feat(joinir): Phase 227 - CarrierRole separation (LoopState vs ConditionOnly)

- Add CarrierRole enum to distinguish state carriers from condition-only carriers
- ConditionOnly carriers (is_digit_pos) skip exit PHI but keep header PHI
- Update all test struct literals with role field
- 877/884 tests PASS (7 pre-existing failures unrelated)

Remaining: ValueId(0) undefined - header PHI initialization for ConditionOnly

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/mir/join_ir/lowering/carrier_info.rs

@@ -18,6 +18,42 @@
 use crate::mir::ValueId;
 use std::collections::BTreeMap; // Phase 222.5-D: HashMap → BTreeMap for determinism
 
+/// Phase 227: CarrierRole - Distinguishes loop state carriers from condition-only carriers
+///
+/// When LoopBodyLocal variables are promoted to carriers, we need to know whether
+/// they carry loop state (need exit PHI) or are only used in conditions (no exit PHI).
+///
+/// # Example
+///
+/// ```ignore
+/// // LoopState carrier: sum needs exit PHI (value persists after loop)
+/// loop(i < n) {
+///     sum = sum + i;  // sum updated in loop body
+/// }
+/// print(sum);  // sum used after loop
+///
+/// // ConditionOnly carrier: is_digit_pos does NOT need exit PHI
+/// loop(p < s.length()) {
+///     local digit_pos = digits.indexOf(s.substring(p, p+1));
+///     if digit_pos < 0 { break; }  // Only used in condition
+///     num_str = num_str + ch;
+///     p = p + 1;
+/// }
+/// // digit_pos not used after loop
+/// ```
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CarrierRole {
+    /// Value needed after loop (sum, result, count, p, num_str)
+    /// - Participates in header PHI (loop iteration)
+    /// - Participates in exit PHI (final value after loop)
+    LoopState,
+
+    /// Only used for loop condition (is_digit_pos, is_whitespace)
+    /// - Participates in header PHI (loop iteration)
+    /// - Does NOT participate in exit PHI (not needed after loop)
+    ConditionOnly,
+}
+
 /// Phase 224-D: Alias for promoted LoopBodyLocal in condition expressions
 ///
 /// When a LoopBodyLocal variable is promoted to a carrier, the original variable
@@ -44,7 +80,7 @@ pub struct ConditionAlias {
 /// Information about a single carrier variable
 #[derive(Debug, Clone)]
 pub struct CarrierVar {
-    /// Variable name (e.g., "sum", "printed")
+    /// Variable name (e.g., "sum", "printed", "is_digit_pos")
     pub name: String,
     /// Host ValueId for this variable (MIR側)
     pub host_id: ValueId,
@@ -56,6 +92,36 @@ pub struct CarrierVar {
     /// - `Some(vid)`: Header PHI生成後にセットされる
     /// - `None`: まだPHI生成前、または該当なし
     pub join_id: Option<ValueId>,
+    /// Phase 227: Role of this carrier (LoopState or ConditionOnly)
+    ///
+    /// - `LoopState`: Value needed after loop (participates in exit PHI)
+    /// - `ConditionOnly`: Only used for loop condition (no exit PHI)
+    pub role: CarrierRole,
+}
+
+impl CarrierVar {
+    /// Create a new CarrierVar with default LoopState role
+    ///
+    /// This is the primary constructor for CarrierVar. Use this instead of
+    /// struct literal syntax to ensure role defaults to LoopState.
+    pub fn new(name: String, host_id: ValueId) -> Self {
+        Self {
+            name,
+            host_id,
+            join_id: None,
+            role: CarrierRole::LoopState,
+        }
+    }
+
+    /// Create a CarrierVar with explicit role
+    pub fn with_role(name: String, host_id: ValueId, role: CarrierRole) -> Self {
+        Self {
+            name,
+            host_id,
+            join_id: None,
+            role,
+        }
+    }
 }
 
 /// Complete carrier information for a loop
@@ -130,6 +196,7 @@ impl CarrierInfo {
                 name: name.clone(),
                 host_id: id,
                 join_id: None, // Phase 177-STRUCT-1: Set by header PHI generation
+                role: CarrierRole::LoopState, // Phase 227: Default to LoopState
             })
             .collect();
 
@@ -189,6 +256,7 @@ impl CarrierInfo {
                 name,
                 host_id,
                 join_id: None, // Phase 177-STRUCT-1: Set by header PHI generation
+                role: CarrierRole::LoopState, // Phase 227: Default to LoopState
             });
         }
 
@@ -507,6 +575,7 @@ mod tests {
             name: name.to_string(),
             host_id: ValueId(id),
             join_id: None, // Phase 177-STRUCT-1
+            role: CarrierRole::LoopState, // Phase 227: Default to LoopState
         }
     }
 

src/mir/join_ir/lowering/carrier_update_emitter.rs

@@ -421,6 +421,7 @@ mod tests {
             name: name.to_string(),
             host_id: ValueId(host_id),
             join_id: None, // Phase 177-STRUCT-1
+            role: crate::mir::join_ir::lowering::carrier_info::CarrierRole::LoopState,
         }
     }
 

src/mir/join_ir/lowering/inline_boundary.rs

@@ -43,6 +43,7 @@
 //! ```
 
 use crate::mir::ValueId;
+use super::carrier_info::CarrierRole;
 
 /// Explicit binding between JoinIR exit value and host variable
 ///
@@ -68,13 +69,13 @@ use crate::mir::ValueId;
 ///
 /// ```text
 /// vec![
-///     LoopExitBinding { carrier_name: "sum", join_exit_value: ValueId(18), host_slot: ValueId(5) },
-///     LoopExitBinding { carrier_name: "count", join_exit_value: ValueId(19), host_slot: ValueId(6) },
+///     LoopExitBinding { carrier_name: "sum", join_exit_value: ValueId(18), host_slot: ValueId(5), role: LoopState },
+///     LoopExitBinding { carrier_name: "count", join_exit_value: ValueId(19), host_slot: ValueId(6), role: LoopState },
 /// ]
 /// ```
 #[derive(Debug, Clone)]
 pub struct LoopExitBinding {
-    /// Carrier variable name (e.g., "sum", "count")
+    /// Carrier variable name (e.g., "sum", "count", "is_digit_pos")
     ///
     /// This is the variable name in the host's variable_map that should
     /// receive the exit value.
@@ -91,6 +92,13 @@ pub struct LoopExitBinding {
     /// This is the host function's ValueId for the variable that should be
     /// updated with the exit PHI result.
     pub host_slot: ValueId,
+
+    /// Phase 227: Role of this carrier (LoopState or ConditionOnly)
+    ///
+    /// Determines whether this carrier should participate in exit PHI:
+    /// - LoopState: Needs exit PHI (value used after loop)
+    /// - ConditionOnly: No exit PHI (only used in loop condition)
+    pub role: CarrierRole,
 }
 
 /// Boundary information for inlining a JoinIR fragment into a host function

src/mir/join_ir/lowering/inline_boundary_builder.rs

@@ -27,6 +27,7 @@
 use crate::mir::ValueId;
 use super::inline_boundary::{JoinInlineBoundary, LoopExitBinding};
 use super::condition_to_joinir::ConditionBinding;
+use super::carrier_info::CarrierRole;
 
 /// Role of a parameter in JoinIR lowering (Phase 200-A)
 ///
@@ -299,6 +300,7 @@ mod tests {
             carrier_name: "sum".to_string(),
             join_exit_value: ValueId(18),
             host_slot: ValueId(5),
+            role: CarrierRole::LoopState,
         };
 
         let boundary = JoinInlineBoundaryBuilder::new()
@@ -346,6 +348,7 @@ mod tests {
                     carrier_name: "sum".to_string(),
                     join_exit_value: ValueId(18),
                     host_slot: ValueId(101),
+                    role: CarrierRole::LoopState,
                 }
             ])
             .with_loop_var_name(Some("i".to_string()))
@@ -372,11 +375,13 @@ mod tests {
                     carrier_name: "i".to_string(),
                     join_exit_value: ValueId(11),
                     host_slot: ValueId(100),
+                    role: CarrierRole::LoopState,
                 },
                 LoopExitBinding {
                     carrier_name: "sum".to_string(),
                     join_exit_value: ValueId(20),
                     host_slot: ValueId(101),
+                    role: CarrierRole::LoopState,
                 }
             ])
             .with_loop_var_name(Some("i".to_string()))

src/mir/join_ir/lowering/loop_update_analyzer.rs

@@ -298,6 +298,7 @@ mod tests {
             name: "count".to_string(),
             host_id: crate::mir::ValueId(0),
             join_id: None, // Phase 177-STRUCT-1
+            role: crate::mir::join_ir::lowering::carrier_info::CarrierRole::LoopState,
         }];
 
         let updates = LoopUpdateAnalyzer::analyze_carrier_updates(&body, &carriers);
@@ -355,6 +356,7 @@ mod tests {
             name: "result".to_string(),
             host_id: crate::mir::ValueId(0),
             join_id: None,
+            role: crate::mir::join_ir::lowering::carrier_info::CarrierRole::LoopState,
         }];
 
         let updates = LoopUpdateAnalyzer::analyze_carrier_updates(&body, &carriers);
@@ -413,6 +415,7 @@ mod tests {
             name: "result".to_string(),
             host_id: crate::mir::ValueId(0),
             join_id: None,
+            role: crate::mir::join_ir::lowering::carrier_info::CarrierRole::LoopState,
         }];
 
         let updates = LoopUpdateAnalyzer::analyze_carrier_updates(&body, &carriers);
@@ -471,6 +474,7 @@ mod tests {
             name: "result".to_string(),
             host_id: crate::mir::ValueId(0),
             join_id: None,
+            role: crate::mir::join_ir::lowering::carrier_info::CarrierRole::LoopState,
         }];
 
         let updates = LoopUpdateAnalyzer::analyze_carrier_updates(&body, &carriers);

src/mir/join_ir/lowering/loop_with_break_minimal.rs

@@ -377,6 +377,23 @@ pub(crate) fn lower_loop_with_break_minimal(
     for (idx, carrier) in carrier_info.carriers.iter().enumerate() {
         let carrier_name = &carrier.name;
 
+        // Phase 227: ConditionOnly carriers don't have update expressions
+        // They just pass through their current value unchanged
+        use crate::mir::join_ir::lowering::carrier_info::CarrierRole;
+        if carrier.role == CarrierRole::ConditionOnly {
+            // ConditionOnly carrier: just pass through the current value
+            // The carrier's ValueId from env is passed unchanged
+            let current_value = env.get(carrier_name).ok_or_else(|| {
+                format!("ConditionOnly carrier '{}' not found in env", carrier_name)
+            })?;
+            updated_carrier_values.push(current_value);
+            eprintln!(
+                "[loop/carrier_update] Phase 227: ConditionOnly carrier '{}' passthrough: {:?}",
+                carrier_name, current_value
+            );
+            continue;
+        }
+
         // Get the update expression for this carrier
         let update_expr = carrier_updates.get(carrier_name).ok_or_else(|| {
             format!(