fix: 修复 switch case 标签冲突与大 switch 寄存器回绕

crates/oxide_compiler/src/compiler.rs

@@ -45,7 +45,7 @@ pub(crate) enum Label {
     ForInStart(u32),
     ForInEnd(u32),
     SwitchEnd(u32),
-    SwitchCase(u32),
+    SwitchCase(u32, u32),
     CatchBody(u32),
     FinallyBody(u32),
     TryEnd(u32),
@@ -111,6 +111,14 @@ impl CompileCtx {
         self.label_counter = 0;
     }
 
+    pub(crate) fn reg_checkpoint(&self) -> u8 {
+        self.next_reg
+    }
+
+    pub(crate) fn restore_reg_checkpoint(&mut self, checkpoint: u8) {
+        self.next_reg = checkpoint;
+    }
+
     pub(crate) fn add_constant(&mut self, c: Constant) -> u16 {
         if let Some(idx) = self.constants.iter().position(|x| x == &c) {
             return idx as u16;

crates/oxide_compiler/src/counter.rs

@@ -143,6 +143,7 @@ impl Compiler {
                 ctx.push_switch(end_label);
 
                 self.count_expression(&sw.discriminant, ctx);
+                let compare_reg_checkpoint = ctx.reg_checkpoint();
 
                 let cases = &sw.cases;
                 for case in cases.iter() {
@@ -151,6 +152,7 @@ impl Compiler {
                         ctx.projected_pc += 1; // EQ
                         ctx.alloc_reg(); // eq result
                         ctx.projected_pc += 1; // JMP_IF_TRUE
+                        ctx.restore_reg_checkpoint(compare_reg_checkpoint);
                     }
                 }
 
@@ -160,7 +162,7 @@ impl Compiler {
                 }
 
                 for (case_idx, case) in cases.iter().enumerate() {
-                    let case_label = Label::SwitchCase(id * 256 + case_idx as u32);
+                    let case_label = Label::SwitchCase(id, case_idx as u32);
                     ctx.label_map.insert(case_label, ctx.projected_pc);
                     for s in &case.consequent {
                         self.count_statement(s, ctx);

crates/oxide_compiler/src/emitter.rs

@@ -299,6 +299,7 @@ impl Compiler {
                 ctx.push_switch(end_label);
 
                 let disc_reg = self.emit_expression(&sw.discriminant, ctx)?;
+                let compare_reg_checkpoint = ctx.reg_checkpoint();
                 let cases = &sw.cases;
 
                 for (case_idx, case) in cases.iter().enumerate() {
@@ -307,10 +308,11 @@ impl Compiler {
                         let eq_reg = ctx.alloc_reg();
                         ctx.emit(opcode::encode(OpCode::EQ, eq_reg, disc_reg, test_reg));
 
-                        let case_label = Label::SwitchCase(id * 256 + case_idx as u32);
+                        let case_label = Label::SwitchCase(id, case_idx as u32);
                         let body_pos = ctx.resolve_label(case_label)?;
                         let offset = (body_pos as isize) - (ctx.bytecode.len() as isize);
                         ctx.emit(opcode::encode_jmp_if_true(eq_reg, offset as i16));
+                        ctx.restore_reg_checkpoint(compare_reg_checkpoint);
                     }
                 }
 

crates/oxide_compiler/tests/compile_stmt_tests.rs

@@ -281,3 +281,25 @@ fn compile_continue_in_switch_errors() {
     });
     assert!(result.is_err(), "continue inside switch should error");
 }
+
+#[test]
+fn compile_large_adjacent_switches_do_not_collide_labels() {
+    let mut source = String::from("var r=0;switch(256){");
+    for i in 0..=256 {
+        source.push_str(&format!("case {i}:"));
+        if i == 256 {
+            source.push_str("r=1;break;");
+        }
+    }
+    source.push_str("}switch(0){case 0:r=r+1;break;}r");
+    let module = compile_source(&source);
+    assert!(
+        module
+            .bytecode
+            .iter()
+            .filter(|&&i| opcode::opcode(i) == OpCode::JMP_IF_TRUE)
+            .count()
+            >= 258,
+        "expected both large switches to compile with distinct case labels"
+    );
+}

crates/oxide_vm/tests/control_flow_tests.rs

@@ -256,3 +256,16 @@ fn eval_break_in_switch_in_loop() {
         "2"
     );
 }
+
+#[test]
+fn eval_large_adjacent_switches_do_not_collide_labels() {
+    let mut source = String::from("var r=0;switch(256){");
+    for i in 0..=256 {
+        source.push_str(&format!("case {i}:"));
+        if i == 256 {
+            source.push_str("r=1;break;");
+        }
+    }
+    source.push_str("}switch(0){case 0:r=r+1;break;}r");
+    assert_eq!(eval(&source), "2");
+}