explodingcamera · explodingcamera · Mar 1, 2025 · Mar 1, 2025
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Support for the custom memory page sizes proposal ([#22](https://github.com/explodingcamera/tinywasm/pull/22) by [@danielstuart14](https://github.com/danielstuart14))
+- Support for the `tail_call` proposal
 
 ### Breaking Changes
 

diff --git a/README.md b/README.md
@@ -37,8 +37,9 @@ TinyWasm passes all WebAssembly MVP tests from the [WebAssembly core testsuite](
 | [**Reference Types**](https://github.com/WebAssembly/reference-types/blob/master/proposals/reference-types/Overview.md)     | 🟢     | 0.7.0            |
 | [**Multiple Memories**](https://github.com/WebAssembly/multi-memory/blob/master/proposals/multi-memory/Overview.md)         | 🟢     | 0.8.0            |
 | [**Custom Page Sizes**](https://github.com/WebAssembly/custom-page-sizes/blob/main/proposals/custom-page-sizes/Overview.md) | 🟢     | `next`           |
+| [**Tail Call**](https://github.com/WebAssembly/tail-call/blob/main/proposals/tail-call/Overview.md)                         | 🟢     | `next`           |
 | [**Memory64**](https://github.com/WebAssembly/memory64/blob/master/proposals/memory64/Overview.md)                          | 🚧     | N/A              |
-| [**Fixed-Width SIMD**](https://github.com/webassembly/simd)                                                                 | 🌑     | N/A              |
+| [**Fixed-Width SIMD**](https://github.com/webassembly/simd)                                                                 | 🚧     | N/A              |
 
 ## Usage
 

diff --git a/crates/parser/src/visit.rs b/crates/parser/src/visit.rs
@@ -158,6 +158,7 @@ macro_rules! impl_visit_operator {
     (@@saturating_float_to_int $($rest:tt)* ) => {};
     (@@bulk_memory $($rest:tt)* ) => {};
     (@@simd $($rest:tt)* ) => {};
+    (@@tail_call $($rest:tt)* ) => {};
 
     (@@$proposal:ident $op:ident $({ $($arg:ident: $argty:ty),* })? => $visit:ident ($($ann:tt)*)) => {
         #[cold]
@@ -181,7 +182,7 @@ impl<'a, R: WasmModuleResources> wasmparser::VisitOperator<'a> for FunctionBuild
 
     define_operands! {
         // basic instructions
-        visit_br(Br, u32), visit_br_if(BrIf, u32), visit_global_get(GlobalGet, u32), visit_i32_const(I32Const, i32), visit_i64_const(I64Const, i64), visit_call(Call, u32), visit_memory_size(MemorySize, u32), visit_memory_grow(MemoryGrow, u32), visit_unreachable(Unreachable), visit_nop(Nop), visit_return(Return), visit_i32_eqz(I32Eqz), visit_i32_eq(I32Eq), visit_i32_ne(I32Ne), visit_i32_lt_s(I32LtS), visit_i32_lt_u(I32LtU), visit_i32_gt_s(I32GtS), visit_i32_gt_u(I32GtU), visit_i32_le_s(I32LeS), visit_i32_le_u(I32LeU), visit_i32_ge_s(I32GeS), visit_i32_ge_u(I32GeU), visit_i64_eqz(I64Eqz), visit_i64_eq(I64Eq), visit_i64_ne(I64Ne), visit_i64_lt_s(I64LtS), visit_i64_lt_u(I64LtU), visit_i64_gt_s(I64GtS), visit_i64_gt_u(I64GtU), visit_i64_le_s(I64LeS), visit_i64_le_u(I64LeU), visit_i64_ge_s(I64GeS), visit_i64_ge_u(I64GeU), visit_f32_eq(F32Eq), visit_f32_ne(F32Ne), visit_f32_lt(F32Lt), visit_f32_gt(F32Gt), visit_f32_le(F32Le), visit_f32_ge(F32Ge), visit_f64_eq(F64Eq), visit_f64_ne(F64Ne), visit_f64_lt(F64Lt), visit_f64_gt(F64Gt), visit_f64_le(F64Le), visit_f64_ge(F64Ge), visit_i32_clz(I32Clz), visit_i32_ctz(I32Ctz), visit_i32_popcnt(I32Popcnt), visit_i32_add(I32Add), visit_i32_sub(I32Sub), visit_i32_mul(I32Mul), visit_i32_div_s(I32DivS), visit_i32_div_u(I32DivU), visit_i32_rem_s(I32RemS), visit_i32_rem_u(I32RemU), visit_i32_and(I32And), visit_i32_or(I32Or), visit_i32_xor(I32Xor), visit_i32_shl(I32Shl), visit_i32_shr_s(I32ShrS), visit_i32_shr_u(I32ShrU), visit_i32_rotl(I32Rotl), visit_i32_rotr(I32Rotr), visit_i64_clz(I64Clz), visit_i64_ctz(I64Ctz), visit_i64_popcnt(I64Popcnt), visit_i64_add(I64Add), visit_i64_sub(I64Sub), visit_i64_mul(I64Mul), visit_i64_div_s(I64DivS), visit_i64_div_u(I64DivU), visit_i64_rem_s(I64RemS), visit_i64_rem_u(I64RemU), visit_i64_and(I64And), visit_i64_or(I64Or), visit_i64_xor(I64Xor), visit_i64_shl(I64Shl), visit_i64_shr_s(I64ShrS), visit_i64_shr_u(I64ShrU), visit_i64_rotl(I64Rotl), visit_i64_rotr(I64Rotr), visit_f32_abs(F32Abs), visit_f32_neg(F32Neg), visit_f32_ceil(F32Ceil), visit_f32_floor(F32Floor), visit_f32_trunc(F32Trunc), visit_f32_nearest(F32Nearest), visit_f32_sqrt(F32Sqrt), visit_f32_add(F32Add), visit_f32_sub(F32Sub), visit_f32_mul(F32Mul), visit_f32_div(F32Div), visit_f32_min(F32Min), visit_f32_max(F32Max), visit_f32_copysign(F32Copysign), visit_f64_abs(F64Abs), visit_f64_neg(F64Neg), visit_f64_ceil(F64Ceil), visit_f64_floor(F64Floor), visit_f64_trunc(F64Trunc), visit_f64_nearest(F64Nearest), visit_f64_sqrt(F64Sqrt), visit_f64_add(F64Add), visit_f64_sub(F64Sub), visit_f64_mul(F64Mul), visit_f64_div(F64Div), visit_f64_min(F64Min), visit_f64_max(F64Max), visit_f64_copysign(F64Copysign), visit_i32_wrap_i64(I32WrapI64), visit_i32_trunc_f32_s(I32TruncF32S), visit_i32_trunc_f32_u(I32TruncF32U), visit_i32_trunc_f64_s(I32TruncF64S), visit_i32_trunc_f64_u(I32TruncF64U), visit_i64_extend_i32_s(I64ExtendI32S), visit_i64_extend_i32_u(I64ExtendI32U), visit_i64_trunc_f32_s(I64TruncF32S), visit_i64_trunc_f32_u(I64TruncF32U), visit_i64_trunc_f64_s(I64TruncF64S), visit_i64_trunc_f64_u(I64TruncF64U), visit_f32_convert_i32_s(F32ConvertI32S), visit_f32_convert_i32_u(F32ConvertI32U), visit_f32_convert_i64_s(F32ConvertI64S), visit_f32_convert_i64_u(F32ConvertI64U), visit_f32_demote_f64(F32DemoteF64), visit_f64_convert_i32_s(F64ConvertI32S), visit_f64_convert_i32_u(F64ConvertI32U), visit_f64_convert_i64_s(F64ConvertI64S), visit_f64_convert_i64_u(F64ConvertI64U), visit_f64_promote_f32(F64PromoteF32), visit_i32_reinterpret_f32(I32ReinterpretF32), visit_i64_reinterpret_f64(I64ReinterpretF64), visit_f32_reinterpret_i32(F32ReinterpretI32), visit_f64_reinterpret_i64(F64ReinterpretI64),
+        visit_br(Br, u32), visit_br_if(BrIf, u32), visit_global_get(GlobalGet, u32), visit_i32_const(I32Const, i32), visit_i64_const(I64Const, i64), visit_call(Call, u32), visit_return_call(ReturnCall, u32), visit_memory_size(MemorySize, u32), visit_memory_grow(MemoryGrow, u32), visit_unreachable(Unreachable), visit_nop(Nop), visit_return(Return), visit_i32_eqz(I32Eqz), visit_i32_eq(I32Eq), visit_i32_ne(I32Ne), visit_i32_lt_s(I32LtS), visit_i32_lt_u(I32LtU), visit_i32_gt_s(I32GtS), visit_i32_gt_u(I32GtU), visit_i32_le_s(I32LeS), visit_i32_le_u(I32LeU), visit_i32_ge_s(I32GeS), visit_i32_ge_u(I32GeU), visit_i64_eqz(I64Eqz), visit_i64_eq(I64Eq), visit_i64_ne(I64Ne), visit_i64_lt_s(I64LtS), visit_i64_lt_u(I64LtU), visit_i64_gt_s(I64GtS), visit_i64_gt_u(I64GtU), visit_i64_le_s(I64LeS), visit_i64_le_u(I64LeU), visit_i64_ge_s(I64GeS), visit_i64_ge_u(I64GeU), visit_f32_eq(F32Eq), visit_f32_ne(F32Ne), visit_f32_lt(F32Lt), visit_f32_gt(F32Gt), visit_f32_le(F32Le), visit_f32_ge(F32Ge), visit_f64_eq(F64Eq), visit_f64_ne(F64Ne), visit_f64_lt(F64Lt), visit_f64_gt(F64Gt), visit_f64_le(F64Le), visit_f64_ge(F64Ge), visit_i32_clz(I32Clz), visit_i32_ctz(I32Ctz), visit_i32_popcnt(I32Popcnt), visit_i32_add(I32Add), visit_i32_sub(I32Sub), visit_i32_mul(I32Mul), visit_i32_div_s(I32DivS), visit_i32_div_u(I32DivU), visit_i32_rem_s(I32RemS), visit_i32_rem_u(I32RemU), visit_i32_and(I32And), visit_i32_or(I32Or), visit_i32_xor(I32Xor), visit_i32_shl(I32Shl), visit_i32_shr_s(I32ShrS), visit_i32_shr_u(I32ShrU), visit_i32_rotl(I32Rotl), visit_i32_rotr(I32Rotr), visit_i64_clz(I64Clz), visit_i64_ctz(I64Ctz), visit_i64_popcnt(I64Popcnt), visit_i64_add(I64Add), visit_i64_sub(I64Sub), visit_i64_mul(I64Mul), visit_i64_div_s(I64DivS), visit_i64_div_u(I64DivU), visit_i64_rem_s(I64RemS), visit_i64_rem_u(I64RemU), visit_i64_and(I64And), visit_i64_or(I64Or), visit_i64_xor(I64Xor), visit_i64_shl(I64Shl), visit_i64_shr_s(I64ShrS), visit_i64_shr_u(I64ShrU), visit_i64_rotl(I64Rotl), visit_i64_rotr(I64Rotr), visit_f32_abs(F32Abs), visit_f32_neg(F32Neg), visit_f32_ceil(F32Ceil), visit_f32_floor(F32Floor), visit_f32_trunc(F32Trunc), visit_f32_nearest(F32Nearest), visit_f32_sqrt(F32Sqrt), visit_f32_add(F32Add), visit_f32_sub(F32Sub), visit_f32_mul(F32Mul), visit_f32_div(F32Div), visit_f32_min(F32Min), visit_f32_max(F32Max), visit_f32_copysign(F32Copysign), visit_f64_abs(F64Abs), visit_f64_neg(F64Neg), visit_f64_ceil(F64Ceil), visit_f64_floor(F64Floor), visit_f64_trunc(F64Trunc), visit_f64_nearest(F64Nearest), visit_f64_sqrt(F64Sqrt), visit_f64_add(F64Add), visit_f64_sub(F64Sub), visit_f64_mul(F64Mul), visit_f64_div(F64Div), visit_f64_min(F64Min), visit_f64_max(F64Max), visit_f64_copysign(F64Copysign), visit_i32_wrap_i64(I32WrapI64), visit_i32_trunc_f32_s(I32TruncF32S), visit_i32_trunc_f32_u(I32TruncF32U), visit_i32_trunc_f64_s(I32TruncF64S), visit_i32_trunc_f64_u(I32TruncF64U), visit_i64_extend_i32_s(I64ExtendI32S), visit_i64_extend_i32_u(I64ExtendI32U), visit_i64_trunc_f32_s(I64TruncF32S), visit_i64_trunc_f32_u(I64TruncF32U), visit_i64_trunc_f64_s(I64TruncF64S), visit_i64_trunc_f64_u(I64TruncF64U), visit_f32_convert_i32_s(F32ConvertI32S), visit_f32_convert_i32_u(F32ConvertI32U), visit_f32_convert_i64_s(F32ConvertI64S), visit_f32_convert_i64_u(F32ConvertI64U), visit_f32_demote_f64(F32DemoteF64), visit_f64_convert_i32_s(F64ConvertI32S), visit_f64_convert_i32_u(F64ConvertI32U), visit_f64_convert_i64_s(F64ConvertI64S), visit_f64_convert_i64_u(F64ConvertI64U), visit_f64_promote_f32(F64PromoteF32), visit_i32_reinterpret_f32(I32ReinterpretF32), visit_i64_reinterpret_f64(I64ReinterpretF64), visit_f32_reinterpret_i32(F32ReinterpretI32), visit_f64_reinterpret_i64(F64ReinterpretI64),
 
         // sign_extension
         visit_i32_extend8_s(I32Extend8S), visit_i32_extend16_s(I32Extend16S), visit_i64_extend8_s(I64Extend8S), visit_i64_extend16_s(I64Extend16S), visit_i64_extend32_s(I64Extend32S),
@@ -431,6 +432,9 @@ impl<'a, R: WasmModuleResources> wasmparser::VisitOperator<'a> for FunctionBuild
     fn visit_call_indirect(&mut self, ty: u32, table: u32) -> Self::Output {
         self.instructions.push(Instruction::CallIndirect(ty, table));
     }
+    fn visit_return_call_indirect(&mut self, ty: u32, table: u32) -> Self::Output {
+        self.instructions.push(Instruction::ReturnCallIndirect(ty, table));
+    }
 
     fn visit_f32_const(&mut self, val: wasmparser::Ieee32) -> Self::Output {
         self.instructions.push(Instruction::F32Const(f32::from_bits(val.bits())));

diff --git a/crates/tinywasm/Cargo.toml b/crates/tinywasm/Cargo.toml
@@ -62,6 +62,10 @@ harness=false
 name="test-wasm-custom-page-sizes"
 harness=false
 
+[[test]]
+name="test-wasm-tail-call"
+harness=false
+
 [[test]]
 name="test-wasm-memory64"
 harness=false

diff --git a/crates/tinywasm/src/interpreter/executor.rs b/crates/tinywasm/src/interpreter/executor.rs
@@ -55,8 +55,11 @@ impl<'store, 'stack> Executor<'store, 'stack> {
             Select128 => self.stack.values.select::<Value128>(),
             SelectRef => self.stack.values.select::<ValueRef>(),
 
-            Call(v) => return self.exec_call_direct(*v),
-            CallIndirect(ty, table) => return self.exec_call_indirect(*ty, *table),
+            Call(v) => return self.exec_call_direct::<false>(*v),
+            CallIndirect(ty, table) => return self.exec_call_indirect::<false>(*ty, *table),
+
+            ReturnCall(v) => return self.exec_call_direct::<true>(*v),
+            ReturnCallIndirect(ty, table) => return self.exec_call_indirect::<true>(*ty, *table),
 
             If(end, el) => self.exec_if(*end, *el, (StackHeight::default(), StackHeight::default())),
             IfWithType(ty, end, el) => self.exec_if(*end, *el, (StackHeight::default(), (*ty).into())),
@@ -314,50 +317,71 @@ impl<'store, 'stack> Executor<'store, 'stack> {
         ControlFlow::Break(Some(Trap::Unreachable.into()))
     }
 
-    fn exec_call(&mut self, wasm_func: Rc<WasmFunction>, owner: ModuleInstanceAddr) -> ControlFlow<Option<Error>> {
-        let locals = self.stack.values.pop_locals(wasm_func.params, wasm_func.locals);
-        let new_call_frame = CallFrame::new_raw(wasm_func, owner, locals, self.stack.blocks.len() as u32);
-        self.cf.incr_instr_ptr(); // skip the call instruction
-        self.stack.call_stack.push(core::mem::replace(&mut self.cf, new_call_frame))?;
-        self.module.swap_with(self.cf.module_addr(), self.store);
+    fn exec_call<const IS_RETURN_CALL: bool>(
+        &mut self,
+        wasm_func: Rc<WasmFunction>,
+        owner: ModuleInstanceAddr,
+    ) -> ControlFlow<Option<Error>> {
+        if !IS_RETURN_CALL {
+            let locals = self.stack.values.pop_locals(wasm_func.params, wasm_func.locals);
+            let new_call_frame = CallFrame::new_raw(wasm_func, owner, locals, self.stack.blocks.len() as u32);
+            self.cf.incr_instr_ptr(); // skip the call instruction
+            self.stack.call_stack.push(core::mem::replace(&mut self.cf, new_call_frame))?;
+            self.module.swap_with(self.cf.module_addr(), self.store);
+        } else {
+            let locals = self.stack.values.pop_locals(wasm_func.params, wasm_func.locals);
+            self.cf.reuse_for(wasm_func, locals, self.stack.blocks.len() as u32, owner);
+            self.module.swap_with(self.cf.module_addr(), self.store);
+        }
+
         ControlFlow::Continue(())
     }
-    fn exec_call_direct(&mut self, v: u32) -> ControlFlow<Option<Error>> {
+    fn exec_call_host(&mut self, host_func: Rc<imports::HostFunction>) -> ControlFlow<Option<Error>> {
+        let params = self.stack.values.pop_params(&host_func.ty.params);
+        let res = host_func
+            .clone()
+            .call(FuncContext { store: self.store, module_addr: self.module.id() }, &params)
+            .to_cf()?;
+        self.stack.values.extend_from_wasmvalues(&res);
+        self.cf.incr_instr_ptr();
+        ControlFlow::Continue(())
+    }
+    fn exec_call_direct<const IS_RETURN_CALL: bool>(&mut self, v: u32) -> ControlFlow<Option<Error>> {
         let func_inst = self.store.get_func(self.module.resolve_func_addr(v));
-        let wasm_func = match &func_inst.func {
-            crate::Function::Wasm(wasm_func) => wasm_func,
-            crate::Function::Host(host_func) => {
-                let func = &host_func.clone();
-                let params = self.stack.values.pop_params(&host_func.ty.params);
-                let res =
-                    func.call(FuncContext { store: self.store, module_addr: self.module.id() }, &params).to_cf()?;
-                self.stack.values.extend_from_wasmvalues(&res);
-                self.cf.incr_instr_ptr();
-                return ControlFlow::Continue(());
-            }
-        };
-
-        self.exec_call(wasm_func.clone(), func_inst.owner)
+        match func_inst.func.clone() {
+            crate::Function::Wasm(wasm_func) => self.exec_call::<IS_RETURN_CALL>(wasm_func, func_inst.owner),
+            crate::Function::Host(host_func) => self.exec_call_host(host_func),
+        }
     }
-    fn exec_call_indirect(&mut self, type_addr: u32, table_addr: u32) -> ControlFlow<Option<Error>> {
+    fn exec_call_indirect<const IS_RETURN_CALL: bool>(
+        &mut self,
+        type_addr: u32,
+        table_addr: u32,
+    ) -> ControlFlow<Option<Error>> {
         // verify that the table is of the right type, this should be validated by the parser already
         let func_ref = {
             let table = self.store.get_table(self.module.resolve_table_addr(table_addr));
             let table_idx: u32 = self.stack.values.pop::<i32>() as u32;
             assert!(table.kind.element_type == ValType::RefFunc, "table is not of type funcref");
-            table
-                .get(table_idx)
-                .map_err(|_| Error::Trap(Trap::UndefinedElement { index: table_idx as usize }))
-                .to_cf()?
-                .addr()
-                .ok_or(Error::Trap(Trap::UninitializedElement { index: table_idx as usize }))
-                .to_cf()?
+            let table = table.get(table_idx).map_err(|_| Trap::UndefinedElement { index: table_idx as usize }.into());
+            let table = table.to_cf()?;
+            table.addr().ok_or(Trap::UninitializedElement { index: table_idx as usize }.into()).to_cf()?
         };
 
         let func_inst = self.store.get_func(func_ref);
         let call_ty = self.module.func_ty(type_addr);
-        let wasm_func = match &func_inst.func {
-            crate::Function::Wasm(f) => f,
+
+        match func_inst.func.clone() {
+            crate::Function::Wasm(wasm_func) => {
+                if unlikely(wasm_func.ty != *call_ty) {
+                    return ControlFlow::Break(Some(
+                        Trap::IndirectCallTypeMismatch { actual: wasm_func.ty.clone(), expected: call_ty.clone() }
+                            .into(),
+                    ));
+                }
+
+                self.exec_call::<IS_RETURN_CALL>(wasm_func, func_inst.owner)
+            }
             crate::Function::Host(host_func) => {
                 if unlikely(host_func.ty != *call_ty) {
                     return ControlFlow::Break(Some(
@@ -366,27 +390,9 @@ impl<'store, 'stack> Executor<'store, 'stack> {
                     ));
                 }
 
-                let host_func = host_func.clone();
-                let params = self.stack.values.pop_params(&host_func.ty.params);
-                let res =
-                    match host_func.call(FuncContext { store: self.store, module_addr: self.module.id() }, &params) {
-                        Ok(res) => res,
-                        Err(e) => return ControlFlow::Break(Some(e)),
-                    };
-
-                self.stack.values.extend_from_wasmvalues(&res);
-                self.cf.incr_instr_ptr();
-                return ControlFlow::Continue(());
+                self.exec_call_host(host_func)
             }
-        };
-
-        if unlikely(wasm_func.ty != *call_ty) {
-            return ControlFlow::Break(Some(
-                Trap::IndirectCallTypeMismatch { actual: wasm_func.ty.clone(), expected: call_ty.clone() }.into(),
-            ));
         }
-
-        self.exec_call(wasm_func.clone(), func_inst.owner)
     }
 
     fn exec_if(&mut self, else_offset: u32, end_offset: u32, (params, results): (StackHeight, StackHeight)) {

diff --git a/crates/tinywasm/src/interpreter/stack/call_stack.rs b/crates/tinywasm/src/interpreter/stack/call_stack.rs
@@ -98,6 +98,20 @@ impl CallFrame {
         }
     }
 
+    pub(crate) fn reuse_for(
+        &mut self,
+        func: Rc<WasmFunction>,
+        locals: Locals,
+        block_depth: u32,
+        module_addr: ModuleInstanceAddr,
+    ) {
+        self.func_instance = func;
+        self.module_addr = module_addr;
+        self.locals = locals;
+        self.block_ptr = block_depth;
+        self.instr_ptr = 0; // Reset to function entry
+    }
+
     /// Break to a block at the given index (relative to the current frame)
     /// Returns `None` if there is no block at the given index (e.g. if we need to return, this is handled by the caller)
     #[inline]