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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/173770">173770</a></dd>
<dt>Author</dt> <dd>benjamin@webkit.org</dd>
<dt>Date</dt> <dd>2014-09-19 13:26:56 -0700 (Fri, 19 Sep 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>CSS JIT: allocate the minimum required register count in debug
https://bugs.webkit.org/show_bug.cgi?id=136933
Patch by Benjamin Poulain <bpoulain@apple.com> on 2014-09-19
Reviewed by Andreas Kling.
It is hard to catch bugs of minimumRegisterRequirements() because every CPU has a different
number of registers available by default.
This patch aims at improving testing by creating artificial register pressure when running
in debug. When running in debug, we no longer allocate all the available registers right away.
Instead, we allocate just enough to satisfy minimumRegisterRequirements().
The expectation with this is that under-allocation would be detected quicker since they would
crash debug builds.
* cssjit/RegisterAllocator.h:
(WebCore::RegisterAllocator::RegisterAllocator):
(WebCore::RegisterAllocator::reserveCallerSavedRegisters):
(WebCore::RegisterAllocator::availableRegisterCount): Deleted.
* cssjit/SelectorCompiler.cpp:
(WebCore::SelectorCompiler::SelectorCodeGenerator::generateSelectorChecker):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorecssjitRegisterAllocatorh">trunk/Source/WebCore/cssjit/RegisterAllocator.h</a></li>
<li><a href="#trunkSourceWebCorecssjitSelectorCompilercpp">trunk/Source/WebCore/cssjit/SelectorCompiler.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (173769 => 173770)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog 2014-09-19 20:26:07 UTC (rev 173769)
+++ trunk/Source/WebCore/ChangeLog 2014-09-19 20:26:56 UTC (rev 173770)
</span><span class="lines">@@ -1,5 +1,29 @@
</span><span class="cx"> 2014-09-19 Benjamin Poulain <bpoulain@apple.com>
</span><span class="cx">
</span><ins>+ CSS JIT: allocate the minimum required register count in debug
+ https://bugs.webkit.org/show_bug.cgi?id=136933
+
+ Reviewed by Andreas Kling.
+
+ It is hard to catch bugs of minimumRegisterRequirements() because every CPU has a different
+ number of registers available by default.
+
+ This patch aims at improving testing by creating artificial register pressure when running
+ in debug. When running in debug, we no longer allocate all the available registers right away.
+ Instead, we allocate just enough to satisfy minimumRegisterRequirements().
+
+ The expectation with this is that under-allocation would be detected quicker since they would
+ crash debug builds.
+
+ * cssjit/RegisterAllocator.h:
+ (WebCore::RegisterAllocator::RegisterAllocator):
+ (WebCore::RegisterAllocator::reserveCallerSavedRegisters):
+ (WebCore::RegisterAllocator::availableRegisterCount): Deleted.
+ * cssjit/SelectorCompiler.cpp:
+ (WebCore::SelectorCompiler::SelectorCodeGenerator::generateSelectorChecker):
+
+2014-09-19 Benjamin Poulain <bpoulain@apple.com>
+
</ins><span class="cx"> Add a size check for CSSSelector
</span><span class="cx"> https://bugs.webkit.org/show_bug.cgi?id=136882
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceWebCorecssjitRegisterAllocatorh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/cssjit/RegisterAllocator.h (173769 => 173770)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/cssjit/RegisterAllocator.h 2014-09-19 20:26:07 UTC (rev 173769)
+++ trunk/Source/WebCore/cssjit/RegisterAllocator.h 2014-09-19 20:26:56 UTC (rev 173770)
</span><span class="lines">@@ -102,7 +102,7 @@
</span><span class="cx">
</span><span class="cx"> class RegisterAllocator {
</span><span class="cx"> public:
</span><del>- RegisterAllocator();
</del><ins>+ RegisterAllocator() { }
</ins><span class="cx"> ~RegisterAllocator();
</span><span class="cx">
</span><span class="cx"> unsigned availableRegisterCount() const { return m_registers.size(); }
</span><span class="lines">@@ -154,6 +154,19 @@
</span><span class="cx"> m_registers.append(registerID);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ unsigned reserveCallerSavedRegisters(unsigned count)
+ {
+#ifdef NDEBUG
+ UNUSED_PARAM(count);
+ unsigned numberToAllocate = WTF_ARRAY_LENGTH(callerSavedRegisters);
+#else
+ unsigned numberToAllocate = std::min<unsigned>(WTF_ARRAY_LENGTH(callerSavedRegisters), count);
+#endif
+ for (unsigned i = 0; i < numberToAllocate; ++i)
+ m_registers.append(callerSavedRegisters[i]);
+ return numberToAllocate;
+ }
+
</ins><span class="cx"> const Vector<JSC::MacroAssembler::RegisterID, calleeSavedRegisterCount>& reserveCalleeSavedRegisters(unsigned count)
</span><span class="cx"> {
</span><span class="cx"> RELEASE_ASSERT(count <= WTF_ARRAY_LENGTH(calleeSavedRegisters));
</span><span class="lines">@@ -247,12 +260,6 @@
</span><span class="cx"> {
</span><span class="cx"> }
</span><span class="cx"> };
</span><del>-
-inline RegisterAllocator::RegisterAllocator()
-{
- for (unsigned i = 0; i < WTF_ARRAY_LENGTH(callerSavedRegisters); ++i)
- m_registers.append(callerSavedRegisters[i]);
-}
</del><span class="cx">
</span><span class="cx"> inline RegisterAllocator::~RegisterAllocator()
</span><span class="cx"> {
</span></span></pre></div>
<a id="trunkSourceWebCorecssjitSelectorCompilercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/cssjit/SelectorCompiler.cpp (173769 => 173770)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/cssjit/SelectorCompiler.cpp 2014-09-19 20:26:07 UTC (rev 173769)
+++ trunk/Source/WebCore/cssjit/SelectorCompiler.cpp 2014-09-19 20:26:56 UTC (rev 173770)
</span><span class="lines">@@ -1351,14 +1351,6 @@
</span><span class="cx">
</span><span class="cx"> void SelectorCodeGenerator::generateSelectorChecker()
</span><span class="cx"> {
</span><del>- StackAllocator::StackReferenceVector calleeSavedRegisterStackReferences;
- bool reservedCalleeSavedRegisters = false;
- unsigned availableRegisterCount = m_registerAllocator.availableRegisterCount();
- unsigned minimumRegisterCountForAttributes = minimumRegisterRequirements(m_selectorFragments);
-#if CSS_SELECTOR_JIT_DEBUGGING
- dataLogF("Compiling with minimum required register count %u\n", minimumRegisterCountForAttributes);
-#endif
-
</del><span class="cx"> Assembler::JumpList failureOnFunctionEntry;
</span><span class="cx"> // Test selector's pseudo element equals to requested PseudoId.
</span><span class="cx"> if (m_selectorContext != SelectorContext::QuerySelector && m_functionType == FunctionType::SelectorCheckerWithCheckingContext) {
</span><span class="lines">@@ -1366,12 +1358,20 @@
</span><span class="cx"> generateRequestedPseudoElementEqualsToSelectorPseudoElement(failureOnFunctionEntry, m_selectorFragments.first(), checkingContextRegister);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ unsigned minimumRegisterCount = minimumRegisterRequirements(m_selectorFragments);
+ unsigned availableRegisterCount = m_registerAllocator.reserveCallerSavedRegisters(minimumRegisterCount);
+#if CSS_SELECTOR_JIT_DEBUGGING
+ dataLogF("Compiling with minimum required register count %u\n", minimumRegisterCount);
+#endif
+
</ins><span class="cx"> bool needsEpilogue = generatePrologue();
</span><span class="cx">
</span><del>- ASSERT(minimumRegisterCountForAttributes <= maximumRegisterCount);
- if (availableRegisterCount < minimumRegisterCountForAttributes) {
</del><ins>+ StackAllocator::StackReferenceVector calleeSavedRegisterStackReferences;
+ bool reservedCalleeSavedRegisters = false;
+ ASSERT(minimumRegisterCount <= maximumRegisterCount);
+ if (availableRegisterCount < minimumRegisterCount) {
</ins><span class="cx"> reservedCalleeSavedRegisters = true;
</span><del>- calleeSavedRegisterStackReferences = m_stackAllocator.push(m_registerAllocator.reserveCalleeSavedRegisters(minimumRegisterCountForAttributes - availableRegisterCount));
</del><ins>+ calleeSavedRegisterStackReferences = m_stackAllocator.push(m_registerAllocator.reserveCalleeSavedRegisters(minimumRegisterCount - availableRegisterCount));
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> m_registerAllocator.allocateRegister(elementAddressRegister);
</span></span></pre>
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