1 files changed, 314 insertions, 0 deletions
diff --git a/js/src/jit/Bailouts.cpp b/js/src/jit/Bailouts.cpp
new file mode 100644
index 000000000..d5172c6a3
--- /dev/null
+++ b/js/src/jit/Bailouts.cpp
@@ -0,0 +1,314 @@
+/* -*- 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 "jit/Bailouts.h"
+
+#include "mozilla/ScopeExit.h"
+
+#include "jscntxt.h"
+
+#include "jit/BaselineJIT.h"
+#include "jit/Ion.h"
+#include "jit/JitCompartment.h"
+#include "jit/JitSpewer.h"
+#include "jit/Snapshots.h"
+#include "vm/TraceLogging.h"
+
+#include "jit/JitFrameIterator-inl.h"
+#include "vm/Probes-inl.h"
+#include "vm/Stack-inl.h"
+
+using namespace js;
+using namespace js::jit;
+
+using mozilla::IsInRange;
+
+uint32_t
+jit::Bailout(BailoutStack* sp, BaselineBailoutInfo** bailoutInfo)
+{
+    JSContext* cx = GetJSContextFromMainThread();
+    MOZ_ASSERT(bailoutInfo);
+
+    // We don't have an exit frame.
+    MOZ_ASSERT(IsInRange(FAKE_JIT_TOP_FOR_BAILOUT, 0, 0x1000) &&
+               IsInRange(FAKE_JIT_TOP_FOR_BAILOUT + sizeof(CommonFrameLayout), 0, 0x1000),
+               "Fake jitTop pointer should be within the first page.");
+    cx->runtime()->jitTop = FAKE_JIT_TOP_FOR_BAILOUT;
+
+    JitActivationIterator jitActivations(cx->runtime());
+    BailoutFrameInfo bailoutData(jitActivations, sp);
+    JitFrameIterator iter(jitActivations);
+    MOZ_ASSERT(!iter.ionScript()->invalidated());
+    CommonFrameLayout* currentFramePtr = iter.current();
+
+    TraceLoggerThread* logger = TraceLoggerForMainThread(cx->runtime());
+    TraceLogTimestamp(logger, TraceLogger_Bailout);
+
+    JitSpew(JitSpew_IonBailouts, "Took bailout! Snapshot offset: %d", iter.snapshotOffset());
+
+    MOZ_ASSERT(IsBaselineEnabled(cx));
+
+    *bailoutInfo = nullptr;
+    uint32_t retval = BailoutIonToBaseline(cx, bailoutData.activation(), iter, false, bailoutInfo,
+                                           /* excInfo = */ nullptr);
+    MOZ_ASSERT(retval == BAILOUT_RETURN_OK ||
+               retval == BAILOUT_RETURN_FATAL_ERROR ||
+               retval == BAILOUT_RETURN_OVERRECURSED);
+    MOZ_ASSERT_IF(retval == BAILOUT_RETURN_OK, *bailoutInfo != nullptr);
+
+    if (retval != BAILOUT_RETURN_OK) {
+        JSScript* script = iter.script();
+        probes::ExitScript(cx, script, script->functionNonDelazifying(),
+                           /* popSPSFrame = */ false);
+    }
+
+    // This condition was wrong when we entered this bailout function, but it
+    // might be true now. A GC might have reclaimed all the Jit code and
+    // invalidated all frames which are currently on the stack. As we are
+    // already in a bailout, we could not switch to an invalidation
+    // bailout. When the code of an IonScript which is on the stack is
+    // invalidated (see InvalidateActivation), we remove references to it and
+    // increment the reference counter for each activation that appear on the
+    // stack. As the bailed frame is one of them, we have to decrement it now.
+    if (iter.ionScript()->invalidated())
+        iter.ionScript()->decrementInvalidationCount(cx->runtime()->defaultFreeOp());
+
+    // NB: Commentary on how |lastProfilingFrame| is set from bailouts.
+    //
+    // Once we return to jitcode, any following frames might get clobbered,
+    // but the current frame will not (as it will be clobbered "in-place"
+    // with a baseline frame that will share the same frame prefix).
+    // However, there may be multiple baseline frames unpacked from this
+    // single Ion frame, which means we will need to once again reset
+    // |lastProfilingFrame| to point to the correct unpacked last frame
+    // in |FinishBailoutToBaseline|.
+    //
+    // In the case of error, the jitcode will jump immediately to an
+    // exception handler, which will unwind the frames and properly set
+    // the |lastProfilingFrame| to point to the frame being resumed into
+    // (see |AutoResetLastProfilerFrameOnReturnFromException|).
+    //
+    // In both cases, we want to temporarily set the |lastProfilingFrame|
+    // to the current frame being bailed out, and then fix it up later.
+    if (cx->runtime()->jitRuntime()->isProfilerInstrumentationEnabled(cx->runtime()))
+        cx->runtime()->jitActivation->setLastProfilingFrame(currentFramePtr);
+
+    return retval;
+}
+
+uint32_t
+jit::InvalidationBailout(InvalidationBailoutStack* sp, size_t* frameSizeOut,
+                         BaselineBailoutInfo** bailoutInfo)
+{
+    sp->checkInvariants();
+
+    JSContext* cx = GetJSContextFromMainThread();
+
+    // We don't have an exit frame.
+    cx->runtime()->jitTop = FAKE_JIT_TOP_FOR_BAILOUT;
+
+    JitActivationIterator jitActivations(cx->runtime());
+    BailoutFrameInfo bailoutData(jitActivations, sp);
+    JitFrameIterator iter(jitActivations);
+    CommonFrameLayout* currentFramePtr = iter.current();
+
+    TraceLoggerThread* logger = TraceLoggerForMainThread(cx->runtime());
+    TraceLogTimestamp(logger, TraceLogger_Invalidation);
+
+    JitSpew(JitSpew_IonBailouts, "Took invalidation bailout! Snapshot offset: %d", iter.snapshotOffset());
+
+    // Note: the frame size must be computed before we return from this function.
+    *frameSizeOut = iter.frameSize();
+
+    MOZ_ASSERT(IsBaselineEnabled(cx));
+
+    *bailoutInfo = nullptr;
+    uint32_t retval = BailoutIonToBaseline(cx, bailoutData.activation(), iter, true, bailoutInfo,
+                                           /* excInfo = */ nullptr);
+    MOZ_ASSERT(retval == BAILOUT_RETURN_OK ||
+               retval == BAILOUT_RETURN_FATAL_ERROR ||
+               retval == BAILOUT_RETURN_OVERRECURSED);
+    MOZ_ASSERT_IF(retval == BAILOUT_RETURN_OK, *bailoutInfo != nullptr);
+
+    if (retval != BAILOUT_RETURN_OK) {
+        // If the bailout failed, then bailout trampoline will pop the
+        // current frame and jump straight to exception handling code when
+        // this function returns.  Any SPS entry pushed for this frame will
+        // be silently forgotten.
+        //
+        // We call ExitScript here to ensure that if the ionScript had SPS
+        // instrumentation, then the SPS entry for it is popped.
+        //
+        // However, if the bailout was during argument check, then a
+        // pseudostack frame would not have been pushed in the first
+        // place, so don't pop anything in that case.
+        JSScript* script = iter.script();
+        probes::ExitScript(cx, script, script->functionNonDelazifying(),
+                           /* popSPSFrame = */ false);
+
+#ifdef JS_JITSPEW
+        JitFrameLayout* frame = iter.jsFrame();
+        JitSpew(JitSpew_IonInvalidate, "Bailout failed (%s)",
+                (retval == BAILOUT_RETURN_FATAL_ERROR) ? "Fatal Error" : "Over Recursion");
+        JitSpew(JitSpew_IonInvalidate, "   calleeToken %p", (void*) frame->calleeToken());
+        JitSpew(JitSpew_IonInvalidate, "   frameSize %u", unsigned(frame->prevFrameLocalSize()));
+        JitSpew(JitSpew_IonInvalidate, "   ra %p", (void*) frame->returnAddress());
+#endif
+    }
+
+    iter.ionScript()->decrementInvalidationCount(cx->runtime()->defaultFreeOp());
+
+    // Make the frame being bailed out the top profiled frame.
+    if (cx->runtime()->jitRuntime()->isProfilerInstrumentationEnabled(cx->runtime()))
+        cx->runtime()->jitActivation->setLastProfilingFrame(currentFramePtr);
+
+    return retval;
+}
+
+BailoutFrameInfo::BailoutFrameInfo(const JitActivationIterator& activations,
+                                   const JitFrameIterator& frame)
+  : machine_(frame.machineState())
+{
+    framePointer_ = (uint8_t*) frame.fp();
+    topFrameSize_ = frame.frameSize();
+    topIonScript_ = frame.ionScript();
+    attachOnJitActivation(activations);
+
+    const OsiIndex* osiIndex = frame.osiIndex();
+    snapshotOffset_ = osiIndex->snapshotOffset();
+}
+
+uint32_t
+jit::ExceptionHandlerBailout(JSContext* cx, const InlineFrameIterator& frame,
+                             ResumeFromException* rfe,
+                             const ExceptionBailoutInfo& excInfo,
+                             bool* overrecursed)
+{
+    // We can be propagating debug mode exceptions without there being an
+    // actual exception pending. For instance, when we return false from an
+    // operation callback like a timeout handler.
+    MOZ_ASSERT_IF(!excInfo.propagatingIonExceptionForDebugMode(), cx->isExceptionPending());
+
+    uint8_t* prevJitTop = cx->runtime()->jitTop;
+    auto restoreJitTop = mozilla::MakeScopeExit([&]() { cx->runtime()->jitTop = prevJitTop; });
+    cx->runtime()->jitTop = FAKE_JIT_TOP_FOR_BAILOUT;
+
+    gc::AutoSuppressGC suppress(cx);
+
+    JitActivationIterator jitActivations(cx->runtime());
+    BailoutFrameInfo bailoutData(jitActivations, frame.frame());
+    JitFrameIterator iter(jitActivations);
+    CommonFrameLayout* currentFramePtr = iter.current();
+
+    BaselineBailoutInfo* bailoutInfo = nullptr;
+    uint32_t retval;
+
+    {
+        // Currently we do not tolerate OOM here so as not to complicate the
+        // exception handling code further.
+        AutoEnterOOMUnsafeRegion oomUnsafe;
+
+        retval = BailoutIonToBaseline(cx, bailoutData.activation(), iter, true,
+                                      &bailoutInfo, &excInfo);
+        if (retval == BAILOUT_RETURN_FATAL_ERROR && cx->isThrowingOutOfMemory())
+            oomUnsafe.crash("ExceptionHandlerBailout");
+    }
+
+    if (retval == BAILOUT_RETURN_OK) {
+        MOZ_ASSERT(bailoutInfo);
+
+        // Overwrite the kind so HandleException after the bailout returns
+        // false, jumping directly to the exception tail.
+        if (excInfo.propagatingIonExceptionForDebugMode())
+            bailoutInfo->bailoutKind = Bailout_IonExceptionDebugMode;
+
+        rfe->kind = ResumeFromException::RESUME_BAILOUT;
+        rfe->target = cx->runtime()->jitRuntime()->getBailoutTail()->raw();
+        rfe->bailoutInfo = bailoutInfo;
+    } else {
+        // Bailout failed. If the overrecursion check failed, clear the
+        // exception to turn this into an uncatchable error, continue popping
+        // all inline frames and have the caller report the error.
+        MOZ_ASSERT(!bailoutInfo);
+
+        if (retval == BAILOUT_RETURN_OVERRECURSED) {
+            *overrecursed = true;
+            if (!excInfo.propagatingIonExceptionForDebugMode())
+                cx->clearPendingException();
+        } else {
+            MOZ_ASSERT(retval == BAILOUT_RETURN_FATAL_ERROR);
+
+            // Crash for now so as not to complicate the exception handling code
+            // further.
+            MOZ_CRASH();
+        }
+    }
+
+    // Make the frame being bailed out the top profiled frame.
+    if (cx->runtime()->jitRuntime()->isProfilerInstrumentationEnabled(cx->runtime()))
+        cx->runtime()->jitActivation->setLastProfilingFrame(currentFramePtr);
+
+    return retval;
+}
+
+// Initialize the decl env Object, call object, and any arguments obj of the
+// current frame.
+bool
+jit::EnsureHasEnvironmentObjects(JSContext* cx, AbstractFramePtr fp)
+{
+    // Ion does not compile eval scripts.
+    MOZ_ASSERT(!fp.isEvalFrame());
+
+    if (fp.isFunctionFrame()) {
+        // Ion does not handle extra var environments due to parameter
+        // expressions yet.
+        MOZ_ASSERT(!fp.callee()->needsExtraBodyVarEnvironment());
+
+        if (!fp.hasInitialEnvironment() && fp.callee()->needsFunctionEnvironmentObjects()) {
+            if (!fp.initFunctionEnvironmentObjects(cx))
+                return false;
+        }
+    }
+
+    return true;
+}
+
+void
+jit::CheckFrequentBailouts(JSContext* cx, JSScript* script, BailoutKind bailoutKind)
+{
+    if (script->hasIonScript()) {
+        // Invalidate if this script keeps bailing out without invalidation. Next time
+        // we compile this script LICM will be disabled.
+        IonScript* ionScript = script->ionScript();
+
+        if (ionScript->bailoutExpected()) {
+            // If we bailout because of the first execution of a basic block,
+            // then we should record which basic block we are returning in,
+            // which should prevent this from happening again.  Also note that
+            // the first execution bailout can be related to an inlined script,
+            // so there is no need to penalize the caller.
+            if (bailoutKind != Bailout_FirstExecution && !script->hadFrequentBailouts())
+                script->setHadFrequentBailouts();
+
+            JitSpew(JitSpew_IonInvalidate, "Invalidating due to too many bailouts");
+
+            Invalidate(cx, script);
+        }
+    }
+}
+
+void
+BailoutFrameInfo::attachOnJitActivation(const JitActivationIterator& jitActivations)
+{
+    MOZ_ASSERT(jitActivations.jitTop() == FAKE_JIT_TOP_FOR_BAILOUT);
+    activation_ = jitActivations->asJit();
+    activation_->setBailoutData(this);
+}
+
+BailoutFrameInfo::~BailoutFrameInfo()
+{
+    activation_->cleanBailoutData();
+}