From 056be42c0be2a4ac43fd50ab3c34c269f24244c9 Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Sat, 1 May 2021 03:19:01 +0430
Subject: [PATCH] LibWasm: Start implementing a naive bytecode interpreter

As the parser now flattens out the instructions and inserts synthetic
nesting/structured instructions where needed, we can treat the whole
thing as a simple parsed bytecode stream.
This currently knows how to execute the following instructions:
- unreachable
- nop
- local.get
- local.set
- {i,f}{32,64}.const
- block
- loop
- if/else
- branch / branch_if
- i32_add
- i32_and/or/xor
- i32_ne

This also extends the 'wasm' utility to optionally execute the first
function in the module with optionally user-supplied arguments.
---
 AK/Debug.h.in                                 |   3 +
 Meta/CMake/all_the_debug_macros.cmake         |   1 +
 .../LibWasm/AbstractMachine/AbstractMachine.h |  37 +-
 .../LibWasm/AbstractMachine/Configuration.cpp |  29 ++
 .../LibWasm/AbstractMachine/Configuration.h   |   6 +-
 .../LibWasm/AbstractMachine/Interpreter.cpp   | 393 +++++++++++++++++-
 .../LibWasm/AbstractMachine/Interpreter.h     |   5 +
 .../Libraries/LibWasm/Printer/Printer.cpp     |   2 +-
 Userland/Libraries/LibWasm/Printer/Printer.h  |   2 +
 Userland/Utilities/wasm.cpp                   |  65 ++-
 10 files changed, 513 insertions(+), 30 deletions(-)

diff --git a/AK/Debug.h.in b/AK/Debug.h.in
index cdbbb622dbe..a037bbdf9bc 100644
--- a/AK/Debug.h.in
+++ b/AK/Debug.h.in
@@ -422,3 +422,6 @@
 #cmakedefine01 WSSCREEN_DEBUG
 #endif
 
+#ifndef WASM_TRACE_DEBUG
+#cmakedefine01 WASM_TRACE_DEBUG
+#endif
diff --git a/Meta/CMake/all_the_debug_macros.cmake b/Meta/CMake/all_the_debug_macros.cmake
index cb8297a1931..e89e4d19620 100644
--- a/Meta/CMake/all_the_debug_macros.cmake
+++ b/Meta/CMake/all_the_debug_macros.cmake
@@ -179,6 +179,7 @@ set(LINE_EDITOR_DEBUG ON)
 set(LANGUAGE_SERVER_DEBUG ON)
 set(GL_DEBUG ON)
 set(WASM_BINPARSER_DEBUG ON)
+set(WASM_TRACE_DEBUG ON)
 set(PDF_DEBUG ON)
 set(SOLITAIRE_DEBUG ON)
 
diff --git a/Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h b/Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h
index f97b747a1f5..badd3422892 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h
+++ b/Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h
@@ -49,7 +49,7 @@ public:
     }
 
     template<typename T>
-    requires(sizeof(T) <= sizeof(u64)) explicit Value(ValueType type, T raw_value)
+    requires(sizeof(T) == sizeof(u64)) explicit Value(ValueType type, T raw_value)
         : m_value(0)
         , m_type(type)
     {
@@ -89,6 +89,33 @@ public:
     {
     }
 
+    Value& operator=(Value&& value)
+    {
+        m_value = move(value.m_value);
+        m_type = move(value.m_type);
+        return *this;
+    }
+
+    template<typename T>
+    Optional<T> to()
+    {
+        Optional<T> result;
+        m_value.visit(
+            [&](auto value) {
+                if constexpr (!IsSame<T, FunctionAddress> && !IsSame<T, ExternAddress>)
+                    result = value;
+            },
+            [&](const FunctionAddress& address) {
+                if constexpr (IsSame<T, FunctionAddress>)
+                    result = address;
+            },
+            [&](const ExternAddress& address) {
+                if constexpr (IsSame<T, ExternAddress>)
+                    result = address;
+            });
+        return result;
+    }
+
     auto& type() const { return m_type; }
     auto& value() const { return m_value; }
 
@@ -317,14 +344,17 @@ private:
 
 class Label {
 public:
-    explicit Label(InstructionPointer continuation)
-        : m_continuation(continuation)
+    explicit Label(size_t arity, InstructionPointer continuation)
+        : m_arity(arity)
+        , m_continuation(continuation)
     {
     }
 
     auto continuation() const { return m_continuation; }
+    auto arity() const { return m_arity; }
 
 private:
+    size_t m_arity { 0 };
     InstructionPointer m_continuation;
 };
 
@@ -342,6 +372,7 @@ public:
 
     auto& module() const { return m_module; }
     auto& locals() const { return m_locals; }
+    auto& locals() { return m_locals; }
     auto& expression() const { return m_expression; }
     auto arity() const { return m_arity; }
 
diff --git a/Userland/Libraries/LibWasm/AbstractMachine/Configuration.cpp b/Userland/Libraries/LibWasm/AbstractMachine/Configuration.cpp
index 6666f8598ff..2da24f00227 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/Configuration.cpp
+++ b/Userland/Libraries/LibWasm/AbstractMachine/Configuration.cpp
@@ -74,4 +74,33 @@ Result Configuration::execute()
     return Result { move(results_moved) };
 }
 
+void Configuration::dump_stack()
+{
+    for (const auto& entry : stack().entries()) {
+        entry.visit(
+            [](const NonnullOwnPtr<Value>& v) {
+                v->value().visit([]<typename T>(const T& v) {
+                    if constexpr (IsIntegral<T> || IsFloatingPoint<T>)
+                        dbgln("    {}", v);
+                    else
+                        dbgln("    *{}", v.value());
+                });
+            },
+            [](const NonnullOwnPtr<Frame>& f) {
+                dbgln("    frame({})", f->arity());
+                for (auto& local : f->locals()) {
+                    local.value().visit([]<typename T>(const T& v) {
+                        if constexpr (IsIntegral<T> || IsFloatingPoint<T>)
+                            dbgln("        {}", v);
+                        else
+                            dbgln("        *{}", v.value());
+                    });
+                }
+            },
+            [](const NonnullOwnPtr<Label>& l) {
+                dbgln("    label({}) -> {}", l->arity(), l->continuation());
+            });
+    }
+}
+
 }
diff --git a/Userland/Libraries/LibWasm/AbstractMachine/Configuration.h b/Userland/Libraries/LibWasm/AbstractMachine/Configuration.h
index c8a944dffc4..56caf7423ba 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/Configuration.h
+++ b/Userland/Libraries/LibWasm/AbstractMachine/Configuration.h
@@ -24,7 +24,7 @@ public:
     {
         m_current_frame = frame.ptr();
         m_stack.push(move(frame));
-        m_stack.push(make<Label>(m_current_frame->expression().instructions().size() - 1));
+        m_stack.push(make<Label>(m_current_frame->arity(), m_current_frame->expression().instructions().size() - 1));
     }
     auto& frame() const { return m_current_frame; }
     auto& frame() { return m_current_frame; }
@@ -34,10 +34,14 @@ public:
     auto& depth() { return m_depth; }
     auto& stack() const { return m_stack; }
     auto& stack() { return m_stack; }
+    auto& store() const { return m_store; }
+    auto& store() { return m_store; }
 
     Result call(FunctionAddress, Vector<Value> arguments);
     Result execute();
 
+    void dump_stack();
+
 private:
     Store& m_store;
     Frame* m_current_frame { nullptr };
diff --git a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
index da4148b2e74..57652cb68aa 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
+++ b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
@@ -4,20 +4,403 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Debug.h>
 #include <LibWasm/AbstractMachine/AbstractMachine.h>
 #include <LibWasm/AbstractMachine/Configuration.h>
 #include <LibWasm/AbstractMachine/Interpreter.h>
 #include <LibWasm/Opcode.h>
+#include <LibWasm/Printer/Printer.h>
 
 namespace Wasm {
 
 void Interpreter::interpret(Configuration& configuration)
 {
-    // FIXME: Interpret stuff
-    dbgln("FIXME: Interpret stuff!");
-    // Push some dummy values
-    for (size_t i = 0; i < configuration.frame()->arity(); ++i)
-        configuration.stack().push(make<Value>(0));
+    auto& instructions = configuration.frame()->expression().instructions();
+    auto max_ip_value = InstructionPointer { instructions.size() };
+    auto& current_ip_value = configuration.ip();
+
+    while (current_ip_value < max_ip_value) {
+        auto& instruction = instructions[current_ip_value.value()];
+        interpret(configuration, current_ip_value, instruction);
+        ++current_ip_value;
+    }
 }
 
+void Interpreter::branch_to_label(Configuration& configuration, LabelIndex index)
+{
+    auto label = configuration.nth_label(index.value());
+    VERIFY(label.has_value());
+    NonnullOwnPtrVector<Value> results;
+    // Pop results in order
+    for (size_t i = 0; i < label->arity(); ++i)
+        results.append(move(configuration.stack().pop().get<NonnullOwnPtr<Value>>()));
+
+    size_t drop_count = index.value() + 1;
+    if (label->continuation() < configuration.ip())
+        --drop_count;
+
+    for (; !configuration.stack().is_empty();) {
+        auto entry = configuration.stack().pop();
+        if (entry.has<NonnullOwnPtr<Label>>()) {
+            if (drop_count-- == 0)
+                break;
+        }
+    }
+
+    // Push results in reverse
+    for (size_t i = results.size(); i > 0; --i)
+        configuration.stack().push(move(static_cast<Vector<NonnullOwnPtr<Value>>&>(results)[i - 1]));
+
+    configuration.ip() = label->continuation() + 1;
+}
+
+ReadonlyBytes Interpreter::load_from_memory(Configuration& configuration, const Instruction& instruction, size_t size)
+{
+    auto& address = configuration.frame()->module().memories().first();
+    auto memory = configuration.store().get(address);
+    VERIFY(memory);
+    auto& arg = instruction.arguments().get<Instruction::MemoryArgument>();
+    auto base = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+    VERIFY(base.has_value());
+    auto instance_address = base.value() + static_cast<i64>(arg.offset);
+    if (instance_address < 0 || static_cast<u64>(instance_address + size) > memory->size()) {
+        dbgln("LibWasm: Memory access out of bounds (expected 0 > {} and {} > {})", instance_address, instance_address + size, memory->size());
+        return {};
+    }
+    return memory->data().bytes().slice(instance_address, size);
+}
+
+void Interpreter::interpret(Configuration& configuration, InstructionPointer& ip, const Instruction& instruction)
+{
+    dbgln_if(WASM_TRACE_DEBUG, "Executing instruction {} at ip {}", instruction_name(instruction.opcode()), ip.value());
+    if constexpr (WASM_TRACE_DEBUG)
+        configuration.dump_stack();
+    switch (instruction.opcode().value()) {
+    case Instructions::unreachable.value():
+        VERIFY_NOT_REACHED(); // FIXME: This is definitely not right :)
+    case Instructions::nop.value():
+        return;
+    case Instructions::local_get.value():
+        configuration.stack().push(make<Value>(configuration.frame()->locals()[instruction.arguments().get<LocalIndex>().value()]));
+        return;
+    case Instructions::local_set.value(): {
+        auto entry = configuration.stack().pop();
+        configuration.frame()->locals()[instruction.arguments().get<LocalIndex>().value()] = move(*entry.get<NonnullOwnPtr<Value>>());
+        return;
+    }
+    case Instructions::i32_const.value():
+        configuration.stack().push(make<Value>(ValueType { ValueType::I32 }, static_cast<i64>(instruction.arguments().get<i32>())));
+        return;
+    case Instructions::i64_const.value():
+        configuration.stack().push(make<Value>(ValueType { ValueType::I64 }, instruction.arguments().get<i64>()));
+        return;
+    case Instructions::f32_const.value():
+        configuration.stack().push(make<Value>(ValueType { ValueType::F32 }, static_cast<double>(instruction.arguments().get<float>())));
+        return;
+    case Instructions::f64_const.value():
+        configuration.stack().push(make<Value>(ValueType { ValueType::F64 }, instruction.arguments().get<double>()));
+        return;
+    case Instructions::block.value(): {
+        size_t arity = 0;
+        auto& args = instruction.arguments().get<Instruction::StructuredInstructionArgs>();
+        if (args.block_type.kind() != BlockType::Empty)
+            arity = 1;
+        configuration.stack().push(make<Label>(arity, args.end_ip));
+        return;
+    }
+    case Instructions::loop.value(): {
+        size_t arity = 0;
+        auto& args = instruction.arguments().get<Instruction::StructuredInstructionArgs>();
+        if (args.block_type.kind() != BlockType::Empty)
+            arity = 1;
+        configuration.stack().push(make<Label>(arity, ip.value() + 1));
+        return;
+    }
+    case Instructions::if_.value(): {
+        size_t arity = 0;
+        auto& args = instruction.arguments().get<Instruction::StructuredInstructionArgs>();
+        if (args.block_type.kind() != BlockType::Empty)
+            arity = 1;
+
+        auto entry = configuration.stack().pop();
+        auto value = entry.get<NonnullOwnPtr<Value>>()->to<i32>();
+        VERIFY(value.has_value());
+        configuration.stack().push(make<Label>(arity, args.end_ip));
+        if (value.value() == 0) {
+            if (args.else_ip.has_value()) {
+                configuration.ip() = args.else_ip.value();
+            } else {
+                configuration.ip() = args.end_ip;
+                configuration.stack().pop();
+            }
+        }
+        return;
+    }
+    case Instructions::structured_end.value():
+        return;
+    case Instructions::structured_else.value(): {
+        auto label = configuration.nth_label(0);
+        VERIFY(label.has_value());
+        NonnullOwnPtrVector<Value> results;
+        // Pop results in order
+        for (size_t i = 0; i < label->arity(); ++i)
+            results.append(move(configuration.stack().pop().get<NonnullOwnPtr<Value>>()));
+
+        // drop all locals
+        for (; !configuration.stack().is_empty();) {
+            auto entry = configuration.stack().pop();
+            if (entry.has<NonnullOwnPtr<Label>>())
+                break;
+        }
+
+        // Push results in reverse
+        for (size_t i = 1; i < results.size() + 1; ++i)
+            configuration.stack().push(move(static_cast<Vector<NonnullOwnPtr<Value>>&>(results)[results.size() - i]));
+
+        if (instruction.opcode() == Instructions::structured_end)
+            return;
+
+        // Jump to the end label
+        configuration.ip() = label->continuation();
+        return;
+    }
+
+    case Instructions::br.value():
+        return branch_to_label(configuration, instruction.arguments().get<LabelIndex>());
+    case Instructions::br_if.value(): {
+        if (configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>().value_or(0) == 0)
+            return;
+        return branch_to_label(configuration, instruction.arguments().get<LabelIndex>());
+    }
+    case Instructions::br_table.value():
+    case Instructions::call.value():
+    case Instructions::call_indirect.value():
+    case Instructions::i32_load.value():
+    case Instructions::i64_load.value():
+    case Instructions::f32_load.value():
+    case Instructions::f64_load.value():
+    case Instructions::i32_load8_s.value():
+        goto unimplemented;
+    case Instructions::i32_load8_u.value(): {
+        auto slice = load_from_memory(configuration, instruction, 1);
+        VERIFY(slice.size() == 1);
+        configuration.stack().push(make<Value>(static_cast<i32>(slice[0])));
+        return;
+    }
+    case Instructions::i32_load16_s.value():
+    case Instructions::i32_load16_u.value():
+    case Instructions::i64_load8_s.value():
+    case Instructions::i64_load8_u.value():
+    case Instructions::i64_load16_s.value():
+    case Instructions::i64_load16_u.value():
+    case Instructions::i64_load32_s.value():
+    case Instructions::i64_load32_u.value():
+    case Instructions::i32_store.value():
+    case Instructions::i64_store.value():
+    case Instructions::f32_store.value():
+    case Instructions::f64_store.value():
+    case Instructions::i32_store8.value():
+    case Instructions::i32_store16.value():
+    case Instructions::i64_store8.value():
+    case Instructions::i64_store16.value():
+    case Instructions::i64_store32.value():
+    case Instructions::local_tee.value():
+    case Instructions::global_get.value():
+    case Instructions::global_set.value():
+    case Instructions::memory_size.value():
+    case Instructions::memory_grow.value():
+    case Instructions::table_get.value():
+    case Instructions::table_set.value():
+    case Instructions::select_typed.value():
+    case Instructions::ref_null.value():
+    case Instructions::ref_func.value():
+    case Instructions::ref_is_null.value():
+    case Instructions::return_.value():
+    case Instructions::drop.value():
+    case Instructions::select.value():
+    case Instructions::i32_eqz.value():
+    case Instructions::i32_eq.value():
+        goto unimplemented;
+    case Instructions::i32_ne.value(): {
+        auto lhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        auto rhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        VERIFY(lhs.has_value());
+        VERIFY(rhs.has_value());
+        configuration.stack().push(make<Value>(lhs.value() != rhs.value()));
+        return;
+    }
+    case Instructions::i32_lts.value():
+    case Instructions::i32_ltu.value():
+    case Instructions::i32_gts.value():
+    case Instructions::i32_gtu.value():
+    case Instructions::i32_les.value():
+    case Instructions::i32_leu.value():
+    case Instructions::i32_ges.value():
+    case Instructions::i32_geu.value():
+    case Instructions::i64_eqz.value():
+    case Instructions::i64_eq.value():
+    case Instructions::i64_ne.value():
+    case Instructions::i64_lts.value():
+    case Instructions::i64_ltu.value():
+    case Instructions::i64_gts.value():
+    case Instructions::i64_gtu.value():
+    case Instructions::i64_les.value():
+    case Instructions::i64_leu.value():
+    case Instructions::i64_ges.value():
+    case Instructions::i64_geu.value():
+    case Instructions::f32_eq.value():
+    case Instructions::f32_ne.value():
+    case Instructions::f32_lt.value():
+    case Instructions::f32_gt.value():
+    case Instructions::f32_le.value():
+    case Instructions::f32_ge.value():
+    case Instructions::f64_eq.value():
+    case Instructions::f64_ne.value():
+    case Instructions::f64_lt.value():
+    case Instructions::f64_gt.value():
+    case Instructions::f64_le.value():
+    case Instructions::f64_ge.value():
+    case Instructions::i32_clz.value():
+    case Instructions::i32_ctz.value():
+    case Instructions::i32_popcnt.value():
+        goto unimplemented;
+    case Instructions::i32_add.value(): {
+        auto lhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        auto rhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        VERIFY(lhs.has_value());
+        VERIFY(rhs.has_value());
+        configuration.stack().push(make<Value>(lhs.value() + rhs.value()));
+        return;
+    }
+    case Instructions::i32_sub.value():
+    case Instructions::i32_mul.value():
+    case Instructions::i32_divs.value():
+    case Instructions::i32_divu.value():
+    case Instructions::i32_rems.value():
+    case Instructions::i32_remu.value():
+        goto unimplemented;
+    case Instructions::i32_and.value(): {
+        auto lhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        auto rhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        VERIFY(lhs.has_value());
+        VERIFY(rhs.has_value());
+        configuration.stack().push(make<Value>(lhs.value() & rhs.value()));
+        return;
+    }
+    case Instructions::i32_or.value(): {
+        auto lhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        auto rhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        VERIFY(lhs.has_value());
+        VERIFY(rhs.has_value());
+        configuration.stack().push(make<Value>(lhs.value() | rhs.value()));
+        return;
+    }
+    case Instructions::i32_xor.value(): {
+        auto lhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        auto rhs = configuration.stack().pop().get<NonnullOwnPtr<Value>>()->to<i32>();
+        VERIFY(lhs.has_value());
+        VERIFY(rhs.has_value());
+        configuration.stack().push(make<Value>(lhs.value() ^ rhs.value()));
+        return;
+    }
+    case Instructions::i32_shl.value():
+    case Instructions::i32_shrs.value():
+    case Instructions::i32_shru.value():
+    case Instructions::i32_rotl.value():
+    case Instructions::i32_rotr.value():
+    case Instructions::i64_clz.value():
+    case Instructions::i64_ctz.value():
+    case Instructions::i64_popcnt.value():
+    case Instructions::i64_add.value():
+    case Instructions::i64_sub.value():
+    case Instructions::i64_mul.value():
+    case Instructions::i64_divs.value():
+    case Instructions::i64_divu.value():
+    case Instructions::i64_rems.value():
+    case Instructions::i64_remu.value():
+    case Instructions::i64_and.value():
+    case Instructions::i64_or.value():
+    case Instructions::i64_xor.value():
+    case Instructions::i64_shl.value():
+    case Instructions::i64_shrs.value():
+    case Instructions::i64_shru.value():
+    case Instructions::i64_rotl.value():
+    case Instructions::i64_rotr.value():
+    case Instructions::f32_abs.value():
+    case Instructions::f32_neg.value():
+    case Instructions::f32_ceil.value():
+    case Instructions::f32_floor.value():
+    case Instructions::f32_trunc.value():
+    case Instructions::f32_nearest.value():
+    case Instructions::f32_sqrt.value():
+    case Instructions::f32_add.value():
+    case Instructions::f32_sub.value():
+    case Instructions::f32_mul.value():
+    case Instructions::f32_div.value():
+    case Instructions::f32_min.value():
+    case Instructions::f32_max.value():
+    case Instructions::f32_copysign.value():
+    case Instructions::f64_abs.value():
+    case Instructions::f64_neg.value():
+    case Instructions::f64_ceil.value():
+    case Instructions::f64_floor.value():
+    case Instructions::f64_trunc.value():
+    case Instructions::f64_nearest.value():
+    case Instructions::f64_sqrt.value():
+    case Instructions::f64_add.value():
+    case Instructions::f64_sub.value():
+    case Instructions::f64_mul.value():
+    case Instructions::f64_div.value():
+    case Instructions::f64_min.value():
+    case Instructions::f64_max.value():
+    case Instructions::f64_copysign.value():
+    case Instructions::i32_wrap_i64.value():
+    case Instructions::i32_trunc_sf32.value():
+    case Instructions::i32_trunc_uf32.value():
+    case Instructions::i32_trunc_sf64.value():
+    case Instructions::i32_trunc_uf64.value():
+    case Instructions::i64_extend_si32.value():
+    case Instructions::i64_extend_ui32.value():
+    case Instructions::i64_trunc_sf32.value():
+    case Instructions::i64_trunc_uf32.value():
+    case Instructions::i64_trunc_sf64.value():
+    case Instructions::i64_trunc_uf64.value():
+    case Instructions::f32_convert_si32.value():
+    case Instructions::f32_convert_ui32.value():
+    case Instructions::f32_convert_si64.value():
+    case Instructions::f32_convert_ui64.value():
+    case Instructions::f32_demote_f64.value():
+    case Instructions::f64_convert_si32.value():
+    case Instructions::f64_convert_ui32.value():
+    case Instructions::f64_convert_si64.value():
+    case Instructions::f64_convert_ui64.value():
+    case Instructions::f64_promote_f32.value():
+    case Instructions::i32_reinterpret_f32.value():
+    case Instructions::i64_reinterpret_f64.value():
+    case Instructions::f32_reinterpret_i32.value():
+    case Instructions::f64_reinterpret_i64.value():
+    case Instructions::i32_trunc_sat_f32_s.value():
+    case Instructions::i32_trunc_sat_f32_u.value():
+    case Instructions::i32_trunc_sat_f64_s.value():
+    case Instructions::i32_trunc_sat_f64_u.value():
+    case Instructions::i64_trunc_sat_f32_s.value():
+    case Instructions::i64_trunc_sat_f32_u.value():
+    case Instructions::i64_trunc_sat_f64_s.value():
+    case Instructions::i64_trunc_sat_f64_u.value():
+    case Instructions::memory_init.value():
+    case Instructions::data_drop.value():
+    case Instructions::memory_copy.value():
+    case Instructions::memory_fill.value():
+    case Instructions::table_init.value():
+    case Instructions::elem_drop.value():
+    case Instructions::table_copy.value():
+    case Instructions::table_grow.value():
+    case Instructions::table_size.value():
+    case Instructions::table_fill.value():
+    default:
+    unimplemented:;
+        dbgln("Instruction '{}' not implemented", instruction_name(instruction.opcode()));
+        return;
+    }
+}
 }
diff --git a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.h b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.h
index 2c3426fc84c..1da5680adfe 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.h
+++ b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.h
@@ -12,6 +12,11 @@ namespace Wasm {
 
 struct Interpreter {
     void interpret(Configuration&);
+
+private:
+    void interpret(Configuration&, InstructionPointer&, const Instruction&);
+    void branch_to_label(Configuration&, LabelIndex);
+    ReadonlyBytes load_from_memory(Configuration&, const Instruction&, size_t);
 };
 
 }
diff --git a/Userland/Libraries/LibWasm/Printer/Printer.cpp b/Userland/Libraries/LibWasm/Printer/Printer.cpp
index f02ac201038..7fd0c3eda22 100644
--- a/Userland/Libraries/LibWasm/Printer/Printer.cpp
+++ b/Userland/Libraries/LibWasm/Printer/Printer.cpp
@@ -14,7 +14,7 @@ struct Names {
     static HashMap<OpCode, String> instruction_names;
 };
 
-static String instruction_name(const OpCode& opcode)
+String instruction_name(const OpCode& opcode)
 {
     return Names::instruction_names.get(opcode).value_or("<unknown>");
 }
diff --git a/Userland/Libraries/LibWasm/Printer/Printer.h b/Userland/Libraries/LibWasm/Printer/Printer.h
index d1104c5ae6d..e4cfcc18ba7 100644
--- a/Userland/Libraries/LibWasm/Printer/Printer.h
+++ b/Userland/Libraries/LibWasm/Printer/Printer.h
@@ -10,6 +10,8 @@
 
 namespace Wasm {
 
+String instruction_name(const OpCode& opcode);
+
 struct Printer {
     explicit Printer(OutputStream& stream, size_t initial_indent = 0)
         : m_stream(stream)
diff --git a/Userland/Utilities/wasm.cpp b/Userland/Utilities/wasm.cpp
index 2f8516ec820..95345bb87e0 100644
--- a/Userland/Utilities/wasm.cpp
+++ b/Userland/Utilities/wasm.cpp
@@ -16,16 +16,31 @@ int main(int argc, char* argv[])
     const char* filename = nullptr;
     bool print = false;
     bool attempt_instantiate = false;
-    bool attemp_execute = false;
+    String exported_function_to_execute;
+    Vector<u64> values_to_push;
 
     Core::ArgsParser parser;
     parser.add_positional_argument(filename, "File name to parse", "file");
     parser.add_option(print, "Print the parsed module", "print", 'p');
     parser.add_option(attempt_instantiate, "Attempt to instantiate the module", "instantiate", 'i');
-    parser.add_option(attemp_execute, "Attempt to execute a function from the module (implies -i)", "execute", 'e');
+    parser.add_option(exported_function_to_execute, "Attempt to execute the named exported function from the module (implies -i)", "execute", 'e', "name");
+    parser.add_option(Core::ArgsParser::Option {
+        .requires_argument = true,
+        .help_string = "Supply arguments to the function (default=0) (expects u64, casts to required type)",
+        .long_name = "arg",
+        .short_name = 0,
+        .value_name = "u64",
+        .accept_value = [&](const char* str) -> bool {
+            if (auto v = StringView { str }.to_uint<u64>(); v.has_value()) {
+                values_to_push.append(v.value());
+                return true;
+            }
+            return false;
+        },
+    });
     parser.parse(argc, argv);
 
-    if (attemp_execute)
+    if (!exported_function_to_execute.is_empty())
         attempt_instantiate = true;
 
     auto result = Core::File::open(filename, Core::OpenMode::ReadOnly);
@@ -80,30 +95,40 @@ int main(int argc, char* argv[])
             }
         }
 
-        if (attemp_execute) {
+        if (!exported_function_to_execute.is_empty()) {
             Optional<Wasm::FunctionAddress> run_address;
             Vector<Wasm::Value> values;
-            // Pick a function that takes no args :P
-            for (auto& address : machine.module_instance().functions()) {
-                auto fn = machine.store().get(address);
-                if (!fn)
-                    continue;
-                if (auto ptr = fn->get_pointer<Wasm::WasmFunction>()) {
-                    const Wasm::FunctionType& ty = ptr->type();
-                    for (auto& param : ty.parameters()) {
-                        values.append(Wasm::Value { param, 0ull });
-                    }
-                    run_address = address;
-                    break;
+            for (auto& entry : machine.module_instance().exports()) {
+                if (entry.name() == exported_function_to_execute) {
+                    if (auto addr = entry.value().get_pointer<Wasm::FunctionAddress>())
+                        run_address = *addr;
                 }
             }
             if (!run_address.has_value()) {
-                warnln("No nullary function, sorry :(");
+                warnln("No such exported function, sorry :(");
                 return 1;
             }
-            outln("Executing ");
-            print_func(*run_address);
-            outln();
+
+            auto instance = machine.store().get(*run_address);
+            VERIFY(instance);
+
+            if (instance->has<Wasm::HostFunction>()) {
+                warnln("Exported function is a host function, cannot run that yet");
+                return 1;
+            }
+
+            for (auto& param : instance->get<Wasm::WasmFunction>().type().parameters()) {
+                if (values_to_push.is_empty())
+                    values.append(Wasm::Value { param, 0ull });
+                else
+                    values.append(Wasm::Value { param, values_to_push.take_last() });
+            }
+
+            if (print) {
+                outln("Executing ");
+                print_func(*run_address);
+                outln();
+            }
 
             auto result = machine.invoke(run_address.value(), move(values));
             if (!result.values().is_empty())