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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/192599">192599</a></dd>
<dt>Author</dt> <dd>mark.lam@apple.com</dd>
<dt>Date</dt> <dd>2015-11-18 16:30:37 -0800 (Wed, 18 Nov 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Remove some unnecessary jumps in snippet code.
https://bugs.webkit.org/show_bug.cgi?id=151415
Reviewed by Geoffrey Garen.
Previously, the snippet generators always emit a jump at the end of the fast
path. In the baseline JIT and FTL, this results in a jump to the very next
instruction. I've change it to assume that the fast path will just fall thru,
and let the client decide instead if it wants/needs a jump or not after the fast
path.
I also changed the generators to provide a didEmitFastPath() query explicitly
declare if they actually generated the fast path, instead of having the client
infer it from an empty endJumpList.
Benchmarks show that perf is neutral with this change (tested on x86_64).
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::compileValueAdd):
(JSC::DFG::SpeculativeJIT::compileArithSub):
* ftl/FTLCompile.cpp:
(JSC::FTL::mmAllocateDataSection):
* jit/JITAddGenerator.cpp:
(JSC::JITAddGenerator::generateFastPath):
* jit/JITAddGenerator.h:
(JSC::JITAddGenerator::didEmitFastPath):
(JSC::JITAddGenerator::endJumpList):
(JSC::JITAddGenerator::slowPathJumpList):
* jit/JITArithmetic.cpp:
(JSC::JIT::emit_op_add):
(JSC::JIT::emit_op_sub):
* jit/JITSubGenerator.cpp:
(JSC::JITSubGenerator::generateFastPath):
* jit/JITSubGenerator.h:
(JSC::JITSubGenerator::didEmitFastPath):
(JSC::JITSubGenerator::endJumpList):
(JSC::JITSubGenerator::slowPathJumpList):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGSpeculativeJITcpp">trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreftlFTLCompilecpp">trunk/Source/JavaScriptCore/ftl/FTLCompile.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorejitJITAddGeneratorcpp">trunk/Source/JavaScriptCore/jit/JITAddGenerator.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorejitJITAddGeneratorh">trunk/Source/JavaScriptCore/jit/JITAddGenerator.h</a></li>
<li><a href="#trunkSourceJavaScriptCorejitJITArithmeticcpp">trunk/Source/JavaScriptCore/jit/JITArithmetic.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorejitJITSubGeneratorcpp">trunk/Source/JavaScriptCore/jit/JITSubGenerator.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorejitJITSubGeneratorh">trunk/Source/JavaScriptCore/jit/JITSubGenerator.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (192598 => 192599)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-11-19 00:20:41 UTC (rev 192598)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-11-19 00:30:37 UTC (rev 192599)
</span><span class="lines">@@ -1,3 +1,43 @@
</span><ins>+2015-11-18 Mark Lam <mark.lam@apple.com>
+
+ Remove some unnecessary jumps in snippet code.
+ https://bugs.webkit.org/show_bug.cgi?id=151415
+
+ Reviewed by Geoffrey Garen.
+
+ Previously, the snippet generators always emit a jump at the end of the fast
+ path. In the baseline JIT and FTL, this results in a jump to the very next
+ instruction. I've change it to assume that the fast path will just fall thru,
+ and let the client decide instead if it wants/needs a jump or not after the fast
+ path.
+
+ I also changed the generators to provide a didEmitFastPath() query explicitly
+ declare if they actually generated the fast path, instead of having the client
+ infer it from an empty endJumpList.
+
+ Benchmarks show that perf is neutral with this change (tested on x86_64).
+
+ * dfg/DFGSpeculativeJIT.cpp:
+ (JSC::DFG::SpeculativeJIT::compileValueAdd):
+ (JSC::DFG::SpeculativeJIT::compileArithSub):
+ * ftl/FTLCompile.cpp:
+ (JSC::FTL::mmAllocateDataSection):
+ * jit/JITAddGenerator.cpp:
+ (JSC::JITAddGenerator::generateFastPath):
+ * jit/JITAddGenerator.h:
+ (JSC::JITAddGenerator::didEmitFastPath):
+ (JSC::JITAddGenerator::endJumpList):
+ (JSC::JITAddGenerator::slowPathJumpList):
+ * jit/JITArithmetic.cpp:
+ (JSC::JIT::emit_op_add):
+ (JSC::JIT::emit_op_sub):
+ * jit/JITSubGenerator.cpp:
+ (JSC::JITSubGenerator::generateFastPath):
+ * jit/JITSubGenerator.h:
+ (JSC::JITSubGenerator::didEmitFastPath):
+ (JSC::JITSubGenerator::endJumpList):
+ (JSC::JITSubGenerator::slowPathJumpList):
+
</ins><span class="cx"> 2015-11-18 Commit Queue <commit-queue@webkit.org>
</span><span class="cx">
</span><span class="cx"> Unreviewed, rolling out r192436 and r192586.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGSpeculativeJITcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp (192598 => 192599)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp 2015-11-19 00:20:41 UTC (rev 192598)
+++ trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp 2015-11-19 00:30:37 UTC (rev 192599)
</span><span class="lines">@@ -2880,6 +2880,9 @@
</span><span class="cx"> leftFPR, rightFPR, scratchGPR, scratchFPR);
</span><span class="cx"> gen.generateFastPath(m_jit);
</span><span class="cx">
</span><ins>+ ASSERT(gen.didEmitFastPath());
+ gen.endJumpList().append(m_jit.jump());
+
</ins><span class="cx"> gen.slowPathJumpList().link(&m_jit);
</span><span class="cx">
</span><span class="cx"> silentSpillAllRegisters(resultRegs);
</span><span class="lines">@@ -3240,6 +3243,9 @@
</span><span class="cx"> leftFPR, rightFPR, scratchGPR, scratchFPR);
</span><span class="cx"> gen.generateFastPath(m_jit);
</span><span class="cx">
</span><ins>+ ASSERT(gen.didEmitFastPath());
+ gen.endJumpList().append(m_jit.jump());
+
</ins><span class="cx"> gen.slowPathJumpList().link(&m_jit);
</span><span class="cx"> silentSpillAllRegisters(resultRegs);
</span><span class="cx"> callOperation(operationValueSub, resultRegs, leftRegs, rightRegs);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreftlFTLCompilecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ftl/FTLCompile.cpp (192598 => 192599)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ftl/FTLCompile.cpp 2015-11-19 00:20:41 UTC (rev 192598)
+++ trunk/Source/JavaScriptCore/ftl/FTLCompile.cpp 2015-11-19 00:30:37 UTC (rev 192599)
</span><span class="lines">@@ -462,6 +462,7 @@
</span><span class="cx"> context.initializeRegisters(fastPathJIT);
</span><span class="cx"> gen.generateFastPath(fastPathJIT);
</span><span class="cx">
</span><ins>+ ASSERT(gen.didEmitFastPath());
</ins><span class="cx"> gen.endJumpList().link(&fastPathJIT);
</span><span class="cx"> context.restoreRegisters(fastPathJIT);
</span><span class="cx"> allocator.restoreReusedRegistersByPopping(fastPathJIT, numberOfBytesUsedToPreserveReusedRegisters,
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitJITAddGeneratorcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/JITAddGenerator.cpp (192598 => 192599)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/JITAddGenerator.cpp 2015-11-19 00:20:41 UTC (rev 192598)
+++ trunk/Source/JavaScriptCore/jit/JITAddGenerator.cpp 2015-11-19 00:30:37 UTC (rev 192599)
</span><span class="lines">@@ -44,10 +44,12 @@
</span><span class="cx"> ASSERT(!m_leftIsConstInt32 || !m_rightIsConstInt32);
</span><span class="cx">
</span><span class="cx"> if (!m_leftType.mightBeNumber() || !m_rightType.mightBeNumber()) {
</span><del>- m_slowPathJumpList.append(jit.jump());
</del><ins>+ ASSERT(!m_didEmitFastPath);
</ins><span class="cx"> return;
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ m_didEmitFastPath = true;
+
</ins><span class="cx"> if (m_leftIsConstInt32 || m_rightIsConstInt32) {
</span><span class="cx"> JSValueRegs var;
</span><span class="cx"> ResultType varType = ResultType::unknownType();
</span><span class="lines">@@ -137,8 +139,6 @@
</span><span class="cx"> // Do doubleVar + doubleVar.
</span><span class="cx"> jit.addDouble(m_rightFPR, m_leftFPR);
</span><span class="cx"> jit.boxDouble(m_leftFPR, m_result);
</span><del>-
- m_endJumpList.append(jit.jump());
</del><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> } // namespace JSC
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitJITAddGeneratorh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/JITAddGenerator.h (192598 => 192599)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/JITAddGenerator.h 2015-11-19 00:20:41 UTC (rev 192598)
+++ trunk/Source/JavaScriptCore/jit/JITAddGenerator.h 2015-11-19 00:30:37 UTC (rev 192599)
</span><span class="lines">@@ -58,6 +58,7 @@
</span><span class="cx">
</span><span class="cx"> void generateFastPath(CCallHelpers&);
</span><span class="cx">
</span><ins>+ bool didEmitFastPath() const { return m_didEmitFastPath; }
</ins><span class="cx"> CCallHelpers::JumpList endJumpList() { return m_endJumpList; }
</span><span class="cx"> CCallHelpers::JumpList slowPathJumpList() { return m_slowPathJumpList; }
</span><span class="cx">
</span><span class="lines">@@ -75,6 +76,7 @@
</span><span class="cx"> FPRReg m_rightFPR;
</span><span class="cx"> GPRReg m_scratchGPR;
</span><span class="cx"> FPRReg m_scratchFPR;
</span><ins>+ bool m_didEmitFastPath { false };
</ins><span class="cx">
</span><span class="cx"> CCallHelpers::JumpList m_endJumpList;
</span><span class="cx"> CCallHelpers::JumpList m_slowPathJumpList;
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitJITArithmeticcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/JITArithmetic.cpp (192598 => 192599)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/JITArithmetic.cpp 2015-11-19 00:20:41 UTC (rev 192598)
+++ trunk/Source/JavaScriptCore/jit/JITArithmetic.cpp 2015-11-19 00:30:37 UTC (rev 192599)
</span><span class="lines">@@ -958,13 +958,14 @@
</span><span class="cx">
</span><span class="cx"> gen.generateFastPath(*this);
</span><span class="cx">
</span><del>- if (!gen.endJumpList().empty()) {
</del><ins>+ if (gen.didEmitFastPath()) {
</ins><span class="cx"> gen.endJumpList().link(this);
</span><span class="cx"> emitPutVirtualRegister(result, resultRegs);
</span><span class="cx">
</span><span class="cx"> addSlowCase(gen.slowPathJumpList());
</span><span class="cx"> } else {
</span><del>- gen.slowPathJumpList().link(this);
</del><ins>+ ASSERT(gen.endJumpList().empty());
+ ASSERT(gen.slowPathJumpList().empty());
</ins><span class="cx"> JITSlowPathCall slowPathCall(this, currentInstruction, slow_path_add);
</span><span class="cx"> slowPathCall.call();
</span><span class="cx"> }
</span><span class="lines">@@ -1006,6 +1007,8 @@
</span><span class="cx"> fpRegT0, fpRegT1, scratchGPR, scratchFPR);
</span><span class="cx">
</span><span class="cx"> gen.generateFastPath(*this);
</span><ins>+
+ ASSERT(gen.didEmitFastPath());
</ins><span class="cx"> gen.endJumpList().link(this);
</span><span class="cx"> emitPutVirtualRegister(result, resultRegs);
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitJITSubGeneratorcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/JITSubGenerator.cpp (192598 => 192599)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/JITSubGenerator.cpp 2015-11-19 00:20:41 UTC (rev 192598)
+++ trunk/Source/JavaScriptCore/jit/JITSubGenerator.cpp 2015-11-19 00:30:37 UTC (rev 192599)
</span><span class="lines">@@ -40,6 +40,9 @@
</span><span class="cx"> ASSERT(m_scratchGPR != m_right.tagGPR());
</span><span class="cx"> ASSERT(m_scratchFPR != InvalidFPRReg);
</span><span class="cx"> #endif
</span><ins>+
+ m_didEmitFastPath = true;
+
</ins><span class="cx"> CCallHelpers::Jump leftNotInt = jit.branchIfNotInt32(m_left);
</span><span class="cx"> CCallHelpers::Jump rightNotInt = jit.branchIfNotInt32(m_right);
</span><span class="cx">
</span><span class="lines">@@ -81,8 +84,6 @@
</span><span class="cx">
</span><span class="cx"> jit.subDouble(m_rightFPR, m_leftFPR);
</span><span class="cx"> jit.boxDouble(m_leftFPR, m_result);
</span><del>-
- m_endJumpList.append(jit.jump());
</del><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> } // namespace JSC
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitJITSubGeneratorh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/JITSubGenerator.h (192598 => 192599)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/JITSubGenerator.h 2015-11-19 00:20:41 UTC (rev 192598)
+++ trunk/Source/JavaScriptCore/jit/JITSubGenerator.h 2015-11-19 00:30:37 UTC (rev 192599)
</span><span class="lines">@@ -51,6 +51,7 @@
</span><span class="cx">
</span><span class="cx"> void generateFastPath(CCallHelpers&);
</span><span class="cx">
</span><ins>+ bool didEmitFastPath() const { return m_didEmitFastPath; }
</ins><span class="cx"> CCallHelpers::JumpList endJumpList() { return m_endJumpList; }
</span><span class="cx"> CCallHelpers::JumpList slowPathJumpList() { return m_slowPathJumpList; }
</span><span class="cx">
</span><span class="lines">@@ -64,6 +65,7 @@
</span><span class="cx"> FPRReg m_rightFPR;
</span><span class="cx"> GPRReg m_scratchGPR;
</span><span class="cx"> FPRReg m_scratchFPR;
</span><ins>+ bool m_didEmitFastPath { false };
</ins><span class="cx">
</span><span class="cx"> CCallHelpers::JumpList m_endJumpList;
</span><span class="cx"> CCallHelpers::JumpList m_slowPathJumpList;
</span></span></pre>
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