Changeset 93466 in webkit for trunk/Source/JavaScriptCore/bytecode

Timestamp:

Aug 19, 2011, 7:17:49 PM (14 years ago)

Author:

[email protected]

Message:

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):

Location:

trunk/Source/JavaScriptCore/bytecode

Files:

• CodeBlock.cpp (modified) (1 diff)
• CodeBlock.h (modified) (3 diffs)
• ValueProfile.h (added)

trunk/Source/JavaScriptCore/bytecode/CodeBlock.cpp

@@ -1433 +1433 @@
 CodeBlock::~CodeBlock()
 {
+#if ENABLE(VERBOSE_VALUE_PROFILE)
+    printf("ValueProfile for %p:\n", this);
+    for (unsigned i = 0; i < numberOfValueProfiles(); ++i) {
+        ValueProfile* profile = valueProfile(i);
+        if (profile->bytecodeOffset < 0) {
+            ASSERT(profile->bytecodeOffset == -1);
+            printf("   arg = %u: ", i + 1);
+        } else
+            printf("   bc = %d: ", profile->bytecodeOffset);
+        printf("samples = %u, int32 = %u, double = %u, cell = %u\n",
+               profile->numberOfSamples(),
+               profile->probabilityOfInt32(),
+               profile->probabilityOfDouble(),
+               profile->probabilityOfCell());
+    }
+#endif
+
 #if ENABLE(JIT)
     for (size_t size = m_structureStubInfos.size(), i = 0; i < size; ++i)

trunk/Source/JavaScriptCore/bytecode/CodeBlock.h

@@ -40 +40 @@
 #include "RegExpObject.h"
 #include "UString.h"
+#include "ValueProfile.h"
 #include <wtf/FastAllocBase.h>
 #include <wtf/PassOwnPtr.h>
 #include <wtf/RefPtr.h>
+#include <wtf/SegmentedVector.h>
 #include <wtf/Vector.h>
 
@@ -382 +384 @@
         MethodCallLinkInfo& methodCallLinkInfo(int index) { return m_methodCallLinkInfos[index]; }
 #endif
+        
+#if ENABLE(VALUE_PROFILER)
+        ValueProfile* addValueProfile(int bytecodeOffset)
+        {
+            m_valueProfiles.append(ValueProfile(bytecodeOffset));
+            return &m_valueProfiles.last();
+        }
+        unsigned numberOfValueProfiles() { return m_valueProfiles.size(); }
+        ValueProfile* valueProfile(int index) { return &m_valueProfiles[index]; }
+        ValueProfile* valueProfileForBytecodeOffset(int bytecodeOffset)
+        {
+            return WTF::genericBinarySearch<ValueProfile, int, getValueProfileBytecodeOffset>(m_valueProfiles, m_valueProfiles.size(), bytecodeOffset);
+        }
+#endif
+
         unsigned globalResolveInfoCount() const
         {
@@ -576 +593 @@
         Vector<CallLinkInfo> m_callLinkInfos;
         Vector<MethodCallLinkInfo> m_methodCallLinkInfos;
+#endif
+#if ENABLE(VALUE_PROFILER)
+        SegmentedVector<ValueProfile, 8> m_valueProfiles;
 #endif