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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/199894">199894</a></dd>
<dt>Author</dt> <dd>commit-queue@webkit.org</dd>
<dt>Date</dt> <dd>2016-04-22 12:27:57 -0700 (Fri, 22 Apr 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>[JSC] Integer Multiply of a number by itself does not need negative zero support
https://bugs.webkit.org/show_bug.cgi?id=156895
Patch by Benjamin Poulain <bpoulain@apple.com> on 2016-04-22
Reviewed by Saam Barati.
You cannot produce negative zero by squaring an integer.
* dfg/DFGFixupPhase.cpp:
(JSC::DFG::FixupPhase::fixupNode):
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::compileArithMul):
Minor codegen fixes:
-Use the right form of multiply for ARM.
-Use a sign-extended 32bit immediates, that's the one with fast forms
in the MacroAssembler.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreassemblerMacroAssemblerARMv7h">trunk/Source/JavaScriptCore/assembler/MacroAssemblerARMv7.h</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGFixupPhasecpp">trunk/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGSpeculativeJITcpp">trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp</a></li>
</ul>
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<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (199893 => 199894)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2016-04-22 19:25:40 UTC (rev 199893)
+++ trunk/Source/JavaScriptCore/ChangeLog 2016-04-22 19:27:57 UTC (rev 199894)
</span><span class="lines">@@ -1,3 +1,21 @@
</span><ins>+2016-04-22 Benjamin Poulain <bpoulain@apple.com>
+
+ [JSC] Integer Multiply of a number by itself does not need negative zero support
+ https://bugs.webkit.org/show_bug.cgi?id=156895
+
+ Reviewed by Saam Barati.
+
+ You cannot produce negative zero by squaring an integer.
+
+ * dfg/DFGFixupPhase.cpp:
+ (JSC::DFG::FixupPhase::fixupNode):
+ * dfg/DFGSpeculativeJIT.cpp:
+ (JSC::DFG::SpeculativeJIT::compileArithMul):
+ Minor codegen fixes:
+ -Use the right form of multiply for ARM.
+ -Use a sign-extended 32bit immediates, that's the one with fast forms
+ in the MacroAssembler.
+
</ins><span class="cx"> 2016-04-21 Darin Adler <darin@apple.com>
</span><span class="cx">
</span><span class="cx"> Follow-on to the build fix.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreassemblerMacroAssemblerARMv7h"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/assembler/MacroAssemblerARMv7.h (199893 => 199894)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/assembler/MacroAssemblerARMv7.h 2016-04-22 19:25:40 UTC (rev 199893)
+++ trunk/Source/JavaScriptCore/assembler/MacroAssemblerARMv7.h 2016-04-22 19:27:57 UTC (rev 199894)
</span><span class="lines">@@ -322,6 +322,11 @@
</span><span class="cx"> m_assembler.smull(dest, dataTempRegister, dest, src);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ void mul32(RegisterID left, RegisterID right, RegisterID dest)
+ {
+ m_assembler.smull(dest, dataTempRegister, left, right);
+ }
+
</ins><span class="cx"> void mul32(TrustedImm32 imm, RegisterID src, RegisterID dest)
</span><span class="cx"> {
</span><span class="cx"> move(imm, dataTempRegister);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGFixupPhasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp (199893 => 199894)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp 2016-04-22 19:25:40 UTC (rev 199893)
+++ trunk/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp 2016-04-22 19:27:57 UTC (rev 199894)
</span><span class="lines">@@ -248,7 +248,8 @@
</span><span class="cx"> fixIntOrBooleanEdge(rightChild);
</span><span class="cx"> if (bytecodeCanTruncateInteger(node->arithNodeFlags()))
</span><span class="cx"> node->setArithMode(Arith::Unchecked);
</span><del>- else if (bytecodeCanIgnoreNegativeZero(node->arithNodeFlags()))
</del><ins>+ else if (bytecodeCanIgnoreNegativeZero(node->arithNodeFlags())
+ || leftChild.node() == rightChild.node())
</ins><span class="cx"> node->setArithMode(Arith::CheckOverflow);
</span><span class="cx"> else
</span><span class="cx"> node->setArithMode(Arith::CheckOverflowAndNegativeZero);
</span><span class="lines">@@ -257,7 +258,8 @@
</span><span class="cx"> if (m_graph.binaryArithShouldSpeculateMachineInt(node, FixupPass)) {
</span><span class="cx"> fixEdge<Int52RepUse>(leftChild);
</span><span class="cx"> fixEdge<Int52RepUse>(rightChild);
</span><del>- if (bytecodeCanIgnoreNegativeZero(node->arithNodeFlags()))
</del><ins>+ if (bytecodeCanIgnoreNegativeZero(node->arithNodeFlags())
+ || leftChild.node() == rightChild.node())
</ins><span class="cx"> node->setArithMode(Arith::CheckOverflow);
</span><span class="cx"> else
</span><span class="cx"> node->setArithMode(Arith::CheckOverflowAndNegativeZero);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGSpeculativeJITcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp (199893 => 199894)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp 2016-04-22 19:25:40 UTC (rev 199893)
+++ trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp 2016-04-22 19:27:57 UTC (rev 199894)
</span><span class="lines">@@ -3964,10 +3964,9 @@
</span><span class="cx"> // We can perform truncated multiplications if we get to this point, because if the
</span><span class="cx"> // fixup phase could not prove that it would be safe, it would have turned us into
</span><span class="cx"> // a double multiplication.
</span><del>- if (!shouldCheckOverflow(node->arithMode())) {
- m_jit.move(reg1, result.gpr());
- m_jit.mul32(reg2, result.gpr());
- } else {
</del><ins>+ if (!shouldCheckOverflow(node->arithMode()))
+ m_jit.mul32(reg1, reg2, result.gpr());
+ else {
</ins><span class="cx"> speculationCheck(
</span><span class="cx"> Overflow, JSValueRegs(), 0,
</span><span class="cx"> m_jit.branchMul32(MacroAssembler::Overflow, reg1, reg2, result.gpr()));
</span><span class="lines">@@ -4031,10 +4030,10 @@
</span><span class="cx"> MacroAssembler::NonZero, resultGPR);
</span><span class="cx"> speculationCheck(
</span><span class="cx"> NegativeZero, JSValueRegs(), 0,
</span><del>- m_jit.branch64(MacroAssembler::LessThan, op1GPR, TrustedImm64(0)));
</del><ins>+ m_jit.branch64(MacroAssembler::LessThan, op1GPR, TrustedImm32(0)));
</ins><span class="cx"> speculationCheck(
</span><span class="cx"> NegativeZero, JSValueRegs(), 0,
</span><del>- m_jit.branch64(MacroAssembler::LessThan, op2GPR, TrustedImm64(0)));
</del><ins>+ m_jit.branch64(MacroAssembler::LessThan, op2GPR, TrustedImm32(0)));
</ins><span class="cx"> resultNonZero.link(&m_jit);
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre>
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