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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/191712">191712</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2015-10-28 17:46:06 -0700 (Wed, 28 Oct 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>[B3] handleCommutativity should canonicalize commutative operations over non-constants
https://bugs.webkit.org/show_bug.cgi?id=150649
Reviewed by Saam Barati.
Turn this: Add(value1, value2)
Into this: Add(value2, value1)
But ony if value2 should come before value1 according to our total ordering. This will allow
CSE to observe the equality between commuted versions of the same operation, since we will
first canonicalize them into the same order.
* b3/B3ReduceStrength.cpp:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreb3B3ReduceStrengthcpp">trunk/Source/JavaScriptCore/b3/B3ReduceStrength.cpp</a></li>
</ul>
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<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (191711 => 191712)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-10-29 00:34:33 UTC (rev 191711)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-10-29 00:46:06 UTC (rev 191712)
</span><span class="lines">@@ -1,5 +1,21 @@
</span><span class="cx"> 2015-10-28 Filip Pizlo <fpizlo@apple.com>
</span><span class="cx">
</span><ins>+ [B3] handleCommutativity should canonicalize commutative operations over non-constants
+ https://bugs.webkit.org/show_bug.cgi?id=150649
+
+ Reviewed by Saam Barati.
+
+ Turn this: Add(value1, value2)
+ Into this: Add(value2, value1)
+
+ But ony if value2 should come before value1 according to our total ordering. This will allow
+ CSE to observe the equality between commuted versions of the same operation, since we will
+ first canonicalize them into the same order.
+
+ * b3/B3ReduceStrength.cpp:
+
+2015-10-28 Filip Pizlo <fpizlo@apple.com>
+
</ins><span class="cx"> Unreviewed, fix the build for case sensitive file systems.
</span><span class="cx">
</span><span class="cx"> * b3/air/AirBasicBlock.h:
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreb3B3ReduceStrengthcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/b3/B3ReduceStrength.cpp (191711 => 191712)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/b3/B3ReduceStrength.cpp 2015-10-29 00:34:33 UTC (rev 191711)
+++ trunk/Source/JavaScriptCore/b3/B3ReduceStrength.cpp 2015-10-29 00:46:06 UTC (rev 191712)
</span><span class="lines">@@ -76,10 +76,6 @@
</span><span class="cx">
</span><span class="cx"> switch (m_value->opcode()) {
</span><span class="cx"> case Add:
</span><del>- // Turn this: Add(constant, value)
- // Into this: Add(value, constant)
- //
- // FIXME: If both non-constant, we should sort the operands.
</del><span class="cx"> handleCommutativity();
</span><span class="cx">
</span><span class="cx"> // Turn this: Add(Add(value, constant1), constant2)
</span><span class="lines">@@ -174,12 +170,32 @@
</span><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ // Turn this: Add(constant, value)
+ // Into this: Add(value, constant)
+ //
+ // Also:
+ // Turn this: Add(value1, value2)
+ // Into this: Add(value2, value1)
+ // If we decide that value2 coming first is the canonical ordering.
</ins><span class="cx"> void handleCommutativity()
</span><span class="cx"> {
</span><del>- if (m_value->child(0)->isConstant() && !m_value->child(1)->isConstant()) {
</del><ins>+ // Leave it alone if the right child is a constant.
+ if (m_value->child(1)->isConstant())
+ return;
+
+ if (m_value->child(0)->isConstant()) {
</ins><span class="cx"> std::swap(m_value->child(0), m_value->child(1));
</span><span class="cx"> m_changed = true;
</span><ins>+ return;
</ins><span class="cx"> }
</span><ins>+
+ // Sort the operands. This is an important canonicalization. We use the index instead of
+ // the address to make this at least slightly deterministic.
+ if (m_value->child(0)->index() > m_value->child(1)->index()) {
+ std::swap(m_value->child(0), m_value->child(1));
+ m_changed = true;
+ return;
+ }
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> void replaceWithNewValue(Value* newValue)
</span></span></pre>
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