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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/168861">168861</a></dd>
<dt>Author</dt> <dd>mhahnenberg@apple.com</dd>
<dt>Date</dt> <dd>2014-05-14 13:48:55 -0700 (Wed, 14 May 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>Inline caching for proxies clobbers baseGPR too early
https://bugs.webkit.org/show_bug.cgi?id=132916
Reviewed by Filip Pizlo.
We clobber baseGPR prior to the Structure checks, so if any of the checks fail then the slow path
gets the target of the proxy rather than the proxy itself. We need to delay the clobbering of baseGPR
until we know the inline cache is going to succeed.
* jit/Repatch.cpp:
(JSC::generateByIdStub):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCorejitRepatchcpp">trunk/Source/JavaScriptCore/jit/Repatch.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (168860 => 168861)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2014-05-14 20:17:24 UTC (rev 168860)
+++ trunk/Source/JavaScriptCore/ChangeLog 2014-05-14 20:48:55 UTC (rev 168861)
</span><span class="lines">@@ -1,3 +1,17 @@
</span><ins>+2014-05-14 Mark Hahnenberg <mhahnenberg@apple.com>
+
+ Inline caching for proxies clobbers baseGPR too early
+ https://bugs.webkit.org/show_bug.cgi?id=132916
+
+ Reviewed by Filip Pizlo.
+
+ We clobber baseGPR prior to the Structure checks, so if any of the checks fail then the slow path
+ gets the target of the proxy rather than the proxy itself. We need to delay the clobbering of baseGPR
+ until we know the inline cache is going to succeed.
+
+ * jit/Repatch.cpp:
+ (JSC::generateByIdStub):
+
</ins><span class="cx"> 2014-05-14 Brent Fulgham <bfulgham@apple.com>
</span><span class="cx">
</span><span class="cx"> [Win] Unreviewed build fix.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitRepatchcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/Repatch.cpp (168860 => 168861)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/Repatch.cpp 2014-05-14 20:17:24 UTC (rev 168860)
+++ trunk/Source/JavaScriptCore/jit/Repatch.cpp 2014-05-14 20:48:55 UTC (rev 168861)
</span><span class="lines">@@ -317,14 +317,21 @@
</span><span class="cx"> MacroAssembler::NotEqual,
</span><span class="cx"> MacroAssembler::Address(baseGPR, JSCell::typeInfoTypeOffset()),
</span><span class="cx"> MacroAssembler::TrustedImm32(PureForwardingProxyType)));
</span><del>- stubJit.loadPtr(MacroAssembler::Address(baseGPR, JSProxy::targetOffset()), baseForGetGPR);
- } else
</del><ins>+
+ stubJit.loadPtr(MacroAssembler::Address(baseGPR, JSProxy::targetOffset()), scratchGPR);
+
+ failureCases.append(branchStructure(stubJit,
+ MacroAssembler::NotEqual,
+ MacroAssembler::Address(scratchGPR, JSCell::structureIDOffset()),
+ structure));
+ } else {
</ins><span class="cx"> baseForGetGPR = baseGPR;
</span><span class="cx">
</span><del>- failureCases.append(branchStructure(stubJit,
- MacroAssembler::NotEqual,
- MacroAssembler::Address(baseForGetGPR, JSCell::structureIDOffset()),
- structure));
</del><ins>+ failureCases.append(branchStructure(stubJit,
+ MacroAssembler::NotEqual,
+ MacroAssembler::Address(baseForGetGPR, JSCell::structureIDOffset()),
+ structure));
+ }
</ins><span class="cx">
</span><span class="cx"> CodeBlock* codeBlock = exec->codeBlock();
</span><span class="cx"> if (structure->typeInfo().newImpurePropertyFiresWatchpoints())
</span><span class="lines">@@ -351,11 +358,20 @@
</span><span class="cx">
</span><span class="cx"> GPRReg baseForAccessGPR;
</span><span class="cx"> if (chain) {
</span><ins>+ // We could have clobbered scratchGPR earlier, so we have to reload from baseGPR to get the target.
+ if (loadTargetFromProxy)
+ stubJit.loadPtr(MacroAssembler::Address(baseGPR, JSProxy::targetOffset()), baseForGetGPR);
</ins><span class="cx"> stubJit.move(MacroAssembler::TrustedImmPtr(protoObject), scratchGPR);
</span><span class="cx"> baseForAccessGPR = scratchGPR;
</span><del>- } else
</del><ins>+ } else {
+ // For proxy objects, we need to do all the Structure checks before moving the baseGPR into
+ // baseForGetGPR because if we fail any of the checks then we would have the wrong value in baseGPR
+ // on the slow path.
+ if (loadTargetFromProxy)
+ stubJit.move(scratchGPR, baseForGetGPR);
</ins><span class="cx"> baseForAccessGPR = baseForGetGPR;
</span><del>-
</del><ins>+ }
+
</ins><span class="cx"> GPRReg loadedValueGPR = InvalidGPRReg;
</span><span class="cx"> if (kind != CallCustomGetter && kind != CallCustomSetter) {
</span><span class="cx"> if (kind == GetValue)
</span></span></pre>
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