src/third_party/mozjs/js/src/jit/arm/BaselineHelpers-arm.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef jit_arm_BaselineHelpers_arm_h
#define jit_arm_BaselineHelpers_arm_h

#ifdef JS_ION

#include "jit/IonMacroAssembler.h"
#include "jit/BaselineFrame.h"
#include "jit/BaselineRegisters.h"
#include "jit/BaselineIC.h"

namespace js {
namespace jit {

// Distance from sp to the top Value inside an IC stub (no return address on the stack on ARM).
static const size_t ICStackValueOffset = 0;

inline void
EmitRestoreTailCallReg(MacroAssembler &masm)
{
    // No-op on ARM because link register is always holding the return address.
}

inline void
EmitCallIC(CodeOffsetLabel *patchOffset, MacroAssembler &masm)
{
    // Move ICEntry offset into BaselineStubReg
    CodeOffsetLabel offset = masm.movWithPatch(ImmWord(-1), BaselineStubReg);
    *patchOffset = offset;

    // Load stub pointer into BaselineStubReg
    masm.loadPtr(Address(BaselineStubReg, ICEntry::offsetOfFirstStub()), BaselineStubReg);

    // Load stubcode pointer from BaselineStubEntry.
    // R2 won't be active when we call ICs, so we can use r0.
    JS_ASSERT(R2 == ValueOperand(r1, r0));
    masm.loadPtr(Address(BaselineStubReg, ICStub::offsetOfStubCode()), r0);

    // Call the stubcode via a direct branch-and-link
    masm.ma_blx(r0);
}

inline void
EmitEnterTypeMonitorIC(MacroAssembler &masm,
                       size_t monitorStubOffset = ICMonitoredStub::offsetOfFirstMonitorStub())
{
    // This is expected to be called from within an IC, when BaselineStubReg
    // is properly initialized to point to the stub.
    masm.loadPtr(Address(BaselineStubReg, (uint32_t) monitorStubOffset), BaselineStubReg);

    // Load stubcode pointer from BaselineStubEntry.
    // R2 won't be active when we call ICs, so we can use r0.
    JS_ASSERT(R2 == ValueOperand(r1, r0));
    masm.loadPtr(Address(BaselineStubReg, ICStub::offsetOfStubCode()), r0);

    // Jump to the stubcode.
    masm.branch(r0);
}

inline void
EmitReturnFromIC(MacroAssembler &masm)
{
    masm.ma_mov(lr, pc);
}

inline void
EmitChangeICReturnAddress(MacroAssembler &masm, Register reg)
{
    masm.ma_mov(reg, lr);
}

inline void
EmitTailCallVM(IonCode *target, MacroAssembler &masm, uint32_t argSize)
{
    // We assume during this that R0 and R1 have been pushed, and that R2 is
    // unused.
    JS_ASSERT(R2 == ValueOperand(r1, r0));

    // Compute frame size.
    masm.movePtr(BaselineFrameReg, r0);
    masm.ma_add(Imm32(BaselineFrame::FramePointerOffset), r0);
    masm.ma_sub(BaselineStackReg, r0);

    // Store frame size without VMFunction arguments for GC marking.
    masm.ma_sub(r0, Imm32(argSize), r1);
    masm.store32(r1, Address(BaselineFrameReg, BaselineFrame::reverseOffsetOfFrameSize()));

    // Push frame descriptor and perform the tail call.
    // BaselineTailCallReg (lr) already contains the return address (as we keep it there through
    // the stub calls), but the VMWrapper code being called expects the return address to also
    // be pushed on the stack.
    JS_ASSERT(BaselineTailCallReg == lr);
    masm.makeFrameDescriptor(r0, IonFrame_BaselineJS);
    masm.push(r0);
    masm.push(lr);
    masm.branch(target);
}

inline void
EmitCreateStubFrameDescriptor(MacroAssembler &masm, Register reg)
{
    // Compute stub frame size. We have to add two pointers: the stub reg and previous
    // frame pointer pushed by EmitEnterStubFrame.
    masm.mov(BaselineFrameReg, reg);
    masm.ma_add(Imm32(sizeof(void *) * 2), reg);
    masm.ma_sub(BaselineStackReg, reg);

    masm.makeFrameDescriptor(reg, IonFrame_BaselineStub);
}

inline void
EmitCallVM(IonCode *target, MacroAssembler &masm)
{
    EmitCreateStubFrameDescriptor(masm, r0);
    masm.push(r0);
    masm.call(target);
}

// Size of vales pushed by EmitEnterStubFrame.
static const uint32_t STUB_FRAME_SIZE = 4 * sizeof(void *);
static const uint32_t STUB_FRAME_SAVED_STUB_OFFSET = sizeof(void *);

inline void
EmitEnterStubFrame(MacroAssembler &masm, Register scratch)
{
    JS_ASSERT(scratch != BaselineTailCallReg);

    // Compute frame size.
    masm.mov(BaselineFrameReg, scratch);
    masm.ma_add(Imm32(BaselineFrame::FramePointerOffset), scratch);
    masm.ma_sub(BaselineStackReg, scratch);

    masm.store32(scratch, Address(BaselineFrameReg, BaselineFrame::reverseOffsetOfFrameSize()));

    // Note: when making changes here,  don't forget to update STUB_FRAME_SIZE
    // if needed.

    // Push frame descriptor and return address.
    masm.makeFrameDescriptor(scratch, IonFrame_BaselineJS);
    masm.push(scratch);
    masm.push(BaselineTailCallReg);

    // Save old frame pointer, stack pointer and stub reg.
    masm.push(BaselineStubReg);
    masm.push(BaselineFrameReg);
    masm.mov(BaselineStackReg, BaselineFrameReg);

    // We pushed 4 words, so the stack is still aligned to 8 bytes.
    masm.checkStackAlignment();
}

inline void
EmitLeaveStubFrame(MacroAssembler &masm, bool calledIntoIon = false)
{
    // Ion frames do not save and restore the frame pointer. If we called
    // into Ion, we have to restore the stack pointer from the frame descriptor.
    // If we performed a VM call, the descriptor has been popped already so
    // in that case we use the frame pointer.
    if (calledIntoIon) {
        masm.pop(ScratchRegister);
        masm.ma_lsr(Imm32(FRAMESIZE_SHIFT), ScratchRegister, ScratchRegister);
        masm.ma_add(ScratchRegister, BaselineStackReg);
    } else {
        masm.mov(BaselineFrameReg, BaselineStackReg);
    }

    masm.pop(BaselineFrameReg);
    masm.pop(BaselineStubReg);

    // Load the return address.
    masm.pop(BaselineTailCallReg);

    // Discard the frame descriptor.
    masm.pop(ScratchRegister);
}

inline void
EmitStowICValues(MacroAssembler &masm, int values)
{
    JS_ASSERT(values >= 0 && values <= 2);
    switch(values) {
      case 1:
        // Stow R0
        masm.pushValue(R0);
        break;
      case 2:
        // Stow R0 and R1
        masm.pushValue(R0);
        masm.pushValue(R1);
        break;
    }
}

inline void
EmitUnstowICValues(MacroAssembler &masm, int values)
{
    JS_ASSERT(values >= 0 && values <= 2);
    switch(values) {
      case 1:
        // Unstow R0
        masm.popValue(R0);
        break;
      case 2:
        // Untow R0 and R1
        masm.popValue(R1);
        masm.popValue(R0);
        break;
    }
}

inline void
EmitCallTypeUpdateIC(MacroAssembler &masm, IonCode *code, uint32_t objectOffset)
{
    JS_ASSERT(R2 == ValueOperand(r1, r0));

    // R0 contains the value that needs to be typechecked.
    // The object we're updating is a boxed Value on the stack, at offset
    // objectOffset from esp, excluding the return address.

    // Save the current BaselineStubReg to stack, as well as the TailCallReg,
    // since on ARM, the LR is live.
    masm.push(BaselineStubReg);
    masm.push(BaselineTailCallReg);

    // This is expected to be called from within an IC, when BaselineStubReg
    // is properly initialized to point to the stub.
    masm.loadPtr(Address(BaselineStubReg, ICUpdatedStub::offsetOfFirstUpdateStub()),
                 BaselineStubReg);

    // TODO: Change r0 uses below to use masm's configurable scratch register instead.

    // Load stubcode pointer from BaselineStubReg into BaselineTailCallReg.
    masm.loadPtr(Address(BaselineStubReg, ICStub::offsetOfStubCode()), r0);

    // Call the stubcode.
    masm.ma_blx(r0);

    // Restore the old stub reg and tailcall reg.
    masm.pop(BaselineTailCallReg);
    masm.pop(BaselineStubReg);

    // The update IC will store 0 or 1 in R1.scratchReg() reflecting if the
    // value in R0 type-checked properly or not.
    Label success;
    masm.cmp32(R1.scratchReg(), Imm32(1));
    masm.j(Assembler::Equal, &success);

    // If the IC failed, then call the update fallback function.
    EmitEnterStubFrame(masm, R1.scratchReg());

    masm.loadValue(Address(BaselineStackReg, STUB_FRAME_SIZE + objectOffset), R1);

    masm.pushValue(R0);
    masm.pushValue(R1);
    masm.push(BaselineStubReg);

    // Load previous frame pointer, push BaselineFrame *.
    masm.loadPtr(Address(BaselineFrameReg, 0), R0.scratchReg());
    masm.pushBaselineFramePtr(R0.scratchReg(), R0.scratchReg());

    EmitCallVM(code, masm);
    EmitLeaveStubFrame(masm);

    // Success at end.
    masm.bind(&success);
}

template <typename AddrType>
inline void
EmitPreBarrier(MacroAssembler &masm, const AddrType &addr, MIRType type)
{
    // on ARM, lr is clobbered by patchableCallPreBarrier.  Save it first.
    masm.push(lr);
    masm.patchableCallPreBarrier(addr, type);
    masm.pop(lr);
}

inline void
EmitStubGuardFailure(MacroAssembler &masm)
{
    JS_ASSERT(R2 == ValueOperand(r1, r0));

    // NOTE: This routine assumes that the stub guard code left the stack in the
    // same state it was in when it was entered.

    // BaselineStubEntry points to the current stub.

    // Load next stub into BaselineStubReg
    masm.loadPtr(Address(BaselineStubReg, ICStub::offsetOfNext()), BaselineStubReg);

    // Load stubcode pointer from BaselineStubEntry into scratch register.
    masm.loadPtr(Address(BaselineStubReg, ICStub::offsetOfStubCode()), r0);

    // Return address is already loaded, just jump to the next stubcode.
    JS_ASSERT(BaselineTailCallReg == lr);
    masm.branch(r0);
}


} // namespace jit
} // namespace js

#endif // JS_ION

#endif /* jit_arm_BaselineHelpers_arm_h */