/*
* Given a frame newer than the entry frame, try to finish it. If it's at a
* return position, pop the frame. If it's at a safe point, execute it in
* Jaeger code. Otherwise, try to interpret until a safe point.
*
* While this function is guaranteed to make progress, it may not actually
* finish or pop the current frame. It can either:
* 1) Finalize a finished frame, or
* 2) Finish and finalize the frame in the Method JIT, or
* 3) Interpret, which can:
* a) Propagate an error, or
* b) Finish the frame, but not finalize it, or
* c) Abruptly leave at any point in the frame, or in a newer frame
* pushed by a call, that has method JIT'd code.
*/
static bool
EvaluateExcessFrame(VMFrame &f, JSStackFrame *entryFrame)
{
JSContext *cx = f.cx;
JSStackFrame *fp = cx->fp();
/*
* A "finished" frame is when the interpreter rested on a STOP,
* RETURN, RETRVAL, etc. We check for finished frames BEFORE looking
* for a safe point. If the frame was finished, we could have already
* called ScriptEpilogue(), and entering the JIT could call it twice.
*/
if (!fp->hasImacropc() && FrameIsFinished(cx))
return HandleFinishedFrame(f, entryFrame);
if (void *ncode = AtSafePoint(cx)) {
if (!JaegerShotAtSafePoint(cx, ncode))
return false;
InlineReturn(f);
AdvanceReturnPC(cx);
return true;
}
return PartialInterpret(f);
}
/* Returns whether the current PC has method JIT'd code. */
static inline void *
AtSafePoint(JSContext *cx)
{
JSStackFrame *fp = cx->fp();
if (fp->hasImacropc())
return false;
JSScript *script = fp->script();
return script->maybeNativeCodeForPC(fp->isConstructing(), cx->regs->pc);
}
/*
* Interprets until either a safe point is reached that has method JIT'd
* code, or the current frame tries to return.
*/
static inline JSBool
PartialInterpret(VMFrame &f)
{
JSContext *cx = f.cx;
JSStackFrame *fp = cx->fp();
#ifdef DEBUG
JSScript *script = fp->script();
JS_ASSERT(!fp->finishedInInterpreter());
JS_ASSERT(fp->hasImacropc() ||
!script->maybeNativeCodeForPC(fp->isConstructing(), cx->regs->pc));
#endif
JSBool ok = JS_TRUE;
ok = Interpret(cx, fp, 0, JSINTERP_SAFEPOINT);
return ok;
}
void *
RunTracer(VMFrame &f)
#endif
{
JSContext *cx = f.cx;
JSStackFrame *entryFrame = f.fp();
TracePointAction tpa;
/* :TODO: nuke PIC? */
if (!cx->traceJitEnabled)
return NULL;
/*
* Force initialization of the entry frame's scope chain and return value,
* if necessary. The tracer can query the scope chain without needing to
* check the HAS_SCOPECHAIN flag, and the frame is guaranteed to have the
* correct return value stored if we trace/interpret through to the end
* of the frame.
*/
entryFrame->scopeChain();
entryFrame->returnValue();
bool blacklist;
uintN inlineCallCount = 0;
void **traceData;
uintN *traceEpoch;
uint32 *loopCounter;
uint32 hits;
#if JS_MONOIC
traceData = &ic.traceData;
traceEpoch = &ic.traceEpoch;
loopCounter = &ic.loopCounter;
*loopCounter = 1;
hits = ic.loopCounterStart;
#else
traceData = NULL;
traceEpoch = NULL;
loopCounter = NULL;
hits = 1;
#endif
tpa = MonitorTracePoint(f.cx, inlineCallCount, &blacklist, traceData, traceEpoch,
loopCounter, hits);
JS_ASSERT(!TRACE_RECORDER(cx));
#if JS_MONOIC
ic.loopCounterStart = *loopCounter;
if (blacklist)
DisableTraceHint(entryFrame->jit(), ic);
#endif
// Even though ExecuteTree() bypasses the interpreter, it should propagate
// error failures correctly.
JS_ASSERT_IF(cx->isExceptionPending(), tpa == TPA_Error);
f.fp() = cx->fp();
JS_ASSERT(f.fp() == cx->fp());
switch (tpa) {
case TPA_Nothing:
return NULL;
case TPA_Error:
if (!HandleErrorInExcessFrame(f, entryFrame, f.fp()->finishedInInterpreter()))
THROWV(NULL);
JS_ASSERT(!cx->fp()->hasImacropc());
break;
case TPA_RanStuff:
case TPA_Recorded:
break;
}
/*
* The tracer could have dropped us off on any frame at any position.
* Well, it could not have removed frames (recursion is disabled).
*
* Frames after the entryFrame cannot be entered via JaegerShotAtSafePoint()
* unless each is at a safe point. We can JaegerShotAtSafePoint these
* frames individually, but we must unwind to the entryFrame.
*
* Note carefully that JaegerShotAtSafePoint can resume methods at
* arbitrary safe points whereas JaegerShot cannot.
*
* If we land on entryFrame without a safe point in sight, we'll end up
* at the RETURN op. This is an edge case with two paths:
*
* 1) The entryFrame is the last inline frame. If it fell on a RETURN,
* move the return value down.
* 2) The entryFrame is NOT the last inline frame. Pop the frame.
*
* In both cases, we hijack the stub to return to the force-return
* trampoline. This trampoline simulates the frame-popping portion of
* emitReturn (except without the benefit of the FrameState) and will
* produce the necessary register state to return to the caller.
*/
restart:
/* Step 1. Finish frames created after the entry frame. */
if (!FinishExcessFrames(f, entryFrame))
THROWV(NULL);
/* IMacros are guaranteed to have been removed by now. */
JS_ASSERT(f.fp() == entryFrame);
JS_ASSERT(!entryFrame->hasImacropc());
/* Step 2. If entryFrame is done, use a special path to return to EnterMethodJIT(). */
if (FrameIsFinished(cx)) {
if (!HandleFinishedFrame(f, entryFrame))
THROWV(NULL);
void *retPtr = JS_FUNC_TO_DATA_PTR(void *,
cx->jaegerCompartment()->forceReturnTrampoline());
*f.returnAddressLocation() = retPtr;
return NULL;
}
/* Step 3. If entryFrame is at a safe point, just leave. */
if (void *ncode = AtSafePoint(cx))
return ncode;
/* Step 4. Do a partial interp, then restart the whole process. */
if (!PartialInterpret(f)) {
if (!HandleErrorInExcessFrame(f, entryFrame))
THROWV(NULL);
}
goto restart;
}
/*
* Called when an error is in progress and the topmost frame could not handle
* it. This will unwind to a given frame, or find and align to an exception
* handler in the process.
*/
static inline bool
HandleErrorInExcessFrame(VMFrame &f, JSStackFrame *stopFp, bool searchedTopmostFrame = true)
{
JSContext *cx = f.cx;
/*
* Callers of this called either Interpret() or JaegerShot(), which would
* have searched for exception handlers already. If we see stopFp, just
* return false. Otherwise, pop the frame, since it's guaranteed useless.
*
* Note that this also guarantees ScriptEpilogue() has been called.
*/
JSStackFrame *fp = cx->fp();
if (searchedTopmostFrame) {
/*
* This is a special case meaning that fp->finishedInInterpreter() is
* true. If so, and fp == stopFp, our only choice is to propagate this
* error up, back to the method JIT, and then to js_InternalThrow,
* where this becomes a special case. See the comment there and bug
* 624100.
*/
if (fp == stopFp)
return false;
/*
* Otherwise, the protocol here (like Invoke) is to assume that the
* execution mode finished the frame, and to just pop it.
*/
InlineReturn(f);
}
/* Remove the bottom frame. */
bool returnOK = false;
for (;;) {
fp = cx->fp();
/* Clear imacros. */
if (fp->hasImacropc()) {
cx->regs->pc = fp->imacropc();
fp->clearImacropc();
}
JS_ASSERT(!fp->hasImacropc());
/* If there's an exception and a handler, set the pc and leave. */
if (cx->isExceptionPending()) {
jsbytecode *pc = FindExceptionHandler(cx);
if (pc) {
cx->regs->pc = pc;
returnOK = true;
break;
}
}
/* Don't unwind if this was the entry frame. */
if (fp == stopFp)
break;
/* Unwind and return. */
returnOK &= bool(js_UnwindScope(cx, 0, returnOK || cx->isExceptionPending()));
returnOK = ScriptEpilogue(cx, fp, returnOK);
InlineReturn(f);
}
JS_ASSERT(&f.regs == cx->regs);
JS_ASSERT_IF(!returnOK, cx->fp() == stopFp);
return returnOK;
}
