Changeset 103218 in webkit for trunk/Source/JavaScriptCore/dfg/DFGNode.h

Timestamp:

Dec 18, 2011, 10:36:05 PM (13 years ago)

Author:

[email protected]

Message:

DFG is too sloppy with register allocation
​https://bugs.webkit.org/show_bug.cgi?id=74835

Reviewed by Gavin Barraclough.

Added assertions that at the end of a successfully generated basic block,
all use counts should be zero. This revealed a number of bugs:

• Array length optimizations were turning a must-generate node into one that is not must-generate, but failing to change the ref count accordingly.

• Indexed property storage optimizations were failing to deref their children, or to deref the indexed property storage node itself. Also, they used the Phantom node as a replacement. But the Phantom node is must-generate, which was causing bizarre issues. So this introduces a Nop node, which should be used in cases where you want a node that is skipped and has no children.

This does not have any significant performance effect, but it should
relieve some register pressure. The main thing this patch adds, though,
are the assertions, which should make it easier to do register allocation
related changes in the future.

• dfg/DFGAbstractState.cpp:

(JSC::DFG::AbstractState::execute):

• dfg/DFGGenerationInfo.h:

(JSC::DFG::GenerationInfo::initConstant):
(JSC::DFG::GenerationInfo::initInteger):
(JSC::DFG::GenerationInfo::initJSValue):
(JSC::DFG::GenerationInfo::initCell):
(JSC::DFG::GenerationInfo::initBoolean):
(JSC::DFG::GenerationInfo::initDouble):
(JSC::DFG::GenerationInfo::initStorage):
(JSC::DFG::GenerationInfo::use):

• dfg/DFGGraph.h:

(JSC::DFG::Graph::clearAndDerefChild1):
(JSC::DFG::Graph::clearAndDerefChild2):
(JSC::DFG::Graph::clearAndDerefChild3):

• dfg/DFGNode.h:

(JSC::DFG::Node::deref):

• dfg/DFGPropagator.cpp:

(JSC::DFG::Propagator::propagateNodePredictions):
(JSC::DFG::Propagator::fixupNode):

• dfg/DFGSpeculativeJIT.cpp:

(JSC::DFG::SpeculativeJIT::compile):

• dfg/DFGSpeculativeJIT32_64.cpp:

(JSC::DFG::SpeculativeJIT::compile):

• dfg/DFGSpeculativeJIT64.cpp:

(JSC::DFG::SpeculativeJIT::compile):

File:

• trunk/Source/JavaScriptCore/dfg/DFGNode.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/dfg/DFGNode.h

@@ -179 +179 @@
     macro(SetLocal, 0) \
     macro(Phantom, NodeMustGenerate) \
+    macro(Nop, 0) \
     macro(Phi, 0) \
     macro(Flush, NodeMustGenerate) \
@@ -836 +837 @@
     }
     
+    void deref()
+    {
+        m_refCount--;
+    }
+    
     NodeIndex child1()
     {