feat: allow for cross switch int transition

Author: indietyp

libs/@local/hashql/mir/src/pass/execution/terminator_placement/mod.rs

@@ -393,13 +393,9 @@ impl PopulateEdgeMatrix {
         terminator: &TerminatorKind,
     ) {
         match terminator {
-            TerminatorKind::Goto(_) => {
+            TerminatorKind::Goto(_) | TerminatorKind::SwitchInt(_) => {
                 self.add_goto_transitions(matrix);
             }
-            TerminatorKind::SwitchInt(_) => {
-                // SwitchInt does not allow additional cross-backend transitions
-                // due to complexity of coordinating branches across backends.
-            }
             TerminatorKind::GraphRead(_) => {
                 self.restrict_to_interpreter_only(matrix);
             }

libs/@local/hashql/mir/src/pass/execution/terminator_placement/tests.rs

@@ -225,7 +225,7 @@ fn goto_allows_cross_backend_non_postgres() {
 }
 
 #[test]
-fn switchint_blocks_cross_backend() {
+fn switchint_allows_cross_backend() {
     let heap = Heap::new();
     let interner = Interner::new(&heap);
     let env = Environment::new(&heap);
@@ -263,7 +263,10 @@ fn switchint_blocks_cross_backend() {
     );
 
     let matrix = costs.of(BasicBlockId::new(0))[0];
-    assert_eq!(matrix.get(TargetId::Interpreter, TargetId::Embedding), None);
+    assert_eq!(
+        matrix.get(TargetId::Interpreter, TargetId::Embedding),
+        Some(cost!(5))
+    );
     // data transfer (1) + backend switch E->I (4) = 5
     assert_eq!(
         matrix.get(TargetId::Embedding, TargetId::Interpreter),
@@ -336,7 +339,7 @@ fn switchint_edge_targets_are_branch_specific() {
     assert!(
         second
             .get(TargetId::Interpreter, TargetId::Embedding)
-            .is_none()
+            .is_some()
     );
     assert!(
         second