Support a proper vmctx that contains more than just memory offset

2019-01-16 16:34:24 +01:00
parent d7434fe5d2
commit a7fa7da7d4
7 changed files with 375 additions and 101 deletions
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,7 +12,7 @@ publish = false
 arrayvec = "0.4"
 dynasm = "0.2.3"
 dynasmrt = "0.2.3"
-wasmparser = "0.21.6"
+wasmparser = { path = "./wasmparser.rs" }
 capstone = "0.5.0"
 failure = "0.1.3"
 failure_derive = "0.1.3"
--- a/src/backend.rs
+++ b/src/backend.rs
@@ -9,6 +9,8 @@ use dynasmrt::{AssemblyOffset, DynamicLabel, DynasmApi, DynasmLabelApi, Executab
 use error::Error;
 use std::{iter, mem};

+use module::VmCtx;
+
 /// Size of a pointer on the target in bytes.
 const WORD_SIZE: u32 = 8;

@@ -770,15 +772,16 @@ macro_rules! load {
                vmctx: GPR,
                (offset, runtime_offset): (i32, Result<i32, GPR>)
            ) {
+                let vmctx_mem_offset = VmCtx::offset_of_memory() as i32;
                match runtime_offset {
                    Ok(imm) => {
                        dynasm!(ctx.asm
-                            ; mov $reg_ty(dst), [Rq(vmctx) + offset + imm]
+                            ; mov $reg_ty(dst), [Rq(vmctx) + offset + imm + vmctx_mem_offset]
                        );
                    }
                    Err(offset_reg) => {
                        dynasm!(ctx.asm
-                            ; mov $reg_ty(dst), [Rq(vmctx) + Rq(offset_reg) + offset]
+                            ; mov $reg_ty(dst), [Rq(vmctx) + Rq(offset_reg) + offset + vmctx_mem_offset]
                        );
                    }
                }
@@ -854,15 +857,16 @@ macro_rules! store {
                vmctx: GPR,
                (offset, runtime_offset): (i32, Result<i32, GPR>)
            ) {
+                let vmctx_mem_offset = VmCtx::offset_of_memory() as i32;
                match runtime_offset {
                    Ok(imm) => {
                        dynasm!(ctx.asm
-                            ; mov [Rq(vmctx) + offset + imm], $reg_ty(src)
+                            ; mov [Rq(vmctx) + offset + imm + vmctx_mem_offset], $reg_ty(src)
                        );
                    }
                    Err(offset_reg) => {
                        dynasm!(ctx.asm
-                            ; mov [Rq(vmctx) + Rq(offset_reg) + offset], $reg_ty(src)
+                            ; mov [Rq(vmctx) + Rq(offset_reg) + offset + vmctx_mem_offset], $reg_ty(src)
                        );
                    }
                }
@@ -1003,6 +1007,16 @@ impl Context<'_> {
    cmp_i64!(i64_gt_s, setg, setnge, |a, b| a > b);
    cmp_i64!(i64_ge_s, setge, setng, |a, b| a >= b);

+    pub fn i32_eqz(&mut self) {
+        self.push(Value::Immediate(0));
+        self.i32_eq();
+    }
+
+    pub fn i64_eqz(&mut self) {
+        self.push(Value::Immediate(0));
+        self.i64_eq();
+    }
+
    /// Pops i32 predicate and branches to the specified label
    /// if the predicate is equal to zero.
    pub fn jump_if_false(&mut self, label: Label) {
@@ -1297,7 +1311,7 @@ impl Context<'_> {
            Value::Local(loc) => StackValue::Local(loc),
            Value::Immediate(i) => StackValue::Immediate(i),
            Value::Temp(gpr) => {
-                if self.block_state.regs.free_scratch() >= 1 {
+                if self.block_state.regs.free_scratch() >= 2 {
                    StackValue::Temp(gpr)
                } else {
                    self.block_state.depth.reserve(1);
@@ -1890,12 +1904,14 @@ impl Context<'_> {
    fn save_volatile(&mut self) -> ArrayVec<[GPR; SCRATCH_REGS.len()]> {
        let mut out = ArrayVec::new();

-        // TODO: If there are no `StackValue::Pop`s that need to be popped
-        //       before we reach our `Temp` value, we can set the `StackValue`
-        //       for the register to be restored to `StackValue::Pop` (and
-        //       release the register!) instead of restoring it.
        for &reg in SCRATCH_REGS.iter() {
-            if !self.block_state.regs.is_free(reg) {
+            if self
+                .block_state
+                .stack
+                .iter()
+                .filter_map(|v| v.location(&self.block_state.locals))
+                .any(|p| p == ValueLocation::Reg(reg))
+            {
                dynasm!(self.asm
                    ; push Rq(reg)
                );
@@ -1995,6 +2011,59 @@ impl Context<'_> {
        self.push(Value::Temp(RAX));
    }

+    pub fn call_indirect(
+        &mut self,
+        valid_indexes: impl IntoIterator<Item = u32>,
+        arg_arity: u32,
+        return_arity: u32,
+    ) {
+        debug_assert!(
+            return_arity == 0 || return_arity == 1,
+            "We don't support multiple return yet"
+        );
+
+        let callee = self.pop();
+        let (callee, callee_needs_release) = self.into_reg(callee);
+
+        let vmctx = StackValue::Local(self.block_state.locals.vmctx_index());
+        let count = self.block_state.stack.len();
+
+        let label = self.create_label();
+        let index_reg = self.block_state.regs.take_scratch_gpr();
+
+        // TODO: Generate faster check using bitsets like GCC does?
+        for index in valid_indexes {
+            dynasm!(self.asm
+                ; lea Rq(index_reg), [=>self.func_starts[index as usize].1]
+                ; cmp Rd(callee), index as i32
+                ; je =>label.0
+            );
+        }
+
+        self.trap();
+        self.define_label(label);
+
+        if callee_needs_release {
+            self.block_state.regs.release_scratch_gpr(callee);
+        }
+
+        // TODO: I believe that this can't cause quadratic runtime but I'm not
+        //       certain.
+        self.block_state
+            .stack
+            .insert(count - arg_arity as usize, vmctx);
+        let cleanup = self.pass_outgoing_args(arg_arity + 1, return_arity, true);
+
+        dynasm!(self.asm
+            ; call Rq(index_reg)
+        );
+
+        self.block_state.regs.release_scratch_gpr(index_reg);
+
+        self.post_call_cleanup(cleanup);
+        self.push_function_return(return_arity);
+    }
+
    /// Call a function with the given index
    pub fn call_direct(&mut self, index: u32, arg_arity: u32, return_arity: u32) {
        debug_assert!(
--- a/src/function_body.rs
+++ b/src/function_body.rs
@@ -330,6 +330,7 @@ pub fn translate(
                }
            }
            Operator::I32Eq => ctx.i32_eq(),
+            Operator::I32Eqz => ctx.i32_eqz(),
            Operator::I32Ne => ctx.i32_neq(),
            Operator::I32LtS => ctx.i32_lt_s(),
            Operator::I32LeS => ctx.i32_le_s(),
@@ -346,6 +347,7 @@ pub fn translate(
            Operator::I32Xor => ctx.i32_xor(),
            Operator::I32Mul => ctx.i32_mul(),
            Operator::I64Eq => ctx.i64_eq(),
+            Operator::I64Eqz => ctx.i64_eqz(),
            Operator::I64Ne => ctx.i64_neq(),
            Operator::I64LtS => ctx.i64_lt_s(),
            Operator::I64LeS => ctx.i64_le_s(),
@@ -382,6 +384,20 @@ pub fn translate(
                    callee_ty.returns.len() as u32,
                );
            }
+            Operator::CallIndirect { index, table_index } => {
+                assert_eq!(table_index, 0);
+
+                let callee_ty = translation_ctx.signature(index);
+
+                // TODO: this implementation assumes that this function is locally defined.
+
+                ctx.call_indirect(
+                    (0..translation_ctx.func_count() as u32)
+                        .filter(|i| translation_ctx.func_type_index(*i) == index),
+                    callee_ty.params.len() as u32,
+                    callee_ty.returns.len() as u32,
+                );
+            }
            Operator::Nop => {}
            op => {
                unimplemented!("{:?}", op);
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,4 @@
-#![feature(plugin, test, const_slice_len, never_type)]
+#![feature(plugin, test, const_slice_len, never_type, alloc_layout_extra)]
 #![plugin(dynasm)]

 extern crate test;
@@ -28,5 +28,4 @@ mod translate_sections;
 #[cfg(test)]
 mod tests;

-pub use module::translate;
-pub use module::TranslatedModule;
+pub use module::{translate, TranslatedModule, ExecutableModule};
--- a/src/module.rs
+++ b/src/module.rs
@@ -1,21 +1,11 @@
 use backend::TranslatedCodeSection;
 use error::Error;
-use std::borrow::Cow;
-use std::mem;
+use std::{
+    hash::{Hash, Hasher},
+    mem,
+};
 use translate_sections;
-use wasmparser::{FuncType, ModuleReader, SectionCode, Type};
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct Signature {
-    params: Cow<'static, [Type]>,
-    returns: Cow<'static, [Type]>,
-}
-
-impl PartialEq<FuncType> for Signature {
-    fn eq(&self, other: &FuncType) -> bool {
-        &self.params[..] == &other.params[..] && &self.returns[..] == &other.returns[..]
-    }
-}
+use wasmparser::{FuncType, MemoryType, ModuleReader, SectionCode, TableType, Type};

 pub trait AsValueType {
    const TYPE: Type;
@@ -51,20 +41,28 @@ impl AsValueType for f64 {
    const TYPE: Type = Type::F64;
 }

-pub trait FunctionArgs {
-    unsafe fn call<T>(self, start: *const u8, vm_ctx: *const u8) -> T;
+pub trait FunctionArgs<O> {
+    type FuncType;
+
+    unsafe fn call(self, func: Self::FuncType, vm_ctx: *const u8) -> O;
+    fn into_func(start: *const u8) -> Self::FuncType;
 }

-type VmCtx = u64;
+type VmCtxPtr = u64;

 macro_rules! impl_function_args {
    ($first:ident $(, $rest:ident)*) => {
-        impl<$first, $($rest),*> FunctionArgs for ($first, $($rest),*) {
+        impl<Output, $first, $($rest),*> FunctionArgs<Output> for ($first, $($rest),*) {
+            type FuncType = unsafe extern "sysv64" fn(VmCtxPtr, $first $(, $rest)*) -> Output;
+
            #[allow(non_snake_case)]
-            unsafe fn call<T>(self, start: *const u8, vm_ctx: *const u8) -> T {
-                let func = mem::transmute::<_, extern "sysv64" fn(VmCtx, $first $(, $rest)*) -> T>(start);
+            unsafe fn call(self, func: Self::FuncType, vm_ctx: *const u8) -> Output {
                let ($first, $($rest),*) = self;
-                func(vm_ctx as VmCtx, $first $(, $rest)*)
+                func(vm_ctx as VmCtxPtr, $first $(, $rest)*)
+            }
+
+            fn into_func(start: *const u8) -> Self::FuncType {
+                unsafe { mem::transmute(start) }
            }
        }

@@ -75,10 +73,15 @@ macro_rules! impl_function_args {
        impl_function_args!($($rest),*);
    };
    () => {
-        impl FunctionArgs for () {
-            unsafe fn call<T>(self, start: *const u8, vm_ctx: *const u8) -> T {
-                let func = mem::transmute::<_, extern "sysv64" fn(VmCtx) -> T>(start);
-                func(vm_ctx as VmCtx)
+        impl<Output> FunctionArgs<Output> for () {
+            type FuncType = unsafe extern "sysv64" fn(VmCtxPtr) -> Output;
+
+            unsafe fn call(self, func: Self::FuncType, vm_ctx: *const u8) -> Output {
+                func(vm_ctx as VmCtxPtr)
+            }
+
+            fn into_func(start: *const u8) -> Self::FuncType {
+                unsafe { mem::transmute(start) }
            }
        }

@@ -90,58 +93,62 @@ macro_rules! impl_function_args {

 impl_function_args!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S);

-#[derive(Default, Debug)]
+#[derive(Default)]
 pub struct TranslatedModule {
    translated_code_section: Option<TranslatedCodeSection>,
    types: FuncTyStore,
-    // Note: This vector should never be deallocated or reallocated or the pointer
-    //       to its contents otherwise invalidated while the JIT'd code is still
-    //       callable.
    // TODO: Should we wrap this in a `Mutex` so that calling functions from multiple
    //       threads doesn't cause data races?
-    memory: Option<Vec<u8>>,
+    table: Option<(TableType, Vec<RuntimeFunc>)>,
+    memory: Option<MemoryType>,
 }

-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub enum ExecutionError {
-    FuncIndexOutOfBounds,
-    TypeMismatch,
+fn quickhash<H: Hash>(h: H) -> u64 {
+    let mut hasher = std::collections::hash_map::DefaultHasher::new();
+    h.hash(&mut hasher);
+    hasher.finish()
 }

 impl TranslatedModule {
-    // For testing only.
-    // TODO: Handle generic signatures.
-    pub fn execute_func<Args: FunctionArgs + TypeList, T: TypeList>(
-        &self,
-        func_idx: u32,
-        args: Args,
-    ) -> Result<T, ExecutionError> {
-        let code_section = self
-            .translated_code_section
-            .as_ref()
-            .expect("no code section");
+    pub fn instantiate(mut self) -> ExecutableModule {
+        use std::alloc::{self, Layout};

-        if func_idx as usize >= self.types.func_ty_indicies.len() {
-            return Err(ExecutionError::FuncIndexOutOfBounds);
+        let slice = self
+            .table
+            .as_mut()
+            .map(|&mut (_, ref mut initial)| {
+                initial.shrink_to_fit();
+                let out = BoxSlice {
+                    ptr: initial.as_mut_ptr(),
+                    len: initial.len(),
+                };
+                mem::forget(mem::replace(initial, Default::default()));
+                out
+            })
+            .unwrap_or(BoxSlice {
+                ptr: std::ptr::NonNull::dangling().as_ptr(),
+                len: 0,
+            });
+
+        let mem_size = self.memory.map(|m| m.limits.initial).unwrap_or(0) as usize;
+        let layout = Layout::new::<VmCtx>()
+            .extend(Layout::array::<u8>(mem_size * WASM_PAGE_SIZE).unwrap())
+            .unwrap()
+            .0;
+
+        let ptr = unsafe { alloc::alloc_zeroed(layout) } as *mut VmCtx;
+
+        unsafe {
+            *ptr = VmCtx {
+                table: slice,
+                mem_size,
+            }
        }

-        let type_ = self.types.func_type(func_idx);
-
-        if (&type_.params[..], &type_.returns[..]) != (Args::TYPE_LIST, T::TYPE_LIST) {
-            return Err(ExecutionError::TypeMismatch);
+        ExecutableModule {
+            module: self,
+            context: Allocation { ptr, layout },
        }
-
-        let start_buf = code_section.func_start(func_idx as usize);
-
-        Ok(unsafe {
-            args.call(
-                start_buf,
-                self.memory
-                    .as_ref()
-                    .map(|b| b.as_ptr())
-                    .unwrap_or(std::ptr::null()),
-            )
-        })
    }

    pub fn disassemble(&self) {
@@ -152,24 +159,144 @@ impl TranslatedModule {
    }
 }

+struct Allocation<T> {
+    ptr: *mut T,
+    layout: std::alloc::Layout,
+}
+
+unsafe impl<T> Send for Allocation<T> where T: Send {}
+unsafe impl<T> Sync for Allocation<T> where T: Sync {}
+
+impl<T> Drop for Allocation<T> {
+    fn drop(&mut self) {
+        if mem::needs_drop::<T>() {
+            unsafe { std::ptr::drop_in_place::<T>(self.ptr) };
+        }
+
+        unsafe { std::alloc::dealloc(self.ptr as _, self.layout) };
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum ExecutionError {
+    FuncIndexOutOfBounds,
+    TypeMismatch,
+}
+
+pub struct ExecutableModule {
+    module: TranslatedModule,
+    context: Allocation<VmCtx>,
+}
+
+impl ExecutableModule {
+    // For testing only.
+    // TODO: Handle generic signatures.
+    pub fn execute_func<Args: FunctionArgs<T> + TypeList, T: TypeList>(
+        &self,
+        func_idx: u32,
+        args: Args,
+    ) -> Result<T, ExecutionError> {
+        let module = &self.module;
+        let code_section = module
+            .translated_code_section
+            .as_ref()
+            .expect("no code section");
+
+        if func_idx as usize >= module.types.func_ty_indicies.len() {
+            return Err(ExecutionError::FuncIndexOutOfBounds);
+        }
+
+        let type_ = module.types.func_type(func_idx);
+
+        if (&type_.params[..], &type_.returns[..]) != (Args::TYPE_LIST, T::TYPE_LIST) {
+            return Err(ExecutionError::TypeMismatch);
+        }
+
+        let start_buf = code_section.func_start(func_idx as usize);
+
+        Ok(unsafe {
+            args.call(
+                Args::into_func(start_buf),
+                self.context.ptr as *const VmCtx as *const u8,
+            )
+        })
+    }
+
+    pub fn disassemble(&self) {
+        self.module.disassemble();
+    }
+}
+
+type FuncRef = unsafe extern "sysv64" fn();
+
+#[repr(C)]
+pub struct RuntimeFunc {
+    sig_hash: u32,
+    func_start: FuncRef,
+}
+
+#[repr(C)]
+struct BoxSlice<T> {
+    len: usize,
+    ptr: *mut T,
+}
+
+#[repr(C)]
+pub struct VmCtx {
+    table: BoxSlice<RuntimeFunc>,
+    mem_size: usize,
+}
+
+unsafe impl Send for VmCtx {}
+unsafe impl Sync for VmCtx {}
+
+impl VmCtx {
+    pub fn offset_of_memory() -> usize {
+        mem::size_of::<Self>()
+    }
+}
+
+impl<T> Drop for BoxSlice<T> {
+    fn drop(&mut self) {
+        unsafe { Vec::from_raw_parts(self.ptr, self.len, self.len) };
+    }
+}
+
 #[derive(Default, Debug)]
 pub struct FuncTyStore {
    types: Vec<FuncType>,
    func_ty_indicies: Vec<u32>,
 }

+const WASM_PAGE_SIZE: usize = 65_536;
+
 impl FuncTyStore {
+    pub fn func_count(&self) -> usize {
+        self.func_ty_indicies.len()
+    }
+
+    pub fn func_type_index(&self, func_idx: u32) -> u32 {
+        self.func_ty_indicies[func_idx as usize]
+    }
+
+    pub fn signature(&self, index: u32) -> &FuncType {
+        &self.types[index as usize]
+    }
+
    pub fn func_type(&self, func_idx: u32) -> &FuncType {
-        // TODO: This assumes that there is no imported functions.
-        let func_ty_idx = self.func_ty_indicies[func_idx as usize];
-        &self.types[func_ty_idx as usize]
+        // TODO: This assumes that there are no imported functions.
+        self.signature(self.func_type_index(func_idx))
    }

    // TODO: type of a global
 }

+pub fn translate(data: &[u8]) -> Result<ExecutableModule, Error> {
+    translate_only(data).map(|m| m.instantiate())
+}
+
 /// Translate from a slice of bytes holding a wasm module.
-pub fn translate(data: &[u8]) -> Result<TranslatedModule, Error> {
+pub fn translate_only(data: &[u8]) -> Result<TranslatedModule, Error> {
    let mut reader = ModuleReader::new(data)?;
    let mut output = TranslatedModule::default();

@@ -214,7 +341,9 @@ pub fn translate(data: &[u8]) -> Result<TranslatedModule, Error> {

    if let SectionCode::Table = section.code {
        let tables = section.get_table_section_reader()?;
-        translate_sections::table(tables)?;
+        let tables = translate_sections::table(tables)?;
+
+        assert!(tables.len() <= 1);

        reader.skip_custom_sections()?;
        if reader.eof() {
@@ -235,7 +364,7 @@ pub fn translate(data: &[u8]) -> Result<TranslatedModule, Error> {
        if !mem.is_empty() {
            let mem = mem[0];
            assert_eq!(Some(mem.limits.initial), mem.limits.maximum);
-            output.memory = Some(vec![0; mem.limits.initial as usize * 65_536]);
+            output.memory = Some(mem);
        }

        reader.skip_custom_sections()?;
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -1,7 +1,7 @@
-use super::{module::ExecutionError, translate, TranslatedModule};
+use super::{module::ExecutionError, translate, ExecutableModule};
 use wabt;

-fn translate_wat(wat: &str) -> TranslatedModule {
+fn translate_wat(wat: &str) -> ExecutableModule {
    let wasm = wabt::wat2wasm(wat).unwrap();
    let compiled = translate(&wasm).unwrap();
    compiled
@@ -20,18 +20,18 @@ fn empty() {
 }

 mod op32 {
-    use super::{translate_wat, TranslatedModule};
+    use super::{translate_wat, ExecutableModule};

    macro_rules! binop_test {
        ($op:ident, $func:expr) => {
            mod $op {
-                use super::{translate_wat, TranslatedModule};
+                use super::{translate_wat, ExecutableModule};
                use std::sync::Once;

                const OP: &str = stringify!($op);

                lazy_static! {
-                    static ref AS_PARAMS: TranslatedModule = translate_wat(&format!(
+                    static ref AS_PARAMS: ExecutableModule = translate_wat(&format!(
                        "
                        (module (func (param i32) (param i32) (result i32)
                            (i32.{op} (get_local 0) (get_local 1))))
@@ -101,7 +101,7 @@ mod op32 {
 }

 mod op64 {
-    use super::{translate_wat, TranslatedModule};
+    use super::{translate_wat, ExecutableModule};

    macro_rules! binop_test {
        ($op:ident, $func:expr) => {
@@ -109,13 +109,13 @@ mod op64 {
        };
        ($op:ident, $func:expr, $retty:ident) => {
            mod $op {
-                use super::{translate_wat, TranslatedModule};
+                use super::{translate_wat, ExecutableModule};

                const RETTY: &str = stringify!($retty);
                const OP: &str = stringify!($op);

                lazy_static! {
-                    static ref AS_PARAMS: TranslatedModule = translate_wat(&format!("
+                    static ref AS_PARAMS: ExecutableModule = translate_wat(&format!("
                        (module (func (param i64) (param i64) (result {retty})
                            (i64.{op} (get_local 0) (get_local 1))))
                    ", retty = RETTY, op = OP));
@@ -200,7 +200,7 @@ quickcheck! {
        "#;

        lazy_static! {
-            static ref TRANSLATED: TranslatedModule = translate_wat(CODE);
+            static ref TRANSLATED: ExecutableModule = translate_wat(CODE);
        }

        let out = TRANSLATED.execute_func::<(u32, u32), u32>(0, (a, b)).unwrap();
@@ -227,7 +227,7 @@ quickcheck! {
        "#;

        lazy_static! {
-            static ref TRANSLATED: TranslatedModule = translate_wat(CODE);
+            static ref TRANSLATED: ExecutableModule = translate_wat(CODE);
        }

        let out = TRANSLATED.execute_func::<(u32, u32), u32>(0, (a, b));
@@ -613,7 +613,7 @@ quickcheck! {
        }

        lazy_static! {
-            static ref TRANSLATED: TranslatedModule = {
+            static ref TRANSLATED: ExecutableModule = {
                let out = translate_wat(CODE);
                out.disassemble();
                out
@@ -871,6 +871,66 @@ fn nested_storage_calls() {

    assert_eq!(translated.execute_func::<(), i32>(0, ()), Ok(1));
 }
+
+#[test]
+fn call_indirect() {
+    const CODE: &str = r#"
+(module
+  (type $over-i64 (func (param i64) (result i64)))
+
+  (table anyfunc
+    (elem
+      $dispatch $fac $fib
+    )
+  )
+
+  (func $dispatch (param i32 i64) (result i64)
+    (call_indirect (type $over-i64) (get_local 1) (get_local 0))
+  )
+
+  (func $fac (type $over-i64)
+    (if (result i64) (i64.eqz (get_local 0))
+      (then (i64.const 1))
+      (else
+        (i64.mul
+          (get_local 0)
+          (call_indirect (type $over-i64)
+            (i64.sub (get_local 0) (i64.const 1))
+            (i32.const 1)
+          )
+        )
+      )
+    )
+  )
+
+  (func $fib (type $over-i64)
+    (if (result i64) (i64.le_u (get_local 0) (i64.const 1))
+      (then (i64.const 1))
+      (else
+        (i64.add
+          (call_indirect (type $over-i64)
+            (i64.sub (get_local 0) (i64.const 2))
+            (i32.const 2)
+          )
+          (call_indirect (type $over-i64)
+            (i64.sub (get_local 0) (i64.const 1))
+            (i32.const 2)
+          )
+        )
+      )
+    )
+  )
+)"#;
+
+    let wasm = wabt::wat2wasm(CODE).unwrap();
+    let module = translate(&wasm).unwrap();
+
+    module.disassemble();
+
+    assert_eq!(module.execute_func::<(i32, i64), i64>(0, (1, 10)).unwrap(), 3628800);
+    assert_eq!(module.execute_func::<(i32, i64), i64>(0, (2, 10)).unwrap(), 89);
+}
+
 #[bench]
 fn bench_fibonacci_compile(b: &mut test::Bencher) {
    let wasm = wabt::wat2wasm(FIBONACCI).unwrap();
--- a/src/translate_sections.rs
+++ b/src/translate_sections.rs
@@ -7,7 +7,8 @@ use wasmparser::{
    CodeSectionReader, Data, DataSectionReader, Element, ElementSectionReader, Export,
    ExportSectionReader, ExternalKind, FuncType, FunctionSectionReader, Global,
    GlobalSectionReader, GlobalType, Import, ImportSectionEntryType, ImportSectionReader,
-    MemorySectionReader, MemoryType, Operator, TableSectionReader, Type, TypeSectionReader,
+    MemorySectionReader, MemoryType, Operator, TableSectionReader, TableType, Type,
+    TypeSectionReader,
 };

 /// Parses the Type section of the wasm module.
@@ -35,11 +36,11 @@ pub fn function(functions: FunctionSectionReader) -> Result<Vec<u32>, Error> {
 }

 /// Parses the Table section of the wasm module.
-pub fn table(tables: TableSectionReader) -> Result<(), Error> {
-    for entry in tables {
-        entry?; // TODO
-    }
-    Ok(())
+pub fn table(tables: TableSectionReader) -> Result<Vec<TableType>, Error> {
+    tables
+        .into_iter()
+        .map(|r| r.map_err(Into::into))
+        .collect()
 }

 /// Parses the Memory section of the wasm module.