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 /* -*- 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/. */

 #include "jsprf.h"

 #include "jit/arm/Simulator-arm.h"

 #include "jit/BaselineIC.h"

 #include "jit/BaselineJIT.h"

 #include "jit/CompileInfo.h"

 #include "jit/IonSpewer.h"

 #include "jit/Recover.h"

 #include "jit/RematerializedFrame.h"

 #include "vm/ArgumentsObject.h"

 #include "vm/Debugger.h"

 #include "vm/TraceLogging.h"

 #include "jsscriptinlines.h"

 #include "jit/IonFrames-inl.h"

 using namespace js;

 using namespace js::jit;

 // BaselineStackBuilder may reallocate its buffer if the current one is too

 // small. To avoid dangling pointers, BufferPointer represents a pointer into

 // this buffer as a pointer to the header and a fixed offset.

 template <typename T>

 class BufferPointer

 {

     BaselineBailoutInfo **header_;

     size_t offset_;

     bool heap_;

   public:

     BufferPointer(BaselineBailoutInfo **header, size_t offset, bool heap)

       : header_(header), offset_(offset), heap_(heap)

     { }

     T *get() const {

         BaselineBailoutInfo *header = *header_;

         if (!heap_)

             return (T*)(header->incomingStack + offset_);

         uint8_t *p = header->copyStackTop - offset_;

         JS_ASSERT(p >= header->copyStackBottom && p < header->copyStackTop);

         return (T*)p;

     }

     T &operator*() const { return *get(); }

     T *operator->() const { return get(); }

 };

 /**

  * BaselineStackBuilder helps abstract the process of rebuilding the C stack on the heap.

  * It takes a bailout iterator and keeps track of the point on the C stack from which

  * the reconstructed frames will be written.

  *

  * It exposes methods to write data into the heap memory storing the reconstructed

  * stack.  It also exposes method to easily calculate addresses.  This includes both the

  * virtual address that a particular value will be at when it's eventually copied onto

  * the stack, as well as the current actual address of that value (whether on the heap

  * allocated portion being constructed or the existing stack).

  *

  * The abstraction handles transparent re-allocation of the heap memory when it

  * needs to be enlarged to accomodate new data.  Similarly to the C stack, the

  * data that's written to the reconstructed stack grows from high to low in memory.

  *

  * The lowest region of the allocated memory contains a BaselineBailoutInfo structure that

  * points to the start and end of the written data.

  */

 struct BaselineStackBuilder

 {

     IonBailoutIterator &iter_;

     IonJSFrameLayout *frame_;

     static size_t HeaderSize() {

         return AlignBytes(sizeof(BaselineBailoutInfo), sizeof(void *));

     };

     size_t bufferTotal_;

     size_t bufferAvail_;

     size_t bufferUsed_;

     uint8_t *buffer_;

     BaselineBailoutInfo *header_;

     size_t framePushed_;

     BaselineStackBuilder(IonBailoutIterator &iter, size_t initialSize)

       : iter_(iter),

         frame_(static_cast<IonJSFrameLayout*>(iter.current())),

         bufferTotal_(initialSize),

         bufferAvail_(0),

         bufferUsed_(0),

         buffer_(nullptr),

         header_(nullptr),

         framePushed_(0)

     {

         JS_ASSERT(bufferTotal_ >= HeaderSize());

     }

     ~BaselineStackBuilder() {

         js_free(buffer_);

     }

     bool init() {

         JS_ASSERT(!buffer_);

         JS_ASSERT(bufferUsed_ == 0);

         buffer_ = reinterpret_cast<uint8_t *>(js_calloc(bufferTotal_));

         if (!buffer_)

             return false;

         bufferAvail_ = bufferTotal_ - HeaderSize();

         bufferUsed_ = 0;

         header_ = reinterpret_cast<BaselineBailoutInfo *>(buffer_);

         header_->incomingStack = reinterpret_cast<uint8_t *>(frame_);

         header_->copyStackTop = buffer_ + bufferTotal_;

         header_->copyStackBottom = header_->copyStackTop;

         header_->setR0 = 0;

         header_->valueR0 = UndefinedValue();

         header_->setR1 = 0;

         header_->valueR1 = UndefinedValue();

         header_->resumeFramePtr = nullptr;

         header_->resumeAddr = nullptr;

         header_->monitorStub = nullptr;

         header_->numFrames = 0;

         return true;

     }

     bool enlarge() {

         JS_ASSERT(buffer_ != nullptr);

         if (bufferTotal_ & mozilla::tl::MulOverflowMask<2>::value)

             return false;

         size_t newSize = bufferTotal_ * 2;

         uint8_t *newBuffer = reinterpret_cast<uint8_t *>(js_calloc(newSize));

         if (!newBuffer)

             return false;

         memcpy((newBuffer + newSize) - bufferUsed_, header_->copyStackBottom, bufferUsed_);

         memcpy(newBuffer, header_, sizeof(BaselineBailoutInfo));

         js_free(buffer_);

         buffer_ = newBuffer;

         bufferTotal_ = newSize;

         bufferAvail_ = newSize - (HeaderSize() + bufferUsed_);

         header_ = reinterpret_cast<BaselineBailoutInfo *>(buffer_);

         header_->copyStackTop = buffer_ + bufferTotal_;

         header_->copyStackBottom = header_->copyStackTop - bufferUsed_;

         return true;

     }

     BaselineBailoutInfo *info() {

         JS_ASSERT(header_ == reinterpret_cast<BaselineBailoutInfo *>(buffer_));

         return header_;

     }

     BaselineBailoutInfo *takeBuffer() {

         JS_ASSERT(header_ == reinterpret_cast<BaselineBailoutInfo *>(buffer_));

         buffer_ = nullptr;

         return header_;

     }

     void resetFramePushed() {

         framePushed_ = 0;

     }

     size_t framePushed() const {

         return framePushed_;

     }

     bool subtract(size_t size, const char *info = nullptr) {

         // enlarge the buffer if need be.

         while (size > bufferAvail_) {

             if (!enlarge())

                 return false;

         }

         // write out element.

         header_->copyStackBottom -= size;

         bufferAvail_ -= size;

         bufferUsed_ += size;

         framePushed_ += size;

         if (info) {

             IonSpew(IonSpew_BaselineBailouts,

                     "      SUB_%03d   %p/%p %-15s",

                     (int) size, header_->copyStackBottom, virtualPointerAtStackOffset(0), info);

         }

         return true;

     }

     template <typename T>

     bool write(const T &t) {

         if (!subtract(sizeof(T)))

             return false;

         memcpy(header_->copyStackBottom, &t, sizeof(T));

         return true;

     }

     template <typename T>

     bool writePtr(T *t, const char *info) {

         if (!write<T *>(t))

             return false;

         if (info)

             IonSpew(IonSpew_BaselineBailouts,

                     "      WRITE_PTR %p/%p %-15s %p",

                     header_->copyStackBottom, virtualPointerAtStackOffset(0), info, t);

         return true;

     }

     bool writeWord(size_t w, const char *info) {

         if (!write<size_t>(w))

             return false;

         if (info) {

             if (sizeof(size_t) == 4) {

                 IonSpew(IonSpew_BaselineBailouts,

                         "      WRITE_WRD %p/%p %-15s %08x",

                         header_->copyStackBottom, virtualPointerAtStackOffset(0), info, w);

             } else {

                 IonSpew(IonSpew_BaselineBailouts,

                         "      WRITE_WRD %p/%p %-15s %016llx",

                         header_->copyStackBottom, virtualPointerAtStackOffset(0), info, w);

             }

         }

         return true;

     }

     bool writeValue(Value val, const char *info) {

         if (!write<Value>(val))

             return false;

         if (info) {

             IonSpew(IonSpew_BaselineBailouts,

                     "      WRITE_VAL %p/%p %-15s %016llx",

                     header_->copyStackBottom, virtualPointerAtStackOffset(0), info,

                     *((uint64_t *) &val));

         }

         return true;

     }

     Value popValue() {

         JS_ASSERT(bufferUsed_ >= sizeof(Value));

         JS_ASSERT(framePushed_ >= sizeof(Value));

         bufferAvail_ += sizeof(Value);

         bufferUsed_ -= sizeof(Value);

         framePushed_ -= sizeof(Value);

         Value result = *((Value *) header_->copyStackBottom);

         header_->copyStackBottom += sizeof(Value);

         return result;

     }

     void popValueInto(PCMappingSlotInfo::SlotLocation loc) {

         JS_ASSERT(PCMappingSlotInfo::ValidSlotLocation(loc));

         switch(loc) {

           case PCMappingSlotInfo::SlotInR0:

             header_->setR0 = 1;

             header_->valueR0 = popValue();

             break;

           case PCMappingSlotInfo::SlotInR1:

             header_->setR1 = 1;

             header_->valueR1 = popValue();

             break;

           default:

             JS_ASSERT(loc == PCMappingSlotInfo::SlotIgnore);

             popValue();

             break;

         }

     }

     void setResumeFramePtr(void *resumeFramePtr) {

         header_->resumeFramePtr = resumeFramePtr;

     }

     void setResumeAddr(void *resumeAddr) {

         header_->resumeAddr = resumeAddr;

     }

     void setMonitorStub(ICStub *stub) {

         header_->monitorStub = stub;

     }

     template <typename T>

     BufferPointer<T> pointerAtStackOffset(size_t offset) {

         if (offset < bufferUsed_) {

             // Calculate offset from copyStackTop.

             offset = header_->copyStackTop - (header_->copyStackBottom + offset);

             return BufferPointer<T>(&header_, offset, /* heap = */ true);

         }

         return BufferPointer<T>(&header_, offset - bufferUsed_, /* heap = */ false);

     }

     BufferPointer<Value> valuePointerAtStackOffset(size_t offset) {

         return pointerAtStackOffset<Value>(offset);

     }

     inline uint8_t *virtualPointerAtStackOffset(size_t offset) {

         if (offset < bufferUsed_)

             return reinterpret_cast<uint8_t *>(frame_) - (bufferUsed_ - offset);

         return reinterpret_cast<uint8_t *>(frame_) + (offset - bufferUsed_);

     }

     inline IonJSFrameLayout *startFrame() {

         return frame_;

     }

     BufferPointer<IonJSFrameLayout> topFrameAddress() {

         return pointerAtStackOffset<IonJSFrameLayout>(0);

     }

     //

     // This method should only be called when the builder is in a state where it is

     // starting to construct the stack frame for the next callee.  This means that

     // the lowest value on the constructed stack is the return address for the previous

     // caller frame.

     //

     // This method is used to compute the value of the frame pointer (e.g. ebp on x86)

     // that would have been saved by the baseline jitcode when it was entered.  In some

     // cases, this value can be bogus since we can ensure that the caller would have saved

     // it anyway.

     //

     void *calculatePrevFramePtr() {

         // Get the incoming frame.

         BufferPointer<IonJSFrameLayout> topFrame = topFrameAddress();

         FrameType type = topFrame->prevType();

         // For IonJS and Entry frames, the "saved" frame pointer in the baseline

         // frame is meaningless, since Ion saves all registers before calling other ion

         // frames, and the entry frame saves all registers too.

         if (type == JitFrame_IonJS || type == JitFrame_Entry)

             return nullptr;

         // BaselineStub - Baseline calling into Ion.

         //  PrevFramePtr needs to point to the BaselineStubFrame's saved frame pointer.

         //      STACK_START_ADDR + IonJSFrameLayout::Size() + PREV_FRAME_SIZE

         //                      - IonBaselineStubFrameLayout::reverseOffsetOfSavedFramePtr()

         if (type == JitFrame_BaselineStub) {

             size_t offset = IonJSFrameLayout::Size() + topFrame->prevFrameLocalSize() +

                             IonBaselineStubFrameLayout::reverseOffsetOfSavedFramePtr();

             return virtualPointerAtStackOffset(offset);

         }

         JS_ASSERT(type == JitFrame_Rectifier);

         // Rectifier - behaviour depends on the frame preceding the rectifier frame, and

         // whether the arch is x86 or not.  The x86 rectifier frame saves the frame pointer,

         // so we can calculate it directly.  For other archs, the previous frame pointer

         // is stored on the stack in the frame that precedes the rectifier frame.

         size_t priorOffset = IonJSFrameLayout::Size() + topFrame->prevFrameLocalSize();

 #if defined(JS_CODEGEN_X86)

         // On X86, the FramePointer is pushed as the first value in the Rectifier frame.

         JS_ASSERT(BaselineFrameReg == FramePointer);

         priorOffset -= sizeof(void *);

         return virtualPointerAtStackOffset(priorOffset);

 #elif defined(JS_CODEGEN_X64) || defined(JS_CODEGEN_ARM) || defined(JS_CODEGEN_MIPS)

         // On X64, ARM and MIPS, the frame pointer save location depends on

         // the caller of the rectifier frame.

         BufferPointer<IonRectifierFrameLayout> priorFrame =

             pointerAtStackOffset<IonRectifierFrameLayout>(priorOffset);

         FrameType priorType = priorFrame->prevType();

         JS_ASSERT(priorType == JitFrame_IonJS || priorType == JitFrame_BaselineStub);

         // If the frame preceding the rectifier is an IonJS frame, then once again

         // the frame pointer does not matter.

         if (priorType == JitFrame_IonJS)

             return nullptr;

         // Otherwise, the frame preceding the rectifier is a BaselineStub frame.

         //  let X = STACK_START_ADDR + IonJSFrameLayout::Size() + PREV_FRAME_SIZE

         //      X + IonRectifierFrameLayout::Size()

         //        + ((IonRectifierFrameLayout *) X)->prevFrameLocalSize()

         //        - BaselineStubFrameLayout::reverseOffsetOfSavedFramePtr()

         size_t extraOffset = IonRectifierFrameLayout::Size() + priorFrame->prevFrameLocalSize() +

                              IonBaselineStubFrameLayout::reverseOffsetOfSavedFramePtr();

         return virtualPointerAtStackOffset(priorOffset + extraOffset);

 #else

 #  error "Bad architecture!"

 #endif

     }

 };

 static inline bool

 IsInlinableFallback(ICFallbackStub *icEntry)

 {

     return icEntry->isCall_Fallback() || icEntry->isGetProp_Fallback() ||

            icEntry->isSetProp_Fallback();

 }

 static inline void*

 GetStubReturnAddress(JSContext *cx, jsbytecode *pc)

 {

     if (IsGetPropPC(pc))

         return cx->compartment()->jitCompartment()->baselineGetPropReturnFromIonAddr();

     if (IsSetPropPC(pc))

         return cx->compartment()->jitCompartment()->baselineSetPropReturnFromIonAddr();

     // This should be a call op of some kind, now.

     JS_ASSERT(IsCallPC(pc));

     return cx->compartment()->jitCompartment()->baselineCallReturnFromIonAddr();

 }

 static inline jsbytecode *

 GetNextNonLoopEntryPc(jsbytecode *pc)

 {

     JSOp op = JSOp(*pc);

     if (op == JSOP_GOTO)

         return pc + GET_JUMP_OFFSET(pc);

     if (op == JSOP_LOOPENTRY || op == JSOP_NOP || op == JSOP_LOOPHEAD)

         return GetNextPc(pc);

     return pc;

 }

 // For every inline frame, we write out the following data:

 //

 //                      |      ...      |

 //                      +---------------+

 //                      |  Descr(???)   |  --- Descr size here is (PREV_FRAME_SIZE)

 //                      +---------------+

 //                      |  ReturnAddr   |

 //             --       +===============+  --- OVERWRITE STARTS HERE  (START_STACK_ADDR)

 //             |        | PrevFramePtr  |

 //             |    +-> +---------------+

 //             |    |   |   Baseline    |

 //             |    |   |    Frame      |

 //             |    |   +---------------+

 //             |    |   |    Fixed0     |

 //             |    |   +---------------+

 //         +--<     |   |     ...       |

 //         |   |    |   +---------------+

 //         |   |    |   |    FixedF     |

 //         |   |    |   +---------------+

 //         |   |    |   |    Stack0     |

 //         |   |    |   +---------------+

 //         |   |    |   |     ...       |

 //         |   |    |   +---------------+

 //         |   |    |   |    StackS     |

 //         |   --   |   +---------------+  --- IF NOT LAST INLINE FRAME,

 //         +------------|  Descr(BLJS)  |  --- CALLING INFO STARTS HERE

 //                  |   +---------------+

 //                  |   |  ReturnAddr   | <-- return into main jitcode after IC

 //             --   |   +===============+

 //             |    |   |    StubPtr    |

 //             |    |   +---------------+

 //             |    +---|   FramePtr    |

 //             |        +---------------+

 //             |        |     ArgA      |

 //             |        +---------------+

 //             |        |     ...       |

 //         +--<         +---------------+

 //         |   |        |     Arg0      |

 //         |   |        +---------------+

 //         |   |        |     ThisV     |

 //         |   --       +---------------+

 //         |            |  ActualArgC   |

 //         |            +---------------+

 //         |            |  CalleeToken  |

 //         |            +---------------+

 //         +------------| Descr(BLStub) |

 //                      +---------------+

 //                      |  ReturnAddr   | <-- return into ICCall_Scripted IC

 //             --       +===============+ --- IF CALLEE FORMAL ARGS > ActualArgC

 //             |        |  UndefinedU   |

 //             |        +---------------+

 //             |        |     ...       |

 //             |        +---------------+

 //             |        |  Undefined0   |

 //             |        +---------------+

 //         +--<         |     ArgA      |

 //         |   |        +---------------+

 //         |   |        |     ...       |

 //         |   |        +---------------+

 //         |   |        |     Arg0      |

 //         |   |        +---------------+

 //         |   |        |     ThisV     |

 //         |   --       +---------------+

 //         |            |  ActualArgC   |

 //         |            +---------------+

 //         |            |  CalleeToken  |

 //         |            +---------------+

 //         +------------|  Descr(Rect)  |

 //                      +---------------+

 //                      |  ReturnAddr   | <-- return into ArgumentsRectifier after call

 //                      +===============+

 //

 static bool

 InitFromBailout(JSContext *cx, HandleScript caller, jsbytecode *callerPC,

                 HandleFunction fun, HandleScript script, IonScript *ionScript,

                 SnapshotIterator &iter, bool invalidate, BaselineStackBuilder &builder,

                 AutoValueVector &startFrameFormals, MutableHandleFunction nextCallee,

                 jsbytecode **callPC, const ExceptionBailoutInfo *excInfo)

 {

     MOZ_ASSERT(script->hasBaselineScript());

     // Are we catching an exception?

     bool catchingException = excInfo && excInfo->catchingException();

     // If we are catching an exception, we are bailing out to a catch or

     // finally block and this is the frame where we will resume. Usually the

     // expression stack should be empty in this case but there can be

     // iterators on the stack.

     uint32_t exprStackSlots;

     if (catchingException)

         exprStackSlots = excInfo->numExprSlots();

     else

         exprStackSlots = iter.numAllocations() - (script->nfixed() + CountArgSlots(script, fun));

     builder.resetFramePushed();

     // Build first baseline frame:

     // +===============+

     // | PrevFramePtr  |

     // +---------------+

     // |   Baseline    |

     // |    Frame      |

     // +---------------+

     // |    Fixed0     |

     // +---------------+

     // |     ...       |

     // +---------------+

     // |    FixedF     |

     // +---------------+

     // |    Stack0     |

     // +---------------+

     // |     ...       |

     // +---------------+

     // |    StackS     |

     // +---------------+  --- IF NOT LAST INLINE FRAME,

     // |  Descr(BLJS)  |  --- CALLING INFO STARTS HERE

     // +---------------+

     // |  ReturnAddr   | <-- return into main jitcode after IC

     // +===============+

     IonSpew(IonSpew_BaselineBailouts, "      Unpacking %s:%d", script->filename(), script->lineno());

     IonSpew(IonSpew_BaselineBailouts, "      [BASELINE-JS FRAME]");

     // Calculate and write the previous frame pointer value.

     // Record the virtual stack offset at this location.  Later on, if we end up

     // writing out a BaselineStub frame for the next callee, we'll need to save the

     // address.

     void *prevFramePtr = builder.calculatePrevFramePtr();

     if (!builder.writePtr(prevFramePtr, "PrevFramePtr"))

         return false;

     prevFramePtr = builder.virtualPointerAtStackOffset(0);

     // Write struct BaselineFrame.

     if (!builder.subtract(BaselineFrame::Size(), "BaselineFrame"))

         return false;

     BufferPointer<BaselineFrame> blFrame = builder.pointerAtStackOffset<BaselineFrame>(0);

     // Initialize BaselineFrame::frameSize

     uint32_t frameSize = BaselineFrame::Size() + BaselineFrame::FramePointerOffset +

                          (sizeof(Value) * (script->nfixed() + exprStackSlots));

     IonSpew(IonSpew_BaselineBailouts, "      FrameSize=%d", (int) frameSize);

     blFrame->setFrameSize(frameSize);

     uint32_t flags = 0;

     // If SPS Profiler is enabled, mark the frame as having pushed an SPS entry.

     // This may be wrong for the last frame of ArgumentCheck bailout, but

     // that will be fixed later.

     if (ionScript->hasSPSInstrumentation()) {

         if (callerPC == nullptr) {

             IonSpew(IonSpew_BaselineBailouts, "      Setting SPS flag on top frame!");

             flags |= BaselineFrame::HAS_PUSHED_SPS_FRAME;

         } else if (js_JitOptions.profileInlineFrames) {

             IonSpew(IonSpew_BaselineBailouts, "      Setting SPS flag on inline frame!");

             flags |= BaselineFrame::HAS_PUSHED_SPS_FRAME;

         }

     }

     // Initialize BaselineFrame's scopeChain and argsObj

     JSObject *scopeChain = nullptr;

     Value returnValue;

     ArgumentsObject *argsObj = nullptr;

     BailoutKind bailoutKind = iter.bailoutKind();

     if (bailoutKind == Bailout_ArgumentCheck) {

         // Temporary hack -- skip the (unused) scopeChain, because it could be

         // bogus (we can fail before the scope chain slot is set). Strip the

         // hasScopeChain flag and this will be fixed up later in |FinishBailoutToBaseline|,

         // which calls |EnsureHasScopeObjects|.

         IonSpew(IonSpew_BaselineBailouts, "      Bailout_ArgumentCheck! (no valid scopeChain)");

         iter.skip();

         // skip |return value|

         iter.skip();

         returnValue = UndefinedValue();

         // Scripts with |argumentsHasVarBinding| have an extra slot.

         if (script->argumentsHasVarBinding()) {

             IonSpew(IonSpew_BaselineBailouts,

                     "      Bailout_ArgumentCheck for script with argumentsHasVarBinding!"

                     "Using empty arguments object");

             iter.skip();

         }

     } else {

         Value v = iter.read();

         if (v.isObject()) {

             scopeChain = &v.toObject();

             if (fun && fun->isHeavyweight())

                 flags |= BaselineFrame::HAS_CALL_OBJ;

         } else {

             JS_ASSERT(v.isUndefined() || v.isMagic(JS_OPTIMIZED_OUT));

             // Get scope chain from function or script.

             if (fun) {

                 // If pcOffset == 0, we may have to push a new call object, so

                 // we leave scopeChain nullptr and enter baseline code before

                 // the prologue.

                 if (iter.pcOffset() != 0 || iter.resumeAfter())

                     scopeChain = fun->environment();

             } else {

                 // For global, compile-and-go scripts the scope chain is the

                 // script's global (Ion does not compile non-compile-and-go

                 // scripts). Also note that it's invalid to resume into the

                 // prologue in this case because the prologue expects the scope

                 // chain in R1 for eval and global scripts.

                 JS_ASSERT(!script->isForEval());

                 JS_ASSERT(script->compileAndGo());

                 scopeChain = &(script->global());

             }

         }

         // Make sure to add HAS_RVAL to flags here because setFlags() below

         // will clobber it.

         returnValue = iter.read();

         flags |= BaselineFrame::HAS_RVAL;

         // If script maybe has an arguments object, the third slot will hold it.

         if (script->argumentsHasVarBinding()) {

             v = iter.read();

             JS_ASSERT(v.isObject() || v.isUndefined() || v.isMagic(JS_OPTIMIZED_OUT));

             if (v.isObject())

                 argsObj = &v.toObject().as<ArgumentsObject>();

         }

     }

     IonSpew(IonSpew_BaselineBailouts, "      ScopeChain=%p", scopeChain);

     blFrame->setScopeChain(scopeChain);

     IonSpew(IonSpew_BaselineBailouts, "      ReturnValue=%016llx", *((uint64_t *) &returnValue));

     blFrame->setReturnValue(returnValue);

     // Do not need to initialize scratchValue field in BaselineFrame.

     blFrame->setFlags(flags);

     // initArgsObjUnchecked modifies the frame's flags, so call it after setFlags.

     if (argsObj)

         blFrame->initArgsObjUnchecked(*argsObj);

     if (fun) {

         // The unpacked thisv and arguments should overwrite the pushed args present

         // in the calling frame.

         Value thisv = iter.read();

         IonSpew(IonSpew_BaselineBailouts, "      Is function!");

         IonSpew(IonSpew_BaselineBailouts, "      thisv=%016llx", *((uint64_t *) &thisv));

         size_t thisvOffset = builder.framePushed() + IonJSFrameLayout::offsetOfThis();

         *builder.valuePointerAtStackOffset(thisvOffset) = thisv;

         JS_ASSERT(iter.numAllocations() >= CountArgSlots(script, fun));

         IonSpew(IonSpew_BaselineBailouts, "      frame slots %u, nargs %u, nfixed %u",

                 iter.numAllocations(), fun->nargs(), script->nfixed());

         if (!callerPC) {

             // This is the first frame. Store the formals in a Vector until we

             // are done. Due to UCE and phi elimination, we could store an

             // UndefinedValue() here for formals we think are unused, but

             // locals may still reference the original argument slot

             // (MParameter/LArgument) and expect the original Value.

             JS_ASSERT(startFrameFormals.empty());

             if (!startFrameFormals.resize(fun->nargs()))

                 return false;

         }

         for (uint32_t i = 0; i < fun->nargs(); i++) {

             Value arg = iter.read();

             IonSpew(IonSpew_BaselineBailouts, "      arg %d = %016llx",

                         (int) i, *((uint64_t *) &arg));

             if (callerPC) {

                 size_t argOffset = builder.framePushed() + IonJSFrameLayout::offsetOfActualArg(i);

                 *builder.valuePointerAtStackOffset(argOffset) = arg;

             } else {

                 startFrameFormals[i] = arg;

             }

         }

     }

     for (uint32_t i = 0; i < script->nfixed(); i++) {

         Value slot = iter.read();

         if (!builder.writeValue(slot, "FixedValue"))

             return false;

     }

     // Get the pc. If we are handling an exception, resume at the pc of the

     // catch or finally block.

     jsbytecode *pc = catchingException ? excInfo->resumePC() : script->offsetToPC(iter.pcOffset());

     bool resumeAfter = catchingException ? false : iter.resumeAfter();

     JSOp op = JSOp(*pc);

     // Fixup inlined JSOP_FUNCALL, JSOP_FUNAPPLY, and accessors on the caller side.

     // On the caller side this must represent like the function wasn't inlined.

     uint32_t pushedSlots = 0;

     AutoValueVector savedCallerArgs(cx);

     bool needToSaveArgs = op == JSOP_FUNAPPLY || IsGetPropPC(pc) || IsSetPropPC(pc);

     if (iter.moreFrames() && (op == JSOP_FUNCALL || needToSaveArgs))

     {

         uint32_t inlined_args = 0;

         if (op == JSOP_FUNCALL)

             inlined_args = 2 + GET_ARGC(pc) - 1;

         else if (op == JSOP_FUNAPPLY)

             inlined_args = 2 + blFrame->numActualArgs();

         else

             inlined_args = 2 + IsSetPropPC(pc);

         JS_ASSERT(exprStackSlots >= inlined_args);

         pushedSlots = exprStackSlots - inlined_args;

         IonSpew(IonSpew_BaselineBailouts,

                 "      pushing %u expression stack slots before fixup",

                 pushedSlots);

         for (uint32_t i = 0; i < pushedSlots; i++) {

             Value v = iter.read();

             if (!builder.writeValue(v, "StackValue"))

                 return false;

         }

         if (op == JSOP_FUNCALL) {

             // When funcall got inlined and the native js_fun_call was bypassed,

             // the stack state is incorrect. To restore correctly it must look like

             // js_fun_call was actually called. This means transforming the stack

             // from |target, this, args| to |js_fun_call, target, this, args|

             // The js_fun_call is never read, so just pushing undefined now.

             IonSpew(IonSpew_BaselineBailouts, "      pushing undefined to fixup funcall");

             if (!builder.writeValue(UndefinedValue(), "StackValue"))

                 return false;

         }

         if (needToSaveArgs) {

             // When an accessor is inlined, the whole thing is a lie. There

             // should never have been a call there. Fix the caller's stack to

             // forget it ever happened.

             // When funapply gets inlined we take all arguments out of the

             // arguments array. So the stack state is incorrect. To restore

             // correctly it must look like js_fun_apply was actually called.

             // This means transforming the stack from |target, this, arg1, ...|

             // to |js_fun_apply, target, this, argObject|.

             // Since the information is never read, we can just push undefined

             // for all values.

             if (op == JSOP_FUNAPPLY) {

                 IonSpew(IonSpew_BaselineBailouts, "      pushing 4x undefined to fixup funapply");

                 if (!builder.writeValue(UndefinedValue(), "StackValue"))

                     return false;

                 if (!builder.writeValue(UndefinedValue(), "StackValue"))

                     return false;

                 if (!builder.writeValue(UndefinedValue(), "StackValue"))

                     return false;

                 if (!builder.writeValue(UndefinedValue(), "StackValue"))

                     return false;

             }

             // Save the actual arguments. They are needed on the callee side

             // as the arguments. Else we can't recover them.

             if (!savedCallerArgs.resize(inlined_args))

                 return false;

             for (uint32_t i = 0; i < inlined_args; i++)

                 savedCallerArgs[i] = iter.read();

             if (IsSetPropPC(pc)) {

                 // We would love to just save all the arguments and leave them

                 // in the stub frame pushed below, but we will lose the inital

                 // argument which the function was called with, which we must

                 // return to the caller, even if the setter internally modifies

                 // its arguments. Stash the initial argument on the stack, to be

                 // later retrieved by the SetProp_Fallback stub.

                 Value initialArg = savedCallerArgs[inlined_args - 1];

                 IonSpew(IonSpew_BaselineBailouts, "     pushing setter's initial argument");

                 if (!builder.writeValue(initialArg, "StackValue"))

                     return false;

             }

             pushedSlots = exprStackSlots;

         }

     }

     IonSpew(IonSpew_BaselineBailouts, "      pushing %u expression stack slots",

                                       exprStackSlots - pushedSlots);

     for (uint32_t i = pushedSlots; i < exprStackSlots; i++) {

         Value v;

         if (!iter.moreFrames() && i == exprStackSlots - 1 &&

             cx->runtime()->hasIonReturnOverride())

         {

             // If coming from an invalidation bailout, and this is the topmost

             // value, and a value override has been specified, don't read from the

             // iterator. Otherwise, we risk using a garbage value.

             JS_ASSERT(invalidate);

             iter.skip();

             IonSpew(IonSpew_BaselineBailouts, "      [Return Override]");

             v = cx->runtime()->takeIonReturnOverride();

         } else if (excInfo && excInfo->propagatingIonExceptionForDebugMode()) {

             // If we are in the middle of propagating an exception from Ion by

             // bailing to baseline due to debug mode, we might not have all

             // the stack if we are at the newest frame.

             //

             // For instance, if calling |f()| pushed an Ion frame which threw,

             // the snapshot expects the return value to be pushed, but it's

             // possible nothing was pushed before we threw. Iterators might

             // still be on the stack, so we can't just drop the stack.

             MOZ_ASSERT(cx->compartment()->debugMode());

             if (iter.moreFrames())

                 v = iter.read();

             else

                 v = MagicValue(JS_OPTIMIZED_OUT);

         } else {

             v = iter.read();

         }

         if (!builder.writeValue(v, "StackValue"))

             return false;

     }

     size_t endOfBaselineJSFrameStack = builder.framePushed();

     // If we are resuming at a LOOPENTRY op, resume at the next op to avoid

     // a bailout -> enter Ion -> bailout loop with --ion-eager. See also

     // ThunkToInterpreter.

     //

     // The algorithm below is the "tortoise and the hare" algorithm. See bug

     // 994444 for more explanation.

     if (!resumeAfter) {

         jsbytecode *fasterPc = pc;

         while (true) {

             pc = GetNextNonLoopEntryPc(pc);

             fasterPc = GetNextNonLoopEntryPc(GetNextNonLoopEntryPc(fasterPc));

             if (fasterPc == pc)

                 break;

         }

         op = JSOp(*pc);

     }

     uint32_t pcOff = script->pcToOffset(pc);

     bool isCall = IsCallPC(pc);

     BaselineScript *baselineScript = script->baselineScript();

 #ifdef DEBUG

     uint32_t expectedDepth;

     bool reachablePC;

     if (!ReconstructStackDepth(cx, script, resumeAfter ? GetNextPc(pc) : pc, &expectedDepth, &reachablePC))

         return false;

     if (reachablePC) {

         if (op != JSOP_FUNAPPLY || !iter.moreFrames() || resumeAfter) {

             if (op == JSOP_FUNCALL) {

                 // For fun.call(this, ...); the reconstructStackDepth will

                 // include the this. When inlining that is not included.

                 // So the exprStackSlots will be one less.

                 JS_ASSERT(expectedDepth - exprStackSlots <= 1);

             } else if (iter.moreFrames() && (IsGetPropPC(pc) || IsSetPropPC(pc))) {

                 // Accessors coming out of ion are inlined via a complete

                 // lie perpetrated by the compiler internally. Ion just rearranges

                 // the stack, and pretends that it looked like a call all along.

                 // This means that the depth is actually one *more* than expected

                 // by the interpreter, as there is now a JSFunction, |this| and [arg],

                 // rather than the expected |this| and [arg]

                 // Note that none of that was pushed, but it's still reflected

                 // in exprStackSlots.

                 JS_ASSERT(exprStackSlots - expectedDepth == 1);

             } else {

                 // For fun.apply({}, arguments) the reconstructStackDepth will

                 // have stackdepth 4, but it could be that we inlined the

                 // funapply. In that case exprStackSlots, will have the real

                 // arguments in the slots and not be 4.

                 JS_ASSERT(exprStackSlots == expectedDepth);

             }

         }

     }

     IonSpew(IonSpew_BaselineBailouts, "      Resuming %s pc offset %d (op %s) (line %d) of %s:%d",

                 resumeAfter ? "after" : "at", (int) pcOff, js_CodeName[op],

                 PCToLineNumber(script, pc), script->filename(), (int) script->lineno());

     IonSpew(IonSpew_BaselineBailouts, "      Bailout kind: %s",

             BailoutKindString(bailoutKind));

 #endif

     // If this was the last inline frame, or we are bailing out to a catch or

     // finally block in this frame, then unpacking is almost done.

     if (!iter.moreFrames() || catchingException) {

         // Last frame, so PC for call to next frame is set to nullptr.

         *callPC = nullptr;

         // If the bailout was a resumeAfter, and the opcode is monitored,

         // then the bailed out state should be in a position to enter

         // into the ICTypeMonitor chain for the op.

         bool enterMonitorChain = false;

         if (resumeAfter && (js_CodeSpec[op].format & JOF_TYPESET)) {

             // Not every monitored op has a monitored fallback stub, e.g.

             // JSOP_NEWOBJECT, which always returns the same type for a

             // particular script/pc location.

             ICEntry &icEntry = baselineScript->icEntryFromPCOffset(pcOff);

             ICFallbackStub *fallbackStub = icEntry.firstStub()->getChainFallback();

             if (fallbackStub->isMonitoredFallback())

                 enterMonitorChain = true;

         }

         uint32_t numCallArgs = isCall ? GET_ARGC(pc) : 0;

         if (resumeAfter && !enterMonitorChain)

             pc = GetNextPc(pc);

         builder.setResumeFramePtr(prevFramePtr);

         if (enterMonitorChain) {

             ICEntry &icEntry = baselineScript->icEntryFromPCOffset(pcOff);

             ICFallbackStub *fallbackStub = icEntry.firstStub()->getChainFallback();

             JS_ASSERT(fallbackStub->isMonitoredFallback());

             IonSpew(IonSpew_BaselineBailouts, "      [TYPE-MONITOR CHAIN]");

             ICMonitoredFallbackStub *monFallbackStub = fallbackStub->toMonitoredFallbackStub();

             ICStub *firstMonStub = monFallbackStub->fallbackMonitorStub()->firstMonitorStub();

             // To enter a monitoring chain, we load the top stack value into R0

             IonSpew(IonSpew_BaselineBailouts, "      Popping top stack value into R0.");

             builder.popValueInto(PCMappingSlotInfo::SlotInR0);

             // Need to adjust the frameSize for the frame to match the values popped

             // into registers.

             frameSize -= sizeof(Value);

             blFrame->setFrameSize(frameSize);

             IonSpew(IonSpew_BaselineBailouts, "      Adjusted framesize -= %d: %d",

                             (int) sizeof(Value), (int) frameSize);

             // If resuming into a JSOP_CALL, baseline keeps the arguments on the

             // stack and pops them only after returning from the call IC.

             // Push undefs onto the stack in anticipation of the popping of the

             // callee, thisv, and actual arguments passed from the caller's frame.

             if (isCall) {

                 builder.writeValue(UndefinedValue(), "CallOp FillerCallee");

                 builder.writeValue(UndefinedValue(), "CallOp FillerThis");

                 for (uint32_t i = 0; i < numCallArgs; i++)

                     builder.writeValue(UndefinedValue(), "CallOp FillerArg");

                 frameSize += (numCallArgs + 2) * sizeof(Value);

                 blFrame->setFrameSize(frameSize);

                 IonSpew(IonSpew_BaselineBailouts, "      Adjusted framesize += %d: %d",

                                 (int) ((numCallArgs + 2) * sizeof(Value)), (int) frameSize);

             }

             // Set the resume address to the return point from the IC, and set

             // the monitor stub addr.

             builder.setResumeAddr(baselineScript->returnAddressForIC(icEntry));

             builder.setMonitorStub(firstMonStub);

             IonSpew(IonSpew_BaselineBailouts, "      Set resumeAddr=%p monitorStub=%p",

                     baselineScript->returnAddressForIC(icEntry), firstMonStub);

         } else {

             // If needed, initialize BaselineBailoutInfo's valueR0 and/or valueR1 with the

             // top stack values.

             PCMappingSlotInfo slotInfo;

             uint8_t *nativeCodeForPC = baselineScript->nativeCodeForPC(script, pc, &slotInfo);

             unsigned numUnsynced = slotInfo.numUnsynced();

             JS_ASSERT(numUnsynced <= 2);

             PCMappingSlotInfo::SlotLocation loc1, loc2;

             if (numUnsynced > 0) {

                 loc1 = slotInfo.topSlotLocation();

                 IonSpew(IonSpew_BaselineBailouts, "      Popping top stack value into %d.",

                             (int) loc1);

                 builder.popValueInto(loc1);

             }

             if (numUnsynced > 1) {

                 loc2 = slotInfo.nextSlotLocation();

                 IonSpew(IonSpew_BaselineBailouts, "      Popping next stack value into %d.",

                             (int) loc2);

                 JS_ASSERT_IF(loc1 != PCMappingSlotInfo::SlotIgnore, loc1 != loc2);

                 builder.popValueInto(loc2);

             }

             // Need to adjust the frameSize for the frame to match the values popped

             // into registers.

             frameSize -= sizeof(Value) * numUnsynced;

             blFrame->setFrameSize(frameSize);

             IonSpew(IonSpew_BaselineBailouts, "      Adjusted framesize -= %d: %d",

                             int(sizeof(Value) * numUnsynced), int(frameSize));

             // If scopeChain is nullptr, then bailout is occurring during argument check.

             // In this case, resume into the prologue.

             uint8_t *opReturnAddr;

             if (scopeChain == nullptr) {

                 // Global and eval scripts expect the scope chain in R1, so only

                 // resume into the prologue for function scripts.

                 JS_ASSERT(fun);

                 JS_ASSERT(numUnsynced == 0);

                 opReturnAddr = baselineScript->prologueEntryAddr();

                 IonSpew(IonSpew_BaselineBailouts, "      Resuming into prologue.");

                 // If bailing into prologue, HAS_PUSHED_SPS_FRAME should not be set on frame.

                 blFrame->unsetPushedSPSFrame();

                 if (cx->runtime()->spsProfiler.enabled()) {

                     if (js_JitOptions.profileInlineFrames) {

                         // If SPS is enabled, there are two corner cases to handle:

                         //  1. If resuming into the prologue, and innermost frame is an inlined

                         //     frame, and bailout is because of argument check failure, then:

                         //          Top SPS profiler entry would be for caller frame.

                         //          Ion would not have set the PC index field on that frame

                         //              (since this bailout happens before MFunctionBoundary).

                         //          Make sure that's done now.

                         //  2. If resuming into the prologue, and the bailout is NOT because of an

                         //     argument check, then:

                         //          Top SPS profiler entry would be for callee frame.

                         //          Ion would already have pushed an SPS entry for this frame.

                         //          The pc for this entry would be set to nullptr.

                         //          Make sure it's set to script->pc.

                         if (caller && bailoutKind == Bailout_ArgumentCheck) {

                             IonSpew(IonSpew_BaselineBailouts, "      Setting PCidx on innermost "

                                     "inlined frame's parent's SPS entry (%s:%d) (pcIdx=%d)!",

                                     caller->filename(), caller->lineno(),

                                     caller->pcToOffset(callerPC));

                             cx->runtime()->spsProfiler.updatePC(caller, callerPC);

                         } else if (bailoutKind != Bailout_ArgumentCheck) {

                             IonSpew(IonSpew_BaselineBailouts,

                                     "      Popping SPS entry for innermost inlined frame");

                             cx->runtime()->spsProfiler.exit(script, fun);

                         }

                     } else {

                         // If not profiling inline frames, then this is logically simpler.

                         //

                         // 1. If resuming into inline code, then the top SPS entry will be

                         // for the outermost caller, and will have an uninitialized PC.

                         // This will be fixed up later in BailoutIonToBaseline.

                         //

                         // 2. If resuming into top-level code prologue, with ArgumentCheck,

                         // no SPS entry will have been pushed.  Can be left alone.

                         //

                         // 3. If resuming into top-level code prologue, without ArgumentCheck,

                         // an SPS entry will have been pushed, and needs to be popped.

                         //

                         // 4. If resuming into top-level code main body, an SPS entry will

                         // have been pushed, and can be left alone.

                         //

                         // Only need to handle case 3 here.

                         if (!caller && bailoutKind != Bailout_ArgumentCheck) {

                             IonSpew(IonSpew_BaselineBailouts,

                                     "      Popping SPS entry for outermost frame");

                             cx->runtime()->spsProfiler.exit(script, fun);

                         }

                     }

                 }

             } else {

                 opReturnAddr = nativeCodeForPC;

             }

             builder.setResumeAddr(opReturnAddr);

             IonSpew(IonSpew_BaselineBailouts, "      Set resumeAddr=%p", opReturnAddr);

         }

         if (cx->runtime()->spsProfiler.enabled()) {

             if (blFrame->hasPushedSPSFrame()) {

                 // Set PC index to 0 for the innermost frame to match what the

                 // interpreter and Baseline do: they update the SPS pc for

                 // JSOP_CALL ops but set it to 0 when running other ops. Ion code

                 // can set the pc to NullPCIndex and this will confuse SPS when

                 // Baseline calls into the VM at non-CALL ops and re-enters JS.

                 IonSpew(IonSpew_BaselineBailouts, "      Setting PCidx for last frame to 0");

                 cx->runtime()->spsProfiler.updatePC(script, script->code());

             }

             // Register bailout with profiler.

             const char *filename = script->filename();

             if (filename == nullptr)

                 filename = "<unknown>";

             unsigned len = strlen(filename) + 200;

             char *buf = js_pod_malloc<char>(len);

             if (buf == nullptr)

                 return false;

             JS_snprintf(buf, len, "%s %s %s on line %d of %s:%d",

                                   BailoutKindString(bailoutKind),

                                   resumeAfter ? "after" : "at",

                                   js_CodeName[op],

                                   int(PCToLineNumber(script, pc)),

                                   filename,

                                   int(script->lineno()));

             cx->runtime()->spsProfiler.markEvent(buf);

             js_free(buf);

         }

         return true;

     }

     *callPC = pc;

     // Write out descriptor of BaselineJS frame.

     size_t baselineFrameDescr = MakeFrameDescriptor((uint32_t) builder.framePushed(),

                                                     JitFrame_BaselineJS);

     if (!builder.writeWord(baselineFrameDescr, "Descriptor"))

         return false;

     // Calculate and write out return address.

     // The icEntry in question MUST have an inlinable fallback stub.

     ICEntry &icEntry = baselineScript->icEntryFromPCOffset(pcOff);

     JS_ASSERT(IsInlinableFallback(icEntry.firstStub()->getChainFallback()));

     if (!builder.writePtr(baselineScript->returnAddressForIC(icEntry), "ReturnAddr"))

         return false;

     // Build baseline stub frame:

     // +===============+

     // |    StubPtr    |

     // +---------------+

     // |   FramePtr    |

     // +---------------+

     // |     ArgA      |

     // +---------------+

     // |     ...       |

     // +---------------+

     // |     Arg0      |

     // +---------------+

     // |     ThisV     |

     // +---------------+

     // |  ActualArgC   |

     // +---------------+

     // |  CalleeToken  |

     // +---------------+

     // | Descr(BLStub) |

     // +---------------+

     // |  ReturnAddr   |

     // +===============+

     IonSpew(IonSpew_BaselineBailouts, "      [BASELINE-STUB FRAME]");

     size_t startOfBaselineStubFrame = builder.framePushed();

     // Write stub pointer.

     JS_ASSERT(IsInlinableFallback(icEntry.fallbackStub()));

     if (!builder.writePtr(icEntry.fallbackStub(), "StubPtr"))

         return false;

     // Write previous frame pointer (saved earlier).

     if (!builder.writePtr(prevFramePtr, "PrevFramePtr"))

         return false;

     prevFramePtr = builder.virtualPointerAtStackOffset(0);

     // Write out actual arguments (and thisv), copied from unpacked stack of BaselineJS frame.

     // Arguments are reversed on the BaselineJS frame's stack values.

     JS_ASSERT(IsIonInlinablePC(pc));

     unsigned actualArgc;

     if (needToSaveArgs) {

         // For FUNAPPLY or an accessor, the arguments are not on the stack anymore,

         // but they are copied in a vector and are written here.

         if (op == JSOP_FUNAPPLY)

             actualArgc = blFrame->numActualArgs();

         else

             actualArgc = IsSetPropPC(pc);

         JS_ASSERT(actualArgc + 2 <= exprStackSlots);

         JS_ASSERT(savedCallerArgs.length() == actualArgc + 2);

         for (unsigned i = 0; i < actualArgc + 1; i++) {

             size_t arg = savedCallerArgs.length() - (i + 1);

             if (!builder.writeValue(savedCallerArgs[arg], "ArgVal"))

                 return false;

         }

     } else {

         actualArgc = GET_ARGC(pc);

         if (op == JSOP_FUNCALL) {

             JS_ASSERT(actualArgc > 0);

             actualArgc--;

         }

         JS_ASSERT(actualArgc + 2 <= exprStackSlots);

         for (unsigned i = 0; i < actualArgc + 1; i++) {

             size_t argSlot = (script->nfixed() + exprStackSlots) - (i + 1);

             if (!builder.writeValue(*blFrame->valueSlot(argSlot), "ArgVal"))

                 return false;

         }

     }

     // In case these arguments need to be copied on the stack again for a rectifier frame,

     // save the framePushed values here for later use.

     size_t endOfBaselineStubArgs = builder.framePushed();

     // Calculate frame size for descriptor.

     size_t baselineStubFrameSize = builder.framePushed() - startOfBaselineStubFrame;

     size_t baselineStubFrameDescr = MakeFrameDescriptor((uint32_t) baselineStubFrameSize,

                                                         JitFrame_BaselineStub);

     // Push actual argc

     if (!builder.writeWord(actualArgc, "ActualArgc"))

         return false;

     // Push callee token (must be a JS Function)

     Value callee;

     if (needToSaveArgs) {

         // The arguments of FUNAPPLY or inlined accessors are not writen to the stack.

         // So get the callee from the specially saved vector.

         callee = savedCallerArgs[0];

     } else {

         uint32_t calleeStackSlot = exprStackSlots - uint32_t(actualArgc + 2);

         size_t calleeOffset = (builder.framePushed() - endOfBaselineJSFrameStack)

             + ((exprStackSlots - (calleeStackSlot + 1)) * sizeof(Value));

         callee = *builder.valuePointerAtStackOffset(calleeOffset);

         IonSpew(IonSpew_BaselineBailouts, "      CalleeStackSlot=%d", (int) calleeStackSlot);

     }

     IonSpew(IonSpew_BaselineBailouts, "      Callee = %016llx", *((uint64_t *) &callee));

     JS_ASSERT(callee.isObject() && callee.toObject().is<JSFunction>());

     JSFunction *calleeFun = &callee.toObject().as<JSFunction>();

     if (!builder.writePtr(CalleeToToken(calleeFun), "CalleeToken"))

         return false;

     nextCallee.set(calleeFun);

     // Push BaselineStub frame descriptor

     if (!builder.writeWord(baselineStubFrameDescr, "Descriptor"))

         return false;

     // Push return address into ICCall_Scripted stub, immediately after the call.

     void *baselineCallReturnAddr = GetStubReturnAddress(cx, pc);

     JS_ASSERT(baselineCallReturnAddr);

     if (!builder.writePtr(baselineCallReturnAddr, "ReturnAddr"))

         return false;

     // If actualArgc >= fun->nargs, then we are done.  Otherwise, we need to push on

     // a reconstructed rectifier frame.

     if (actualArgc >= calleeFun->nargs())

         return true;

     // Push a reconstructed rectifier frame.

     // +===============+

     // |  UndefinedU   |

     // +---------------+

     // |     ...       |

     // +---------------+

     // |  Undefined0   |

     // +---------------+

     // |     ArgA      |

     // +---------------+

     // |     ...       |

     // +---------------+

     // |     Arg0      |

     // +---------------+

     // |     ThisV     |

     // +---------------+

     // |  ActualArgC   |

     // +---------------+

     // |  CalleeToken  |

     // +---------------+

     // |  Descr(Rect)  |

     // +---------------+

     // |  ReturnAddr   |

     // +===============+

     IonSpew(IonSpew_BaselineBailouts, "      [RECTIFIER FRAME]");

     size_t startOfRectifierFrame = builder.framePushed();

     // On x86-only, the frame pointer is saved again in the rectifier frame.

 #if defined(JS_CODEGEN_X86)

     if (!builder.writePtr(prevFramePtr, "PrevFramePtr-X86Only"))

         return false;

 #endif

     // Push undefined for missing arguments.

     for (unsigned i = 0; i < (calleeFun->nargs() - actualArgc); i++) {

         if (!builder.writeValue(UndefinedValue(), "FillerVal"))

             return false;

     }

     // Copy arguments + thisv from BaselineStub frame.

     if (!builder.subtract((actualArgc + 1) * sizeof(Value), "CopiedArgs"))

         return false;

     BufferPointer<uint8_t> stubArgsEnd =

         builder.pointerAtStackOffset<uint8_t>(builder.framePushed() - endOfBaselineStubArgs);

     IonSpew(IonSpew_BaselineBailouts, "      MemCpy from %p", stubArgsEnd.get());

     memcpy(builder.pointerAtStackOffset<uint8_t>(0).get(), stubArgsEnd.get(),

            (actualArgc + 1) * sizeof(Value));

     // Calculate frame size for descriptor.

     size_t rectifierFrameSize = builder.framePushed() - startOfRectifierFrame;

     size_t rectifierFrameDescr = MakeFrameDescriptor((uint32_t) rectifierFrameSize,

                                                      JitFrame_Rectifier);

     // Push actualArgc

     if (!builder.writeWord(actualArgc, "ActualArgc"))

         return false;

     // Push calleeToken again.

     if (!builder.writePtr(CalleeToToken(calleeFun), "CalleeToken"))

         return false;

     // Push rectifier frame descriptor

     if (!builder.writeWord(rectifierFrameDescr, "Descriptor"))

         return false;

     // Push return address into the ArgumentsRectifier code, immediately after the ioncode

     // call.

     void *rectReturnAddr = cx->runtime()->jitRuntime()->getArgumentsRectifierReturnAddr();

     JS_ASSERT(rectReturnAddr);

     if (!builder.writePtr(rectReturnAddr, "ReturnAddr"))

         return false;

     return true;

 }

 uint32_t

 jit::BailoutIonToBaseline(JSContext *cx, JitActivation *activation, IonBailoutIterator &iter,

                           bool invalidate, BaselineBailoutInfo **bailoutInfo,

                           const ExceptionBailoutInfo *excInfo)

 {

     JS_ASSERT(bailoutInfo != nullptr);

     JS_ASSERT(*bailoutInfo == nullptr);

     TraceLogger *logger = TraceLoggerForMainThread(cx->runtime());

     TraceLogStopEvent(logger, TraceLogger::IonMonkey);

     TraceLogStartEvent(logger, TraceLogger::Baseline);

     // The caller of the top frame must be one of the following:

     //      IonJS - Ion calling into Ion.

     //      BaselineStub - Baseline calling into Ion.

     //      Entry - Interpreter or other calling into Ion.

     //      Rectifier - Arguments rectifier calling into Ion.

     JS_ASSERT(iter.isIonJS());

     FrameType prevFrameType = iter.prevType();

     JS_ASSERT(prevFrameType == JitFrame_IonJS ||

               prevFrameType == JitFrame_BaselineStub ||

               prevFrameType == JitFrame_Entry ||

               prevFrameType == JitFrame_Rectifier);

     // All incoming frames are going to look like this:

     //

     //      +---------------+

     //      |     ...       |

     //      +---------------+

     //      |     Args      |

     //      |     ...       |

     //      +---------------+

     //      |    ThisV      |

     //      +---------------+

     //      |  ActualArgC   |

     //      +---------------+

     //      |  CalleeToken  |

     //      +---------------+

     //      |  Descriptor   |

     //      +---------------+

     //      |  ReturnAddr   |

     //      +---------------+

     //      |    |||||      | <---- Overwrite starting here.

     //      |    |||||      |

     //      |    |||||      |

     //      +---------------+

     IonSpew(IonSpew_BaselineBailouts, "Bailing to baseline %s:%u (IonScript=%p) (FrameType=%d)",

             iter.script()->filename(), iter.script()->lineno(), (void *) iter.ionScript(),

             (int) prevFrameType);

     bool catchingException;

     bool propagatingExceptionForDebugMode;

     if (excInfo) {

         catchingException = excInfo->catchingException();

         propagatingExceptionForDebugMode = excInfo->propagatingIonExceptionForDebugMode();

         if (catchingException)

             IonSpew(IonSpew_BaselineBailouts, "Resuming in catch or finally block");

         if (propagatingExceptionForDebugMode)

             IonSpew(IonSpew_BaselineBailouts, "Resuming in-place for debug mode");

     } else {

         catchingException = false;

         propagatingExceptionForDebugMode = false;

     }

     IonSpew(IonSpew_BaselineBailouts, "  Reading from snapshot offset %u size %u",

             iter.snapshotOffset(), iter.ionScript()->snapshotsListSize());

     if (!excInfo)

         iter.ionScript()->incNumBailouts();

     iter.script()->updateBaselineOrIonRaw();

     // Allocate buffer to hold stack replacement data.

     BaselineStackBuilder builder(iter, 1024);

     if (!builder.init())

         return BAILOUT_RETURN_FATAL_ERROR;

     IonSpew(IonSpew_BaselineBailouts, "  Incoming frame ptr = %p", builder.startFrame());

     SnapshotIterator snapIter(iter);

     RootedFunction callee(cx, iter.maybeCallee());

     RootedScript scr(cx, iter.script());

     if (callee) {

         IonSpew(IonSpew_BaselineBailouts, "  Callee function (%s:%u)",

                 scr->filename(), scr->lineno());

     } else {

         IonSpew(IonSpew_BaselineBailouts, "  No callee!");

     }

     if (iter.isConstructing())

         IonSpew(IonSpew_BaselineBailouts, "  Constructing!");

     else

         IonSpew(IonSpew_BaselineBailouts, "  Not constructing!");

     IonSpew(IonSpew_BaselineBailouts, "  Restoring frames:");

     size_t frameNo = 0;

     // Reconstruct baseline frames using the builder.

     RootedScript caller(cx);

     jsbytecode *callerPC = nullptr;

     RootedFunction fun(cx, callee);

     AutoValueVector startFrameFormals(cx);

     RootedScript topCaller(cx);

     jsbytecode *topCallerPC = nullptr;

     while (true) {

         MOZ_ASSERT(snapIter.instruction()->isResumePoint());

         if (frameNo > 0) {

             TraceLogStartEvent(logger, TraceLogCreateTextId(logger, scr));

             TraceLogStartEvent(logger, TraceLogger::Baseline);

         }

         IonSpew(IonSpew_BaselineBailouts, "    FrameNo %d", frameNo);

         // If we are bailing out to a catch or finally block in this frame,

         // pass excInfo to InitFromBailout and don't unpack any other frames.

         bool handleException = (catchingException && excInfo->frameNo() == frameNo);

         // We also need to pass excInfo if we're bailing out in place for

         // debug mode.

         bool passExcInfo = handleException || propagatingExceptionForDebugMode;

         jsbytecode *callPC = nullptr;

         RootedFunction nextCallee(cx, nullptr);

         if (!InitFromBailout(cx, caller, callerPC, fun, scr, iter.ionScript(),

                              snapIter, invalidate, builder, startFrameFormals,

                              &nextCallee, &callPC, passExcInfo ? excInfo : nullptr))

         {

             return BAILOUT_RETURN_FATAL_ERROR;

         }

         if (!snapIter.moreFrames()) {

             JS_ASSERT(!callPC);

             break;

         }

         if (handleException)

             break;

         JS_ASSERT(nextCallee);

         JS_ASSERT(callPC);

         caller = scr;

         callerPC = callPC;

         fun = nextCallee;

         scr = fun->existingScriptForInlinedFunction();

         // Save top caller info for adjusting SPS frames later.

         if (!topCaller) {

             JS_ASSERT(frameNo == 0);

             topCaller = caller;

             topCallerPC = callerPC;

         }

         frameNo++;

         snapIter.nextInstruction();

     }

     IonSpew(IonSpew_BaselineBailouts, "  Done restoring frames");

     // If there were multiple inline frames unpacked, and inline frame profiling

     // is off, then the current top SPS frame is for the outermost caller, and

     // has an uninitialized PC.  Initialize it now.

     if (frameNo > 0 && !js_JitOptions.profileInlineFrames)

         cx->runtime()->spsProfiler.updatePC(topCaller, topCallerPC);

     BailoutKind bailoutKind = snapIter.bailoutKind();

     if (!startFrameFormals.empty()) {

         // Set the first frame's formals, see the comment in InitFromBailout.

         Value *argv = builder.startFrame()->argv() + 1; // +1 to skip |this|.

         mozilla::PodCopy(argv, startFrameFormals.begin(), startFrameFormals.length());

     }

     // Do stack check.

     bool overRecursed = false;

     BaselineBailoutInfo *info = builder.info();

     uint8_t *newsp = info->incomingStack - (info->copyStackTop - info->copyStackBottom);

 #ifdef JS_ARM_SIMULATOR

     if (Simulator::Current()->overRecursed(uintptr_t(newsp)))

         overRecursed = true;

 #else

     JS_CHECK_RECURSION_WITH_SP_DONT_REPORT(cx, newsp, overRecursed = true);

 #endif

     if (overRecursed) {

         IonSpew(IonSpew_BaselineBailouts, "  Overrecursion check failed!");

         return BAILOUT_RETURN_OVERRECURSED;

     }

     // Take the reconstructed baseline stack so it doesn't get freed when builder destructs.

     info = builder.takeBuffer();

     info->numFrames = frameNo + 1;

     info->bailoutKind = bailoutKind;

     *bailoutInfo = info;

     return BAILOUT_RETURN_OK;

 }

 static bool

 HandleBoundsCheckFailure(JSContext *cx, HandleScript outerScript, HandleScript innerScript)

 {

     IonSpew(IonSpew_Bailouts, "Bounds check failure %s:%d, inlined into %s:%d",

             innerScript->filename(), innerScript->lineno(),

             outerScript->filename(), outerScript->lineno());

     JS_ASSERT(!outerScript->ionScript()->invalidated());

     // TODO: Currently this mimic's Ion's handling of this case.  Investigate setting

     // the flag on innerScript as opposed to outerScript, and maybe invalidating both

     // inner and outer scripts, instead of just the outer one.

     if (!outerScript->failedBoundsCheck())

         outerScript->setFailedBoundsCheck();

     IonSpew(IonSpew_BaselineBailouts, "Invalidating due to bounds check failure");

     return Invalidate(cx, outerScript);

 }

 static bool

 HandleShapeGuardFailure(JSContext *cx, HandleScript outerScript, HandleScript innerScript)

 {

     IonSpew(IonSpew_Bailouts, "Shape guard failure %s:%d, inlined into %s:%d",

             innerScript->filename(), innerScript->lineno(),

             outerScript->filename(), outerScript->lineno());

     JS_ASSERT(!outerScript->ionScript()->invalidated());

     // TODO: Currently this mimic's Ion's handling of this case.  Investigate setting

     // the flag on innerScript as opposed to outerScript, and maybe invalidating both

     // inner and outer scripts, instead of just the outer one.

     outerScript->setFailedShapeGuard();

     IonSpew(IonSpew_BaselineBailouts, "Invalidating due to shape guard failure");

     return Invalidate(cx, outerScript);

 }

 static bool

 HandleBaselineInfoBailout(JSContext *cx, JSScript *outerScript, JSScript *innerScript)

 {

     IonSpew(IonSpew_Bailouts, "Baseline info failure %s:%d, inlined into %s:%d",

             innerScript->filename(), innerScript->lineno(),

             outerScript->filename(), outerScript->lineno());

     JS_ASSERT(!outerScript->ionScript()->invalidated());

     IonSpew(IonSpew_BaselineBailouts, "Invalidating due to invalid baseline info");

     return Invalidate(cx, outerScript);

 }

 static bool

 CopyFromRematerializedFrame(JSContext *cx, JitActivation *act, uint8_t *fp, size_t inlineDepth,

                             BaselineFrame *frame)

 {

     RematerializedFrame *rematFrame = act->lookupRematerializedFrame(fp, inlineDepth);

     // We might not have rematerialized a frame if the user never requested a

     // Debugger.Frame for it.

     if (!rematFrame)

         return true;

     MOZ_ASSERT(rematFrame->script() == frame->script());

     MOZ_ASSERT(rematFrame->numActualArgs() == frame->numActualArgs());

     frame->setScopeChain(rematFrame->scopeChain());

     frame->thisValue() = rematFrame->thisValue();

     for (unsigned i = 0; i < frame->numActualArgs(); i++)

         frame->argv()[i] = rematFrame->argv()[i];

     for (size_t i = 0; i < frame->script()->nfixed(); i++)

         *frame->valueSlot(i) = rematFrame->locals()[i];

     IonSpew(IonSpew_BaselineBailouts,

             "  Copied from rematerialized frame at (%p,%u)",

             fp, inlineDepth);

     if (cx->compartment()->debugMode())

         return Debugger::handleIonBailout(cx, rematFrame, frame);

     return true;

 }

 uint32_t

 jit::FinishBailoutToBaseline(BaselineBailoutInfo *bailoutInfo)

 {

     // The caller pushes R0 and R1 on the stack without rooting them.

     // Since GC here is very unlikely just suppress it.

     JSContext *cx = GetJSContextFromJitCode();

     js::gc::AutoSuppressGC suppressGC(cx);

     IonSpew(IonSpew_BaselineBailouts, "  Done restoring frames");

     // Check that we can get the current script's PC.

 #ifdef DEBUG

     jsbytecode *pc;

     cx->currentScript(&pc);

     IonSpew(IonSpew_BaselineBailouts, "  Got pc=%p", pc);

 #endif

     uint32_t numFrames = bailoutInfo->numFrames;

     JS_ASSERT(numFrames > 0);

     BailoutKind bailoutKind = bailoutInfo->bailoutKind;

     // Free the bailout buffer.

     js_free(bailoutInfo);

     bailoutInfo = nullptr;

     // Ensure the frame has a call object if it needs one. If the scope chain

     // is nullptr, we will enter baseline code at the prologue so no need to do

     // anything in that case.

     BaselineFrame *topFrame = GetTopBaselineFrame(cx);

     if (topFrame->scopeChain() && !EnsureHasScopeObjects(cx, topFrame))

         return false;

     // Create arguments objects for bailed out frames, to maintain the invariant

     // that script->needsArgsObj() implies frame->hasArgsObj().

     RootedScript innerScript(cx, nullptr);

     RootedScript outerScript(cx, nullptr);

     JS_ASSERT(cx->currentlyRunningInJit());

     JitFrameIterator iter(cx);

     uint8_t *outerFp = nullptr;

     uint32_t frameno = 0;

     while (frameno < numFrames) {

         JS_ASSERT(!iter.isIonJS());

         if (iter.isBaselineJS()) {

             BaselineFrame *frame = iter.baselineFrame();

             MOZ_ASSERT(frame->script()->hasBaselineScript());

             // If the frame doesn't even have a scope chain set yet, then it's resuming

             // into the the prologue before the scope chain is initialized.  Any

             // necessary args object will also be initialized there.

             if (frame->scopeChain() && frame->script()->needsArgsObj()) {

                 ArgumentsObject *argsObj;

                 if (frame->hasArgsObj()) {

                     argsObj = &frame->argsObj();

                 } else {

                     argsObj = ArgumentsObject::createExpected(cx, frame);

                     if (!argsObj)

                         return false;

                 }

                 // The arguments is a local binding and needsArgsObj does not

                 // check if it is clobbered. Ensure that the local binding

                 // restored during bailout before storing the arguments object

                 // to the slot.

                 RootedScript script(cx, frame->script());

                 SetFrameArgumentsObject(cx, frame, script, argsObj);

             }

             if (frameno == 0)

                 innerScript = frame->script();

             if (frameno == numFrames - 1) {

                 outerScript = frame->script();

                 outerFp = iter.fp();

             }

             frameno++;

         }

         ++iter;

     }

     MOZ_ASSERT(innerScript);

     MOZ_ASSERT(outerScript);

     MOZ_ASSERT(outerFp);

     // If we rematerialized Ion frames due to debug mode toggling, copy their

     // values into the baseline frame. We need to do this even when debug mode

     // is off, as we should respect the mutations made while debug mode was

     // on.

     JitActivation *act = cx->mainThread().activation()->asJit();

     if (act->hasRematerializedFrame(outerFp)) {

         JitFrameIterator iter(cx);

         size_t inlineDepth = numFrames;

         while (inlineDepth > 0) {

             if (iter.isBaselineJS() &&

                 !CopyFromRematerializedFrame(cx, act, outerFp, --inlineDepth,

                                              iter.baselineFrame()))

             {

                 return false;

             }

             ++iter;

         }

         // After copying from all the rematerialized frames, remove them from

         // the table to keep the table up to date.

         act->removeRematerializedFrame(outerFp);

     }

     IonSpew(IonSpew_BaselineBailouts,

             "  Restored outerScript=(%s:%u,%u) innerScript=(%s:%u,%u) (bailoutKind=%u)",

             outerScript->filename(), outerScript->lineno(), outerScript->getUseCount(),

             innerScript->filename(), innerScript->lineno(), innerScript->getUseCount(),

             (unsigned) bailoutKind);

     switch (bailoutKind) {

       case Bailout_Normal:

         // Do nothing.

         break;

       case Bailout_ArgumentCheck:

         // Do nothing, bailout will resume before the argument monitor ICs.

         break;

       case Bailout_BoundsCheck:

         if (!HandleBoundsCheckFailure(cx, outerScript, innerScript))

             return false;

         break;

       case Bailout_ShapeGuard:

         if (!HandleShapeGuardFailure(cx, outerScript, innerScript))

             return false;

         break;

       case Bailout_BaselineInfo:

         if (!HandleBaselineInfoBailout(cx, outerScript, innerScript))

             return false;

         break;

       case Bailout_IonExceptionDebugMode:

         // Return false to resume in HandleException with reconstructed

         // baseline frame.

         return false;

       default:

         MOZ_ASSUME_UNREACHABLE("Unknown bailout kind!");

     }

     if (!CheckFrequentBailouts(cx, outerScript))

         return false;

     return true;

 }