Changeset 121511 in webkit for trunk/Source/JavaScriptCore/dfg/DFGOSRExitCompiler.cpp

Timestamp:

Jun 28, 2012, 7:40:14 PM (13 years ago)

Author:

[email protected]

Message:

DFG recompilation heuristics should be based on count, not rate
​https://bugs.webkit.org/show_bug.cgi?id=90146

Reviewed by Oliver Hunt.

This removes a bunch of code that was previously trying to prevent spurious
reoptimizations if a large enough majority of executions of a code block did
not result in OSR exit. It turns out that this code was purely harmful. This
patch removes all of that logic and replaces it with a dead-simple
heuristic: if you exit more than N times (where N is an exponential function
of the number of times the code block has already been recompiled) then we
will recompile.

This appears to be a broad ~1% win on many benchmarks large and small.

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::CodeBlock):

• bytecode/CodeBlock.h:

(JSC::CodeBlock::osrExitCounter):
(JSC::CodeBlock::countOSRExit):
(CodeBlock):
(JSC::CodeBlock::addressOfOSRExitCounter):
(JSC::CodeBlock::offsetOfOSRExitCounter):
(JSC::CodeBlock::adjustedExitCountThreshold):
(JSC::CodeBlock::exitCountThresholdForReoptimization):
(JSC::CodeBlock::exitCountThresholdForReoptimizationFromLoop):
(JSC::CodeBlock::shouldReoptimizeNow):
(JSC::CodeBlock::shouldReoptimizeFromLoopNow):

• bytecode/ExecutionCounter.cpp:

(JSC::ExecutionCounter::setThreshold):

• bytecode/ExecutionCounter.h:

(ExecutionCounter):
(JSC::ExecutionCounter::clippedThreshold):

• dfg/DFGJITCompiler.cpp:

(JSC::DFG::JITCompiler::compileBody):

• dfg/DFGOSRExit.cpp:

(JSC::DFG::OSRExit::considerAddingAsFrequentExitSiteSlow):

• dfg/DFGOSRExitCompiler.cpp:

(JSC::DFG::OSRExitCompiler::handleExitCounts):

• dfg/DFGOperations.cpp:
• jit/JITStubs.cpp:

(JSC::DEFINE_STUB_FUNCTION):

• runtime/Options.cpp:

(Options):
(JSC::Options::initializeOptions):

• runtime/Options.h:

(Options):

File:

• trunk/Source/JavaScriptCore/dfg/DFGOSRExitCompiler.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/dfg/DFGOSRExitCompiler.cpp

@@ -105 +105 @@
     m_jit.move(AssemblyHelpers::TrustedImmPtr(m_jit.codeBlock()), GPRInfo::regT0);
     
-    AssemblyHelpers::JumpList tooFewFails;
+    AssemblyHelpers::Jump tooFewFails;
     
-    if (exit.m_kind == InadequateCoverage) {
-        // Proceed based on the assumption that we can profitably optimize this code once
-        // it has executed enough times.
-        
-        m_jit.load32(AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfForcedOSRExitCounter()), GPRInfo::regT2);
-        m_jit.load32(AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfSpeculativeSuccessCounter()), GPRInfo::regT1);
-        m_jit.add32(AssemblyHelpers::TrustedImm32(1), GPRInfo::regT2);
-        m_jit.add32(AssemblyHelpers::TrustedImm32(-1), GPRInfo::regT1);
-        m_jit.store32(GPRInfo::regT2, AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfForcedOSRExitCounter()));
-        m_jit.store32(GPRInfo::regT1, AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfSpeculativeSuccessCounter()));
-        
-        m_jit.move(AssemblyHelpers::TrustedImmPtr(m_jit.baselineCodeBlock()), GPRInfo::regT0);
-
-        tooFewFails.append(m_jit.branch32(AssemblyHelpers::BelowOrEqual, GPRInfo::regT2, AssemblyHelpers::TrustedImm32(Options::forcedOSRExitCountForReoptimization)));
-
-    } else {
-        // Proceed based on the assumption that we can handle these exits so long as they
-        // don't get too frequent.
-        
-        m_jit.load32(AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfSpeculativeFailCounter()), GPRInfo::regT2);
-        m_jit.load32(AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfSpeculativeSuccessCounter()), GPRInfo::regT1);
-        m_jit.add32(AssemblyHelpers::TrustedImm32(1), GPRInfo::regT2);
-        m_jit.add32(AssemblyHelpers::TrustedImm32(-1), GPRInfo::regT1);
-        m_jit.store32(GPRInfo::regT2, AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfSpeculativeFailCounter()));
-        m_jit.store32(GPRInfo::regT1, AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfSpeculativeSuccessCounter()));
+    m_jit.load32(AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfOSRExitCounter()), GPRInfo::regT2);
+    m_jit.add32(AssemblyHelpers::TrustedImm32(1), GPRInfo::regT2);
+    m_jit.store32(GPRInfo::regT2, AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfOSRExitCounter()));
+    m_jit.move(AssemblyHelpers::TrustedImmPtr(m_jit.baselineCodeBlock()), GPRInfo::regT0);
+    tooFewFails = m_jit.branch32(AssemblyHelpers::BelowOrEqual, GPRInfo::regT2, AssemblyHelpers::TrustedImm32(m_jit.codeBlock()->exitCountThresholdForReoptimization()));
     
-        m_jit.move(AssemblyHelpers::TrustedImmPtr(m_jit.baselineCodeBlock()), GPRInfo::regT0);
-    
-        tooFewFails.append(m_jit.branch32(AssemblyHelpers::BelowOrEqual, GPRInfo::regT2, AssemblyHelpers::TrustedImm32(m_jit.codeBlock()->largeFailCountThreshold())));
-        m_jit.mul32(AssemblyHelpers::TrustedImm32(Options::desiredSpeculativeSuccessFailRatio), GPRInfo::regT2, GPRInfo::regT2);
-    
-        tooFewFails.append(m_jit.branch32(AssemblyHelpers::BelowOrEqual, GPRInfo::regT2, GPRInfo::regT1));
-    }
-
     // Reoptimize as soon as possible.
 #if !NUMBER_OF_ARGUMENT_REGISTERS
@@ -160 +132 @@
             m_jit.baselineCodeBlock());
     m_jit.store32(AssemblyHelpers::TrustedImm32(-targetValue), AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfJITExecuteCounter()));
+    targetValue = ExecutionCounter::clippedThreshold(m_jit.codeBlock()->globalObject(), targetValue);
     m_jit.store32(AssemblyHelpers::TrustedImm32(targetValue), AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfJITExecutionActiveThreshold()));
     m_jit.store32(AssemblyHelpers::TrustedImm32(ExecutionCounter::formattedTotalCount(targetValue)), AssemblyHelpers::Address(GPRInfo::regT0, CodeBlock::offsetOfJITExecutionTotalCount()));