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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/183825">183825</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2015-05-05 13:42:44 -0700 (Tue, 05 May 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>FTL SwitchString slow case creates duplicate switch cases
https://bugs.webkit.org/show_bug.cgi?id=144634
Reviewed by Geoffrey Garen.
The problem of duplicate switches is sufficiently annoying that I fixed the issue and also
added mostly-debug-only asserts to catch such issues earlier.
* bytecode/CallVariant.cpp:
(JSC::variantListWithVariant): Assertion to prevent similar bugs.
* ftl/FTLLowerDFGToLLVM.cpp:
(JSC::FTL::LowerDFGToLLVM::switchStringRecurse): Assertion to prevent similar bugs.
(JSC::FTL::LowerDFGToLLVM::switchStringSlow): This is the bug.
* jit/BinarySwitch.cpp:
(JSC::BinarySwitch::BinarySwitch): Assertion to prevent similar bugs.
* jit/Repatch.cpp:
(JSC::linkPolymorphicCall): Assertion to prevent similar bugs.
* tests/stress/ftl-switch-string-slow-duplicate-cases.js: Added. This tests the FTL SwitchString bug. It was previously crashing every time.
(foo):
(cat):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecodeCallVariantcpp">trunk/Source/JavaScriptCore/bytecode/CallVariant.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreftlFTLLowerDFGToLLVMcpp">trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorejitBinarySwitchcpp">trunk/Source/JavaScriptCore/jit/BinarySwitch.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorejitRepatchcpp">trunk/Source/JavaScriptCore/jit/Repatch.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoretestsstressftlswitchstringslowduplicatecasesjs">trunk/Source/JavaScriptCore/tests/stress/ftl-switch-string-slow-duplicate-cases.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (183824 => 183825)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-05-05 20:14:07 UTC (rev 183824)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-05-05 20:42:44 UTC (rev 183825)
</span><span class="lines">@@ -1,3 +1,26 @@
</span><ins>+2015-05-05 Filip Pizlo <fpizlo@apple.com>
+
+ FTL SwitchString slow case creates duplicate switch cases
+ https://bugs.webkit.org/show_bug.cgi?id=144634
+
+ Reviewed by Geoffrey Garen.
+
+ The problem of duplicate switches is sufficiently annoying that I fixed the issue and also
+ added mostly-debug-only asserts to catch such issues earlier.
+
+ * bytecode/CallVariant.cpp:
+ (JSC::variantListWithVariant): Assertion to prevent similar bugs.
+ * ftl/FTLLowerDFGToLLVM.cpp:
+ (JSC::FTL::LowerDFGToLLVM::switchStringRecurse): Assertion to prevent similar bugs.
+ (JSC::FTL::LowerDFGToLLVM::switchStringSlow): This is the bug.
+ * jit/BinarySwitch.cpp:
+ (JSC::BinarySwitch::BinarySwitch): Assertion to prevent similar bugs.
+ * jit/Repatch.cpp:
+ (JSC::linkPolymorphicCall): Assertion to prevent similar bugs.
+ * tests/stress/ftl-switch-string-slow-duplicate-cases.js: Added. This tests the FTL SwitchString bug. It was previously crashing every time.
+ (foo):
+ (cat):
+
</ins><span class="cx"> 2015-05-05 Basile Clement <basile_clement@apple.com>
</span><span class="cx">
</span><span class="cx"> Fix debug builds after r183812
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecodeCallVariantcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecode/CallVariant.cpp (183824 => 183825)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecode/CallVariant.cpp 2015-05-05 20:14:07 UTC (rev 183824)
+++ trunk/Source/JavaScriptCore/bytecode/CallVariant.cpp 2015-05-05 20:42:44 UTC (rev 183825)
</span><span class="lines">@@ -27,6 +27,7 @@
</span><span class="cx"> #include "CallVariant.h"
</span><span class="cx">
</span><span class="cx"> #include "JSCInlines.h"
</span><ins>+#include <wtf/ListDump.h>
</ins><span class="cx">
</span><span class="cx"> namespace JSC {
</span><span class="cx">
</span><span class="lines">@@ -68,6 +69,19 @@
</span><span class="cx"> }
</span><span class="cx"> if (!!variantToAdd)
</span><span class="cx"> result.append(variantToAdd);
</span><ins>+
+ if (!ASSERT_DISABLED) {
+ for (unsigned i = 0; i < result.size(); ++i) {
+ for (unsigned j = i + 1; j < result.size(); ++j) {
+ if (result[i] != result[j])
+ continue;
+
+ dataLog("variantListWithVariant(", listDump(list), ", ", variantToAdd, ") failed: got duplicates in result: ", listDump(result), "\n");
+ RELEASE_ASSERT_NOT_REACHED();
+ }
+ }
+ }
+
</ins><span class="cx"> return result;
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreftlFTLLowerDFGToLLVMcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp (183824 => 183825)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp 2015-05-05 20:14:07 UTC (rev 183824)
+++ trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp 2015-05-05 20:42:44 UTC (rev 183825)
</span><span class="lines">@@ -52,6 +52,7 @@
</span><span class="cx"> #include <atomic>
</span><span class="cx"> #include <dlfcn.h>
</span><span class="cx"> #include <llvm/InitializeLLVM.h>
</span><ins>+#include <unordered_set>
</ins><span class="cx"> #include <wtf/ProcessID.h>
</span><span class="cx">
</span><span class="cx"> #if ENABLE(FTL_NATIVE_CALL_INLINING)
</span><span class="lines">@@ -6476,6 +6477,8 @@
</span><span class="cx">
</span><span class="cx"> Vector<SwitchCase> switchCases;
</span><span class="cx"> for (unsigned i = 0; i < characterCases.size(); ++i) {
</span><ins>+ if (i)
+ DFG_ASSERT(m_graph, m_node, characterCases[i - 1].character < characterCases[i].character);
</ins><span class="cx"> switchCases.append(SwitchCase(
</span><span class="cx"> m_out.constInt8(characterCases[i].character), characterBlocks[i], Weight()));
</span><span class="cx"> }
</span><span class="lines">@@ -6506,12 +6509,47 @@
</span><span class="cx"> StringJumpTable& table = codeBlock()->stringSwitchJumpTable(data->switchTableIndex);
</span><span class="cx">
</span><span class="cx"> Vector<SwitchCase> cases;
</span><ins>+ std::unordered_set<int32_t> alreadyHandled; // These may be negative, or zero, or probably other stuff, too. We don't want to mess with HashSet's corner cases and we don't really care about throughput here.
</ins><span class="cx"> for (unsigned i = 0; i < data->cases.size(); ++i) {
</span><ins>+ // FIXME: The fact that we're using the bytecode's switch table means that the
+ // following DFG IR transformation would be invalid.
+ //
+ // Original code:
+ // switch (v) {
+ // case "foo":
+ // case "bar":
+ // things();
+ // break;
+ // default:
+ // break;
+ // }
+ //
+ // New code:
+ // switch (v) {
+ // case "foo":
+ // instrumentFoo();
+ // goto _things;
+ // case "bar":
+ // instrumentBar();
+ // _things:
+ // things();
+ // break;
+ // default:
+ // break;
+ // }
+ //
+ // Luckily, we don't currently do any such transformation. But it's kind of silly that
+ // this is an issue.
+ // https://bugs.webkit.org/show_bug.cgi?id=144635
+
</ins><span class="cx"> DFG::SwitchCase myCase = data->cases[i];
</span><span class="cx"> StringJumpTable::StringOffsetTable::iterator iter =
</span><span class="cx"> table.offsetTable.find(myCase.value.stringImpl());
</span><span class="cx"> DFG_ASSERT(m_graph, m_node, iter != table.offsetTable.end());
</span><span class="cx">
</span><ins>+ if (!alreadyHandled.insert(iter->value.branchOffset).second)
+ continue;
+
</ins><span class="cx"> cases.append(SwitchCase(
</span><span class="cx"> m_out.constInt32(iter->value.branchOffset),
</span><span class="cx"> lowBlock(myCase.target.block), Weight(myCase.target.count)));
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitBinarySwitchcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/BinarySwitch.cpp (183824 => 183825)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/BinarySwitch.cpp 2015-05-05 20:14:07 UTC (rev 183824)
+++ trunk/Source/JavaScriptCore/jit/BinarySwitch.cpp 2015-05-05 20:42:44 UTC (rev 183825)
</span><span class="lines">@@ -46,7 +46,12 @@
</span><span class="cx">
</span><span class="cx"> for (unsigned i = 0; i < cases.size(); ++i)
</span><span class="cx"> m_cases.append(Case(cases[i], i));
</span><ins>+
</ins><span class="cx"> std::sort(m_cases.begin(), m_cases.end());
</span><ins>+
+ for (unsigned i = 1; i < m_cases.size(); ++i)
+ RELEASE_ASSERT(m_cases[i - 1] < m_cases[i]);
+
</ins><span class="cx"> build(0, false, m_cases.size());
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitRepatchcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/Repatch.cpp (183824 => 183825)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/Repatch.cpp 2015-05-05 20:14:07 UTC (rev 183824)
+++ trunk/Source/JavaScriptCore/jit/Repatch.cpp 2015-05-05 20:42:44 UTC (rev 183825)
</span><span class="lines">@@ -49,6 +49,7 @@
</span><span class="cx"> #include "StructureRareDataInlines.h"
</span><span class="cx"> #include "StructureStubClearingWatchpoint.h"
</span><span class="cx"> #include "ThunkGenerators.h"
</span><ins>+#include <wtf/CommaPrinter.h>
</ins><span class="cx"> #include <wtf/ListDump.h>
</span><span class="cx"> #include <wtf/StringPrintStream.h>
</span><span class="cx">
</span><span class="lines">@@ -1828,15 +1829,35 @@
</span><span class="cx"> if (callerCodeBlock->jitType() != JITCode::topTierJIT())
</span><span class="cx"> fastCounts = std::make_unique<uint32_t[]>(callCases.size());
</span><span class="cx">
</span><del>- for (size_t i = callCases.size(); i--;) {
</del><ins>+ for (size_t i = 0; i < callCases.size(); ++i) {
</ins><span class="cx"> if (fastCounts)
</span><span class="cx"> fastCounts[i] = 0;
</span><span class="cx">
</span><span class="cx"> CallVariant variant = callCases[i].variant();
</span><ins>+ int64_t newCaseValue;
</ins><span class="cx"> if (isClosureCall)
</span><del>- caseValues[i] = bitwise_cast<intptr_t>(variant.executable());
</del><ins>+ newCaseValue = bitwise_cast<intptr_t>(variant.executable());
</ins><span class="cx"> else
</span><del>- caseValues[i] = bitwise_cast<intptr_t>(variant.function());
</del><ins>+ newCaseValue = bitwise_cast<intptr_t>(variant.function());
+
+ if (!ASSERT_DISABLED) {
+ for (size_t j = 0; j < i; ++j) {
+ if (caseValues[j] != newCaseValue)
+ continue;
+
+ dataLog("ERROR: Attempt to add duplicate case value.\n");
+ dataLog("Existing case values: ");
+ CommaPrinter comma;
+ for (size_t k = 0; k < i; ++k)
+ dataLog(comma, caseValues[k]);
+ dataLog("\n");
+ dataLog("Attempting to add: ", newCaseValue, "\n");
+ dataLog("Variant list: ", listDump(callCases), "\n");
+ RELEASE_ASSERT_NOT_REACHED();
+ }
+ }
+
+ caseValues[i] = newCaseValue;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> GPRReg fastCountsBaseGPR =
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressftlswitchstringslowduplicatecasesjs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/ftl-switch-string-slow-duplicate-cases.js (0 => 183825)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/ftl-switch-string-slow-duplicate-cases.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/ftl-switch-string-slow-duplicate-cases.js 2015-05-05 20:42:44 UTC (rev 183825)
</span><span class="lines">@@ -0,0 +1,31 @@
</span><ins>+function foo(s) {
+ switch (s) {
+ case "ƑẦǏŁ":
+ case "ÌŅ":
+ case "ṤĻŐⱲ":
+ case "ṔÄȚĦ":
+ return 42;
+ case "due":
+ case "to":
+ case "16-bit":
+ case "strings":
+ return 43;
+ default:
+ return 44;
+ }
+}
+
+noInline(foo);
+
+function cat(a, b) {
+ return a + b;
+}
+
+for (var i = 0; i < 10000; ++i) {
+ var result = foo(cat("16-", "bit"));
+ if (result != 43)
+ throw "Error: bad result (1): " + result;
+ result = foo("ƑẦǏŁ");
+ if (result != 42)
+ throw "Error: bad result (2): " + result;
+}
</ins></span></pre>
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