/*
- * Copyright (C) 2007, 2008 Apple Inc. All rights reserved.
+ * Copyright (C) 2007, 2008, 2012 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
#define SymbolTable_h
#include "JSObject.h"
-#include "UString.h"
-#include <wtf/AlwaysInline.h>
+#include "Watchpoint.h"
+#include <wtf/HashTraits.h>
+#include <wtf/text/StringImpl.h>
namespace JSC {
- static ALWAYS_INLINE int missingSymbolMarker() { return std::numeric_limits<int>::max(); }
+class Watchpoint;
+class WatchpointSet;
- // The bit twiddling in this class assumes that every register index is a
- // reasonably small positive or negative number, and therefore has its high
- // four bits all set or all unset.
+struct SlowArgument {
+ enum Status {
+ Normal = 0,
+ Captured = 1,
+ Deleted = 2
+ };
- struct SymbolTableEntry {
- SymbolTableEntry()
- : m_bits(0)
- {
- }
+ SlowArgument()
+ : status(Normal)
+ , index(0)
+ {
+ }
- SymbolTableEntry(int index)
- {
- ASSERT(isValidIndex(index));
- pack(index, false, false);
- }
+ Status status;
+ int index; // If status is 'Deleted', index is bogus.
+};
+
+static ALWAYS_INLINE int missingSymbolMarker() { return std::numeric_limits<int>::max(); }
- SymbolTableEntry(int index, unsigned attributes)
+// The bit twiddling in this class assumes that every register index is a
+// reasonably small positive or negative number, and therefore has its high
+// four bits all set or all unset.
+
+// In addition to implementing semantics-mandated variable attributes and
+// implementation-mandated variable indexing, this class also implements
+// watchpoints to be used for JIT optimizations. Because watchpoints are
+// meant to be relatively rare, this class optimizes heavily for the case
+// that they are not being used. To that end, this class uses the thin-fat
+// idiom: either it is thin, in which case it contains an in-place encoded
+// word that consists of attributes, the index, and a bit saying that it is
+// thin; or it is fat, in which case it contains a pointer to a malloc'd
+// data structure and a bit saying that it is fat. The malloc'd data
+// structure will be malloced a second time upon copy, to preserve the
+// property that in-place edits to SymbolTableEntry do not manifest in any
+// copies. However, the malloc'd FatEntry data structure contains a ref-
+// counted pointer to a shared WatchpointSet. Thus, in-place edits of the
+// WatchpointSet will manifest in all copies. Here's a picture:
+//
+// SymbolTableEntry --> FatEntry --> WatchpointSet
+//
+// If you make a copy of a SymbolTableEntry, you will have:
+//
+// original: SymbolTableEntry --> FatEntry --> WatchpointSet
+// copy: SymbolTableEntry --> FatEntry -----^
+
+struct SymbolTableEntry {
+ // Use the SymbolTableEntry::Fast class, either via implicit cast or by calling
+ // getFast(), when you (1) only care about isNull(), getIndex(), and isReadOnly(),
+ // and (2) you are in a hot path where you need to minimize the number of times
+ // that you branch on isFat() when getting the bits().
+ class Fast {
+ public:
+ Fast()
+ : m_bits(SlimFlag)
{
- ASSERT(isValidIndex(index));
- pack(index, attributes & ReadOnly, attributes & DontEnum);
}
+ ALWAYS_INLINE Fast(const SymbolTableEntry& entry)
+ : m_bits(entry.bits())
+ {
+ }
+
bool isNull() const
{
- return !m_bits;
+ return !(m_bits & ~SlimFlag);
}
int getIndex() const
{
- return m_bits >> FlagBits;
+ return static_cast<int>(m_bits >> FlagBits);
}
-
+
+ bool isReadOnly() const
+ {
+ return m_bits & ReadOnlyFlag;
+ }
+
unsigned getAttributes() const
{
unsigned attributes = 0;
return attributes;
}
- void setAttributes(unsigned attributes)
- {
- pack(getIndex(), attributes & ReadOnly, attributes & DontEnum);
- }
-
- bool isReadOnly() const
+ bool isFat() const
{
- return m_bits & ReadOnlyFlag;
+ return !(m_bits & SlimFlag);
}
-
+
private:
- static const unsigned ReadOnlyFlag = 0x1;
- static const unsigned DontEnumFlag = 0x2;
- static const unsigned NotNullFlag = 0x4;
- static const unsigned FlagBits = 3;
+ friend struct SymbolTableEntry;
+ intptr_t m_bits;
+ };
- void pack(int index, bool readOnly, bool dontEnum)
- {
- m_bits = (index << FlagBits) | NotNullFlag;
- if (readOnly)
- m_bits |= ReadOnlyFlag;
- if (dontEnum)
- m_bits |= DontEnumFlag;
- }
-
- bool isValidIndex(int index)
- {
- return ((index << FlagBits) >> FlagBits) == index;
- }
+ SymbolTableEntry()
+ : m_bits(SlimFlag)
+ {
+ }
- int m_bits;
- };
+ SymbolTableEntry(int index)
+ : m_bits(SlimFlag)
+ {
+ ASSERT(isValidIndex(index));
+ pack(index, false, false);
+ }
- struct SymbolTableIndexHashTraits {
- typedef SymbolTableEntry TraitType;
- static SymbolTableEntry emptyValue() { return SymbolTableEntry(); }
- static const bool emptyValueIsZero = true;
- static const bool needsDestruction = false;
- };
+ SymbolTableEntry(int index, unsigned attributes)
+ : m_bits(SlimFlag)
+ {
+ ASSERT(isValidIndex(index));
+ pack(index, attributes & ReadOnly, attributes & DontEnum);
+ }
+
+ ~SymbolTableEntry()
+ {
+ freeFatEntry();
+ }
+
+ SymbolTableEntry(const SymbolTableEntry& other)
+ : m_bits(SlimFlag)
+ {
+ *this = other;
+ }
+
+ SymbolTableEntry& operator=(const SymbolTableEntry& other)
+ {
+ if (UNLIKELY(other.isFat()))
+ return copySlow(other);
+ freeFatEntry();
+ m_bits = other.m_bits;
+ return *this;
+ }
+
+ bool isNull() const
+ {
+ return !(bits() & ~SlimFlag);
+ }
+
+ int getIndex() const
+ {
+ return static_cast<int>(bits() >> FlagBits);
+ }
+
+ ALWAYS_INLINE Fast getFast() const
+ {
+ return Fast(*this);
+ }
+
+ ALWAYS_INLINE Fast getFast(bool& wasFat) const
+ {
+ Fast result;
+ wasFat = isFat();
+ if (wasFat)
+ result.m_bits = fatEntry()->m_bits | SlimFlag;
+ else
+ result.m_bits = m_bits;
+ return result;
+ }
+
+ unsigned getAttributes() const
+ {
+ return getFast().getAttributes();
+ }
- typedef HashMap<RefPtr<StringImpl>, SymbolTableEntry, IdentifierRepHash, HashTraits<RefPtr<StringImpl> >, SymbolTableIndexHashTraits> SymbolTable;
+ void setAttributes(unsigned attributes)
+ {
+ pack(getIndex(), attributes & ReadOnly, attributes & DontEnum);
+ }
- class SharedSymbolTable : public SymbolTable, public RefCounted<SharedSymbolTable> {
+ bool isReadOnly() const
+ {
+ return bits() & ReadOnlyFlag;
+ }
+
+ bool couldBeWatched();
+
+ // Notify an opportunity to create a watchpoint for a variable. This is
+ // idempotent and fail-silent. It is idempotent in the sense that if
+ // a watchpoint set had already been created, then another one will not
+ // be created. Hence two calls to this method have the same effect as
+ // one call. It is also fail-silent, in the sense that if a watchpoint
+ // set had been created and had already been invalidated, then this will
+ // just return. This means that couldBeWatched() may return false even
+ // immediately after a call to attemptToWatch().
+ void attemptToWatch();
+
+ bool* addressOfIsWatched();
+
+ void addWatchpoint(Watchpoint*);
+
+ WatchpointSet* watchpointSet()
+ {
+ return fatEntry()->m_watchpoints.get();
+ }
+
+ ALWAYS_INLINE void notifyWrite()
+ {
+ if (LIKELY(!isFat()))
+ return;
+ notifyWriteSlow();
+ }
+
+private:
+ static const intptr_t SlimFlag = 0x1;
+ static const intptr_t ReadOnlyFlag = 0x2;
+ static const intptr_t DontEnumFlag = 0x4;
+ static const intptr_t NotNullFlag = 0x8;
+ static const intptr_t FlagBits = 4;
+
+ class FatEntry {
WTF_MAKE_FAST_ALLOCATED;
public:
- static PassRefPtr<SharedSymbolTable> create() { return adoptRef(new SharedSymbolTable); }
- private:
- SharedSymbolTable() { }
+ FatEntry(intptr_t bits)
+ : m_bits(bits & ~SlimFlag)
+ {
+ }
+
+ intptr_t m_bits; // always has FatFlag set and exactly matches what the bits would have been if this wasn't fat.
+
+ RefPtr<WatchpointSet> m_watchpoints;
};
+ SymbolTableEntry& copySlow(const SymbolTableEntry&);
+ JS_EXPORT_PRIVATE void notifyWriteSlow();
+
+ bool isFat() const
+ {
+ return !(m_bits & SlimFlag);
+ }
+
+ const FatEntry* fatEntry() const
+ {
+ ASSERT(isFat());
+ return bitwise_cast<const FatEntry*>(m_bits);
+ }
+
+ FatEntry* fatEntry()
+ {
+ ASSERT(isFat());
+ return bitwise_cast<FatEntry*>(m_bits);
+ }
+
+ FatEntry* inflate()
+ {
+ if (LIKELY(isFat()))
+ return fatEntry();
+ return inflateSlow();
+ }
+
+ FatEntry* inflateSlow();
+
+ ALWAYS_INLINE intptr_t bits() const
+ {
+ if (isFat())
+ return fatEntry()->m_bits;
+ return m_bits;
+ }
+
+ ALWAYS_INLINE intptr_t& bits()
+ {
+ if (isFat())
+ return fatEntry()->m_bits;
+ return m_bits;
+ }
+
+ void freeFatEntry()
+ {
+ if (LIKELY(!isFat()))
+ return;
+ freeFatEntrySlow();
+ }
+
+ JS_EXPORT_PRIVATE void freeFatEntrySlow();
+
+ void pack(int index, bool readOnly, bool dontEnum)
+ {
+ ASSERT(!isFat());
+ intptr_t& bitsRef = bits();
+ bitsRef = (static_cast<intptr_t>(index) << FlagBits) | NotNullFlag | SlimFlag;
+ if (readOnly)
+ bitsRef |= ReadOnlyFlag;
+ if (dontEnum)
+ bitsRef |= DontEnumFlag;
+ }
+
+ bool isValidIndex(int index)
+ {
+ return ((static_cast<intptr_t>(index) << FlagBits) >> FlagBits) == static_cast<intptr_t>(index);
+ }
+
+ intptr_t m_bits;
+};
+
+struct SymbolTableIndexHashTraits : HashTraits<SymbolTableEntry> {
+ static const bool needsDestruction = true;
+};
+
+typedef HashMap<RefPtr<StringImpl>, SymbolTableEntry, IdentifierRepHash, HashTraits<RefPtr<StringImpl> >, SymbolTableIndexHashTraits> SymbolTable;
+
+class SharedSymbolTable : public JSCell, public SymbolTable {
+public:
+ typedef JSCell Base;
+
+ static SharedSymbolTable* create(VM& vm)
+ {
+ SharedSymbolTable* sharedSymbolTable = new (NotNull, allocateCell<SharedSymbolTable>(vm.heap)) SharedSymbolTable(vm);
+ sharedSymbolTable->finishCreation(vm);
+ return sharedSymbolTable;
+ }
+ static const bool needsDestruction = true;
+ static const bool hasImmortalStructure = true;
+ static void destroy(JSCell*);
+
+ static Structure* createStructure(VM& vm, JSGlobalObject* globalObject, JSValue prototype)
+ {
+ return Structure::create(vm, globalObject, prototype, TypeInfo(LeafType, StructureFlags), &s_info);
+ }
+
+ bool usesNonStrictEval() { return m_usesNonStrictEval; }
+ void setUsesNonStrictEval(bool usesNonStrictEval) { m_usesNonStrictEval = usesNonStrictEval; }
+
+ int captureStart() { return m_captureStart; }
+ void setCaptureStart(int captureStart) { m_captureStart = captureStart; }
+
+ int captureEnd() { return m_captureEnd; }
+ void setCaptureEnd(int captureEnd) { m_captureEnd = captureEnd; }
+
+ int captureCount() { return m_captureEnd - m_captureStart; }
+
+ int parameterCount() { return m_parameterCountIncludingThis - 1; }
+ int parameterCountIncludingThis() { return m_parameterCountIncludingThis; }
+ void setParameterCountIncludingThis(int parameterCountIncludingThis) { m_parameterCountIncludingThis = parameterCountIncludingThis; }
+
+ // 0 if we don't capture any arguments; parameterCount() in length if we do.
+ const SlowArgument* slowArguments() { return m_slowArguments.get(); }
+ void setSlowArguments(PassOwnArrayPtr<SlowArgument> slowArguments) { m_slowArguments = slowArguments; }
+
+ static JS_EXPORTDATA const ClassInfo s_info;
+
+private:
+ SharedSymbolTable(VM& vm)
+ : JSCell(vm, vm.sharedSymbolTableStructure.get())
+ , m_parameterCountIncludingThis(0)
+ , m_usesNonStrictEval(false)
+ , m_captureStart(0)
+ , m_captureEnd(0)
+ {
+ }
+
+ int m_parameterCountIncludingThis;
+ bool m_usesNonStrictEval;
+
+ int m_captureStart;
+ int m_captureEnd;
+
+ OwnArrayPtr<SlowArgument> m_slowArguments;
+};
+
} // namespace JSC
#endif // SymbolTable_h
projects / apple / javascriptcore.git / blobdiff