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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/179477">179477</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2015-02-02 10:15:44 -0800 (Mon, 02 Feb 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Converting Flushes and PhantomLocals to Phantoms requires an OSR availability analysis rather than just using the SetLocal's child
https://bugs.webkit.org/show_bug.cgi?id=141107
Reviewed by Michael Saboff.
See the bugzilla for a discussion of the problem. This addresses the problem by ensuring
that Flushes are always strength-reduced to PhantomLocals, and CPS rethreading does a mini
OSR availability analysis to determine the right MovHint value to use for the Phantom.
* dfg/DFGCPSRethreadingPhase.cpp:
(JSC::DFG::CPSRethreadingPhase::CPSRethreadingPhase):
(JSC::DFG::CPSRethreadingPhase::freeUnnecessaryNodes):
(JSC::DFG::CPSRethreadingPhase::clearVariables):
(JSC::DFG::CPSRethreadingPhase::canonicalizeFlushOrPhantomLocalFor):
(JSC::DFG::CPSRethreadingPhase::canonicalizeLocalsInBlock):
(JSC::DFG::CPSRethreadingPhase::clearVariablesAtHeadAndTail): Deleted.
* dfg/DFGNode.h:
(JSC::DFG::Node::convertPhantomToPhantomLocal):
(JSC::DFG::Node::convertFlushToPhantomLocal):
(JSC::DFG::Node::convertToPhantomLocal): Deleted.
* dfg/DFGStrengthReductionPhase.cpp:
(JSC::DFG::StrengthReductionPhase::handleNode):
* tests/stress/inline-call-that-doesnt-use-all-args.js: Added.
(foo):
(bar):
(baz):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGCPSRethreadingPhasecpp">trunk/Source/JavaScriptCore/dfg/DFGCPSRethreadingPhase.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGNodeh">trunk/Source/JavaScriptCore/dfg/DFGNode.h</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGStrengthReductionPhasecpp">trunk/Source/JavaScriptCore/dfg/DFGStrengthReductionPhase.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoretestsstressinlinecallthatdoesntuseallargsjs">trunk/Source/JavaScriptCore/tests/stress/inline-call-that-doesnt-use-all-args.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (179476 => 179477)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-02-02 18:12:32 UTC (rev 179476)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-02-02 18:15:44 UTC (rev 179477)
</span><span class="lines">@@ -1,3 +1,32 @@
</span><ins>+2015-01-30 Filip Pizlo <fpizlo@apple.com>
+
+ Converting Flushes and PhantomLocals to Phantoms requires an OSR availability analysis rather than just using the SetLocal's child
+ https://bugs.webkit.org/show_bug.cgi?id=141107
+
+ Reviewed by Michael Saboff.
+
+ See the bugzilla for a discussion of the problem. This addresses the problem by ensuring
+ that Flushes are always strength-reduced to PhantomLocals, and CPS rethreading does a mini
+ OSR availability analysis to determine the right MovHint value to use for the Phantom.
+
+ * dfg/DFGCPSRethreadingPhase.cpp:
+ (JSC::DFG::CPSRethreadingPhase::CPSRethreadingPhase):
+ (JSC::DFG::CPSRethreadingPhase::freeUnnecessaryNodes):
+ (JSC::DFG::CPSRethreadingPhase::clearVariables):
+ (JSC::DFG::CPSRethreadingPhase::canonicalizeFlushOrPhantomLocalFor):
+ (JSC::DFG::CPSRethreadingPhase::canonicalizeLocalsInBlock):
+ (JSC::DFG::CPSRethreadingPhase::clearVariablesAtHeadAndTail): Deleted.
+ * dfg/DFGNode.h:
+ (JSC::DFG::Node::convertPhantomToPhantomLocal):
+ (JSC::DFG::Node::convertFlushToPhantomLocal):
+ (JSC::DFG::Node::convertToPhantomLocal): Deleted.
+ * dfg/DFGStrengthReductionPhase.cpp:
+ (JSC::DFG::StrengthReductionPhase::handleNode):
+ * tests/stress/inline-call-that-doesnt-use-all-args.js: Added.
+ (foo):
+ (bar):
+ (baz):
+
</ins><span class="cx"> 2015-01-31 Michael Saboff <msaboff@apple.com>
</span><span class="cx">
</span><span class="cx"> Crash (DFG assertion) beneath AbstractInterpreter::verifyEdge() @ http://experilous.com/1/planet-generator/2014-09-28/version-1
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGCPSRethreadingPhasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGCPSRethreadingPhase.cpp (179476 => 179477)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGCPSRethreadingPhase.cpp 2015-02-02 18:12:32 UTC (rev 179476)
+++ trunk/Source/JavaScriptCore/dfg/DFGCPSRethreadingPhase.cpp 2015-02-02 18:15:44 UTC (rev 179477)
</span><span class="lines">@@ -1,5 +1,5 @@
</span><span class="cx"> /*
</span><del>- * Copyright (C) 2013, 2014 Apple Inc. All rights reserved.
</del><ins>+ * Copyright (C) 2013-2015 Apple Inc. All rights reserved.
</ins><span class="cx"> *
</span><span class="cx"> * Redistribution and use in source and binary forms, with or without
</span><span class="cx"> * modification, are permitted provided that the following conditions
</span><span class="lines">@@ -39,6 +39,7 @@
</span><span class="cx"> public:
</span><span class="cx"> CPSRethreadingPhase(Graph& graph)
</span><span class="cx"> : Phase(graph, "CPS rethreading")
</span><ins>+ , m_availableForOSR(OperandsLike, graph.block(0)->variablesAtHead)
</ins><span class="cx"> {
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -98,7 +99,7 @@
</span><span class="cx"> case Phi:
</span><span class="cx"> case SetArgument:
</span><span class="cx"> case SetLocal:
</span><del>- node->convertToPhantomLocal();
</del><ins>+ node->convertPhantomToPhantomLocal();
</ins><span class="cx"> break;
</span><span class="cx"> default:
</span><span class="cx"> ASSERT(node->child1()->hasResult());
</span><span class="lines">@@ -119,15 +120,19 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> template<OperandKind operandKind>
</span><del>- void clearVariablesAtHeadAndTail()
</del><ins>+ void clearVariables()
</ins><span class="cx"> {
</span><span class="cx"> ASSERT(
</span><span class="cx"> m_block->variablesAtHead.sizeFor<operandKind>()
</span><span class="cx"> == m_block->variablesAtTail.sizeFor<operandKind>());
</span><ins>+ ASSERT(
+ m_block->variablesAtHead.sizeFor<operandKind>()
+ == m_availableForOSR.sizeFor<operandKind>());
</ins><span class="cx">
</span><span class="cx"> for (unsigned i = m_block->variablesAtHead.sizeFor<operandKind>(); i--;) {
</span><del>- m_block->variablesAtHead.atFor<operandKind>(i) = 0;
- m_block->variablesAtTail.atFor<operandKind>(i) = 0;
</del><ins>+ m_block->variablesAtHead.atFor<operandKind>(i) = nullptr;
+ m_block->variablesAtTail.atFor<operandKind>(i) = nullptr;
+ m_availableForOSR.atFor<operandKind>(i) = Edge();
</ins><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -259,13 +264,10 @@
</span><span class="cx"> // for the purpose of OSR. PhantomLocal(SetLocal) means: at this point I
</span><span class="cx"> // know that I would have read the value written by that SetLocal. This is
</span><span class="cx"> // redundant and inefficient, since really it just means that we want to
</span><del>- // be keeping the operand to the SetLocal alive. The SetLocal may die, and
- // we'll be fine because OSR tracks dead SetLocals.
</del><ins>+ // keep the last MovHinted value of that local alive.
</ins><span class="cx">
</span><del>- // So we turn this into a Phantom on the child of the SetLocal.
-
</del><ins>+ node->children.setChild1(m_availableForOSR.atFor<operandKind>(idx));
</ins><span class="cx"> node->convertToPhantom();
</span><del>- node->children.setChild1(otherNode->child1());
</del><span class="cx"> return;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -311,8 +313,8 @@
</span><span class="cx"> return;
</span><span class="cx"> ASSERT(m_block->isReachable);
</span><span class="cx">
</span><del>- clearVariablesAtHeadAndTail<ArgumentOperand>();
- clearVariablesAtHeadAndTail<LocalOperand>();
</del><ins>+ clearVariables<ArgumentOperand>();
+ clearVariables<LocalOperand>();
</ins><span class="cx">
</span><span class="cx"> // Assumes that all phi references have been removed. Assumes that things that
</span><span class="cx"> // should be live have a non-zero ref count, but doesn't assume that the ref
</span><span class="lines">@@ -382,6 +384,10 @@
</span><span class="cx"> canonicalizeSetArgument(node);
</span><span class="cx"> break;
</span><span class="cx">
</span><ins>+ case MovHint:
+ m_availableForOSR.operand(node->unlinkedLocal()) = node->child1();
+ break;
+
</ins><span class="cx"> default:
</span><span class="cx"> break;
</span><span class="cx"> }
</span><span class="lines">@@ -522,6 +528,7 @@
</span><span class="cx"> Vector<PhiStackEntry, 128> m_argumentPhiStack;
</span><span class="cx"> Vector<PhiStackEntry, 128> m_localPhiStack;
</span><span class="cx"> Vector<Node*, 128> m_flushedLocalOpWorklist;
</span><ins>+ Operands<Edge> m_availableForOSR;
</ins><span class="cx"> };
</span><span class="cx">
</span><span class="cx"> bool performCPSRethreading(Graph& graph)
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGNodeh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGNode.h (179476 => 179477)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGNode.h 2015-02-02 18:12:32 UTC (rev 179476)
+++ trunk/Source/JavaScriptCore/dfg/DFGNode.h 2015-02-02 18:15:44 UTC (rev 179477)
</span><span class="lines">@@ -1,5 +1,5 @@
</span><span class="cx"> /*
</span><del>- * Copyright (C) 2011, 2012, 2013, 2014 Apple Inc. All rights reserved.
</del><ins>+ * Copyright (C) 2011-2015 Apple Inc. All rights reserved.
</ins><span class="cx"> *
</span><span class="cx"> * Redistribution and use in source and binary forms, with or without
</span><span class="cx"> * modification, are permitted provided that the following conditions
</span><span class="lines">@@ -538,7 +538,7 @@
</span><span class="cx"> children = AdjacencyList();
</span><span class="cx"> }
</span><span class="cx">
</span><del>- void convertToPhantomLocal()
</del><ins>+ void convertPhantomToPhantomLocal()
</ins><span class="cx"> {
</span><span class="cx"> ASSERT(m_op == Phantom && (child1()->op() == Phi || child1()->op() == SetLocal || child1()->op() == SetArgument));
</span><span class="cx"> m_op = PhantomLocal;
</span><span class="lines">@@ -546,6 +546,13 @@
</span><span class="cx"> children.setChild1(Edge());
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ void convertFlushToPhantomLocal()
+ {
+ ASSERT(m_op == Flush);
+ m_op = PhantomLocal;
+ children = AdjacencyList();
+ }
+
</ins><span class="cx"> void convertToGetLocal(VariableAccessData* variable, Node* phi)
</span><span class="cx"> {
</span><span class="cx"> ASSERT(m_op == GetLocalUnlinked);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGStrengthReductionPhasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGStrengthReductionPhase.cpp (179476 => 179477)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGStrengthReductionPhase.cpp 2015-02-02 18:12:32 UTC (rev 179476)
+++ trunk/Source/JavaScriptCore/dfg/DFGStrengthReductionPhase.cpp 2015-02-02 18:15:44 UTC (rev 179477)
</span><span class="lines">@@ -1,5 +1,5 @@
</span><span class="cx"> /*
</span><del>- * Copyright (C) 2013, 2014 Apple Inc. All rights reserved.
</del><ins>+ * Copyright (C) 2013-2015 Apple Inc. All rights reserved.
</ins><span class="cx"> *
</span><span class="cx"> * Redistribution and use in source and binary forms, with or without
</span><span class="cx"> * modification, are permitted provided that the following conditions
</span><span class="lines">@@ -280,10 +280,10 @@
</span><span class="cx"> if (!setLocal)
</span><span class="cx"> break;
</span><span class="cx">
</span><del>- m_node->convertToPhantom();
- Node* dataNode = setLocal->child1().node();
- DFG_ASSERT(m_graph, m_node, dataNode->hasResult());
- m_node->child1() = dataNode->defaultEdge();
</del><ins>+ // The Flush should become a PhantomLocal at this point. This means that we want the
+ // local's value during OSR, but we don't care if the value is stored to the stack. CPS
+ // rethreading can canonicalize PhantomLocals for us.
+ m_node->convertFlushToPhantomLocal();
</ins><span class="cx"> m_graph.dethread();
</span><span class="cx"> m_changed = true;
</span><span class="cx"> break;
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressinlinecallthatdoesntuseallargsjs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/inline-call-that-doesnt-use-all-args.js (0 => 179477)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/inline-call-that-doesnt-use-all-args.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/inline-call-that-doesnt-use-all-args.js 2015-02-02 18:15:44 UTC (rev 179477)
</span><span class="lines">@@ -0,0 +1,27 @@
</span><ins>+function foo(a, b, c) {
+ return 42;
+}
+
+function bar(a, b, c) {
+ return a + b + c;
+}
+
+function baz(f, o) {
+ return f(o[0], o[1], o[2]);
+}
+
+noInline(baz);
+
+var o = new Float32Array(3);
+o[0] = 1;
+o[1] = 2;
+o[2] = 3;
+for (var i = 0; i < 10000; ++i) {
+ var result = baz(foo, o);
+ if (result != 42)
+ throw "Error: bad result in loop: " + result;
+}
+
+var result = baz(bar, o);
+if (result != 6)
+ throw "Error: bad result in loop: " + result;
</ins></span></pre>
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