C++ Code::callArgAreaSizeInBytes方法代码示例

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.........