ZJIT: Fix definite assignment to work with multiple entry blocks

Author: tekknolagi

zjit/src/hir.rs

@@ -4165,11 +4165,13 @@ impl Function {
         // missing location.
         let mut assigned_in = vec![None; self.num_blocks()];
         let rpo = self.rpo();
-        // Begin with every block having every variable defined, except for the entry block, which
-        // starts with nothing defined.
-        assigned_in[self.entry_block.0] = Some(InsnSet::with_capacity(self.insns.len()));
+        // Begin with every block having every variable defined, except for the entry blocks, which
+        // start with nothing defined.
+        let entry_blocks = self.entry_blocks();
         for &block in &rpo {
-            if block != self.entry_block {
+            if entry_blocks.contains(&block) {
+                assigned_in[block.0] = Some(InsnSet::with_capacity(self.insns.len()));
+            } else {
                 let mut all_ones = InsnSet::with_capacity(self.insns.len());
                 all_ones.insert_all();
                 assigned_in[block.0] = Some(all_ones);