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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/204837">204837</a></dd>
<dt>Author</dt> <dd>carlosgc@webkit.org</dd>
<dt>Date</dt> <dd>2016-08-23 08:17:13 -0700 (Tue, 23 Aug 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/199277">r199277</a> - Allocation sinking SSA Defs are allowed to have replacements
https://bugs.webkit.org/show_bug.cgi?id=156444
Reviewed by Filip Pizlo.
Consider the following program and the annotations that explain why
the SSA defs we create in allocation sinking can have replacements.
function foo(a1) {
let o1 = {x: 20, y: 50};
let o2 = {y: 40, o1: o1};
let o3 = {};
// We're Defing a new variable here, call it o3_field.
// o3_field is defing the value that is the result of
// a GetByOffset that gets eliminated through allocation sinking.
o3.field = o1.y;
dontCSE();
// This control flow is here to not allow the phase to consult
// its local SSA mapping (which properly handles replacements)
// for the value of o3_field.
if (a1) {
a1 = true;
} else {
a1 = false;
}
// Here, we ask for the reaching def of o3_field, and assert
// it doesn't have a replacement. It does have a replacement
// though. The original Def was the GetByOffset. We replaced
// that GetByOffset with the value of the o1_y variable.
let value = o3.field;
assert(value === 50);
}
* dfg/DFGObjectAllocationSinkingPhase.cpp:
* tests/stress/allocation-sinking-defs-may-have-replacements.js: Added.
(dontCSE):
(assert):
(foo):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#releasesWebKitGTKwebkit212SourceJavaScriptCoreChangeLog">releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#releasesWebKitGTKwebkit212SourceJavaScriptCoredfgDFGObjectAllocationSinkingPhasecpp">releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/dfg/DFGObjectAllocationSinkingPhase.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#releasesWebKitGTKwebkit212SourceJavaScriptCoretestsstressallocationsinkingdefsmayhavereplacementsjs">releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/tests/stress/allocation-sinking-defs-may-have-replacements.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="releasesWebKitGTKwebkit212SourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/ChangeLog (204836 => 204837)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/ChangeLog 2016-08-23 13:53:03 UTC (rev 204836)
+++ releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/ChangeLog 2016-08-23 15:17:13 UTC (rev 204837)
</span><span class="lines">@@ -1,3 +1,48 @@
</span><ins>+2016-04-09 Saam barati <sbarati@apple.com>
+
+ Allocation sinking SSA Defs are allowed to have replacements
+ https://bugs.webkit.org/show_bug.cgi?id=156444
+
+ Reviewed by Filip Pizlo.
+
+ Consider the following program and the annotations that explain why
+ the SSA defs we create in allocation sinking can have replacements.
+
+ function foo(a1) {
+ let o1 = {x: 20, y: 50};
+ let o2 = {y: 40, o1: o1};
+ let o3 = {};
+
+ // We're Defing a new variable here, call it o3_field.
+ // o3_field is defing the value that is the result of
+ // a GetByOffset that gets eliminated through allocation sinking.
+ o3.field = o1.y;
+
+ dontCSE();
+
+ // This control flow is here to not allow the phase to consult
+ // its local SSA mapping (which properly handles replacements)
+ // for the value of o3_field.
+ if (a1) {
+ a1 = true;
+ } else {
+ a1 = false;
+ }
+
+ // Here, we ask for the reaching def of o3_field, and assert
+ // it doesn't have a replacement. It does have a replacement
+ // though. The original Def was the GetByOffset. We replaced
+ // that GetByOffset with the value of the o1_y variable.
+ let value = o3.field;
+ assert(value === 50);
+ }
+
+ * dfg/DFGObjectAllocationSinkingPhase.cpp:
+ * tests/stress/allocation-sinking-defs-may-have-replacements.js: Added.
+ (dontCSE):
+ (assert):
+ (foo):
+
</ins><span class="cx"> 2016-05-23 Geoffrey Garen <ggaren@apple.com>
</span><span class="cx">
</span><span class="cx"> REGRESSION (196374): deleting a global property is expensive
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit212SourceJavaScriptCoredfgDFGObjectAllocationSinkingPhasecpp"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/dfg/DFGObjectAllocationSinkingPhase.cpp (204836 => 204837)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/dfg/DFGObjectAllocationSinkingPhase.cpp 2016-08-23 13:53:03 UTC (rev 204836)
+++ releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/dfg/DFGObjectAllocationSinkingPhase.cpp 2016-08-23 15:17:13 UTC (rev 204837)
</span><span class="lines">@@ -1862,7 +1862,8 @@
</span><span class="cx"> ASSERT(def->value());
</span><span class="cx">
</span><span class="cx"> Node* result = def->value();
</span><del>-
</del><ins>+ if (result->replacement())
+ result = result->replacement();
</ins><span class="cx"> ASSERT(!result->replacement());
</span><span class="cx">
</span><span class="cx"> m_localMapping.add(location, result);
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit212SourceJavaScriptCoretestsstressallocationsinkingdefsmayhavereplacementsjs"></a>
<div class="addfile"><h4>Added: releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/tests/stress/allocation-sinking-defs-may-have-replacements.js (0 => 204837)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/tests/stress/allocation-sinking-defs-may-have-replacements.js (rev 0)
+++ releases/WebKitGTK/webkit-2.12/Source/JavaScriptCore/tests/stress/allocation-sinking-defs-may-have-replacements.js 2016-08-23 15:17:13 UTC (rev 204837)
</span><span class="lines">@@ -0,0 +1,31 @@
</span><ins>+function dontCSE() { }
+noInline(dontCSE);
+
+function assert(b) {
+ if (!b)
+ throw new Error("Bad assertion");
+}
+noInline(assert);
+
+function foo(a1) {
+ let o1 = {x: 20, y: 50};
+ let o2 = {y: 40, o1: o1};
+ let o3 = {};
+
+ o3.field = o1.y;
+
+ dontCSE();
+
+ if (a1) {
+ a1 = true;
+ } else {
+ a1 = false;
+ }
+
+ let value = o3.field;
+ assert(value === 50);
+}
+noInline(foo);
+
+for (let i = 0; i < 100000; i++)
+ foo(i);
</ins></span></pre>
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