From 7c3f1eafdeb2b7f9fb3f6deee214628f242349f3 Mon Sep 17 00:00:00 2001
From: nyash-codex <codex@nyash.local>
Date: Wed, 19 Nov 2025 23:53:41 +0900
Subject: [PATCH] loopform: add exit PHI fallthrough for body-local vars

---
 src/mir/phi_core/loopform_builder.rs | 35 ++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/src/mir/phi_core/loopform_builder.rs b/src/mir/phi_core/loopform_builder.rs
index 875aa53e..510216c8 100644
--- a/src/mir/phi_core/loopform_builder.rs
+++ b/src/mir/phi_core/loopform_builder.rs
@@ -412,6 +412,41 @@ impl LoopFormBuilder {
                 .push((branch_source_block, carrier.header_phi));
         }
 
+        // Phase 25.1c/k: Add header fallthrough for body-local variables
+        // Body-local variables (declared inside loop body) are not in pinned/carriers,
+        // but they need exit PHI with header fallthrough when accessed after loop.
+        // Collect all variables from exit_snapshots and add header values for body-locals.
+        let mut body_local_names: std::collections::HashSet<String> = std::collections::HashSet::new();
+        for (_block_id, snapshot) in exit_snapshots {
+            for var_name in snapshot.keys() {
+                // Check if this variable is NOT in pinned/carriers (= body-local)
+                let is_pinned = self.pinned.iter().any(|p| &p.name == var_name);
+                let is_carrier = self.carriers.iter().any(|c| &c.name == var_name);
+                if !is_pinned && !is_carrier {
+                    body_local_names.insert(var_name.clone());
+                }
+            }
+        }
+
+        if debug && !body_local_names.is_empty() {
+            eprintln!("[DEBUG/exit_phi] Found {} body-local variables in exit_snapshots", body_local_names.len());
+        }
+
+        // Get header variable map and add fallthrough for body-locals
+        for var_name in &body_local_names {
+            if let Some(header_value) = ops.get_variable_at_block(var_name, self.header_id) {
+                all_vars
+                    .entry(var_name.clone())
+                    .or_default()
+                    .push((branch_source_block, header_value));
+                if debug {
+                    eprintln!("[DEBUG/exit_phi] Added header fallthrough for body-local '{}': {:?}", var_name, header_value);
+                }
+            } else if debug {
+                eprintln!("[DEBUG/exit_phi] ⚠️ Body-local '{}' not found at header block", var_name);
+            }
+        }
+
         // 📦 Hotfix 6: Get actual CFG predecessors for exit block
         let exit_preds = ops.get_block_predecessors(exit_id);
         if debug {