webkitgtk-2.16.5HEADwebkitgtk-2.16.5master

1 files changed, 636 insertions, 0 deletions

diff --git a/Source/JavaScriptCore/wasm/WasmFunctionParser.h b/Source/JavaScriptCore/wasm/WasmFunctionParser.h
new file mode 100644
index 000000000..64e3b36d3
--- /dev/null
+++ b/Source/JavaScriptCore/wasm/WasmFunctionParser.h
@@ -0,0 +1,636 @@
+/*
+ * Copyright (C) 2016 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#if ENABLE(WEBASSEMBLY)
+
+#include "WasmParser.h"
+#include <wtf/DataLog.h>
+
+namespace JSC { namespace Wasm {
+
+enum class BlockType {
+    If,
+    Block,
+    Loop,
+    TopLevel
+};
+
+template<typename Context>
+class FunctionParser : public Parser<void> {
+public:
+    typedef typename Context::ExpressionType ExpressionType;
+    typedef typename Context::ControlType ControlType;
+    typedef typename Context::ExpressionList ExpressionList;
+
+    FunctionParser(VM*, Context&, const uint8_t* functionStart, size_t functionLength, const Signature*, const ModuleInformation&, const Vector<SignatureIndex>&);
+
+    Result WARN_UNUSED_RETURN parse();
+
+    struct ControlEntry {
+        ExpressionList enclosedExpressionStack;
+        ControlType controlData;
+    };
+
+private:
+    static const bool verbose = false;
+
+    PartialResult WARN_UNUSED_RETURN parseBody();
+    PartialResult WARN_UNUSED_RETURN parseExpression(OpType);
+    PartialResult WARN_UNUSED_RETURN parseUnreachableExpression(OpType);
+    PartialResult WARN_UNUSED_RETURN unifyControl(Vector<ExpressionType>&, unsigned level);
+
+#define WASM_TRY_POP_EXPRESSION_STACK_INTO(result, what) do {                               \
+        WASM_PARSER_FAIL_IF(m_expressionStack.isEmpty(), "can't pop empty stack in " what); \
+        result = m_expressionStack.takeLast();                                              \
+    } while (0)
+
+    template<OpType>
+    PartialResult WARN_UNUSED_RETURN unaryCase();
+
+    template<OpType>
+    PartialResult WARN_UNUSED_RETURN binaryCase();
+
+#define WASM_TRY_ADD_TO_CONTEXT(add_expression) WASM_FAIL_IF_HELPER_FAILS(m_context.add_expression)
+
+    // FIXME add a macro as above for WASM_TRY_APPEND_TO_CONTROL_STACK https://bugs.webkit.org/show_bug.cgi?id=165862
+
+    Context& m_context;
+    ExpressionList m_expressionStack;
+    Vector<ControlEntry> m_controlStack;
+    const Signature* m_signature;
+    const ModuleInformation& m_info;
+    const Vector<SignatureIndex>& m_moduleSignatureIndicesToUniquedSignatureIndices;
+    unsigned m_unreachableBlocks { 0 };
+};
+
+template<typename Context>
+FunctionParser<Context>::FunctionParser(VM* vm, Context& context, const uint8_t* functionStart, size_t functionLength, const Signature* signature, const ModuleInformation& info, const Vector<SignatureIndex>& moduleSignatureIndicesToUniquedSignatureIndices)
+    : Parser(vm, functionStart, functionLength)
+    , m_context(context)
+    , m_signature(signature)
+    , m_info(info)
+    , m_moduleSignatureIndicesToUniquedSignatureIndices(moduleSignatureIndicesToUniquedSignatureIndices)
+{
+    if (verbose)
+        dataLogLn("Parsing function starting at: ", (uintptr_t)functionStart, " of length: ", functionLength);
+}
+
+template<typename Context>
+auto FunctionParser<Context>::parse() -> Result
+{
+    uint32_t localCount;
+
+    WASM_PARSER_FAIL_IF(!m_context.addArguments(m_signature), "can't add ", m_signature->argumentCount(), " arguments to Function");
+    WASM_PARSER_FAIL_IF(!parseVarUInt32(localCount), "can't get local count");
+    WASM_PARSER_FAIL_IF(localCount == std::numeric_limits<uint32_t>::max(), "Function section's local count is too big ", localCount);
+
+    for (uint32_t i = 0; i < localCount; ++i) {
+        uint32_t numberOfLocals;
+        Type typeOfLocal;
+
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(numberOfLocals), "can't get Function's number of locals in group ", i);
+        WASM_PARSER_FAIL_IF(numberOfLocals == std::numeric_limits<uint32_t>::max(), "Function section's ", i, "th local group count is too big ", numberOfLocals);
+        WASM_PARSER_FAIL_IF(!parseValueType(typeOfLocal), "can't get Function local's type in group ", i);
+        WASM_PARSER_FAIL_IF(!m_context.addLocal(typeOfLocal, numberOfLocals), "can't add ", numberOfLocals, " Function locals from group ", i);
+    }
+
+    WASM_FAIL_IF_HELPER_FAILS(parseBody());
+
+    return { };
+}
+
+template<typename Context>
+auto FunctionParser<Context>::parseBody() -> PartialResult
+{
+    m_controlStack.append({ ExpressionList(), m_context.addTopLevel(m_signature->returnType()) });
+    uint8_t op;
+    while (m_controlStack.size()) {
+        WASM_PARSER_FAIL_IF(!parseUInt8(op), "can't decode opcode");
+        WASM_PARSER_FAIL_IF(!isValidOpType(op), "invalid opcode ", op);
+
+        if (verbose) {
+            dataLogLn("processing op (", m_unreachableBlocks, "): ",  RawPointer(reinterpret_cast<void*>(op)), ", ", makeString(static_cast<OpType>(op)), " at offset: ", RawPointer(reinterpret_cast<void*>(m_offset)));
+            m_context.dump(m_controlStack, &m_expressionStack);
+        }
+
+        if (m_unreachableBlocks)
+            WASM_FAIL_IF_HELPER_FAILS(parseUnreachableExpression(static_cast<OpType>(op)));
+        else
+            WASM_FAIL_IF_HELPER_FAILS(parseExpression(static_cast<OpType>(op)));
+    }
+
+    ASSERT(op == OpType::End);
+    return { };
+}
+
+template<typename Context>
+template<OpType op>
+auto FunctionParser<Context>::binaryCase() -> PartialResult
+{
+    ExpressionType right;
+    ExpressionType left;
+    ExpressionType result;
+
+    WASM_TRY_POP_EXPRESSION_STACK_INTO(right, "binary right");
+    WASM_TRY_POP_EXPRESSION_STACK_INTO(left, "binary left");
+    WASM_TRY_ADD_TO_CONTEXT(template addOp<op>(left, right, result));
+
+    m_expressionStack.append(result);
+    return { };
+}
+
+template<typename Context>
+template<OpType op>
+auto FunctionParser<Context>::unaryCase() -> PartialResult
+{
+    ExpressionType value;
+    ExpressionType result;
+
+    WASM_TRY_POP_EXPRESSION_STACK_INTO(value, "unary");
+    WASM_TRY_ADD_TO_CONTEXT(template addOp<op>(value, result));
+
+    m_expressionStack.append(result);
+    return { };
+}
+
+template<typename Context>
+auto FunctionParser<Context>::parseExpression(OpType op) -> PartialResult
+{
+    switch (op) {
+#define CREATE_CASE(name, id, b3op, inc) case OpType::name: return binaryCase<OpType::name>();
+    FOR_EACH_WASM_BINARY_OP(CREATE_CASE)
+#undef CREATE_CASE
+
+#define CREATE_CASE(name, id, b3op, inc) case OpType::name: return unaryCase<OpType::name>();
+    FOR_EACH_WASM_UNARY_OP(CREATE_CASE)
+#undef CREATE_CASE
+
+    case Select: {
+        ExpressionType condition;
+        ExpressionType zero;
+        ExpressionType nonZero;
+
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(condition, "select condition");
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(zero, "select zero");
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(nonZero, "select non-zero");
+
+        ExpressionType result;
+        WASM_TRY_ADD_TO_CONTEXT(addSelect(condition, nonZero, zero, result));
+
+        m_expressionStack.append(result);
+        return { };
+    }
+
+#define CREATE_CASE(name, id, b3op, inc) case OpType::name:
+    FOR_EACH_WASM_MEMORY_LOAD_OP(CREATE_CASE) {
+        uint32_t alignment;
+        uint32_t offset;
+        ExpressionType pointer;
+        ExpressionType result;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(alignment), "can't get load alignment");
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(offset), "can't get load offset");
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(pointer, "load pointer");
+        WASM_TRY_ADD_TO_CONTEXT(load(static_cast<LoadOpType>(op), pointer, result, offset));
+        m_expressionStack.append(result);
+        return { };
+    }
+
+    FOR_EACH_WASM_MEMORY_STORE_OP(CREATE_CASE) {
+        uint32_t alignment;
+        uint32_t offset;
+        ExpressionType value;
+        ExpressionType pointer;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(alignment), "can't get store alignment");
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(offset), "can't get store offset");
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(value, "store value");
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(pointer, "store pointer");
+        WASM_TRY_ADD_TO_CONTEXT(store(static_cast<StoreOpType>(op), pointer, value, offset));
+        return { };
+    }
+#undef CREATE_CASE
+
+    case F32Const: {
+        uint32_t constant;
+        WASM_PARSER_FAIL_IF(!parseUInt32(constant), "can't parse 32-bit floating-point constant");
+        m_expressionStack.append(m_context.addConstant(F32, constant));
+        return { };
+    }
+
+    case I32Const: {
+        int32_t constant;
+        WASM_PARSER_FAIL_IF(!parseVarInt32(constant), "can't parse 32-bit constant");
+        m_expressionStack.append(m_context.addConstant(I32, constant));
+        return { };
+    }
+
+    case F64Const: {
+        uint64_t constant;
+        WASM_PARSER_FAIL_IF(!parseUInt64(constant), "can't parse 64-bit floating-point constant");
+        m_expressionStack.append(m_context.addConstant(F64, constant));
+        return { };
+    }
+
+    case I64Const: {
+        int64_t constant;
+        WASM_PARSER_FAIL_IF(!parseVarInt64(constant), "can't parse 64-bit constant");
+        m_expressionStack.append(m_context.addConstant(I64, constant));
+        return { };
+    }
+
+    case GetLocal: {
+        uint32_t index;
+        ExpressionType result;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(index), "can't get index for get_local");
+        WASM_PARSER_FAIL_IF(!m_context.getLocal(index, result), "can't get_local at index", index);
+        m_expressionStack.append(result);
+        return { };
+    }
+
+    case SetLocal: {
+        uint32_t index;
+        ExpressionType value;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(index), "can't get index for set_local");
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(value, "set_local");
+        WASM_TRY_ADD_TO_CONTEXT(setLocal(index, value));
+        return { };
+    }
+
+    case TeeLocal: {
+        uint32_t index;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(index), "can't get index for tee_local");
+        WASM_PARSER_FAIL_IF(m_expressionStack.isEmpty(), "can't tee_local on empty expression stack");
+        WASM_TRY_ADD_TO_CONTEXT(setLocal(index, m_expressionStack.last()));
+        return { };
+    }
+
+    case GetGlobal: {
+        uint32_t index;
+        ExpressionType result;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(index), "can't get get_global's index");
+        WASM_TRY_ADD_TO_CONTEXT(getGlobal(index, result));
+        m_expressionStack.append(result);
+        return { };
+    }
+
+    case SetGlobal: {
+        uint32_t index;
+        ExpressionType value;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(index), "can't get set_global's index");
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(value, "set_global value");
+        WASM_TRY_ADD_TO_CONTEXT(setGlobal(index, value));
+        return m_context.setGlobal(index, value);
+    }
+
+    case Call: {
+        uint32_t functionIndex;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(functionIndex), "can't parse call's function index");
+        WASM_PARSER_FAIL_IF(functionIndex >= m_info.functionIndexSpaceSize(), "call function index ", functionIndex, " exceeds function index space ", m_info.functionIndexSpaceSize());
+
+        SignatureIndex calleeSignatureIndex = m_info.signatureIndexFromFunctionIndexSpace(functionIndex);
+        const Signature* calleeSignature = SignatureInformation::get(m_vm, calleeSignatureIndex);
+        WASM_PARSER_FAIL_IF(calleeSignature->argumentCount() > m_expressionStack.size(), "call function index ", functionIndex, " has ", calleeSignature->argumentCount(), " arguments, but the expression stack currently holds ", m_expressionStack.size(), " values");
+
+        size_t firstArgumentIndex = m_expressionStack.size() - calleeSignature->argumentCount();
+        Vector<ExpressionType> args;
+        WASM_PARSER_FAIL_IF(!args.tryReserveCapacity(calleeSignature->argumentCount()), "can't allocate enough memory for call's ", calleeSignature->argumentCount(), " arguments");
+        for (size_t i = firstArgumentIndex; i < m_expressionStack.size(); ++i)
+            args.uncheckedAppend(m_expressionStack[i]);
+        m_expressionStack.shrink(firstArgumentIndex);
+
+        ExpressionType result = Context::emptyExpression;
+        WASM_TRY_ADD_TO_CONTEXT(addCall(functionIndex, calleeSignature, args, result));
+
+        if (result != Context::emptyExpression)
+            m_expressionStack.append(result);
+
+        return { };
+    }
+
+    case CallIndirect: {
+        uint32_t signatureIndex;
+        uint8_t reserved;
+        WASM_PARSER_FAIL_IF(!m_info.tableInformation, "call_indirect is only valid when a table is defined or imported");
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(signatureIndex), "can't get call_indirect's signature index");
+        WASM_PARSER_FAIL_IF(!parseVarUInt1(reserved), "can't get call_indirect's reserved byte");
+        WASM_PARSER_FAIL_IF(reserved, "call_indirect's 'reserved' varuint1 must be 0x0");
+        WASM_PARSER_FAIL_IF(m_moduleSignatureIndicesToUniquedSignatureIndices.size() <= signatureIndex, "call_indirect's signature index ", signatureIndex, " exceeds known signatures ", m_moduleSignatureIndicesToUniquedSignatureIndices.size());
+
+        SignatureIndex calleeSignatureIndex = m_moduleSignatureIndicesToUniquedSignatureIndices[signatureIndex];
+        const Signature* calleeSignature = SignatureInformation::get(m_vm, calleeSignatureIndex);
+        size_t argumentCount = calleeSignature->argumentCount() + 1; // Add the callee's index.
+        WASM_PARSER_FAIL_IF(argumentCount > m_expressionStack.size(), "call_indirect expects ", argumentCount, " arguments, but the expression stack currently holds ", m_expressionStack.size(), " values");
+
+        Vector<ExpressionType> args;
+        WASM_PARSER_FAIL_IF(!args.tryReserveCapacity(argumentCount), "can't allocate enough memory for ", argumentCount, " call_indirect arguments");
+        size_t firstArgumentIndex = m_expressionStack.size() - argumentCount;
+        for (size_t i = firstArgumentIndex; i < m_expressionStack.size(); ++i)
+            args.uncheckedAppend(m_expressionStack[i]);
+        m_expressionStack.shrink(firstArgumentIndex);
+
+        ExpressionType result = Context::emptyExpression;
+        WASM_TRY_ADD_TO_CONTEXT(addCallIndirect(calleeSignature, calleeSignatureIndex, args, result));
+
+        if (result != Context::emptyExpression)
+            m_expressionStack.append(result);
+
+        return { };
+    }
+
+    case Block: {
+        Type inlineSignature;
+        WASM_PARSER_FAIL_IF(!parseResultType(inlineSignature), "can't get block's inline signature");
+        m_controlStack.append({ WTFMove(m_expressionStack), m_context.addBlock(inlineSignature) });
+        m_expressionStack = ExpressionList();
+        return { };
+    }
+
+    case Loop: {
+        Type inlineSignature;
+        WASM_PARSER_FAIL_IF(!parseResultType(inlineSignature), "can't get loop's inline signature");
+        m_controlStack.append({ WTFMove(m_expressionStack), m_context.addLoop(inlineSignature) });
+        m_expressionStack = ExpressionList();
+        return { };
+    }
+
+    case If: {
+        Type inlineSignature;
+        ExpressionType condition;
+        ControlType control;
+        WASM_PARSER_FAIL_IF(!parseResultType(inlineSignature), "can't get if's inline signature");
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(condition, "if condition");
+        WASM_TRY_ADD_TO_CONTEXT(addIf(condition, inlineSignature, control));
+        m_controlStack.append({ WTFMove(m_expressionStack), control });
+        m_expressionStack = ExpressionList();
+        return { };
+    }
+
+    case Else: {
+        WASM_PARSER_FAIL_IF(m_controlStack.size() == 1, "can't use else block at the top-level of a function");
+        WASM_TRY_ADD_TO_CONTEXT(addElse(m_controlStack.last().controlData, m_expressionStack));
+        m_expressionStack.shrink(0);
+        return { };
+    }
+
+    case Br:
+    case BrIf: {
+        uint32_t target;
+        ExpressionType condition = Context::emptyExpression;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(target), "can't get br / br_if's target");
+        WASM_PARSER_FAIL_IF(target >= m_controlStack.size(), "br / br_if's target ", target, " exceeds control stack size ", m_controlStack.size());
+        if (op == BrIf)
+            WASM_TRY_POP_EXPRESSION_STACK_INTO(condition, "br / br_if condition");
+        else
+            m_unreachableBlocks = 1;
+
+        ControlType& data = m_controlStack[m_controlStack.size() - 1 - target].controlData;
+
+        WASM_TRY_ADD_TO_CONTEXT(addBranch(data, condition, m_expressionStack));
+        return { };
+    }
+
+    case BrTable: {
+        uint32_t numberOfTargets;
+        uint32_t defaultTarget;
+        ExpressionType condition;
+        Vector<ControlType*> targets;
+
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(numberOfTargets), "can't get the number of targets for br_table");
+        WASM_PARSER_FAIL_IF(numberOfTargets == std::numeric_limits<uint32_t>::max(), "br_table's number of targets is too big ", numberOfTargets);
+
+        WASM_PARSER_FAIL_IF(!targets.tryReserveCapacity(numberOfTargets), "can't allocate memory for ", numberOfTargets, " br_table targets");
+        for (uint32_t i = 0; i < numberOfTargets; ++i) {
+            uint32_t target;
+            WASM_PARSER_FAIL_IF(!parseVarUInt32(target), "can't get ", i, "th target for br_table");
+            WASM_PARSER_FAIL_IF(target >= m_controlStack.size(), "br_table's ", i, "th target ", target, " exceeds control stack size ", m_controlStack.size());
+            targets.uncheckedAppend(&m_controlStack[m_controlStack.size() - 1 - target].controlData);
+        }
+
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(defaultTarget), "can't get default target for br_table");
+        WASM_PARSER_FAIL_IF(defaultTarget >= m_controlStack.size(), "br_table's default target ", defaultTarget, " exceeds control stack size ", m_controlStack.size());
+
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(condition, "br_table condition");
+        WASM_TRY_ADD_TO_CONTEXT(addSwitch(condition, targets, m_controlStack[m_controlStack.size() - 1 - defaultTarget].controlData, m_expressionStack));
+
+        m_unreachableBlocks = 1;
+        return { };
+    }
+
+    case Return: {
+        ExpressionList returnValues;
+        if (m_signature->returnType() != Void) {
+            ExpressionType returnValue;
+            WASM_TRY_POP_EXPRESSION_STACK_INTO(returnValue, "return");
+            returnValues.append(returnValue);
+        }
+
+        WASM_TRY_ADD_TO_CONTEXT(addReturn(m_controlStack[0].controlData, returnValues));
+        m_unreachableBlocks = 1;
+        return { };
+    }
+
+    case End: {
+        ControlEntry data = m_controlStack.takeLast();
+        // FIXME: This is a little weird in that it will modify the expressionStack for the result of the block.
+        // That's a little too effectful for me but I don't have a better API right now.
+        // see: https://bugs.webkit.org/show_bug.cgi?id=164353
+        WASM_TRY_ADD_TO_CONTEXT(endBlock(data, m_expressionStack));
+        m_expressionStack.swap(data.enclosedExpressionStack);
+        return { };
+    }
+
+    case Unreachable: {
+        WASM_TRY_ADD_TO_CONTEXT(addUnreachable());
+        m_unreachableBlocks = 1;
+        return { };
+    }
+
+    case Drop: {
+        WASM_PARSER_FAIL_IF(!m_expressionStack.size(), "can't drop on empty stack");
+        m_expressionStack.takeLast();
+        return { };
+    }
+
+    case Nop: {
+        return { };
+    }
+
+    case GrowMemory: {
+        WASM_PARSER_FAIL_IF(!m_info.memory, "grow_memory is only valid if a memory is defined or imported");
+
+        uint8_t reserved;
+        WASM_PARSER_FAIL_IF(!parseVarUInt1(reserved), "can't parse reserved varUint1 for grow_memory");
+        WASM_PARSER_FAIL_IF(reserved != 0, "reserved varUint1 for grow_memory must be zero");
+
+        ExpressionType delta;
+        WASM_TRY_POP_EXPRESSION_STACK_INTO(delta, "expect an i32 argument to grow_memory on the stack");
+
+        ExpressionType result;
+        WASM_TRY_ADD_TO_CONTEXT(addGrowMemory(delta, result));
+        m_expressionStack.append(result);
+
+        return { };
+    }
+
+    case CurrentMemory: {
+        WASM_PARSER_FAIL_IF(!m_info.memory, "current_memory is only valid if a memory is defined or imported");
+
+        uint8_t reserved;
+        WASM_PARSER_FAIL_IF(!parseVarUInt1(reserved), "can't parse reserved varUint1 for current_memory");
+        WASM_PARSER_FAIL_IF(reserved != 0, "reserved varUint1 for current_memory must be zero");
+
+        ExpressionType result;
+        WASM_TRY_ADD_TO_CONTEXT(addCurrentMemory(result));
+        m_expressionStack.append(result);
+
+        return { };
+    }
+    }
+
+    ASSERT_NOT_REACHED();
+    return { };
+}
+
+// FIXME: We should try to use the same decoder function for both unreachable and reachable code. https://bugs.webkit.org/show_bug.cgi?id=165965
+template<typename Context>
+auto FunctionParser<Context>::parseUnreachableExpression(OpType op) -> PartialResult
+{
+    ASSERT(m_unreachableBlocks);
+#define CREATE_CASE(name, id, b3op, inc) case OpType::name:
+    switch (op) {
+    case Else: {
+        if (m_unreachableBlocks > 1)
+            return { };
+
+        ControlEntry& data = m_controlStack.last();
+        m_unreachableBlocks = 0;
+        WASM_TRY_ADD_TO_CONTEXT(addElseToUnreachable(data.controlData));
+        m_expressionStack.shrink(0);
+        return { };
+    }
+
+    case End: {
+        if (m_unreachableBlocks == 1) {
+            ControlEntry data = m_controlStack.takeLast();
+            WASM_TRY_ADD_TO_CONTEXT(addEndToUnreachable(data));
+            m_expressionStack.swap(data.enclosedExpressionStack);
+        }
+        m_unreachableBlocks--;
+        return { };
+    }
+
+    case Loop:
+    case If:
+    case Block: {
+        m_unreachableBlocks++;
+        Type unused;
+        WASM_PARSER_FAIL_IF(!parseResultType(unused), "can't get inline type for ", op, " in unreachable context");
+        return { };
+    }
+
+    case BrTable: {
+        uint32_t numberOfTargets;
+        uint32_t unused;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(numberOfTargets), "can't get the number of targets for br_table in unreachable context");
+        WASM_PARSER_FAIL_IF(numberOfTargets == std::numeric_limits<uint32_t>::max(), "br_table's number of targets is too big ", numberOfTargets);
+
+        for (uint32_t i = 0; i < numberOfTargets; ++i)
+            WASM_PARSER_FAIL_IF(!parseVarUInt32(unused), "can't get ", i, "th target for br_table in unreachable context");
+
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(unused), "can't get default target for br_table in unreachable context");
+        return { };
+    }
+
+    case CallIndirect: {
+        uint32_t unused;
+        uint8_t unused2;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(unused), "can't get call_indirect's signature index in unreachable context");
+        WASM_PARSER_FAIL_IF(!parseVarUInt1(unused2), "can't get call_indirect's reserved byte in unreachable context");
+        return { };
+    }
+
+    case F32Const: {
+        uint32_t unused;
+        WASM_PARSER_FAIL_IF(!parseUInt32(unused), "can't parse 32-bit floating-point constant");
+        return { };
+    }
+
+    case F64Const: {
+        uint64_t constant;
+        WASM_PARSER_FAIL_IF(!parseUInt64(constant), "can't parse 64-bit floating-point constant");
+        return { };
+    }
+
+    // two immediate cases
+    FOR_EACH_WASM_MEMORY_LOAD_OP(CREATE_CASE)
+    FOR_EACH_WASM_MEMORY_STORE_OP(CREATE_CASE) {
+        uint32_t unused;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(unused), "can't get first immediate for ", op, " in unreachable context");
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(unused), "can't get second immediate for ", op, " in unreachable context");
+        return { };
+    }
+
+    // one immediate cases
+    case I32Const:
+    case I64Const:
+    case SetLocal:
+    case GetLocal:
+    case TeeLocal:
+    case GetGlobal:
+    case SetGlobal:
+    case Br:
+    case BrIf:
+    case Call: {
+        uint32_t unused;
+        WASM_PARSER_FAIL_IF(!parseVarUInt32(unused), "can't get immediate for ", op, " in unreachable context");
+        return { };
+    }
+
+    case GrowMemory:
+    case CurrentMemory: {
+        uint8_t reserved;
+        WASM_PARSER_FAIL_IF(!parseVarUInt1(reserved), "can't parse reserved varUint1 for grow_memory/current_memory");
+        return { };
+    }
+
+    // no immediate cases
+    FOR_EACH_WASM_BINARY_OP(CREATE_CASE)
+    FOR_EACH_WASM_UNARY_OP(CREATE_CASE)
+    case Unreachable:
+    case Nop:
+    case Return:
+    case Select:
+    case Drop: {
+        return { };
+    }
+    }
+#undef CREATE_CASE
+    RELEASE_ASSERT_NOT_REACHED();
+}
+
+} } // namespace JSC::Wasm
+
+#endif // ENABLE(WEBASSEMBLY)