The JSC JIT currently has no facility to profile and report
the types of values
https://bugs.webkit.org/show_bug.cgi?id=65901
Reviewed by Gavin Barraclough.
Added the ability to profile the values seen at function calls (both
arguments and results) and heap loads. This is done with emphasis
on performance. A value profiling site consists of: add, and,
move, and store; no branching is necessary. Each value profiling
site (called a ValueProfile) has a ring buffer of 8 recently-seen
values. ValueProfiles are stored in the CodeBlock; there will be
one for each argument (excluding this) and each heap load or callsite.
Each time a value profiling site executes, it stores the value into
a pseudo-random element in the ValueProfile buffer. The point is
that for frequently executed code, we will have 8 somewhat recent
values in the buffer and will be able to not only figure out what
type it is, but also to be able to reason about the actual values
if we wish to do so.
This feature is currently disabled by default. When enabled, it
results in a 3.7% slow-down on SunSpider.
* JavaScriptCore.xcodeproj/project.pbxproj:
* bytecode/CodeBlock.cpp:
(JSC::CodeBlock::~CodeBlock):
* bytecode/CodeBlock.h:
(JSC::CodeBlock::addValueProfile):
(JSC::CodeBlock::numberOfValueProfiles):
(JSC::CodeBlock::valueProfile):
(JSC::CodeBlock::valueProfileForBytecodeOffset):
* bytecode/ValueProfile.h: Added.
(JSC::ValueProfile::ValueProfile):
(JSC::ValueProfile::numberOfSamples):
(JSC::ValueProfile::computeProbability):
(JSC::ValueProfile::numberOfInt32s):
(JSC::ValueProfile::numberOfDoubles):
(JSC::ValueProfile::numberOfCells):
(JSC::ValueProfile::probabilityOfInt32):
(JSC::ValueProfile::probabilityOfDouble):
(JSC::ValueProfile::probabilityOfCell):
(JSC::getValueProfileBytecodeOffset):
* jit/JIT.cpp:
(JSC::JIT::privateCompileSlowCases):
(JSC::JIT::privateCompile):
* jit/JIT.h:
(JSC::JIT::emitValueProfilingSite):
* jit/JITCall.cpp:
(JSC::JIT::emit_op_call_put_result):
* jit/JITInlineMethods.h:
(JSC::JIT::emitValueProfilingSite):
* jit/JITPropertyAccess.cpp:
(JSC::JIT::emit_op_get_by_val):
(JSC::JIT::emitSlow_op_get_by_val):
(JSC::JIT::emit_op_method_check):
(JSC::JIT::emit_op_get_by_id):
(JSC::JIT::emitSlow_op_get_by_id):
* jit/JSInterfaceJIT.h:
* wtf/Platform.h:
* wtf/StdLibExtras.h:
(WTF::binarySearch):
(WTF::genericBinarySearch):
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@93466 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/JavaScriptCore/bytecode/ValueProfile.h b/Source/JavaScriptCore/bytecode/ValueProfile.h
new file mode 100644
index 0000000..3890f7a
--- /dev/null
+++ b/Source/JavaScriptCore/bytecode/ValueProfile.h
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2011 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ * its contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef ValueProfile_h
+#define ValueProfile_h
+
+#include "WriteBarrier.h"
+
+namespace JSC {
+
+#if ENABLE(VALUE_PROFILER)
+struct ValueProfile {
+ static const unsigned logNumberOfBuckets = 3; // 8 buckets
+ static const unsigned numberOfBuckets = 1 << logNumberOfBuckets;
+ static const unsigned bucketIndexMask = numberOfBuckets - 1;
+ static const unsigned certainty = numberOfBuckets * numberOfBuckets;
+ static const unsigned majority = certainty / 2;
+
+ ValueProfile(int bytecodeOffset)
+ : bytecodeOffset(bytecodeOffset)
+ {
+ for (unsigned i = 0; i < numberOfBuckets; ++i)
+ buckets[i].setWithoutWriteBarrier(JSValue());
+ }
+
+ unsigned numberOfSamples() const
+ {
+ unsigned result = 0;
+ for (unsigned i = 0; i < numberOfBuckets; ++i) {
+ if (!!buckets[i])
+ result++;
+ }
+ return result;
+ }
+
+ static unsigned computeProbability(unsigned counts, unsigned numberOfSamples)
+ {
+ if (!numberOfSamples)
+ return 0;
+ return counts * certainty / numberOfSamples;
+ }
+
+ unsigned numberOfInt32s() const
+ {
+ unsigned result = 0;
+ for (unsigned i = 0; i < numberOfBuckets; ++i) {
+ if (!!buckets[i] && buckets[i].get().isInt32())
+ result++;
+ }
+ return result;
+ }
+
+ unsigned numberOfDoubles() const
+ {
+ unsigned result = 0;
+ for (unsigned i = 0; i < numberOfBuckets; ++i) {
+ if (!!buckets[i] && buckets[i].get().isDouble())
+ result++;
+ }
+ return result;
+ }
+
+ unsigned numberOfCells() const
+ {
+ unsigned result = 0;
+ for (unsigned i = 0; i < numberOfBuckets; ++i) {
+ if (!!buckets[i] && buckets[i].get().isCell())
+ result++;
+ }
+ return result;
+ }
+
+ // These methods are not particularly optimized, in that they will each
+ // perform two passes over the buckets array. However, they are
+ // probably the best bet unless you are sure that you will be making
+ // these calls with high frequency.
+
+ unsigned probabilityOfInt32() const
+ {
+ return computeProbability(numberOfInt32s(), numberOfSamples());
+ }
+
+ unsigned probabilityOfDouble() const
+ {
+ return computeProbability(numberOfDoubles(), numberOfSamples());
+ }
+
+ unsigned probabilityOfCell() const
+ {
+ return computeProbability(numberOfCells(), numberOfSamples());
+ }
+
+ int bytecodeOffset; // -1 for prologue
+ WriteBarrierBase<Unknown> buckets[numberOfBuckets];
+};
+
+inline int getValueProfileBytecodeOffset(ValueProfile* valueProfile)
+{
+ return valueProfile->bytecodeOffset;
+}
+#endif
+
+}
+
+#endif
+
