C++ Code::frameSize方法代码示例

ValueRep StackmapSpecial::repForArg(Code& code, const Arg& arg)
{
    switch (arg.kind()) {
    case Arg::Tmp:
        return ValueRep::reg(arg.reg());
        break;
    case Arg::Imm:
    case Arg::Imm64:
        return ValueRep::constant(arg.value());
        break;
    case Arg::Addr:
        if (arg.base() == Tmp(GPRInfo::callFrameRegister))
            return ValueRep::stack(arg.offset());
        ASSERT(arg.base() == Tmp(MacroAssembler::stackPointerRegister));
        return ValueRep::stack(arg.offset() - code.frameSize());
    default:
        ASSERT_NOT_REACHED();
        return ValueRep();
    }
}

void lowerStackArgs(Code& code)
{
    PhaseScope phaseScope(code, "lowerStackArgs");

    // Now we need to deduce how much argument area we need.
    for (BasicBlock* block : code) {
        for (Inst& inst : *block) {
            for (Arg& arg : inst.args) {
                if (arg.isCallArg()) {
                    // For now, we assume that we use 8 bytes of the call arg. But that's not
                    // such an awesome assumption.
                    // FIXME: https://bugs.webkit.org/show_bug.cgi?id=150454
                    ASSERT(arg.offset() >= 0);
                    code.requestCallArgAreaSizeInBytes(arg.offset() + 8);
                }
            }
        }
    }

    code.setFrameSize(code.frameSize() + code.callArgAreaSizeInBytes());

    // Finally, transform the code to use Addr's instead of StackSlot's. This is a lossless
    // transformation since we can search the StackSlots array to figure out which StackSlot any
    // offset-from-FP refers to.

    InsertionSet insertionSet(code);
    for (BasicBlock* block : code) {
        // FIXME We can keep track of the last large offset which was materialized in this block, and reuse the register
        // if it hasn't been clobbered instead of renetating imm+add+addr every time. https://bugs.webkit.org/show_bug.cgi?id=171387

        for (unsigned instIndex = 0; instIndex < block->size(); ++instIndex) {
            Inst& inst = block->at(instIndex);

            inst.forEachArg(
                [&] (Arg& arg, Arg::Role role, Bank, Width width) {
                    auto stackAddr = [&] (Value::OffsetType offsetFromFP) -> Arg {
                        int32_t offsetFromSP = offsetFromFP + code.frameSize();

                        if (inst.admitsExtendedOffsetAddr(arg)) {
                            // Stackmaps and patchpoints expect addr inputs relative to SP or FP only. We might as well
                            // not even bother generating an addr with valid form for these opcodes since extended offset
                            // addr is always valid.
                            return Arg::extendedOffsetAddr(offsetFromFP);
                        }

                        Arg result = Arg::addr(Air::Tmp(GPRInfo::callFrameRegister), offsetFromFP);
                        if (result.isValidForm(width))
                            return result;

                        result = Arg::addr(Air::Tmp(MacroAssembler::stackPointerRegister), offsetFromSP);
                        if (result.isValidForm(width))
                            return result;
#if CPU(ARM64)
                        ASSERT(pinnedExtendedOffsetAddrRegister());
                        Air::Tmp tmp = Air::Tmp(*pinnedExtendedOffsetAddrRegister());

                        Arg largeOffset = Arg::isValidImmForm(offsetFromSP) ? Arg::imm(offsetFromSP) : Arg::bigImm(offsetFromSP);
                        insertionSet.insert(instIndex, Move, inst.origin, largeOffset, tmp);
                        insertionSet.insert(instIndex, Add64, inst.origin, Air::Tmp(MacroAssembler::stackPointerRegister), tmp);
                        result = Arg::addr(tmp, 0);
                        return result;
#elif CPU(X86_64)
                        // Can't happen on x86: immediates are always big enough for frame size.
                        RELEASE_ASSERT_NOT_REACHED();
#else
#error Unhandled architecture.
#endif
                    };

                    switch (arg.kind()) {
                    case Arg::Stack: {
                        StackSlot* slot = arg.stackSlot();
                        if (Arg::isZDef(role)
                            && slot->kind() == StackSlotKind::Spill
                            && slot->byteSize() > bytes(width)) {
                            // Currently we only handle this simple case because it's the only one
                            // that arises: ZDef's are only 32-bit right now. So, when we hit these
                            // assertions it means that we need to implement those other kinds of
                            // zero fills.
                            RELEASE_ASSERT(slot->byteSize() == 8);
                            RELEASE_ASSERT(width == Width32);

                            RELEASE_ASSERT(isValidForm(StoreZero32, Arg::Stack));
                            insertionSet.insert(
                                instIndex + 1, StoreZero32, inst.origin,
                                stackAddr(arg.offset() + 4 + slot->offsetFromFP()));
                        }
                        arg = stackAddr(arg.offset() + slot->offsetFromFP());
                        break;
                    }
                    case Arg::CallArg:
                        arg = stackAddr(arg.offset() - code.frameSize());
                        break;
                    default:
                        break;
                    }
                }
            );
        }
        insertionSet.execute(block);
//.........这里部分代码省略.........

void generate(Code& code, CCallHelpers& jit)
{
    TimingScope timingScope("Air::generate");

    DisallowMacroScratchRegisterUsage disallowScratch(jit);

    // And now, we generate code.
    jit.emitFunctionPrologue();
    if (code.frameSize())
        jit.addPtr(CCallHelpers::TrustedImm32(-code.frameSize()), MacroAssembler::stackPointerRegister);

    GenerationContext context;
    context.code = &code;
    IndexMap<BasicBlock, CCallHelpers::Label> blockLabels(code.size());
    IndexMap<BasicBlock, CCallHelpers::JumpList> blockJumps(code.size());

    auto link = [&] (CCallHelpers::Jump jump, BasicBlock* target) {
        if (blockLabels[target].isSet()) {
            jump.linkTo(blockLabels[target], &jit);
            return;
        }

        blockJumps[target].append(jump);
    };

    for (BasicBlock* block : code) {
        blockJumps[block].link(&jit);
        blockLabels[block] = jit.label();
        ASSERT(block->size() >= 1);
        for (unsigned i = 0; i < block->size() - 1; ++i) {
            CCallHelpers::Jump jump = block->at(i).generate(jit, context);
            ASSERT_UNUSED(jump, !jump.isSet());
        }

        if (block->last().opcode == Jump
            && block->successorBlock(0) == code.findNextBlock(block))
            continue;

        if (block->last().opcode == Ret) {
            // We currently don't represent the full prologue/epilogue in Air, so we need to
            // have this override.
            if (code.frameSize())
                jit.emitFunctionEpilogue();
            else
                jit.emitFunctionEpilogueWithEmptyFrame();
            jit.ret();
            continue;
        }
        
        CCallHelpers::Jump jump = block->last().generate(jit, context);
        switch (block->numSuccessors()) {
        case 0:
            ASSERT(!jump.isSet());
            break;
        case 1:
            link(jump, block->successorBlock(0));
            break;
        case 2:
            link(jump, block->successorBlock(0));
            if (block->successorBlock(1) != code.findNextBlock(block))
                link(jit.jump(), block->successorBlock(1));
            break;
        default:
            RELEASE_ASSERT_NOT_REACHED();
            break;
        }
    }

    for (auto& latePath : context.latePaths)
        latePath->run(jit, context);
}

void allocateStack(Code& code)
{
    PhaseScope phaseScope(code, "allocateStack");

    // Perform an escape analysis over stack slots. An escaping stack slot is one that is locked or
    // is explicitly escaped in the code.
    IndexSet<StackSlot> escapingStackSlots;
    for (StackSlot* slot : code.stackSlots()) {
        if (slot->isLocked())
            escapingStackSlots.add(slot);
    }
    for (BasicBlock* block : code) {
        for (Inst& inst : *block) {
            inst.forEachArg(
                [&] (Arg& arg, Arg::Role role, Arg::Type, Arg::Width) {
                    if (role == Arg::UseAddr && arg.isStack())
                        escapingStackSlots.add(arg.stackSlot());
                });
        }
    }

    // Allocate all of the escaped slots in order. This is kind of a crazy algorithm to allow for
    // the possibility of stack slots being assigned frame offsets before we even get here.
    ASSERT(!code.frameSize());
    Vector<StackSlot*> assignedEscapedStackSlots;
    Vector<StackSlot*> escapedStackSlotsWorklist;
    for (StackSlot* slot : code.stackSlots()) {
        if (escapingStackSlots.contains(slot)) {
            if (slot->offsetFromFP())
                assignedEscapedStackSlots.append(slot);
            else
                escapedStackSlotsWorklist.append(slot);
        } else {
            // It would be super strange to have an unlocked stack slot that has an offset already.
            ASSERT(!slot->offsetFromFP());
        }
    }
    // This is a fairly expensive loop, but it's OK because we'll usually only have a handful of
    // escaped stack slots.
    while (!escapedStackSlotsWorklist.isEmpty()) {
        StackSlot* slot = escapedStackSlotsWorklist.takeLast();
        assign(slot, assignedEscapedStackSlots);
        assignedEscapedStackSlots.append(slot);
    }

    // Now we handle the anonymous slots.
    StackSlotLiveness liveness(code);
    IndexMap<StackSlot, HashSet<StackSlot*>> interference(code.stackSlots().size());
    Vector<StackSlot*> slots;

    for (BasicBlock* block : code) {
        StackSlotLiveness::LocalCalc localCalc(liveness, block);

        auto interfere = [&] (Inst& inst) {
            if (verbose)
                dataLog("Interfering: ", WTF::pointerListDump(localCalc.live()), "\n");

            inst.forEachArg(
                [&] (Arg& arg, Arg::Role role, Arg::Type, Arg::Width) {
                    if (!Arg::isDef(role))
                        return;
                    if (!arg.isStack())
                        return;
                    StackSlot* slot = arg.stackSlot();
                    if (slot->kind() != StackSlotKind::Anonymous)
                        return;

                    for (StackSlot* otherSlot : localCalc.live()) {
                        interference[slot].add(otherSlot);
                        interference[otherSlot].add(slot);
                    }
                });
        };

        for (unsigned instIndex = block->size(); instIndex--;) {
            if (verbose)
                dataLog("Analyzing: ", block->at(instIndex), "\n");
            Inst& inst = block->at(instIndex);
            interfere(inst);
            localCalc.execute(instIndex);
        }
        Inst nop;
        interfere(nop);
    }

    if (verbose) {
        for (StackSlot* slot : code.stackSlots())
            dataLog("Interference of ", pointerDump(slot), ": ", pointerListDump(interference[slot]), "\n");
    }

    // Now we assign stack locations. At its heart this algorithm is just first-fit. For each
    // StackSlot we just want to find the offsetFromFP that is closest to zero while ensuring no
    // overlap with other StackSlots that this overlaps with.
    Vector<StackSlot*> otherSlots = assignedEscapedStackSlots;
    for (StackSlot* slot : code.stackSlots()) {
        if (slot->offsetFromFP()) {
            // Already assigned an offset.
            continue;
        }

//.........这里部分代码省略.........

void allocateStack(Code& code)
{
    PhaseScope phaseScope(code, "allocateStack");

    // Perform an escape analysis over stack slots. An escaping stack slot is one that is locked or
    // is explicitly escaped in the code.
    IndexSet<StackSlot> escapingStackSlots;
    for (StackSlot* slot : code.stackSlots()) {
        if (slot->isLocked())
            escapingStackSlots.add(slot);
    }
    for (BasicBlock* block : code) {
        for (Inst& inst : *block) {
            inst.forEachArg(
                [&] (Arg& arg, Arg::Role role, Arg::Type, Arg::Width) {
                    if (role == Arg::UseAddr && arg.isStack())
                        escapingStackSlots.add(arg.stackSlot());
                });
        }
    }

    // Allocate all of the escaped slots in order. This is kind of a crazy algorithm to allow for
    // the possibility of stack slots being assigned frame offsets before we even get here.
    ASSERT(!code.frameSize());
    Vector<StackSlot*> assignedEscapedStackSlots;
    Vector<StackSlot*> escapedStackSlotsWorklist;
    for (StackSlot* slot : code.stackSlots()) {
        if (escapingStackSlots.contains(slot)) {
            if (slot->offsetFromFP())
                assignedEscapedStackSlots.append(slot);
            else
                escapedStackSlotsWorklist.append(slot);
        } else {
            // It would be super strange to have an unlocked stack slot that has an offset already.
            ASSERT(!slot->offsetFromFP());
        }
    }
    // This is a fairly expensive loop, but it's OK because we'll usually only have a handful of
    // escaped stack slots.
    while (!escapedStackSlotsWorklist.isEmpty()) {
        StackSlot* slot = escapedStackSlotsWorklist.takeLast();
        assign(slot, assignedEscapedStackSlots);
        assignedEscapedStackSlots.append(slot);
    }

    // Now we handle the anonymous slots.
    StackSlotLiveness liveness(code);
    IndexMap<StackSlot, HashSet<StackSlot*>> interference(code.stackSlots().size());
    Vector<StackSlot*> slots;

    for (BasicBlock* block : code) {
        StackSlotLiveness::LocalCalc localCalc(liveness, block);

        auto interfere = [&] (unsigned instIndex) {
            if (verbose)
                dataLog("Interfering: ", WTF::pointerListDump(localCalc.live()), "\n");

            Inst::forEachDef<Arg>(
                block->get(instIndex), block->get(instIndex + 1),
                [&] (Arg& arg, Arg::Role, Arg::Type, Arg::Width) {
                    if (!arg.isStack())
                        return;
                    StackSlot* slot = arg.stackSlot();
                    if (slot->kind() != StackSlotKind::Anonymous)
                        return;

                    for (StackSlot* otherSlot : localCalc.live()) {
                        interference[slot].add(otherSlot);
                        interference[otherSlot].add(slot);
                    }
                });
        };

        for (unsigned instIndex = block->size(); instIndex--;) {
            if (verbose)
                dataLog("Analyzing: ", block->at(instIndex), "\n");

            // Kill dead stores. For simplicity we say that a store is killable if it has only late
            // defs and those late defs are to things that are dead right now. We only do that
            // because that's the only kind of dead stack store we will see here.
            Inst& inst = block->at(instIndex);
            if (!inst.hasNonArgEffects()) {
                bool ok = true;
                inst.forEachArg(
                    [&] (Arg& arg, Arg::Role role, Arg::Type, Arg::Width) {
                        if (Arg::isEarlyDef(role)) {
                            ok = false;
                            return;
                        }
                        if (!Arg::isLateDef(role))
                            return;
                        if (!arg.isStack()) {
                            ok = false;
                            return;
                        }
                        StackSlot* slot = arg.stackSlot();
                        if (slot->kind() != StackSlotKind::Anonymous) {
                            ok = false;
                            return;
                        }
//.........这里部分代码省略.........