refactor: Extract pattern lowerers from control_flow.rs (Phase 2)

- Created joinir/patterns/ subdirectory
- Extracted Pattern 1: pattern1_minimal.rs (Simple While)
- Extracted Pattern 2: pattern2_with_break.rs (Loop with Break)
- Extracted Pattern 3: pattern3_with_if_phi.rs (Loop with If-Else PHI)
- Created patterns/mod.rs dispatcher
- Removed ~410 lines from main control_flow.rs
- Zero breaking changes, all tests pass

src/mir/builder/control_flow/joinir/mod.rs

@@ -0,0 +1,7 @@
+//! JoinIR integration for control flow
+//!
+//! This module contains JoinIR-related control flow logic:
+//! - Pattern lowerers (patterns/)
+//! - Routing logic (future Phase 3)
+
+pub(in crate::mir::builder) mod patterns;

src/mir/builder/control_flow/joinir/patterns/mod.rs

@@ -0,0 +1,10 @@
+//! Pattern lowerers for different loop constructs
+//!
+//! Phase 2: Extracted from control_flow.rs
+//! - Pattern 1: Simple While Loop (pattern1_minimal.rs)
+//! - Pattern 2: Loop with Conditional Break (pattern2_with_break.rs)
+//! - Pattern 3: Loop with If-Else PHI (pattern3_with_if_phi.rs)
+
+pub(in crate::mir::builder) mod pattern1_minimal;
+pub(in crate::mir::builder) mod pattern2_with_break;
+pub(in crate::mir::builder) mod pattern3_with_if_phi;

src/mir/builder/control_flow/joinir/patterns/pattern1_minimal.rs

@@ -0,0 +1,156 @@
+//! Pattern 1: Simple While Loop minimal lowerer
+
+use crate::ast::ASTNode;
+use crate::mir::builder::MirBuilder;
+use crate::mir::ValueId;
+
+impl MirBuilder {
+    /// Phase 188-Impl-1-F: Pattern 1 (Simple While Loop) minimal lowerer
+    ///
+    /// This bypasses the LoopFrontendBinding JSON path and directly calls
+    /// the Pattern 1 minimal lowerer for apps/tests/loop_min_while.hako
+    ///
+    /// # Phase 188-Impl-2: Host Variable Integration
+    ///
+    /// Extracts the loop variable from the host function (e.g., `i` from `i < 3`)
+    /// and passes it to the Pattern 1 lowerer along with a ValueId allocator.
+    ///
+    /// # Pipeline
+    /// 1. Extract loop variable name from condition
+    /// 2. Look up ValueId in host variable_map
+    /// 3. Create Pattern1Context with host variable + allocator
+    /// 4. Call simple_while_minimal::lower_simple_while_minimal() → JoinModule
+    /// 5. convert_join_module_to_mir_with_meta() → MirModule
+    /// 6. Merge MIR blocks into current_function
+    pub(in crate::mir::builder) fn cf_loop_pattern1_minimal(
+        &mut self,
+        condition: &ASTNode,
+        _body: &[ASTNode],
+        _func_name: &str,
+        debug: bool,
+    ) -> Result<Option<ValueId>, String> {
+        use crate::mir::join_ir::lowering::simple_while_minimal::{
+            lower_simple_while_minimal, Pattern1Context,
+        };
+        use crate::mir::join_ir_vm_bridge::convert_join_module_to_mir_with_meta;
+        use crate::mir::BasicBlockId;
+        use std::collections::{BTreeMap, BTreeSet};
+
+        if debug {
+            eprintln!("[cf_loop/joinir/pattern1] Calling Pattern 1 minimal lowerer");
+        }
+
+        // Phase 188-Impl-2: Extract loop variable from condition
+        // For `i < 3`, extract `i` and look up its ValueId in variable_map
+        let loop_var_name = self.extract_loop_variable_from_condition(condition)?;
+        let loop_var_id = self
+            .variable_map
+            .get(&loop_var_name)
+            .copied()
+            .ok_or_else(|| {
+                format!(
+                    "[cf_loop/pattern1] Loop variable '{}' not found in variable_map",
+                    loop_var_name
+                )
+            })?;
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern1] Loop variable '{}' → {:?}",
+                loop_var_name, loop_var_id
+            );
+        }
+
+        // Create a minimal LoopScopeShape (Phase 188: hardcoded for loop_min_while.hako)
+        // Pattern 1 lowerer ignores the scope anyway, so this is just a placeholder
+        use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
+        let scope = LoopScopeShape {
+            header: BasicBlockId(0),
+            body: BasicBlockId(0),
+            latch: BasicBlockId(0),
+            exit: BasicBlockId(0),
+            pinned: BTreeSet::new(),
+            carriers: BTreeSet::new(),
+            body_locals: BTreeSet::new(),
+            exit_live: BTreeSet::new(),
+            progress_carrier: None,
+            variable_definitions: BTreeMap::new(),
+        };
+
+        // Phase 188-Impl-2: Create Pattern1Context with host variable + allocator
+        // Clone value_gen to move into closure
+        let mut value_gen_clone = self.value_gen.clone();
+        let ctx = Pattern1Context {
+            loop_var: loop_var_id,
+            value_allocator: Box::new(move || value_gen_clone.next()),
+        };
+
+        // Call Pattern 1 lowerer with host context
+        let join_module = match lower_simple_while_minimal(scope, Some(ctx)) {
+            Some(module) => module,
+            None => {
+                if debug {
+                    eprintln!("[cf_loop/joinir/pattern1] Pattern 1 lowerer returned None");
+                }
+                return Ok(None);
+            }
+        };
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern1] JoinModule generated with {} functions",
+                join_module.functions.len()
+            );
+        }
+
+        // Convert JoinModule to MirModule
+        // Phase 188: Pass empty meta map since Pattern 1 lowerer doesn't use metadata
+        use crate::mir::join_ir::frontend::JoinFuncMetaMap;
+        let empty_meta: JoinFuncMetaMap = BTreeMap::new();
+
+        let mir_module = convert_join_module_to_mir_with_meta(&join_module, &empty_meta)
+            .map_err(|e| format!("[cf_loop/joinir/pattern1] MIR conversion failed: {:?}", e))?;
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern1] MirModule generated with {} functions",
+                mir_module.functions.len()
+            );
+        }
+
+        // Merge JoinIR blocks into current function
+        // Phase 188-Impl-3: Create and pass JoinInlineBoundary for Pattern 1
+        let boundary = crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary::new_inputs_only(
+            vec![ValueId(0)],      // JoinIR's main() parameter (loop variable)
+            vec![loop_var_id],     // Host's loop variable
+        );
+        // Phase 189: Discard exit PHI result (Pattern 1 returns void)
+        let _ = self.merge_joinir_mir_blocks(&mir_module, Some(&boundary), debug)?;
+
+        // Phase 188-Impl-4-FIX: Return Void instead of trying to emit Const
+        //
+        // PROBLEM: Emitting instructions after merge_joinir_mir_blocks is fragile because:
+        // 1. merge creates exit block and switches to it
+        // 2. We try to add Const to exit block
+        // 3. But subsequent code (return statement) might overwrite the block
+        //
+        // SOLUTION: Loops don't produce values - they return Void.
+        // The subsequent "return 0" statement will emit its own Const + Return.
+        //
+        // This is cleaner because:
+        // - Loop lowering doesn't need to know about the return value
+        // - The return statement handles its own code generation
+        // - No risk of instructions being lost due to block management issues
+
+        let void_val = crate::mir::builder::emission::constant::emit_void(self);
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern1] Loop complete, returning Void {:?}",
+                void_val
+            );
+        }
+
+        Ok(Some(void_val))
+    }
+}

src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs

@@ -0,0 +1,127 @@
+//! Pattern 2: Loop with Conditional Break minimal lowerer
+
+use crate::ast::ASTNode;
+use crate::mir::builder::MirBuilder;
+use crate::mir::ValueId;
+
+impl MirBuilder {
+    /// Phase 188-Impl-2: Pattern 2 (Loop with Conditional Break) minimal lowerer
+    ///
+    /// Similar to Pattern 1, but handles loops with break statements.
+    ///
+    /// # Steps
+    /// 1. Extract loop variable from condition
+    /// 2. Generate JoinIR using loop_with_break_minimal
+    /// 3. Convert JoinModule → MirModule
+    /// 4. Create JoinInlineBoundary for input mapping
+    /// 5. Merge MIR blocks into current_function
+    /// 6. Return Void (loop doesn't produce values)
+    pub(in crate::mir::builder) fn cf_loop_pattern2_with_break(
+        &mut self,
+        condition: &ASTNode,
+        _body: &[ASTNode],
+        _func_name: &str,
+        debug: bool,
+    ) -> Result<Option<ValueId>, String> {
+        use crate::mir::join_ir::lowering::loop_with_break_minimal::lower_loop_with_break_minimal;
+        use crate::mir::join_ir_vm_bridge::convert_join_module_to_mir_with_meta;
+        use crate::mir::BasicBlockId;
+        use std::collections::{BTreeMap, BTreeSet};
+
+        if debug {
+            eprintln!("[cf_loop/joinir/pattern2] Calling Pattern 2 minimal lowerer");
+        }
+
+        // Phase 188-Impl-2: Extract loop variable from condition
+        // For `i < 3`, extract `i` and look up its ValueId in variable_map
+        let loop_var_name = self.extract_loop_variable_from_condition(condition)?;
+        let loop_var_id = self
+            .variable_map
+            .get(&loop_var_name)
+            .copied()
+            .ok_or_else(|| {
+                format!(
+                    "[cf_loop/pattern2] Loop variable '{}' not found in variable_map",
+                    loop_var_name
+                )
+            })?;
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern2] Loop variable '{}' → {:?}",
+                loop_var_name, loop_var_id
+            );
+        }
+
+        // Create a minimal LoopScopeShape (Phase 188: hardcoded for joinir_min_loop.hako)
+        // Pattern 2 lowerer ignores the scope anyway, so this is just a placeholder
+        use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
+        let scope = LoopScopeShape {
+            header: BasicBlockId(0),
+            body: BasicBlockId(0),
+            latch: BasicBlockId(0),
+            exit: BasicBlockId(0),
+            pinned: BTreeSet::new(),
+            carriers: BTreeSet::new(),
+            body_locals: BTreeSet::new(),
+            exit_live: BTreeSet::new(),
+            progress_carrier: None,
+            variable_definitions: BTreeMap::new(),
+        };
+
+        // Call Pattern 2 lowerer
+        let join_module = match lower_loop_with_break_minimal(scope) {
+            Some(module) => module,
+            None => {
+                if debug {
+                    eprintln!("[cf_loop/joinir/pattern2] Pattern 2 lowerer returned None");
+                }
+                return Ok(None);
+            }
+        };
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern2] JoinModule generated with {} functions",
+                join_module.functions.len()
+            );
+        }
+
+        // Convert JoinModule to MirModule
+        // Phase 188: Pass empty meta map since Pattern 2 lowerer doesn't use metadata
+        use crate::mir::join_ir::frontend::JoinFuncMetaMap;
+        let empty_meta: JoinFuncMetaMap = BTreeMap::new();
+
+        let mir_module = convert_join_module_to_mir_with_meta(&join_module, &empty_meta)
+            .map_err(|e| format!("[cf_loop/joinir/pattern2] MIR conversion failed: {:?}", e))?;
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern2] MirModule generated with {} functions",
+                mir_module.functions.len()
+            );
+        }
+
+        // Merge JoinIR blocks into current function
+        // Phase 188-Impl-2: Create and pass JoinInlineBoundary for Pattern 2
+        let boundary = crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary::new_inputs_only(
+            vec![ValueId(0)],      // JoinIR's main() parameter (loop variable init)
+            vec![loop_var_id],     // Host's loop variable
+        );
+        // Phase 189: Discard exit PHI result (Pattern 2 returns void)
+        let _ = self.merge_joinir_mir_blocks(&mir_module, Some(&boundary), debug)?;
+
+        // Phase 188-Impl-2: Return Void (loops don't produce values)
+        // The subsequent "return i" statement will emit its own Load + Return
+        let void_val = crate::mir::builder::emission::constant::emit_void(self);
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern2] Loop complete, returning Void {:?}",
+                void_val
+            );
+        }
+
+        Ok(Some(void_val))
+    }
+}

src/mir/builder/control_flow/joinir/patterns/pattern3_with_if_phi.rs

@@ -0,0 +1,149 @@
+//! Pattern 3: Loop with If-Else PHI minimal lowerer
+
+use crate::ast::ASTNode;
+use crate::mir::builder::MirBuilder;
+use crate::mir::ValueId;
+
+impl MirBuilder {
+    /// Phase 188-Impl-3: Pattern 3 (Loop with If-Else PHI) minimal lowerer
+    ///
+    /// Handles loops with if-else statements that assign to carrier variables.
+    ///
+    /// # Steps
+    /// 1. Extract loop variables (carriers: i + sum)
+    /// 2. Generate JoinIR using loop_with_if_phi_minimal
+    /// 3. Convert JoinModule → MirModule
+    /// 4. Create JoinInlineBoundary for input mapping
+    /// 5. Merge MIR blocks into current_function
+    /// 6. Return Void (loop doesn't produce values)
+    pub(in crate::mir::builder) fn cf_loop_pattern3_with_if_phi(
+        &mut self,
+        condition: &ASTNode,
+        _body: &[ASTNode],
+        _func_name: &str,
+        debug: bool,
+    ) -> Result<Option<ValueId>, String> {
+        use crate::mir::join_ir::lowering::loop_with_if_phi_minimal::lower_loop_with_if_phi_pattern;
+        use crate::mir::join_ir_vm_bridge::convert_join_module_to_mir_with_meta;
+        use crate::mir::BasicBlockId;
+        use std::collections::{BTreeMap, BTreeSet};
+
+        if debug {
+            eprintln!("[cf_loop/joinir/pattern3] Calling Pattern 3 minimal lowerer");
+        }
+
+        // Phase 188-Impl-3: Extract loop variable from condition
+        // For `i <= 5`, extract `i` and look up its ValueId in variable_map
+        let loop_var_name = self.extract_loop_variable_from_condition(condition)?;
+        let loop_var_id = self
+            .variable_map
+            .get(&loop_var_name)
+            .copied()
+            .ok_or_else(|| {
+                format!(
+                    "[cf_loop/pattern3] Loop variable '{}' not found in variable_map",
+                    loop_var_name
+                )
+            })?;
+
+        // Phase 188-Impl-3: Also get the accumulator variable (sum)
+        // For Pattern 3, we need both i and sum
+        let sum_var_id = self
+            .variable_map
+            .get("sum")
+            .copied()
+            .ok_or_else(|| {
+                format!(
+                    "[cf_loop/pattern3] Accumulator variable 'sum' not found in variable_map"
+                )
+            })?;
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern3] Loop variables: '{}' → {:?}, 'sum' → {:?}",
+                loop_var_name, loop_var_id, sum_var_id
+            );
+        }
+
+        // Create a minimal LoopScopeShape (Phase 188: hardcoded for loop_if_phi.hako)
+        // Pattern 3 lowerer ignores the scope anyway, so this is just a placeholder
+        use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
+        let scope = LoopScopeShape {
+            header: BasicBlockId(0),
+            body: BasicBlockId(0),
+            latch: BasicBlockId(0),
+            exit: BasicBlockId(0),
+            pinned: BTreeSet::new(),
+            carriers: BTreeSet::new(),
+            body_locals: BTreeSet::new(),
+            exit_live: BTreeSet::new(),
+            progress_carrier: None,
+            variable_definitions: BTreeMap::new(),
+        };
+
+        // Call Pattern 3 lowerer
+        let join_module = match lower_loop_with_if_phi_pattern(scope) {
+            Some(module) => module,
+            None => {
+                if debug {
+                    eprintln!("[cf_loop/joinir/pattern3] Pattern 3 lowerer returned None");
+                }
+                return Ok(None);
+            }
+        };
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern3] JoinModule generated with {} functions",
+                join_module.functions.len()
+            );
+        }
+
+        // Convert JoinModule to MirModule
+        // Phase 188: Pass empty meta map since Pattern 3 lowerer doesn't use metadata
+        use crate::mir::join_ir::frontend::JoinFuncMetaMap;
+        let empty_meta: JoinFuncMetaMap = BTreeMap::new();
+
+        let mir_module = convert_join_module_to_mir_with_meta(&join_module, &empty_meta)
+            .map_err(|e| format!("[cf_loop/joinir/pattern3] MIR conversion failed: {:?}", e))?;
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern3] MirModule generated with {} functions",
+                mir_module.functions.len()
+            );
+        }
+
+        // Merge JoinIR blocks into current function
+        // Phase 190: Use explicit LoopExitBinding for Pattern 3
+        // Pattern 3 has TWO carriers: i and sum
+        self.trace_varmap("pattern3_before_merge");
+        let boundary = crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary::new_with_exit_bindings(
+            vec![ValueId(0), ValueId(1)],      // JoinIR's main() parameters (i, sum init)
+            vec![loop_var_id, sum_var_id],     // Host's loop variables
+            vec![
+                crate::mir::join_ir::lowering::inline_boundary::LoopExitBinding {
+                    carrier_name: "sum".to_string(),
+                    join_exit_value: ValueId(18),  // k_exit's parameter (sum_final)
+                    host_slot: sum_var_id,          // variable_map["sum"]
+                }
+            ],
+        );
+        let _exit_phi_result = self.merge_joinir_mir_blocks(&mir_module, Some(&boundary), debug)?;
+        self.trace_varmap("pattern3_after_merge");
+
+        // Phase 189-Refine: variable_map の更新は merge_joinir_mir_blocks 内で
+        // JoinInlineBoundary.host_outputs を用いて行われる。
+        // この関数では Void を返すだけでよい（戻り値は後続の `return sum` が扱う）。
+        let void_val = crate::mir::builder::emission::constant::emit_void(self);
+
+        if debug {
+            eprintln!(
+                "[cf_loop/joinir/pattern3] Loop complete, returning Void {:?}",
+                void_val
+            );
+        }
+
+        Ok(Some(void_val))
+    }
+}

src/mir/builder/control_flow/mod.rs

@@ -1,9 +1,9 @@
 //! Control-flow entrypoints (if/loop/try/throw) centralized here.
 //!
 //! This module is being modularized in phases:
-//! - Phase 1: Debug utilities
+//! - Phase 1: Debug utilities (debug.rs) ✅
-//! - Phase 2: Pattern lowerers
+//! - Phase 2: Pattern lowerers (joinir/patterns/) ✅
-//! - Phase 3: JoinIR routing
+//! - Phase 3: JoinIR routing (future)
 //! - Phase 4-19: Additional modularization (future)
 
 use super::{Effect, EffectMask, MirInstruction, ValueId};
@@ -12,6 +12,9 @@ use crate::ast::ASTNode;
 // Phase 1: Debug utilities
 pub(in crate::mir::builder) mod debug;
 
+// Phase 2: JoinIR integration (patterns)
+pub(in crate::mir::builder) mod joinir;
+
 impl super::MirBuilder {
     /// Control-flow: block
     pub(super) fn cf_block(&mut self, statements: Vec<ASTNode>) -> Result<ValueId, String> {
@@ -412,416 +415,6 @@ impl super::MirBuilder {
         Ok(Some(void_val))
     }
 
-    /// Phase 188-Impl-1-F: Pattern 1 (Simple While Loop) minimal lowerer
-    ///
-    /// This bypasses the LoopFrontendBinding JSON path and directly calls
-    /// the Pattern 1 minimal lowerer for apps/tests/loop_min_while.hako
-    ///
-    /// # Phase 188-Impl-2: Host Variable Integration
-    ///
-    /// Extracts the loop variable from the host function (e.g., `i` from `i < 3`)
-    /// and passes it to the Pattern 1 lowerer along with a ValueId allocator.
-    ///
-    /// # Pipeline
-    /// 1. Extract loop variable name from condition
-    /// 2. Look up ValueId in host variable_map
-    /// 3. Create Pattern1Context with host variable + allocator
-    /// 4. Call simple_while_minimal::lower_simple_while_minimal() → JoinModule
-    /// 5. convert_join_module_to_mir_with_meta() → MirModule
-    /// 6. Merge MIR blocks into current_function
-    fn cf_loop_pattern1_minimal(
-        &mut self,
-        condition: &ASTNode,
-        _body: &[ASTNode],
-        _func_name: &str,
-        debug: bool,
-    ) -> Result<Option<ValueId>, String> {
-        use crate::mir::join_ir::lowering::simple_while_minimal::{
-            lower_simple_while_minimal, Pattern1Context,
-        };
-        use crate::mir::join_ir_vm_bridge::convert_join_module_to_mir_with_meta;
-        use crate::mir::BasicBlockId;
-        use std::collections::{BTreeMap, BTreeSet};
-
-        if debug {
-            eprintln!("[cf_loop/joinir/pattern1] Calling Pattern 1 minimal lowerer");
-        }
-
-        // Phase 188-Impl-2: Extract loop variable from condition
-        // For `i < 3`, extract `i` and look up its ValueId in variable_map
-        let loop_var_name = self.extract_loop_variable_from_condition(condition)?;
-        let loop_var_id = self
-            .variable_map
-            .get(&loop_var_name)
-            .copied()
-            .ok_or_else(|| {
-                format!(
-                    "[cf_loop/pattern1] Loop variable '{}' not found in variable_map",
-                    loop_var_name
-                )
-            })?;
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern1] Loop variable '{}' → {:?}",
-                loop_var_name, loop_var_id
-            );
-        }
-
-        // Create a minimal LoopScopeShape (Phase 188: hardcoded for loop_min_while.hako)
-        // Pattern 1 lowerer ignores the scope anyway, so this is just a placeholder
-        use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
-        let scope = LoopScopeShape {
-            header: BasicBlockId(0),
-            body: BasicBlockId(0),
-            latch: BasicBlockId(0),
-            exit: BasicBlockId(0),
-            pinned: BTreeSet::new(),
-            carriers: BTreeSet::new(),
-            body_locals: BTreeSet::new(),
-            exit_live: BTreeSet::new(),
-            progress_carrier: None,
-            variable_definitions: BTreeMap::new(),
-        };
-
-        // Phase 188-Impl-2: Create Pattern1Context with host variable + allocator
-        // Clone value_gen to move into closure
-        let mut value_gen_clone = self.value_gen.clone();
-        let ctx = Pattern1Context {
-            loop_var: loop_var_id,
-            value_allocator: Box::new(move || value_gen_clone.next()),
-        };
-
-        // Call Pattern 1 lowerer with host context
-        let join_module = match lower_simple_while_minimal(scope, Some(ctx)) {
-            Some(module) => module,
-            None => {
-                if debug {
-                    eprintln!("[cf_loop/joinir/pattern1] Pattern 1 lowerer returned None");
-                }
-                return Ok(None);
-            }
-        };
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern1] JoinModule generated with {} functions",
-                join_module.functions.len()
-            );
-        }
-
-        // Convert JoinModule to MirModule
-        // Phase 188: Pass empty meta map since Pattern 1 lowerer doesn't use metadata
-        use crate::mir::join_ir::frontend::JoinFuncMetaMap;
-        let empty_meta: JoinFuncMetaMap = BTreeMap::new();
-
-        let mir_module = convert_join_module_to_mir_with_meta(&join_module, &empty_meta)
-            .map_err(|e| format!("[cf_loop/joinir/pattern1] MIR conversion failed: {:?}", e))?;
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern1] MirModule generated with {} functions",
-                mir_module.functions.len()
-            );
-        }
-
-        // Merge JoinIR blocks into current function
-        // Phase 188-Impl-3: Create and pass JoinInlineBoundary for Pattern 1
-        let boundary = crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary::new_inputs_only(
-            vec![ValueId(0)],      // JoinIR's main() parameter (loop variable)
-            vec![loop_var_id],     // Host's loop variable
-        );
-        // Phase 189: Discard exit PHI result (Pattern 1 returns void)
-        let _ = self.merge_joinir_mir_blocks(&mir_module, Some(&boundary), debug)?;
-
-        // Phase 188-Impl-4-FIX: Return Void instead of trying to emit Const
-        //
-        // PROBLEM: Emitting instructions after merge_joinir_mir_blocks is fragile because:
-        // 1. merge creates exit block and switches to it
-        // 2. We try to add Const to exit block
-        // 3. But subsequent code (return statement) might overwrite the block
-        //
-        // SOLUTION: Loops don't produce values - they return Void.
-        // The subsequent "return 0" statement will emit its own Const + Return.
-        //
-        // This is cleaner because:
-        // - Loop lowering doesn't need to know about the return value
-        // - The return statement handles its own code generation
-        // - No risk of instructions being lost due to block management issues
-
-        let void_val = crate::mir::builder::emission::constant::emit_void(self);
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern1] Loop complete, returning Void {:?}",
-                void_val
-            );
-        }
-
-        Ok(Some(void_val))
-    }
-
-    /// Phase 188-Impl-2: Pattern 2 (Loop with Conditional Break) minimal lowerer
-    ///
-    /// Similar to Pattern 1, but handles loops with break statements.
-    ///
-    /// # Steps
-    /// 1. Extract loop variable from condition
-    /// 2. Generate JoinIR using loop_with_break_minimal
-    /// 3. Convert JoinModule → MirModule
-    /// 4. Create JoinInlineBoundary for input mapping
-    /// 5. Merge MIR blocks into current_function
-    /// 6. Return Void (loop doesn't produce values)
-    fn cf_loop_pattern2_with_break(
-        &mut self,
-        condition: &ASTNode,
-        _body: &[ASTNode],
-        _func_name: &str,
-        debug: bool,
-    ) -> Result<Option<ValueId>, String> {
-        use crate::mir::join_ir::lowering::loop_with_break_minimal::lower_loop_with_break_minimal;
-        use crate::mir::join_ir_vm_bridge::convert_join_module_to_mir_with_meta;
-        use crate::mir::BasicBlockId;
-        use std::collections::{BTreeMap, BTreeSet};
-
-        if debug {
-            eprintln!("[cf_loop/joinir/pattern2] Calling Pattern 2 minimal lowerer");
-        }
-
-        // Phase 188-Impl-2: Extract loop variable from condition
-        // For `i < 3`, extract `i` and look up its ValueId in variable_map
-        let loop_var_name = self.extract_loop_variable_from_condition(condition)?;
-        let loop_var_id = self
-            .variable_map
-            .get(&loop_var_name)
-            .copied()
-            .ok_or_else(|| {
-                format!(
-                    "[cf_loop/pattern2] Loop variable '{}' not found in variable_map",
-                    loop_var_name
-                )
-            })?;
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern2] Loop variable '{}' → {:?}",
-                loop_var_name, loop_var_id
-            );
-        }
-
-        // Create a minimal LoopScopeShape (Phase 188: hardcoded for joinir_min_loop.hako)
-        // Pattern 2 lowerer ignores the scope anyway, so this is just a placeholder
-        use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
-        let scope = LoopScopeShape {
-            header: BasicBlockId(0),
-            body: BasicBlockId(0),
-            latch: BasicBlockId(0),
-            exit: BasicBlockId(0),
-            pinned: BTreeSet::new(),
-            carriers: BTreeSet::new(),
-            body_locals: BTreeSet::new(),
-            exit_live: BTreeSet::new(),
-            progress_carrier: None,
-            variable_definitions: BTreeMap::new(),
-        };
-
-        // Call Pattern 2 lowerer
-        let join_module = match lower_loop_with_break_minimal(scope) {
-            Some(module) => module,
-            None => {
-                if debug {
-                    eprintln!("[cf_loop/joinir/pattern2] Pattern 2 lowerer returned None");
-                }
-                return Ok(None);
-            }
-        };
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern2] JoinModule generated with {} functions",
-                join_module.functions.len()
-            );
-        }
-
-        // Convert JoinModule to MirModule
-        // Phase 188: Pass empty meta map since Pattern 2 lowerer doesn't use metadata
-        use crate::mir::join_ir::frontend::JoinFuncMetaMap;
-        let empty_meta: JoinFuncMetaMap = BTreeMap::new();
-
-        let mir_module = convert_join_module_to_mir_with_meta(&join_module, &empty_meta)
-            .map_err(|e| format!("[cf_loop/joinir/pattern2] MIR conversion failed: {:?}", e))?;
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern2] MirModule generated with {} functions",
-                mir_module.functions.len()
-            );
-        }
-
-        // Merge JoinIR blocks into current function
-        // Phase 188-Impl-2: Create and pass JoinInlineBoundary for Pattern 2
-        let boundary = crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary::new_inputs_only(
-            vec![ValueId(0)],      // JoinIR's main() parameter (loop variable init)
-            vec![loop_var_id],     // Host's loop variable
-        );
-        // Phase 189: Discard exit PHI result (Pattern 2 returns void)
-        let _ = self.merge_joinir_mir_blocks(&mir_module, Some(&boundary), debug)?;
-
-        // Phase 188-Impl-2: Return Void (loops don't produce values)
-        // The subsequent "return i" statement will emit its own Load + Return
-        let void_val = crate::mir::builder::emission::constant::emit_void(self);
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern2] Loop complete, returning Void {:?}",
-                void_val
-            );
-        }
-
-        Ok(Some(void_val))
-    }
-
-    /// Phase 188-Impl-3: Pattern 3 (Loop with If-Else PHI) minimal lowerer
-    ///
-    /// Handles loops with if-else statements that assign to carrier variables.
-    ///
-    /// # Steps
-    /// 1. Extract loop variables (carriers: i + sum)
-    /// 2. Generate JoinIR using loop_with_if_phi_minimal
-    /// 3. Convert JoinModule → MirModule
-    /// 4. Create JoinInlineBoundary for input mapping
-    /// 5. Merge MIR blocks into current_function
-    /// 6. Return Void (loop doesn't produce values)
-    fn cf_loop_pattern3_with_if_phi(
-        &mut self,
-        condition: &ASTNode,
-        _body: &[ASTNode],
-        _func_name: &str,
-        debug: bool,
-    ) -> Result<Option<ValueId>, String> {
-        use crate::mir::join_ir::lowering::loop_with_if_phi_minimal::lower_loop_with_if_phi_pattern;
-        use crate::mir::join_ir_vm_bridge::convert_join_module_to_mir_with_meta;
-        use crate::mir::BasicBlockId;
-        use std::collections::{BTreeMap, BTreeSet};
-
-        if debug {
-            eprintln!("[cf_loop/joinir/pattern3] Calling Pattern 3 minimal lowerer");
-        }
-
-        // Phase 188-Impl-3: Extract loop variable from condition
-        // For `i <= 5`, extract `i` and look up its ValueId in variable_map
-        let loop_var_name = self.extract_loop_variable_from_condition(condition)?;
-        let loop_var_id = self
-            .variable_map
-            .get(&loop_var_name)
-            .copied()
-            .ok_or_else(|| {
-                format!(
-                    "[cf_loop/pattern3] Loop variable '{}' not found in variable_map",
-                    loop_var_name
-                )
-            })?;
-
-        // Phase 188-Impl-3: Also get the accumulator variable (sum)
-        // For Pattern 3, we need both i and sum
-        let sum_var_id = self
-            .variable_map
-            .get("sum")
-            .copied()
-            .ok_or_else(|| {
-                format!(
-                    "[cf_loop/pattern3] Accumulator variable 'sum' not found in variable_map"
-                )
-            })?;
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern3] Loop variables: '{}' → {:?}, 'sum' → {:?}",
-                loop_var_name, loop_var_id, sum_var_id
-            );
-        }
-
-        // Create a minimal LoopScopeShape (Phase 188: hardcoded for loop_if_phi.hako)
-        // Pattern 3 lowerer ignores the scope anyway, so this is just a placeholder
-        use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
-        let scope = LoopScopeShape {
-            header: BasicBlockId(0),
-            body: BasicBlockId(0),
-            latch: BasicBlockId(0),
-            exit: BasicBlockId(0),
-            pinned: BTreeSet::new(),
-            carriers: BTreeSet::new(),
-            body_locals: BTreeSet::new(),
-            exit_live: BTreeSet::new(),
-            progress_carrier: None,
-            variable_definitions: BTreeMap::new(),
-        };
-
-        // Call Pattern 3 lowerer
-        let join_module = match lower_loop_with_if_phi_pattern(scope) {
-            Some(module) => module,
-            None => {
-                if debug {
-                    eprintln!("[cf_loop/joinir/pattern3] Pattern 3 lowerer returned None");
-                }
-                return Ok(None);
-            }
-        };
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern3] JoinModule generated with {} functions",
-                join_module.functions.len()
-            );
-        }
-
-        // Convert JoinModule to MirModule
-        // Phase 188: Pass empty meta map since Pattern 3 lowerer doesn't use metadata
-        use crate::mir::join_ir::frontend::JoinFuncMetaMap;
-        let empty_meta: JoinFuncMetaMap = BTreeMap::new();
-
-        let mir_module = convert_join_module_to_mir_with_meta(&join_module, &empty_meta)
-            .map_err(|e| format!("[cf_loop/joinir/pattern3] MIR conversion failed: {:?}", e))?;
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern3] MirModule generated with {} functions",
-                mir_module.functions.len()
-            );
-        }
-
-        // Merge JoinIR blocks into current function
-        // Phase 190: Use explicit LoopExitBinding for Pattern 3
-        // Pattern 3 has TWO carriers: i and sum
-        self.trace_varmap("pattern3_before_merge");
-        let boundary = crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary::new_with_exit_bindings(
-            vec![ValueId(0), ValueId(1)],      // JoinIR's main() parameters (i, sum init)
-            vec![loop_var_id, sum_var_id],     // Host's loop variables
-            vec![
-                crate::mir::join_ir::lowering::inline_boundary::LoopExitBinding {
-                    carrier_name: "sum".to_string(),
-                    join_exit_value: ValueId(18),  // k_exit's parameter (sum_final)
-                    host_slot: sum_var_id,          // variable_map["sum"]
-                }
-            ],
-        );
-        let exit_phi_result = self.merge_joinir_mir_blocks(&mir_module, Some(&boundary), debug)?;
-        self.trace_varmap("pattern3_after_merge");
-
-        // Phase 189-Refine: variable_map の更新は merge_joinir_mir_blocks 内で
-        // JoinInlineBoundary.host_outputs を用いて行われる。
-        // この関数では Void を返すだけでよい（戻り値は後続の `return sum` が扱う）。
-        let void_val = crate::mir::builder::emission::constant::emit_void(self);
-
-        if debug {
-            eprintln!(
-                "[cf_loop/joinir/pattern3] Loop complete, returning Void {:?}",
-                void_val
-            );
-        }
-
-        Ok(Some(void_val))
-    }
 
     /// Phase 49-3.2: Merge JoinIR-generated MIR blocks into current_function
     ///