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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/184920">184920</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2015-05-27 14:29:09 -0700 (Wed, 27 May 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>JIT-generated store barrier code should assume the buffer pointer and capacity to be compile-time constants
https://bugs.webkit.org/show_bug.cgi?id=145404
Reviewed by Andreas Kling.
We never change the capacity of a write barrier buffer. We never repoint the buffer
pointer. So, the JIT shouldn't load those from memory; it should take advantage of the
fact that these are compile-time constants.
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::storeToWriteBarrierBuffer):
* ftl/FTLLowerDFGToLLVM.cpp:
(JSC::FTL::LowerDFGToLLVM::emitStoreBarrier):
* heap/WriteBarrierBuffer.h:
(JSC::WriteBarrierBuffer::currentIndexAddress):
(JSC::WriteBarrierBuffer::capacity):
(JSC::WriteBarrierBuffer::buffer):
(JSC::WriteBarrierBuffer::currentIndexOffset): Deleted.
(JSC::WriteBarrierBuffer::capacityOffset): Deleted.
(JSC::WriteBarrierBuffer::bufferOffset): Deleted.
* jit/Repatch.cpp:
(JSC::emitPutTransitionStubAndGetOldStructure):</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="#trunkSourceJavaScriptCoreftlFTLLowerDFGToLLVMcpp">trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapWriteBarrierBuffercpp">trunk/Source/JavaScriptCore/heap/WriteBarrierBuffer.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapWriteBarrierBufferh">trunk/Source/JavaScriptCore/heap/WriteBarrierBuffer.h</a></li>
<li><a href="#trunkSourceJavaScriptCorejitRepatchcpp">trunk/Source/JavaScriptCore/jit/Repatch.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (184919 => 184920)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-05-27 21:21:51 UTC (rev 184919)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-05-27 21:29:09 UTC (rev 184920)
</span><span class="lines">@@ -1,3 +1,28 @@
</span><ins>+2015-05-26 Filip Pizlo <fpizlo@apple.com>
+
+ JIT-generated store barrier code should assume the buffer pointer and capacity to be compile-time constants
+ https://bugs.webkit.org/show_bug.cgi?id=145404
+
+ Reviewed by Andreas Kling.
+
+ We never change the capacity of a write barrier buffer. We never repoint the buffer
+ pointer. So, the JIT shouldn't load those from memory; it should take advantage of the
+ fact that these are compile-time constants.
+
+ * dfg/DFGSpeculativeJIT.cpp:
+ (JSC::DFG::SpeculativeJIT::storeToWriteBarrierBuffer):
+ * ftl/FTLLowerDFGToLLVM.cpp:
+ (JSC::FTL::LowerDFGToLLVM::emitStoreBarrier):
+ * heap/WriteBarrierBuffer.h:
+ (JSC::WriteBarrierBuffer::currentIndexAddress):
+ (JSC::WriteBarrierBuffer::capacity):
+ (JSC::WriteBarrierBuffer::buffer):
+ (JSC::WriteBarrierBuffer::currentIndexOffset): Deleted.
+ (JSC::WriteBarrierBuffer::capacityOffset): Deleted.
+ (JSC::WriteBarrierBuffer::bufferOffset): Deleted.
+ * jit/Repatch.cpp:
+ (JSC::emitPutTransitionStubAndGetOldStructure):
+
</ins><span class="cx"> 2015-05-27 Geoffrey Garen <ggaren@apple.com>
</span><span class="cx">
</span><span class="cx"> REGRESSION: These sorting idioms used by Peacekeeper and Browsermark are ~20X slower
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGSpeculativeJITcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp (184919 => 184920)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp 2015-05-27 21:21:51 UTC (rev 184919)
+++ trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp 2015-05-27 21:29:09 UTC (rev 184920)
</span><span class="lines">@@ -6125,15 +6125,14 @@
</span><span class="cx"> void SpeculativeJIT::storeToWriteBarrierBuffer(GPRReg cell, GPRReg scratch1, GPRReg scratch2)
</span><span class="cx"> {
</span><span class="cx"> ASSERT(scratch1 != scratch2);
</span><del>- WriteBarrierBuffer* writeBarrierBuffer = &m_jit.vm()->heap.m_writeBarrierBuffer;
- m_jit.move(TrustedImmPtr(writeBarrierBuffer), scratch1);
- m_jit.load32(MacroAssembler::Address(scratch1, WriteBarrierBuffer::currentIndexOffset()), scratch2);
- JITCompiler::Jump needToFlush = m_jit.branch32(MacroAssembler::AboveOrEqual, scratch2, MacroAssembler::Address(scratch1, WriteBarrierBuffer::capacityOffset()));
</del><ins>+ WriteBarrierBuffer& writeBarrierBuffer = m_jit.vm()->heap.m_writeBarrierBuffer;
+ m_jit.load32(writeBarrierBuffer.currentIndexAddress(), scratch2);
+ JITCompiler::Jump needToFlush = m_jit.branch32(MacroAssembler::AboveOrEqual, scratch2, MacroAssembler::TrustedImm32(writeBarrierBuffer.capacity()));
</ins><span class="cx">
</span><span class="cx"> m_jit.add32(TrustedImm32(1), scratch2);
</span><del>- m_jit.store32(scratch2, MacroAssembler::Address(scratch1, WriteBarrierBuffer::currentIndexOffset()));
</del><ins>+ m_jit.store32(scratch2, writeBarrierBuffer.currentIndexAddress());
</ins><span class="cx">
</span><del>- m_jit.loadPtr(MacroAssembler::Address(scratch1, WriteBarrierBuffer::bufferOffset()), scratch1);
</del><ins>+ m_jit.move(TrustedImmPtr(writeBarrierBuffer.buffer()), scratch1);
</ins><span class="cx"> // We use an offset of -sizeof(void*) because we already added 1 to scratch2.
</span><span class="cx"> m_jit.storePtr(cell, MacroAssembler::BaseIndex(scratch1, scratch2, MacroAssembler::ScalePtr, static_cast<int32_t>(-sizeof(void*))));
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreftlFTLLowerDFGToLLVMcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp (184919 => 184920)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp 2015-05-27 21:21:51 UTC (rev 184919)
+++ trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp 2015-05-27 21:29:09 UTC (rev 184920)
</span><span class="lines">@@ -7874,17 +7874,17 @@
</span><span class="cx">
</span><span class="cx"> // Append to the write barrier buffer.
</span><span class="cx"> LBasicBlock lastNext = m_out.appendTo(isMarkedAndNotRemembered, bufferHasSpace);
</span><del>- LValue currentBufferIndex = m_out.load32(m_out.absolute(&vm().heap.writeBarrierBuffer().m_currentIndex));
- LValue bufferCapacity = m_out.load32(m_out.absolute(&vm().heap.writeBarrierBuffer().m_capacity));
</del><ins>+ LValue currentBufferIndex = m_out.load32(m_out.absolute(vm().heap.writeBarrierBuffer().currentIndexAddress()));
+ LValue bufferCapacity = m_out.constInt32(vm().heap.writeBarrierBuffer().capacity());
</ins><span class="cx"> m_out.branch(
</span><span class="cx"> m_out.lessThan(currentBufferIndex, bufferCapacity),
</span><span class="cx"> usually(bufferHasSpace), rarely(bufferIsFull));
</span><span class="cx">
</span><span class="cx"> // Buffer has space, store to it.
</span><span class="cx"> m_out.appendTo(bufferHasSpace, bufferIsFull);
</span><del>- LValue writeBarrierBufferBase = m_out.loadPtr(m_out.absolute(&vm().heap.writeBarrierBuffer().m_buffer));
</del><ins>+ LValue writeBarrierBufferBase = m_out.constIntPtr(vm().heap.writeBarrierBuffer().buffer());
</ins><span class="cx"> m_out.storePtr(base, m_out.baseIndex(m_heaps.WriteBarrierBuffer_bufferContents, writeBarrierBufferBase, m_out.zeroExtPtr(currentBufferIndex)));
</span><del>- m_out.store32(m_out.add(currentBufferIndex, m_out.constInt32(1)), m_out.absolute(&vm().heap.writeBarrierBuffer().m_currentIndex));
</del><ins>+ m_out.store32(m_out.add(currentBufferIndex, m_out.constInt32(1)), m_out.absolute(vm().heap.writeBarrierBuffer().currentIndexAddress()));
</ins><span class="cx"> m_out.jump(continuation);
</span><span class="cx">
</span><span class="cx"> // Buffer is out of space, flush it.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapWriteBarrierBuffercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/WriteBarrierBuffer.cpp (184919 => 184920)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/WriteBarrierBuffer.cpp 2015-05-27 21:21:51 UTC (rev 184919)
+++ trunk/Source/JavaScriptCore/heap/WriteBarrierBuffer.cpp 2015-05-27 21:29:09 UTC (rev 184920)
</span><span class="lines">@@ -44,7 +44,6 @@
</span><span class="cx"> WriteBarrierBuffer::~WriteBarrierBuffer()
</span><span class="cx"> {
</span><span class="cx"> fastFree(m_buffer);
</span><del>- m_buffer = 0;
</del><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> void WriteBarrierBuffer::flush(Heap& heap)
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapWriteBarrierBufferh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/WriteBarrierBuffer.h (184919 => 184920)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/WriteBarrierBuffer.h 2015-05-27 21:21:51 UTC (rev 184919)
+++ trunk/Source/JavaScriptCore/heap/WriteBarrierBuffer.h 2015-05-27 21:29:09 UTC (rev 184920)
</span><span class="lines">@@ -1,5 +1,5 @@
</span><span class="cx"> /*
</span><del>- * Copyright (C) 2013 Apple Inc. All rights reserved.
</del><ins>+ * Copyright (C) 2013, 2015 Apple Inc. All rights reserved.
</ins><span class="cx"> *
</span><span class="cx"> * Redistribution and use in source and binary forms, with or without
</span><span class="cx"> * modification, are permitted provided that the following conditions
</span><span class="lines">@@ -33,10 +33,7 @@
</span><span class="cx"> class Heap;
</span><span class="cx"> class JSCell;
</span><span class="cx">
</span><del>-namespace FTL { class LowerDFGToLLVM; }
-
</del><span class="cx"> class WriteBarrierBuffer {
</span><del>- friend class FTL::LowerDFGToLLVM;
</del><span class="cx"> public:
</span><span class="cx"> WriteBarrierBuffer(unsigned capacity);
</span><span class="cx"> ~WriteBarrierBuffer();
</span><span class="lines">@@ -45,25 +42,25 @@
</span><span class="cx"> void flush(Heap&);
</span><span class="cx"> void reset();
</span><span class="cx">
</span><del>- static ptrdiff_t currentIndexOffset()
</del><ins>+ unsigned* currentIndexAddress()
</ins><span class="cx"> {
</span><del>- return OBJECT_OFFSETOF(WriteBarrierBuffer, m_currentIndex);
</del><ins>+ return &m_currentIndex;
</ins><span class="cx"> }
</span><span class="cx">
</span><del>- static ptrdiff_t capacityOffset()
</del><ins>+ unsigned capacity() const
</ins><span class="cx"> {
</span><del>- return OBJECT_OFFSETOF(WriteBarrierBuffer, m_capacity);
</del><ins>+ return m_capacity;
</ins><span class="cx"> }
</span><span class="cx">
</span><del>- static ptrdiff_t bufferOffset()
</del><ins>+ JSCell** buffer()
</ins><span class="cx"> {
</span><del>- return OBJECT_OFFSETOF(WriteBarrierBuffer, m_buffer);
</del><ins>+ return m_buffer;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> private:
</span><span class="cx"> unsigned m_currentIndex;
</span><del>- unsigned m_capacity;
- JSCell** m_buffer;
</del><ins>+ const unsigned m_capacity;
+ JSCell** const m_buffer;
</ins><span class="cx"> };
</span><span class="cx">
</span><span class="cx"> } // namespace JSC
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitRepatchcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/Repatch.cpp (184919 => 184920)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/Repatch.cpp 2015-05-27 21:21:51 UTC (rev 184919)
+++ trunk/Source/JavaScriptCore/jit/Repatch.cpp 2015-05-27 21:29:09 UTC (rev 184920)
</span><span class="lines">@@ -1169,16 +1169,15 @@
</span><span class="cx"> MacroAssembler::Call callFlushWriteBarrierBuffer;
</span><span class="cx"> MacroAssembler::Jump ownerIsRememberedOrInEden = stubJit.jumpIfIsRememberedOrInEden(baseGPR);
</span><span class="cx"> {
</span><del>- WriteBarrierBuffer* writeBarrierBuffer = &stubJit.vm()->heap.writeBarrierBuffer();
- stubJit.move(MacroAssembler::TrustedImmPtr(writeBarrierBuffer), scratchGPR1);
- stubJit.load32(MacroAssembler::Address(scratchGPR1, WriteBarrierBuffer::currentIndexOffset()), scratchGPR2);
</del><ins>+ WriteBarrierBuffer& writeBarrierBuffer = stubJit.vm()->heap.writeBarrierBuffer();
+ stubJit.load32(writeBarrierBuffer.currentIndexAddress(), scratchGPR2);
</ins><span class="cx"> MacroAssembler::Jump needToFlush =
</span><del>- stubJit.branch32(MacroAssembler::AboveOrEqual, scratchGPR2, MacroAssembler::Address(scratchGPR1, WriteBarrierBuffer::capacityOffset()));
</del><ins>+ stubJit.branch32(MacroAssembler::AboveOrEqual, scratchGPR2, MacroAssembler::TrustedImm32(writeBarrierBuffer.capacity()));
</ins><span class="cx">
</span><span class="cx"> stubJit.add32(MacroAssembler::TrustedImm32(1), scratchGPR2);
</span><del>- stubJit.store32(scratchGPR2, MacroAssembler::Address(scratchGPR1, WriteBarrierBuffer::currentIndexOffset()));
</del><ins>+ stubJit.store32(scratchGPR2, writeBarrierBuffer.currentIndexAddress());
</ins><span class="cx">
</span><del>- stubJit.loadPtr(MacroAssembler::Address(scratchGPR1, WriteBarrierBuffer::bufferOffset()), scratchGPR1);
</del><ins>+ stubJit.move(MacroAssembler::TrustedImmPtr(writeBarrierBuffer.buffer()), scratchGPR1);
</ins><span class="cx"> // We use an offset of -sizeof(void*) because we already added 1 to scratchGPR2.
</span><span class="cx"> stubJit.storePtr(baseGPR, MacroAssembler::BaseIndex(scratchGPR1, scratchGPR2, MacroAssembler::ScalePtr, static_cast<int32_t>(-sizeof(void*))));
</span><span class="cx">
</span></span></pre>
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