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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/199690">199690</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2016-04-18 15:09:27 -0700 (Mon, 18 Apr 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Disable AVX.
Rubber stampted by Benjamin Poulain.
AVX is silly. If you use it and some of your other code isn't careful with float register bits, you
will run 10x slower. We could fix the underlying issue, but it's better to stay away from this odd
instruction subset.
This fixes a massive regression on some real code.
* assembler/MacroAssemblerX86Common.h:
(JSC::MacroAssemblerX86Common::supportsAVX):
(JSC::MacroAssemblerX86Common::updateEax1EcxFlags):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreassemblerMacroAssemblerX86Commonh">trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h</a></li>
</ul>
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<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (199689 => 199690)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2016-04-18 21:53:02 UTC (rev 199689)
+++ trunk/Source/JavaScriptCore/ChangeLog 2016-04-18 22:09:27 UTC (rev 199690)
</span><span class="lines">@@ -1,5 +1,21 @@
</span><span class="cx"> 2016-04-18 Filip Pizlo <fpizlo@apple.com>
</span><span class="cx">
</span><ins>+ Disable AVX.
+
+ Rubber stampted by Benjamin Poulain.
+
+ AVX is silly. If you use it and some of your other code isn't careful with float register bits, you
+ will run 10x slower. We could fix the underlying issue, but it's better to stay away from this odd
+ instruction subset.
+
+ This fixes a massive regression on some real code.
+
+ * assembler/MacroAssemblerX86Common.h:
+ (JSC::MacroAssemblerX86Common::supportsAVX):
+ (JSC::MacroAssemblerX86Common::updateEax1EcxFlags):
+
+2016-04-18 Filip Pizlo <fpizlo@apple.com>
+
</ins><span class="cx"> ToThis should have a fast path based on type info flags
</span><span class="cx"> https://bugs.webkit.org/show_bug.cgi?id=156712
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreassemblerMacroAssemblerX86Commonh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h (199689 => 199690)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h 2016-04-18 21:53:02 UTC (rev 199689)
+++ trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h 2016-04-18 22:09:27 UTC (rev 199690)
</span><span class="lines">@@ -2620,9 +2620,8 @@
</span><span class="cx">
</span><span class="cx"> static bool supportsAVX()
</span><span class="cx"> {
</span><del>- if (s_avxCheckState == CPUIDCheckState::NotChecked)
- updateEax1EcxFlags();
- return s_avxCheckState == CPUIDCheckState::Set;
</del><ins>+ // AVX still causes mysterious regressions and those regressions can be massive.
+ return false;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> static void updateEax1EcxFlags()
</span></span></pre>
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