src/third_party/mozjs/js/src/jit/BaselineJIT.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_BaselineJIT_h
#define jit_BaselineJIT_h

#ifdef JS_ION

#include "jscntxt.h"
#include "jscompartment.h"

#include "IonCode.h"
#include "IonMacroAssembler.h"
#include "Bailouts.h"

#include "ds/LifoAlloc.h"

namespace js {
namespace jit {

class StackValue;
struct ICEntry;
class ICStub;

class PCMappingSlotInfo
{
    uint8_t slotInfo_;

  public:
    // SlotInfo encoding:
    //  Bits 0 & 1: number of slots at top of stack which are unsynced.
    //  Bits 2 & 3: SlotLocation of top slot value (only relevant if numUnsynced > 0).
    //  Bits 3 & 4: SlotLocation of next slot value (only relevant if numUnsynced > 1).
    enum SlotLocation { SlotInR0 = 0, SlotInR1 = 1, SlotIgnore = 3 };

    PCMappingSlotInfo()
      : slotInfo_(0)
    { }

    explicit PCMappingSlotInfo(uint8_t slotInfo)
      : slotInfo_(slotInfo)
    { }

    static inline bool ValidSlotLocation(SlotLocation loc) {
        return (loc == SlotInR0) || (loc == SlotInR1) || (loc == SlotIgnore);
    }

    static SlotLocation ToSlotLocation(const StackValue *stackVal);

    inline static PCMappingSlotInfo MakeSlotInfo() { return PCMappingSlotInfo(0); }

    inline static PCMappingSlotInfo MakeSlotInfo(SlotLocation topSlotLoc) {
        JS_ASSERT(ValidSlotLocation(topSlotLoc));
        return PCMappingSlotInfo(1 | (topSlotLoc << 2));
    }

    inline static PCMappingSlotInfo MakeSlotInfo(SlotLocation topSlotLoc, SlotLocation nextSlotLoc) {
        JS_ASSERT(ValidSlotLocation(topSlotLoc));
        JS_ASSERT(ValidSlotLocation(nextSlotLoc));
        return PCMappingSlotInfo(2 | (topSlotLoc << 2) | (nextSlotLoc) << 4);
    }

    inline unsigned numUnsynced() const {
        return slotInfo_ & 0x3;
    }
    inline SlotLocation topSlotLocation() const {
        return static_cast<SlotLocation>((slotInfo_ >> 2) & 0x3);
    }
    inline SlotLocation nextSlotLocation() const {
        return static_cast<SlotLocation>((slotInfo_ >> 4) & 0x3);
    }
    inline uint8_t toByte() const {
        return slotInfo_;
    }
};

// A CompactBuffer is used to store native code offsets (relative to the
// previous pc) and PCMappingSlotInfo bytes. To allow binary search into this
// table, we maintain a second table of "index" entries. Every X ops, the
// compiler will add an index entry, so that from the index entry to the
// actual native code offset, we have to iterate at most X times.
struct PCMappingIndexEntry
{
    // jsbytecode offset.
    uint32_t pcOffset;

    // Native code offset.
    uint32_t nativeOffset;

    // Offset in the CompactBuffer where data for pcOffset starts.
    uint32_t bufferOffset;
};

struct BaselineScript
{
  public:
    static const uint32_t MAX_JSSCRIPT_LENGTH = 0x0fffffffu;

  private:
    // Code pointer containing the actual method.
    HeapPtr<IonCode> method_;

    // Allocated space for fallback stubs.
    FallbackICStubSpace fallbackStubSpace_;

    // Native code offset right before the scope chain is initialized.
    uint32_t prologueOffset_;

    // The offsets for the toggledJump instructions for SPS update ICs.
#ifdef DEBUG
    mozilla::DebugOnly<bool> spsOn_;
#endif
    uint32_t spsPushToggleOffset_;

  public:
    enum Flag {
        // Flag set by JSScript::argumentsOptimizationFailed. Similar to
        // JSScript::needsArgsObj_, but can be read from JIT code.
        NEEDS_ARGS_OBJ = 1 << 0,

        // Flag set when discarding JIT code, to indicate this script is
        // on the stack and should not be discarded.
        ACTIVE         = 1 << 1
    };

  private:
    uint32_t flags_;

  private:
    void trace(JSTracer *trc);

    uint32_t icEntriesOffset_;
    uint32_t icEntries_;

    uint32_t pcMappingIndexOffset_;
    uint32_t pcMappingIndexEntries_;

    uint32_t pcMappingOffset_;
    uint32_t pcMappingSize_;

  public:
    // Do not call directly, use BaselineScript::New. This is public for cx->new_.
    BaselineScript(uint32_t prologueOffset, uint32_t spsPushToggleOffset);

    static BaselineScript *New(JSContext *cx, uint32_t prologueOffset,
                               uint32_t spsPushToggleOffset, size_t icEntries,
                               size_t pcMappingIndexEntries, size_t pcMappingSize);
    static void Trace(JSTracer *trc, BaselineScript *script);
    static void Destroy(FreeOp *fop, BaselineScript *script);

    void purgeOptimizedStubs(Zone *zone);

    static inline size_t offsetOfMethod() {
        return offsetof(BaselineScript, method_);
    }

    void sizeOfIncludingThis(JSMallocSizeOfFun mallocSizeOf, size_t *data,
                             size_t *fallbackStubs) const {
        *data = mallocSizeOf(this);

        // data already includes the ICStubSpace itself, so use
        // sizeOfExcludingThis.
        *fallbackStubs = fallbackStubSpace_.sizeOfExcludingThis(mallocSizeOf);
    }

    bool active() const {
        return flags_ & ACTIVE;
    }
    void setActive() {
        flags_ |= ACTIVE;
    }
    void resetActive() {
        flags_ &= ~ACTIVE;
    }

    void setNeedsArgsObj() {
        flags_ |= NEEDS_ARGS_OBJ;
    }

    uint32_t prologueOffset() const {
        return prologueOffset_;
    }
    uint8_t *prologueEntryAddr() const {
        return method_->raw() + prologueOffset_;
    }

    ICEntry *icEntryList() {
        return (ICEntry *)(reinterpret_cast<uint8_t *>(this) + icEntriesOffset_);
    }
    PCMappingIndexEntry *pcMappingIndexEntryList() {
        return (PCMappingIndexEntry *)(reinterpret_cast<uint8_t *>(this) + pcMappingIndexOffset_);
    }
    uint8_t *pcMappingData() {
        return reinterpret_cast<uint8_t *>(this) + pcMappingOffset_;
    }
    FallbackICStubSpace *fallbackStubSpace() {
        return &fallbackStubSpace_;
    }

    IonCode *method() const {
        return method_;
    }
    void setMethod(IonCode *code) {
        JS_ASSERT(!method_);
        method_ = code;
    }

    void toggleBarriers(bool enabled) {
        method()->togglePreBarriers(enabled);
    }

    ICEntry &icEntry(size_t index);
    ICEntry *maybeICEntryFromReturnOffset(CodeOffsetLabel returnOffset);
    ICEntry &icEntryFromReturnOffset(CodeOffsetLabel returnOffset);
    ICEntry &icEntryFromPCOffset(uint32_t pcOffset);
    ICEntry &icEntryFromPCOffset(uint32_t pcOffset, ICEntry *prevLookedUpEntry);
    ICEntry *maybeICEntryFromReturnAddress(uint8_t *returnAddr);
    ICEntry &icEntryFromReturnAddress(uint8_t *returnAddr);
    uint8_t *returnAddressForIC(const ICEntry &ent);

    size_t numICEntries() const {
        return icEntries_;
    }

    void copyICEntries(HandleScript script, const ICEntry *entries, MacroAssembler &masm);
    void adoptFallbackStubs(FallbackICStubSpace *stubSpace);

    PCMappingIndexEntry &pcMappingIndexEntry(size_t index);
    CompactBufferReader pcMappingReader(size_t indexEntry);

    size_t numPCMappingIndexEntries() const {
        return pcMappingIndexEntries_;
    }

    void copyPCMappingIndexEntries(const PCMappingIndexEntry *entries);

    void copyPCMappingEntries(const CompactBufferWriter &entries);
    uint8_t *nativeCodeForPC(JSScript *script, jsbytecode *pc, PCMappingSlotInfo *slotInfo = NULL);
    jsbytecode *pcForReturnOffset(JSScript *script, uint32_t nativeOffset);
    jsbytecode *pcForReturnAddress(JSScript *script, uint8_t *nativeAddress);

    // Toggle debug traps (used for breakpoints and step mode) in the script.
    // If |pc| is NULL, toggle traps for all ops in the script. Else, only
    // toggle traps at |pc|.
    void toggleDebugTraps(JSScript *script, jsbytecode *pc);

    void toggleSPS(bool enable);

    void noteAccessedGetter(uint32_t pcOffset);

    static size_t offsetOfFlags() {
        return offsetof(BaselineScript, flags_);
    }

    static void writeBarrierPre(Zone *zone, BaselineScript *script);
};

inline bool
IsBaselineEnabled(JSContext *cx)
{
    return cx->hasOption(JSOPTION_BASELINE);
}

MethodStatus
CanEnterBaselineMethod(JSContext *cx, RunState &state);

MethodStatus
CanEnterBaselineAtBranch(JSContext *cx, StackFrame *fp, bool newType);

IonExecStatus
EnterBaselineMethod(JSContext *cx, RunState &state);

IonExecStatus
EnterBaselineAtBranch(JSContext *cx, StackFrame *fp, jsbytecode *pc);

void
FinishDiscardBaselineScript(FreeOp *fop, JSScript *script);

void
SizeOfBaselineData(JSScript *script, JSMallocSizeOfFun mallocSizeOf, size_t *data,
                   size_t *fallbackStubs);

void
ToggleBaselineSPS(JSRuntime *runtime, bool enable);

struct BaselineBailoutInfo
{
    // Pointer into the current C stack, where overwriting will start.
    uint8_t *incomingStack;

    // The top and bottom heapspace addresses of the reconstructed stack
    // which will be copied to the bottom.
    uint8_t *copyStackTop;
    uint8_t *copyStackBottom;

    // Fields to store the top-of-stack baseline values that are held
    // in registers.  The setR0 and setR1 fields are flags indicating
    // whether each one is initialized.
    uint32_t setR0;
    Value valueR0;
    uint32_t setR1;
    Value valueR1;

    // The value of the frame pointer register on resume.
    void *resumeFramePtr;

    // The native code address to resume into.
    void *resumeAddr;

    // If resuming into a TypeMonitor IC chain, this field holds the
    // address of the first stub in that chain.  If this field is
    // set, then the actual jitcode resumed into is the jitcode for
    // the first stub, not the resumeAddr above.  The resumeAddr
    // above, in this case, is pushed onto the stack so that the
    // TypeMonitor chain can tail-return into the main jitcode when done.
    ICStub *monitorStub;

    // Number of baseline frames to push on the stack.
    uint32_t numFrames;

    // The bailout kind.
    BailoutKind bailoutKind;
};

uint32_t
BailoutIonToBaseline(JSContext *cx, JitActivation *activation, IonBailoutIterator &iter,
                     bool invalidate, BaselineBailoutInfo **bailoutInfo);

// Mark baseline scripts on the stack as active, so that they are not discarded
// during GC.
void
MarkActiveBaselineScripts(Zone *zone);

} // namespace jit
} // namespace js

#endif // JS_ION

#endif /* jit_BaselineJIT_h */