fix(mir): conservative PHI box for If/Loop and Stage1 resolver SSA

src/mir/phi_core/loopform_builder.rs

@@ -331,8 +331,15 @@ impl LoopFormBuilder {
                 .push((branch_source_block, carrier.header_phi));
         }
 
+        // 📦 Hotfix 6: Get actual CFG predecessors for exit block
+        let exit_preds = ops.get_block_predecessors(exit_id);
+        if debug {
+            eprintln!("[DEBUG/exit_phi] Exit block predecessors: {:?}", exit_preds);
+        }
+
         // Add break snapshot values
         // 📦 Hotfix 2: Skip non-existent blocks (幽霊ブロック対策)
+        // 📦 Hotfix 6: Skip blocks not in CFG predecessors (unreachable continuation対策)
         for (block_id, snapshot) in exit_snapshots {
             // Validate block existence before adding to PHI inputs
             if !ops.block_exists(*block_id) {
@@ -342,6 +349,15 @@ impl LoopFormBuilder {
                 continue;  // Skip ghost blocks
             }
 
+            // Hotfix 6: Skip blocks not in actual CFG predecessors
+            // This catches unreachable continuation blocks created after break/continue
+            if !exit_preds.contains(block_id) {
+                if debug {
+                    eprintln!("[DEBUG/exit_phi] ⚠️ Skipping block {:?} (not in CFG predecessors)", block_id);
+                }
+                continue;  // Skip blocks not actually branching to exit
+            }
+
             for (var_name, &value) in snapshot {
                 all_vars
                     .entry(var_name.clone())
@@ -409,6 +425,11 @@ pub trait LoopFormOps {
     /// Used to skip non-existent blocks when building exit PHIs.
     fn block_exists(&self, block: BasicBlockId) -> bool;
 
+    /// 📦 Get actual CFG predecessors for a block (Hotfix 6: PHI input validation)
+    /// Returns the set of blocks that actually branch to this block in the CFG.
+    /// Used to validate exit PHI inputs against actual control flow.
+    fn get_block_predecessors(&self, block: BasicBlockId) -> std::collections::HashSet<BasicBlockId>;
+
     /// Check if a variable is a function parameter
     fn is_parameter(&self, name: &str) -> bool;
 
@@ -520,6 +541,11 @@ mod tests {
                 true
             }
 
+            fn get_block_predecessors(&self, _block: BasicBlockId) -> std::collections::HashSet<BasicBlockId> {
+                // MockOps: return empty set (no CFG in test)
+                std::collections::HashSet::new()
+            }
+
             fn is_parameter(&self, name: &str) -> bool {
                 self.params.iter().any(|p| p == name)
             }