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<title>[192596] trunk/Source/JavaScriptCore</title>
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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/192596">192596</a></dd>
<dt>Author</dt> <dd>keith_miller@apple.com</dd>
<dt>Date</dt> <dd>2015-11-18 16:01:32 -0800 (Wed, 18 Nov 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>[JSC] TailCalls should not trigger assertion failures when running with the jsc profiler on.
https://bugs.webkit.org/show_bug.cgi?id=151359
Reviewed by Geoffrey Garen.
If we have the profiler on when parsing tail calls in the dfg we would emit a CountExecutions node
following a TailCall node as our bytecode for tail calls always emits a op_ret following an op_tail_call.
This trips assertions that no nodes follow a terminal in a basic block. This patch fixes this issue by
not emiting a CountExecutions when we have a tail call that is terminal i.e. the tail caller is not
inlined into another function or the tail caller is inlined but is in tail position itself.
* dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::handleCall):
(JSC::DFG::ByteCodeParser::handleVarargsCall):
(JSC::DFG::ByteCodeParser::parseBlock):
* tests/stress/tail-call-profiler.js: Added.
(tail):
(inlineTail):
(inlineTailVarArgs):
(inlineTailTernary):
(body):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGByteCodeParsercpp">trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoretestsstresstailcallprofilerjs">trunk/Source/JavaScriptCore/tests/stress/tail-call-profiler.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (192595 => 192596)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-11-18 23:48:48 UTC (rev 192595)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-11-19 00:01:32 UTC (rev 192596)
</span><span class="lines">@@ -1,3 +1,27 @@
</span><ins>+2015-11-17 Keith Miller <keith_miller@apple.com>
+
+ [JSC] TailCalls should not trigger assertion failures when running with the jsc profiler on.
+ https://bugs.webkit.org/show_bug.cgi?id=151359
+
+ Reviewed by Geoffrey Garen.
+
+ If we have the profiler on when parsing tail calls in the dfg we would emit a CountExecutions node
+ following a TailCall node as our bytecode for tail calls always emits a op_ret following an op_tail_call.
+ This trips assertions that no nodes follow a terminal in a basic block. This patch fixes this issue by
+ not emiting a CountExecutions when we have a tail call that is terminal i.e. the tail caller is not
+ inlined into another function or the tail caller is inlined but is in tail position itself.
+
+ * dfg/DFGByteCodeParser.cpp:
+ (JSC::DFG::ByteCodeParser::handleCall):
+ (JSC::DFG::ByteCodeParser::handleVarargsCall):
+ (JSC::DFG::ByteCodeParser::parseBlock):
+ * tests/stress/tail-call-profiler.js: Added.
+ (tail):
+ (inlineTail):
+ (inlineTailVarArgs):
+ (inlineTailTernary):
+ (body):
+
</ins><span class="cx"> 2015-11-18 Benjamin Poulain <bpoulain@apple.com>
</span><span class="cx">
</span><span class="cx"> [JSC] Make LBasicBlock into an alias for B3::BasicBlock. #ifdef anything that does not compile
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGByteCodeParsercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp (192595 => 192596)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp 2015-11-18 23:48:48 UTC (rev 192595)
+++ trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp 2015-11-19 00:01:32 UTC (rev 192596)
</span><span class="lines">@@ -176,18 +176,19 @@
</span><span class="cx"> // Helper for min and max.
</span><span class="cx"> template<typename ChecksFunctor>
</span><span class="cx"> bool handleMinMax(int resultOperand, NodeType op, int registerOffset, int argumentCountIncludingThis, const ChecksFunctor& insertChecks);
</span><del>-
</del><ins>+
</ins><span class="cx"> // Handle calls. This resolves issues surrounding inlining and intrinsics.
</span><del>- void handleCall(
</del><ins>+ enum Terminality { Terminal, NonTerminal };
+ Terminality handleCall(
</ins><span class="cx"> int result, NodeType op, InlineCallFrame::Kind, unsigned instructionSize,
</span><span class="cx"> Node* callTarget, int argCount, int registerOffset, CallLinkStatus,
</span><span class="cx"> SpeculatedType prediction);
</span><del>- void handleCall(
</del><ins>+ Terminality handleCall(
</ins><span class="cx"> int result, NodeType op, CallMode, unsigned instructionSize,
</span><span class="cx"> Node* callTarget, int argCount, int registerOffset, CallLinkStatus);
</span><del>- void handleCall(int result, NodeType op, CallMode, unsigned instructionSize, int callee, int argCount, int registerOffset);
- void handleCall(Instruction* pc, NodeType op, CallMode);
- void handleVarargsCall(Instruction* pc, NodeType op, CallMode);
</del><ins>+ Terminality handleCall(int result, NodeType op, CallMode, unsigned instructionSize, int callee, int argCount, int registerOffset);
+ Terminality handleCall(Instruction* pc, NodeType op, CallMode);
+ Terminality handleVarargsCall(Instruction* pc, NodeType op, CallMode);
</ins><span class="cx"> void emitFunctionChecks(CallVariant, Node* callTarget, VirtualRegister thisArgumnt);
</span><span class="cx"> void emitArgumentPhantoms(int registerOffset, int argumentCountIncludingThis);
</span><span class="cx"> unsigned inliningCost(CallVariant, int argumentCountIncludingThis, CallMode); // Return UINT_MAX if it's not an inlining candidate. By convention, intrinsics have a cost of 1.
</span><span class="lines">@@ -1131,16 +1132,16 @@
</span><span class="cx"> m_exitOK = false; \
</span><span class="cx"> return shouldContinueParsing
</span><span class="cx">
</span><del>-void ByteCodeParser::handleCall(Instruction* pc, NodeType op, CallMode callMode)
</del><ins>+ByteCodeParser::Terminality ByteCodeParser::handleCall(Instruction* pc, NodeType op, CallMode callMode)
</ins><span class="cx"> {
</span><span class="cx"> ASSERT(OPCODE_LENGTH(op_call) == OPCODE_LENGTH(op_construct));
</span><span class="cx"> ASSERT(OPCODE_LENGTH(op_call) == OPCODE_LENGTH(op_tail_call));
</span><del>- handleCall(
</del><ins>+ return handleCall(
</ins><span class="cx"> pc[1].u.operand, op, callMode, OPCODE_LENGTH(op_call),
</span><span class="cx"> pc[2].u.operand, pc[3].u.operand, -pc[4].u.operand);
</span><span class="cx"> }
</span><span class="cx">
</span><del>-void ByteCodeParser::handleCall(
</del><ins>+ByteCodeParser::Terminality ByteCodeParser::handleCall(
</ins><span class="cx"> int result, NodeType op, CallMode callMode, unsigned instructionSize,
</span><span class="cx"> int callee, int argumentCountIncludingThis, int registerOffset)
</span><span class="cx"> {
</span><span class="lines">@@ -1150,22 +1151,22 @@
</span><span class="cx"> m_inlineStackTop->m_profiledBlock, currentCodeOrigin(),
</span><span class="cx"> m_inlineStackTop->m_callLinkInfos, m_callContextMap);
</span><span class="cx">
</span><del>- handleCall(
</del><ins>+ return handleCall(
</ins><span class="cx"> result, op, callMode, instructionSize, callTarget,
</span><span class="cx"> argumentCountIncludingThis, registerOffset, callLinkStatus);
</span><span class="cx"> }
</span><span class="cx">
</span><del>-void ByteCodeParser::handleCall(
</del><ins>+ByteCodeParser::Terminality ByteCodeParser::handleCall(
</ins><span class="cx"> int result, NodeType op, CallMode callMode, unsigned instructionSize,
</span><span class="cx"> Node* callTarget, int argumentCountIncludingThis, int registerOffset,
</span><span class="cx"> CallLinkStatus callLinkStatus)
</span><span class="cx"> {
</span><del>- handleCall(
</del><ins>+ return handleCall(
</ins><span class="cx"> result, op, InlineCallFrame::kindFor(callMode), instructionSize, callTarget, argumentCountIncludingThis,
</span><span class="cx"> registerOffset, callLinkStatus, getPrediction());
</span><span class="cx"> }
</span><span class="cx">
</span><del>-void ByteCodeParser::handleCall(
</del><ins>+ByteCodeParser::Terminality ByteCodeParser::handleCall(
</ins><span class="cx"> int result, NodeType op, InlineCallFrame::Kind kind, unsigned instructionSize,
</span><span class="cx"> Node* callTarget, int argumentCountIncludingThis, int registerOffset,
</span><span class="cx"> CallLinkStatus callLinkStatus, SpeculatedType prediction)
</span><span class="lines">@@ -1182,8 +1183,11 @@
</span><span class="cx"> // Oddly, this conflates calls that haven't executed with calls that behaved sufficiently polymorphically
</span><span class="cx"> // that we cannot optimize them.
</span><span class="cx">
</span><del>- addCall(result, op, OpInfo(), callTarget, argumentCountIncludingThis, registerOffset, prediction);
- return;
</del><ins>+ Node* callNode = addCall(result, op, OpInfo(), callTarget, argumentCountIncludingThis, registerOffset, prediction);
+ if (callNode->op() == TailCall)
+ return Terminal;
+ ASSERT(callNode->op() != TailCallVarargs);
+ return NonTerminal;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> unsigned nextOffset = m_currentIndex + instructionSize;
</span><span class="lines">@@ -1193,13 +1197,17 @@
</span><span class="cx"> if (handleInlining(callTarget, result, callLinkStatus, registerOffset, virtualRegisterForArgument(0, registerOffset), VirtualRegister(), 0, argumentCountIncludingThis, nextOffset, op, kind, prediction)) {
</span><span class="cx"> if (m_graph.compilation())
</span><span class="cx"> m_graph.compilation()->noticeInlinedCall();
</span><del>- return;
</del><ins>+ return NonTerminal;
</ins><span class="cx"> }
</span><span class="cx">
</span><del>- addCall(result, op, callOpInfo, callTarget, argumentCountIncludingThis, registerOffset, prediction);
</del><ins>+ Node* callNode = addCall(result, op, callOpInfo, callTarget, argumentCountIncludingThis, registerOffset, prediction);
+ if (callNode->op() == TailCall)
+ return Terminal;
+ ASSERT(callNode->op() != TailCallVarargs);
+ return NonTerminal;
</ins><span class="cx"> }
</span><span class="cx">
</span><del>-void ByteCodeParser::handleVarargsCall(Instruction* pc, NodeType op, CallMode callMode)
</del><ins>+ByteCodeParser::Terminality ByteCodeParser::handleVarargsCall(Instruction* pc, NodeType op, CallMode callMode)
</ins><span class="cx"> {
</span><span class="cx"> ASSERT(OPCODE_LENGTH(op_call_varargs) == OPCODE_LENGTH(op_construct_varargs));
</span><span class="cx"> ASSERT(OPCODE_LENGTH(op_call_varargs) == OPCODE_LENGTH(op_tail_call_varargs));
</span><span class="lines">@@ -1228,7 +1236,7 @@
</span><span class="cx"> && handleInlining(callTarget, result, callLinkStatus, firstFreeReg, VirtualRegister(thisReg), VirtualRegister(arguments), firstVarArgOffset, 0, m_currentIndex + OPCODE_LENGTH(op_call_varargs), op, InlineCallFrame::varargsKindFor(callMode), prediction)) {
</span><span class="cx"> if (m_graph.compilation())
</span><span class="cx"> m_graph.compilation()->noticeInlinedCall();
</span><del>- return;
</del><ins>+ return NonTerminal;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> CallVarargsData* data = m_graph.m_callVarargsData.add();
</span><span class="lines">@@ -1239,7 +1247,7 @@
</span><span class="cx"> if (op == TailCallVarargs) {
</span><span class="cx"> if (allInlineFramesAreTailCalls()) {
</span><span class="cx"> addToGraph(op, OpInfo(data), OpInfo(), callTarget, get(VirtualRegister(arguments)), thisChild);
</span><del>- return;
</del><ins>+ return Terminal;
</ins><span class="cx"> }
</span><span class="cx"> op = TailCallVarargsInlinedCaller;
</span><span class="cx"> }
</span><span class="lines">@@ -1248,6 +1256,7 @@
</span><span class="cx"> VirtualRegister resultReg(result);
</span><span class="cx"> if (resultReg.isValid())
</span><span class="cx"> set(resultReg, call);
</span><ins>+ return NonTerminal;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> void ByteCodeParser::emitFunctionChecks(CallVariant callee, Node* callTarget, VirtualRegister thisArgumentReg)
</span><span class="lines">@@ -3180,9 +3189,8 @@
</span><span class="cx"> // to be true.
</span><span class="cx"> // We also don't insert a jump if the block already has a terminal,
</span><span class="cx"> // which could happen after a tail call.
</span><del>- ASSERT(m_currentBlock->isEmpty() || !m_currentBlock->terminal()
- || m_currentBlock->terminal()->op() == TailCall || m_currentBlock->terminal()->op() == TailCallVarargs);
- if (!m_currentBlock->isEmpty() && !m_currentBlock->terminal())
</del><ins>+ ASSERT(m_currentBlock->isEmpty() || !m_currentBlock->terminal());
+ if (!m_currentBlock->isEmpty())
</ins><span class="cx"> addToGraph(Jump, OpInfo(m_currentIndex));
</span><span class="cx"> return shouldContinueParsing;
</span><span class="cx"> }
</span><span class="lines">@@ -3796,12 +3804,7 @@
</span><span class="cx"> // === Block terminators. ===
</span><span class="cx">
</span><span class="cx"> case op_jmp: {
</span><del>- if (m_currentBlock->terminal()) {
- // We could be the dummy jump to a return after a non-inlined, non-emulated tail call in a ternary operator
- Node* terminal = m_currentBlock->terminal();
- ASSERT_UNUSED(terminal, terminal->op() == TailCall || terminal->op() == TailCallVarargs);
- LAST_OPCODE(op_jmp);
- }
</del><ins>+ ASSERT(!m_currentBlock->terminal());
</ins><span class="cx"> int relativeOffset = currentInstruction[1].u.operand;
</span><span class="cx"> addToGraph(Jump, OpInfo(m_currentIndex + relativeOffset));
</span><span class="cx"> if (relativeOffset <= 0)
</span><span class="lines">@@ -3973,12 +3976,7 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> case op_ret:
</span><del>- if (m_currentBlock->terminal()) {
- // We could be the dummy return after a non-inlined, non-emulated tail call
- Node* terminal = m_currentBlock->terminal();
- ASSERT_UNUSED(terminal, terminal->op() == TailCall || terminal->op() == TailCallVarargs);
- LAST_OPCODE(op_ret);
- }
</del><ins>+ ASSERT(!m_currentBlock->terminal());
</ins><span class="cx"> if (inlineCallFrame()) {
</span><span class="cx"> flushForReturn();
</span><span class="cx"> if (m_inlineStackTop->m_returnValue.isValid())
</span><span class="lines">@@ -4031,18 +4029,24 @@
</span><span class="cx">
</span><span class="cx"> case op_call:
</span><span class="cx"> handleCall(currentInstruction, Call, CallMode::Regular);
</span><del>- // Verify that handleCall(), which could have inlined the callee, didn't trash m_currentInstruction
</del><ins>+ // Verify that handleCall(), which could have inlined the callee, didn't trash m_currentInstruction.
</ins><span class="cx"> ASSERT(m_currentInstruction == currentInstruction);
</span><span class="cx"> NEXT_OPCODE(op_call);
</span><span class="cx">
</span><del>- case op_tail_call:
</del><ins>+ case op_tail_call: {
</ins><span class="cx"> flushForReturn();
</span><del>- handleCall(currentInstruction, TailCall, CallMode::Tail);
- // Verify that handleCall(), which could have inlined the callee, didn't trash m_currentInstruction
</del><ins>+ Terminality terminality = handleCall(currentInstruction, TailCall, CallMode::Tail);
+ // Verify that handleCall(), which could have inlined the callee, didn't trash m_currentInstruction.
</ins><span class="cx"> ASSERT(m_currentInstruction == currentInstruction);
</span><del>- // We let the following op_ret handle cases related to
- // inlining to keep things simple.
- NEXT_OPCODE(op_tail_call);
</del><ins>+ // If the call is terminal then we should not parse any further bytecodes as the TailCall will exit the function.
+ // If the call is not terminal, however, then we want the subsequent op_ret/op_jumpt to update metadata and clean
+ // things up.
+ if (terminality == NonTerminal) {
+ NEXT_OPCODE(op_tail_call);
+ } else {
+ LAST_OPCODE(op_tail_call);
+ }
+ }
</ins><span class="cx">
</span><span class="cx"> case op_construct:
</span><span class="cx"> handleCall(currentInstruction, Construct, CallMode::Construct);
</span><span class="lines">@@ -4055,8 +4059,15 @@
</span><span class="cx">
</span><span class="cx"> case op_tail_call_varargs: {
</span><span class="cx"> flushForReturn();
</span><del>- handleVarargsCall(currentInstruction, TailCallVarargs, CallMode::Tail);
- NEXT_OPCODE(op_tail_call_varargs);
</del><ins>+ Terminality terminality = handleVarargsCall(currentInstruction, TailCallVarargs, CallMode::Tail);
+ // If the call is terminal then we should not parse any further bytecodes as the TailCall will exit the function.
+ // If the call is not terminal, however, then we want the subsequent op_ret/op_jumpt to update metadata and clean
+ // things up.
+ if (terminality == NonTerminal) {
+ NEXT_OPCODE(op_tail_call_varargs);
+ } else {
+ LAST_OPCODE(op_tail_call_varargs);
+ }
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> case op_construct_varargs: {
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstresstailcallprofilerjs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/tail-call-profiler.js (0 => 192596)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/tail-call-profiler.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/tail-call-profiler.js 2015-11-19 00:01:32 UTC (rev 192596)
</span><span class="lines">@@ -0,0 +1,29 @@
</span><ins>+//@ runProfiler
+// This tests the profiler DFG node, CountExecution, plays nicely with TailCalls.
+
+"use strict";
+
+function tail(a) { return 1; }
+noInline(tail);
+
+function inlineTail(a) {
+ return tail(a);
+}
+
+function inlineTailVarArgs(a) {
+ return tail(...[a])
+}
+
+function inlineTailTernary(a) {
+ return true ? tail(a) : null;
+}
+
+function body() {
+ for (var i = 0; i < 10000; i++) {
+ inlineTail(1);
+ inlineTailVarArgs(1);
+ inlineTailTernary(1)
+ }
+}
+
+body();
</ins></span></pre>
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