- let data = &mut self.basic_blocks[bb];
- data.statements.extend(new_stmts);
- data.terminator = Some(terminator);
+ let statements_to_merge =
+ merged_blocks.iter().map(|&i| self.basic_blocks[i].statements.len()).sum();
+
+ if statements_to_merge > 0 {
+ let mut statements = std::mem::take(&mut self.basic_blocks[bb].statements);
+ statements.reserve(statements_to_merge);
+ for &from in &merged_blocks {
+ statements.append(&mut self.basic_blocks[from].statements);
+ }
+ self.basic_blocks[bb].statements = statements;
+ }
+
+ self.basic_blocks[bb].terminator = Some(terminator);