fallback: NYASH_JOINIR_DEBUG (deprecated)
+    if let Ok(v) = std::env::var("NYASH_JOINIR_DEBUG") {
+        warn_alias_once("NYASH_JOINIR_DEBUG", "HAKO_JOINIR_DEBUG");
+        return v.parse().unwrap_or(0);
+    }
+    0
 }
 
 // VM legacy by-name call fallback was removed (Phase 2 complete).

src/mir/join_ir/lowering/if_merge.rs

@@ -11,7 +11,7 @@ use crate::mir::{BasicBlockId, MirFunction, MirInstruction, ValueId};
 use std::collections::HashSet;
 
 pub struct IfMergeLowerer {
-    debug: bool,
+    debug_level: u8,
 }
 
 /// 検出された IfMerge パターン情報
@@ -30,8 +30,13 @@ struct IfBranch {
 }
 
 impl IfMergeLowerer {
-    pub fn new(debug: bool) -> Self {
+    pub fn new(debug_level: u8) -> Self {
-        Self { debug }
+        Self { debug_level }
+    }
+
+    /// Phase 33-8: debug-level backward compat wrapper
+    pub fn with_debug(debug: bool) -> Self {
+        Self { debug_level: if debug { 1 } else { 0 } }
     }
 
     /// if/else が IfMerge に lowering できるかチェック
@@ -47,13 +52,25 @@ impl IfMergeLowerer {
     ) -> Option<JoinInst> {
         let pattern = self.find_if_merge_pattern(func, if_block_id)?;
 
-        if self.debug {
+        // Phase 33-8: Level 1 - Basic lowering info
+        if self.debug_level >= 1 {
             eprintln!(
-                "[IfMergeLowerer] lowering to IfMerge with {} merge pairs",
+                "[IfMergeLowerer] ✅ lowering to IfMerge with {} merge pairs",
                 pattern.merge_pairs.len()
             );
         }
 
+        // Phase 33-8: Level 3 - Full merge details
+        if self.debug_level >= 3 {
+            eprintln!("[IfMergeLowerer] cond: {:?}", pattern.cond);
+            for (i, pair) in pattern.merge_pairs.iter().enumerate() {
+                eprintln!(
+                    "[IfMergeLowerer]   pair[{}]: dst={:?}, then={:?}, else={:?}",
+                    i, pair.dst, pair.then_val, pair.else_val
+                );
+            }
+        }
+
         // IfMerge 命令を生成
         Some(JoinInst::IfMerge {
             cond: pattern.cond,
@@ -99,9 +116,10 @@ impl IfMergeLowerer {
         );
 
         if !is_then_return || !is_else_return {
-            if self.debug {
+            // Phase 33-8: Level 2 - Pattern matching details
+            if self.debug_level >= 2 {
                 eprintln!(
-                    "[IfMergeLowerer] not return pattern (then={}, else={})",
+                    "[IfMergeLowerer] ❌ not return pattern (then={}, else={})",
                     is_then_return, is_else_return
                 );
             }
@@ -112,7 +130,8 @@ impl IfMergeLowerer {
         let then_writes = self.extract_written_vars(&then_block.instructions);
         let else_writes = self.extract_written_vars(&else_block.instructions);
 
-        if self.debug {
+        // Phase 33-8: Level 3 - Full variable dump
+        if self.debug_level >= 3 {
             eprintln!(
                 "[IfMergeLowerer] then writes: {:?}, else writes: {:?}",
                 then_writes, else_writes
@@ -123,8 +142,9 @@ impl IfMergeLowerer {
         let common_writes: HashSet<_> = then_writes.intersection(&else_writes).copied().collect();
 
         if common_writes.is_empty() {
-            if self.debug {
+            // Phase 33-8: Level 2 - Pattern matching details
-                eprintln!("[IfMergeLowerer] no common writes found");
+            if self.debug_level >= 2 {
+                eprintln!("[IfMergeLowerer] ❌ no common writes found");
             }
             return None;
         }
@@ -230,7 +250,10 @@ mod tests {
 
     #[test]
     fn test_if_merge_lowerer_creation() {
-        let lowerer = IfMergeLowerer::new(false);
+        let lowerer = IfMergeLowerer::new(0);
-        assert!(!lowerer.debug);
+        assert_eq!(lowerer.debug_level, 0);
+
+        let lowerer_compat = IfMergeLowerer::with_debug(true);
+        assert_eq!(lowerer_compat.debug_level, 1);
     }
 }

src/mir/join_ir/lowering/if_select.rs

@@ -6,7 +6,7 @@ use crate::mir::join_ir::JoinInst;
 use crate::mir::{BasicBlockId, MirFunction, MirInstruction, ValueId};
 
 pub struct IfSelectLowerer {
-    debug: bool,
+    debug_level: u8,
 }
 
 /// If/Else パターンの分類
@@ -37,8 +37,13 @@ struct IfBranch {
 }
 
 impl IfSelectLowerer {
-    pub fn new(debug: bool) -> Self {
+    pub fn new(debug_level: u8) -> Self {
-        Self { debug }
+        Self { debug_level }
+    }
+
+    /// Phase 33-8: debug-level backward compat wrapper
+    pub fn with_debug(debug: bool) -> Self {
+        Self { debug_level: if debug { 1 } else { 0 } }
     }
 
     /// if/else が Select に lowering できるかチェック
@@ -54,13 +59,22 @@ impl IfSelectLowerer {
     ) -> Option<JoinInst> {
         let pattern = self.find_if_pattern(func, if_block_id)?;
 
-        if self.debug {
+        // Phase 33-8: Level 1 - Basic lowering info
+        if self.debug_level >= 1 {
             eprintln!(
-                "[IfSelectLowerer] lowering {:?} pattern to Select",
+                "[IfSelectLowerer] ✅ lowering {:?} pattern to Select",
                 pattern.pattern_type
             );
         }
 
+        // Phase 33-8: Level 3 - Full pattern details
+        if self.debug_level >= 3 {
+            eprintln!("[IfSelectLowerer] cond: {:?}", pattern.cond);
+            eprintln!("[IfSelectLowerer] then_val: {:?}", pattern.then_val);
+            eprintln!("[IfSelectLowerer] else_val: {:?}", pattern.else_val);
+            eprintln!("[IfSelectLowerer] dst: {:?}", pattern.dst);
+        }
+
         // Select 命令を生成
         let dst = pattern.dst.unwrap_or(pattern.then_val);
 
@@ -99,8 +113,9 @@ impl IfSelectLowerer {
 
         // 3. simple パターンのチェック
         if let Some(pattern) = self.try_match_simple_pattern(&branch, then_block, else_block) {
-            if self.debug {
+            // Phase 33-8: Level 2 - Pattern matching details
-                eprintln!("[IfSelectLowerer] matched simple pattern");
+            if self.debug_level >= 2 {
+                eprintln!("[IfSelectLowerer] ✅ matched simple pattern");
             }
             return Some(pattern);
         }
@@ -108,14 +123,16 @@ impl IfSelectLowerer {
         // 4. local パターンのチェック
         if let Some(pattern) = self.try_match_local_pattern(func, &branch, then_block, else_block)
         {
-            if self.debug {
+            // Phase 33-8: Level 2 - Pattern matching details
-                eprintln!("[IfSelectLowerer] matched local pattern");
+            if self.debug_level >= 2 {
+                eprintln!("[IfSelectLowerer] ✅ matched local pattern");
             }
             return Some(pattern);
         }
 
-        if self.debug {
+        // Phase 33-8: Level 2 - Pattern matching details
-            eprintln!("[IfSelectLowerer] no pattern matched");
+        if self.debug_level >= 2 {
+            eprintln!("[IfSelectLowerer] ❌ no pattern matched");
         }
         None
     }

src/mir/join_ir/lowering/mod.rs

@@ -73,15 +73,29 @@ pub fn try_lower_if_to_joinir(
         return None;
     }
 
-    // 2. Phase 33-7: 関数名ガード拡張（テスト + Stage-1/Stage-B 候補）
+    // Phase 33-8: デバッグログレベル取得（0-3）
-    let is_allowed = func.signature.name.starts_with("IfSelectTest.")
+    let debug_level = crate::config::env::joinir_debug_level();
-        || func.signature.name.starts_with("IfMergeTest.") // Phase 33-7
+    let _debug = debug || debug_level >= 1;
-        || func.signature.name.starts_with("Stage1JsonScannerTestBox.") // Phase 33-5 test
+
-        || func.signature.name == "JsonShapeToMap._read_value_from_pair/1"
+    // 2. Phase 33-8: 関数名ガード拡張（テスト + Stage-1 rollout + 明示承認）
-        || func.signature.name == "Stage1JsonScannerBox.value_start_after_key_pos/2";
+    let is_allowed =
+        // Test functions (always enabled)
+        func.signature.name.starts_with("IfSelectTest.") ||
+        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 {
+        if debug_level >= 2 {
             eprintln!(
                 "[try_lower_if_to_joinir] skipping non-allowed function: {}",
                 func.signature.name
@@ -90,15 +104,19 @@ pub fn try_lower_if_to_joinir(
         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);
+    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 {
+            if debug_level >= 1 {
                 eprintln!(
-                    "[try_lower_if_to_joinir] IfMerge lowering used for {}",
+                    "[try_lower_if_to_joinir] ✅ IfMerge lowering used for {}",
                     func.signature.name
                 );
             }
@@ -107,10 +125,10 @@ pub fn try_lower_if_to_joinir(
     }
 
     // 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);
+    let if_select_lowerer = if_select::IfSelectLowerer::new(debug_level);
 
     if !if_select_lowerer.can_lower_to_select(func, block_id) {
-        if debug {
+        if debug_level >= 1 {
             eprintln!(
                 "[try_lower_if_to_joinir] pattern not matched for {}",
                 func.signature.name
@@ -121,9 +139,9 @@ pub fn try_lower_if_to_joinir(
 
     let result = if_select_lowerer.lower_if_to_select(func, block_id);
 
-    if result.is_some() && debug {
+    if result.is_some() && debug_level >= 1 {
         eprintln!(
-            "[try_lower_if_to_joinir] Select lowering used for {}",
+            "[try_lower_if_to_joinir] ✅ Select lowering used for {}",
             func.signature.name
         );
     }

tools/joinir_ab_test.sh

@@ -0,0 +1,72 @@
+#!/bin/bash
+# Phase 33-8: A/B test automation for JoinIR lowering
+#
+# Usage:
+#   tools/joinir_ab_test.sh <test_file.hako>
+#
+# Example:
+#   tools/joinir_ab_test.sh apps/tests/joinir_if_merge_simple.hako
+
+set -euo pipefail
+
+test_case=$1  # e.g., "apps/tests/joinir_if_merge_simple.hako"
+
+if [ ! -f "$test_case" ]; then
+    echo "❌ Test file not found: $test_case"
+    exit 1
+fi
+
+echo "🧪 Testing: $test_case"
+echo ""
+
+# Route A: Traditional if_phi
+echo "=== Route A (if_phi) ==="
+HAKO_JOINIR_IF_SELECT=0 \
+NYASH_PARSER_STAGE3=1 \
+HAKO_PARSER_STAGE3=1 \
+    ./target/release/hakorune "$test_case" \
+    > /tmp/route_a.out 2>&1
+route_a_rc=$?
+echo "Route A RC: $route_a_rc"
+echo ""
+
+# Route B: JoinIR Select/IfMerge
+echo "=== Route B (JoinIR) ==="
+HAKO_JOINIR_IF_SELECT=1 \
+HAKO_JOINIR_STAGE1=1 \
+HAKO_JOINIR_DEBUG=1 \
+NYASH_PARSER_STAGE3=1 \
+HAKO_PARSER_STAGE3=1 \
+    ./target/release/hakorune "$test_case" \
+    > /tmp/route_b.out 2>&1
+route_b_rc=$?
+echo "Route B RC: $route_b_rc"
+echo ""
+
+# Comparison
+echo "=== 📊 Comparison ==="
+
+# RC check
+if [ $route_a_rc -eq $route_b_rc ]; then
+    echo "✅ RC matched: $route_a_rc"
+else
+    echo "❌ RC mismatch: A=$route_a_rc, B=$route_b_rc"
+    exit 1
+fi
+
+# Output check (ignore debug logs starting with '[')
+if diff <(grep -v '^\[' /tmp/route_a.out) <(grep -v '^\[' /tmp/route_b.out); then
+    echo "✅ Output matched"
+else
+    echo "❌ Output differs:"
+    diff <(grep -v '^\[' /tmp/route_a.out) <(grep -v '^\[' /tmp/route_b.out) || true
+    exit 1
+fi
+
+# Extract lowering info from Route B
+echo ""
+echo "=== 🔍 Lowering Info ==="
+grep -E "IfMerge|IfSelect|if_phi" /tmp/route_b.out || echo "⚠️ No lowering info found"
+
+echo ""
+echo "🎉 A/B test PASSED for $test_case"