Source/JavaScriptCore/wasm/WasmCallingConvention.h

/*
 * Copyright (C) 2016-2018 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
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 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#if ENABLE(WEBASSEMBLY)

#include "AllowMacroScratchRegisterUsage.h"
#include "CallFrame.h"
#include "LinkBuffer.h"
#include "RegisterAtOffsetList.h"
#include "RegisterSet.h"
#include "WasmFormat.h"
#include "WasmTypeDefinition.h"
#include "WasmValueLocation.h"

namespace JSC { namespace Wasm {

constexpr unsigned numberOfLLIntCalleeSaveRegisters = 2;

using ArgumentLocation = ValueLocation;
enum class CallRole : uint8_t {
    Caller,
    Callee,
};

struct CallInformation {
    CallInformation(Vector<ArgumentLocation>&& parameters, Vector<ArgumentLocation, 1>&& returnValues, size_t stackOffset)
        : params(WTFMove(parameters))
        , results(WTFMove(returnValues))
        , headerAndArgumentStackSizeInBytes(stackOffset)
    { }

    RegisterAtOffsetList computeResultsOffsetList()
    {
        RegisterSet usedResultRegisters;
        for (ValueLocation loc : results) {
            if (loc.isGPR()) {
                usedResultRegisters.set(loc.jsr().payloadGPR());
#if USE(JSVALUE32_64)
                usedResultRegisters.set(loc.jsr().tagGPR());
#endif
            } else if (loc.isFPR())
                usedResultRegisters.set(loc.fpr());
        }

        RegisterAtOffsetList savedRegs(usedResultRegisters, RegisterAtOffsetList::ZeroBased);
        return savedRegs;
    }

    bool argumentsIncludeI64 { false };
    bool resultsIncludeI64 { false };
    Vector<ArgumentLocation> params;
    Vector<ArgumentLocation, 1> results;
    // As a callee this includes CallerFrameAndPC as a caller it does not.
    size_t headerAndArgumentStackSizeInBytes;
};

class WasmCallingConvention {
public:
    static constexpr unsigned headerSizeInBytes = CallFrame::headerSizeInRegisters * sizeof(Register);

    WasmCallingConvention(Vector<JSValueRegs>&& jsrs, Vector<FPRReg>&& fprs, Vector<GPRReg>&& scratches, RegisterSet&& calleeSaves, RegisterSet&& callerSaves)
        : jsrArgs(WTFMove(jsrs))
        , fprArgs(WTFMove(fprs))
        , prologueScratchGPRs(WTFMove(scratches))
        , calleeSaveRegisters(WTFMove(calleeSaves))
        , callerSaveRegisters(WTFMove(callerSaves))
    { }

    WTF_MAKE_NONCOPYABLE(WasmCallingConvention);

private:
    template<typename RegType>
    ArgumentLocation marshallLocationImpl(CallRole role, const Vector<RegType>& regArgs, size_t& count, size_t& stackOffset) const
    {
        if (count < regArgs.size())
            return ArgumentLocation { regArgs[count++] };

        count++;
        ArgumentLocation result = role == CallRole::Caller ? ArgumentLocation::stackArgument(stackOffset) : ArgumentLocation::stack(stackOffset);
        stackOffset += sizeof(Register);
        return result;
    }

    ArgumentLocation marshallLocation(CallRole role, Type valueType, size_t& gpArgumentCount, size_t& fpArgumentCount, size_t& stackOffset) const
    {
        ASSERT(isValueType(valueType));
        switch (valueType.kind) {
        case TypeKind::I32:
        case TypeKind::I64:
        case TypeKind::Funcref:
        case TypeKind::Externref:
        case TypeKind::Ref:
        case TypeKind::RefNull:
        case TypeKind::Rtt:
            return marshallLocationImpl(role, jsrArgs, gpArgumentCount, stackOffset);
        case TypeKind::F32:
        case TypeKind::F64:
            return marshallLocationImpl(role, fprArgs, fpArgumentCount, stackOffset);
        default:
            break;
        }
        RELEASE_ASSERT_NOT_REACHED();
    }

public:
    CallInformation callInformationFor(const TypeDefinition& type, CallRole role = CallRole::Caller) const
    {
        const auto& signature = *type.as<FunctionSignature>();
        bool argumentsIncludeI64 = false;
        bool resultsIncludeI64 = false;
        size_t gpArgumentCount = 0;
        size_t fpArgumentCount = 0;
        size_t argStackOffset = headerSizeInBytes + sizeof(Register);
        if (role == CallRole::Caller)
            argStackOffset -= sizeof(CallerFrameAndPC);

        Vector<ArgumentLocation> params(signature.argumentCount());
        for (size_t i = 0; i < signature.argumentCount(); ++i) {
            argumentsIncludeI64 |= signature.argumentType(i).isI64();
            params[i] = marshallLocation(role, signature.argumentType(i), gpArgumentCount, fpArgumentCount, argStackOffset);
        }
        gpArgumentCount = 0;
        fpArgumentCount = 0;
        size_t resultStackOffset = headerSizeInBytes + sizeof(Register);
        if (role == CallRole::Caller)
            resultStackOffset -= sizeof(CallerFrameAndPC);

        Vector<ArgumentLocation, 1> results(signature.returnCount());
        for (size_t i = 0; i < signature.returnCount(); ++i) {
            resultsIncludeI64 |= signature.returnType(i).isI64();
            results[i] = marshallLocation(role, signature.returnType(i), gpArgumentCount, fpArgumentCount, resultStackOffset);
        }

        CallInformation result(WTFMove(params), WTFMove(results), std::max(argStackOffset, resultStackOffset));
        result.argumentsIncludeI64 = argumentsIncludeI64;
        result.resultsIncludeI64 = resultsIncludeI64;
        return result;
    }

    const Vector<JSValueRegs> jsrArgs;
    const Vector<FPRReg> fprArgs;
    const Vector<GPRReg> prologueScratchGPRs;
    const RegisterSet calleeSaveRegisters;
    const RegisterSet callerSaveRegisters;
};

class JSCallingConvention {
public:
    static constexpr unsigned headerSizeInBytes = CallFrame::headerSizeInRegisters * sizeof(Register);

    // vmEntryToWasm passes the JSWebAssemblyInstance corresponding to Wasm::Context*'s
    // instance as the first JS argument when we're not using fast TLS to hold the
    // Wasm::Context*'s instance.
    static constexpr ptrdiff_t instanceStackOffset = CallFrameSlot::thisArgument * sizeof(EncodedJSValue);

    JSCallingConvention(Vector<JSValueRegs>&& gprs, Vector<FPRReg>&& fprs, RegisterSet&& calleeSaves, RegisterSet&& callerSaves)
        : jsrArgs(WTFMove(gprs))
        , fprArgs(WTFMove(fprs))
        , calleeSaveRegisters(WTFMove(calleeSaves))
        , callerSaveRegisters(WTFMove(callerSaves))
    { }

    WTF_MAKE_NONCOPYABLE(JSCallingConvention);
private:
    template <typename RegType>
    ArgumentLocation marshallLocationImpl(CallRole role, const Vector<RegType>& regArgs, size_t& count, size_t& stackOffset) const
    {
        if (count < regArgs.size())
            return ArgumentLocation { regArgs[count++] };

        count++;
        ArgumentLocation result = role == CallRole::Caller ? ArgumentLocation::stackArgument(stackOffset) : ArgumentLocation::stack(stackOffset);
        stackOffset += sizeof(Register);
        return result;
    }

    ArgumentLocation marshallLocation(CallRole role, Type valueType, size_t& gpArgumentCount, size_t& fpArgumentCount, size_t& stackOffset) const
    {
        ASSERT(isValueType(valueType));
        switch (valueType.kind) {
        case TypeKind::I32:
        case TypeKind::I64:
        case TypeKind::Funcref:
        case TypeKind::Externref:
        case TypeKind::Ref:
        case TypeKind::RefNull:
            return marshallLocationImpl(role, jsrArgs, gpArgumentCount, stackOffset);
        case TypeKind::F32:
        case TypeKind::F64:
            return marshallLocationImpl(role, fprArgs, fpArgumentCount, stackOffset);
        default:
            break;
        }
        RELEASE_ASSERT_NOT_REACHED();
    }

public:
    CallInformation callInformationFor(const TypeDefinition& signature, CallRole role = CallRole::Callee) const
    {
        size_t gpArgumentCount = 0;
        size_t fpArgumentCount = 0;
        size_t stackOffset = headerSizeInBytes + sizeof(Register); // Skip the this value since wasm doesn't use it and we sometimes put the context there.
        if (role == CallRole::Caller)
            stackOffset -= sizeof(CallerFrameAndPC);

        Vector<ArgumentLocation> params;
        for (size_t i = 0; i < signature.as<FunctionSignature>()->argumentCount(); ++i)
            params.append(marshallLocation(role, signature.as<FunctionSignature>()->argumentType(i), gpArgumentCount, fpArgumentCount, stackOffset));

        Vector<ArgumentLocation, 1> results { ArgumentLocation { JSRInfo::returnValueJSR } };
        return CallInformation(WTFMove(params), WTFMove(results), stackOffset);
    }

    const Vector<JSValueRegs> jsrArgs;
    const Vector<FPRReg> fprArgs;
    const RegisterSet calleeSaveRegisters;
    const RegisterSet callerSaveRegisters;
};

const JSCallingConvention& jsCallingConvention();
const WasmCallingConvention& wasmCallingConvention();

} } // namespace JSC::Wasm

#endif // ENABLE(WEBASSEMBLY)