[JSC] PredictionPropagation should not be in the top 5 heaviest phases

https://bugs.webkit.org/show_bug.cgi?id=156891

Patch by Benjamin Poulain <bpoulain@apple.com> on 2016-04-22
Reviewed by Mark Lam.

In DFG, PredictionPropagation is often way too high in profiles.
It is a simple phase, it should not be that hot.

Most of the time is spent accessing memory. This patch attempts
to reduce that.

First, propagate() is split in processInvariants() and propagates().
The step processInvariants() sets all the types for nodes for which
the type does not depends on other nodes.

Adding processInvariants() lowers two hotspot inside PredictionPropagation:
speculationFromValue() and setPrediction().

Next, to avoid touching all the nodes at every operation, we keep
track of the nodes that actually need propagate().
The vector m_dependentNodes keeps the list of those nodes and propagate()
only need to process them at each phase.

This is a smaller gain because growing m_dependentNodes negates
some of the gains.

On 3d-cube, this moves PredictionPropagation from fifth position
to ninth. A lot of the remaining overhead is caused by double-voting
and cannot be fixed by moving stuff around.

* dfg/DFGPredictionPropagationPhase.cpp:
(JSC::DFG::PredictionPropagationPhase::propagateToFixpoint): Deleted.
(JSC::DFG::PredictionPropagationPhase::propagate): Deleted.
(JSC::DFG::PredictionPropagationPhase::propagateForward): Deleted.
(JSC::DFG::PredictionPropagationPhase::propagateBackward): Deleted.
(JSC::DFG::PredictionPropagationPhase::doDoubleVoting): Deleted.
(JSC::DFG::PredictionPropagationPhase::doRoundOfDoubleVoting): Deleted.
(JSC::DFG::PredictionPropagationPhase::propagateThroughArgumentPositions): Deleted.

Canonical link: https://commits.webkit.org/175045@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@199933 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/JavaScriptCore/ChangeLog

@@ -1,3 +1,44 @@
+2016-04-22  Benjamin Poulain  <bpoulain@apple.com>
+
+        [JSC] PredictionPropagation should not be in the top 5 heaviest phases
+        https://bugs.webkit.org/show_bug.cgi?id=156891
+
+        Reviewed by Mark Lam.
+
+        In DFG, PredictionPropagation is often way too high in profiles.
+        It is a simple phase, it should not be that hot.
+
+        Most of the time is spent accessing memory. This patch attempts
+        to reduce that.
+
+        First, propagate() is split in processInvariants() and propagates().
+        The step processInvariants() sets all the types for nodes for which
+        the type does not depends on other nodes.
+
+        Adding processInvariants() lowers two hotspot inside PredictionPropagation:
+        speculationFromValue() and setPrediction().
+
+        Next, to avoid touching all the nodes at every operation, we keep
+        track of the nodes that actually need propagate().
+        The vector m_dependentNodes keeps the list of those nodes and propagate()
+        only need to process them at each phase.
+
+        This is a smaller gain because growing m_dependentNodes negates
+        some of the gains.
+
+        On 3d-cube, this moves PredictionPropagation from fifth position
+        to ninth. A lot of the remaining overhead is caused by double-voting
+        and cannot be fixed by moving stuff around.
+
+        * dfg/DFGPredictionPropagationPhase.cpp:
+        (JSC::DFG::PredictionPropagationPhase::propagateToFixpoint): Deleted.
+        (JSC::DFG::PredictionPropagationPhase::propagate): Deleted.
+        (JSC::DFG::PredictionPropagationPhase::propagateForward): Deleted.
+        (JSC::DFG::PredictionPropagationPhase::propagateBackward): Deleted.
+        (JSC::DFG::PredictionPropagationPhase::doDoubleVoting): Deleted.
+        (JSC::DFG::PredictionPropagationPhase::doRoundOfDoubleVoting): Deleted.
+        (JSC::DFG::PredictionPropagationPhase::propagateThroughArgumentPositions): Deleted.
+
 2016-04-22  Geoffrey Garen  <ggaren@apple.com>
 
         super should be available in object literals