Changeset 121073 in webkit for trunk/Source/JavaScriptCore/ChangeLog

Timestamp:

Jun 22, 2012, 4:32:59 PM (13 years ago)

Author:

[email protected]

Message:

DFG tier-up should happen in prologues, not epilogues
​https://bugs.webkit.org/show_bug.cgi?id=89752

Reviewed by Geoffrey Garen.

This change has two outcomes:

1) Slightly reduces the likelihood that a function will be optimized both
standalone and via inlining. Previously, if you had a call sequence like foo()
calls bar() exactly once, and nobody else calls bar(), then bar() would get
optimized first (because it returns first) and then foo() gets optimized. If foo()
can inline bar() then that means that bar() gets optimized twice. But now, if we
optimize in prologues, then foo() will be optimized first. If it inlines bar(),
that means that there will no longer be any calls to bar().

2) It lets us kill some code in JITStubs. Epilogue tier-up was very different from
loop tier-up, since epilogue tier-up should not attempt OSR. But prologue tier-up
requires OSR (albeit really easy OSR since it's the top of the compilation unit),
so it becomes just like loop tier-up. As a result, we now have one optimization
hook (cti_optimize) instead of two (cti_optimize_from_loop and
cti_optimize_from_ret).

As a consequence of not having an optimization check in epilogues, the OSR exit
code must now trigger reoptimization itself instead of just signaling the epilogue
check to fire.

This also adds the ability to count the number of DFG compilations, which was
useful for debugging this patch and might be useful for other things in the future.

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::reoptimize):
(JSC):

• bytecode/CodeBlock.h:

(CodeBlock):

• dfg/DFGByteCodeParser.cpp:

(JSC::DFG::ByteCodeParser::parseCodeBlock):

• dfg/DFGDriver.cpp:

(DFG):
(JSC::DFG::getNumCompilations):
(JSC::DFG::compile):

• dfg/DFGDriver.h:

(DFG):

• dfg/DFGOSRExitCompiler.cpp:

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

• dfg/DFGOperations.cpp:
• dfg/DFGOperations.h:
• jit/JIT.cpp:

(JSC::JIT::emitOptimizationCheck):

• jit/JIT.h:
• jit/JITCall32_64.cpp:

(JSC::JIT::emit_op_ret):
(JSC::JIT::emit_op_ret_object_or_this):

• jit/JITOpcodes.cpp:

(JSC::JIT::emit_op_ret):
(JSC::JIT::emit_op_ret_object_or_this):
(JSC::JIT::emit_op_enter):

• jit/JITOpcodes32_64.cpp:

(JSC::JIT::emit_op_enter):

• jit/JITStubs.cpp:

(JSC::DEFINE_STUB_FUNCTION):

• jit/JITStubs.h:

File:

• trunk/Source/JavaScriptCore/ChangeLog (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2012-06-22  Filip Pizlo  <[email protected]>
+
+        DFG tier-up should happen in prologues, not epilogues
+        https://bugs.webkit.org/show_bug.cgi?id=89752
+
+        Reviewed by Geoffrey Garen.
+
+        This change has two outcomes:
+        
+        1) Slightly reduces the likelihood that a function will be optimized both
+        standalone and via inlining.  Previously, if you had a call sequence like foo() 
+        calls bar() exactly once, and nobody else calls bar(), then bar() would get
+        optimized first (because it returns first) and then foo() gets optimized.  If foo()
+        can inline bar() then that means that bar() gets optimized twice.  But now, if we
+        optimize in prologues, then foo() will be optimized first.  If it inlines bar(),
+        that means that there will no longer be any calls to bar().
+        
+        2) It lets us kill some code in JITStubs.  Epilogue tier-up was very different from
+        loop tier-up, since epilogue tier-up should not attempt OSR.  But prologue tier-up
+        requires OSR (albeit really easy OSR since it's the top of the compilation unit),
+        so it becomes just like loop tier-up.  As a result, we now have one optimization
+        hook (cti_optimize) instead of two (cti_optimize_from_loop and
+        cti_optimize_from_ret).
+        
+        As a consequence of not having an optimization check in epilogues, the OSR exit
+        code must now trigger reoptimization itself instead of just signaling the epilogue
+        check to fire.
+        
+        This also adds the ability to count the number of DFG compilations, which was
+        useful for debugging this patch and might be useful for other things in the future.
+
+        * bytecode/CodeBlock.cpp:
+        (JSC::CodeBlock::reoptimize):
+        (JSC):
+        * bytecode/CodeBlock.h:
+        (CodeBlock):
+        * dfg/DFGByteCodeParser.cpp:
+        (JSC::DFG::ByteCodeParser::parseCodeBlock):
+        * dfg/DFGDriver.cpp:
+        (DFG):
+        (JSC::DFG::getNumCompilations):
+        (JSC::DFG::compile):
+        * dfg/DFGDriver.h:
+        (DFG):
+        * dfg/DFGOSRExitCompiler.cpp:
+        (JSC::DFG::OSRExitCompiler::handleExitCounts):
+        * dfg/DFGOperations.cpp:
+        * dfg/DFGOperations.h:
+        * jit/JIT.cpp:
+        (JSC::JIT::emitOptimizationCheck):
+        * jit/JIT.h:
+        * jit/JITCall32_64.cpp:
+        (JSC::JIT::emit_op_ret):
+        (JSC::JIT::emit_op_ret_object_or_this):
+        * jit/JITOpcodes.cpp:
+        (JSC::JIT::emit_op_ret):
+        (JSC::JIT::emit_op_ret_object_or_this):
+        (JSC::JIT::emit_op_enter):
+        * jit/JITOpcodes32_64.cpp:
+        (JSC::JIT::emit_op_enter):
+        * jit/JITStubs.cpp:
+        (JSC::DEFINE_STUB_FUNCTION):
+        * jit/JITStubs.h:
+
 2012-06-20  Mark Hahnenberg  <[email protected]>