Author: [email protected]
Date: Thu Jul 16 05:56:50 2009
New Revision: 2486
Modified:
branches/bleeding_edge/src/arm/ic-arm.cc
branches/bleeding_edge/src/arm/simulator-arm.cc
branches/bleeding_edge/src/ia32/assembler-ia32.cc
branches/bleeding_edge/src/ia32/assembler-ia32.h
branches/bleeding_edge/src/ia32/ic-ia32.cc
branches/bleeding_edge/src/objects.cc
branches/bleeding_edge/src/objects.h
branches/bleeding_edge/src/utils.h
Log:
Changed hash table to use more of the hash value when probing.
Review URL: http://codereview.chromium.org/155350
Modified: branches/bleeding_edge/src/arm/ic-arm.cc
==============================================================================
--- branches/bleeding_edge/src/arm/ic-arm.cc (original)
+++ branches/bleeding_edge/src/arm/ic-arm.cc Thu Jul 16 05:56:50 2009
@@ -103,16 +103,20 @@
// Generate an unrolled loop that performs a few probes before
// giving up. Measurements done on Gmail indicate that 2 probes
// cover ~93% of loads from dictionaries.
- static const int kProbes = 4;
- for (int i = 0; i < kProbes; i++) {
- // Compute the masked index: (hash + i + i * i) & mask.
+ static const uint32_t kProbes =
+ HashTable<StringDictionaryShape, String*>::kNofFastProbes;
+ static const uint32_t kShift =
+ HashTable<StringDictionaryShape, String*>::kHashRotateShift;
+
+ for (uint32_t i = 0; i < kProbes; i++) {
+ // Compute the masked index.
__ ldr(t1, FieldMemOperand(r2, String::kLengthOffset));
__ mov(t1, Operand(t1, LSR, String::kHashShift));
if (i > 0) {
- __ add(t1, t1, Operand(StringDictionary::GetProbeOffset(i)));
+ __ and_(t1, r3, Operand(t1, ROR, (kShift * i) % kBitsPerInt));
+ } else {
+ __ and_(t1, t1, Operand(r3));
}
- __ and_(t1, t1, Operand(r3));
-
// Scale the index by multiplying by the element size.
ASSERT(StringDictionary::kEntrySize == 3);
__ add(t1, t1, Operand(t1, LSL, 1)); // t1 = t1 * 3
Modified: branches/bleeding_edge/src/arm/simulator-arm.cc
==============================================================================
--- branches/bleeding_edge/src/arm/simulator-arm.cc (original)
+++ branches/bleeding_edge/src/arm/simulator-arm.cc Thu Jul 16 05:56:50 2009
@@ -45,6 +45,7 @@
using ::v8::internal::OS;
using ::v8::internal::ReadLine;
using ::v8::internal::DeleteArray;
+using ::v8::internal::RotateRight;
// This macro provides a platform independent use of sscanf. The reason for
// SScanF not being implemented in a platform independent was through
@@ -817,7 +818,12 @@
}
case ROR: {
- UNIMPLEMENTED();
+ ASSERT(shift_amount > 0);
+ uint32_t uresult = static_cast<uint32_t>(result);
+ uresult = RotateRight(uresult, shift_amount - 1);
+ *carry_out = (uresult & 1) == 1;
+ uresult = RotateRight(uresult, 1);
+ result = static_cast<int32_t>(uresult);
break;
}
Modified: branches/bleeding_edge/src/ia32/assembler-ia32.cc
==============================================================================
--- branches/bleeding_edge/src/ia32/assembler-ia32.cc (original)
+++ branches/bleeding_edge/src/ia32/assembler-ia32.cc Thu Jul 16 05:56:50
2009
@@ -1240,6 +1240,16 @@
}
+void Assembler::ror(Register dst, uint32_t count) {
+ EnsureSpace ensure_space(this);
+ last_pc_ = pc_;
+ EMIT(0xC1);
+ emit_operand(ecx, Operand(dst));
+ ASSERT(count < 32);
+ EMIT(count);
+}
+
+
void Assembler::bt(const Operand& dst, Register src) {
EnsureSpace ensure_space(this);
last_pc_ = pc_;
Modified: branches/bleeding_edge/src/ia32/assembler-ia32.h
==============================================================================
--- branches/bleeding_edge/src/ia32/assembler-ia32.h (original)
+++ branches/bleeding_edge/src/ia32/assembler-ia32.h Thu Jul 16 05:56:50
2009
@@ -597,6 +597,9 @@
void xor_(const Operand& src, Register dst);
void xor_(const Operand& dst, const Immediate& x);
+ // Rotate dist right count times, asserts count < 32.
+ void ror(Register dst, uint32_t count);
+
// Bit operations.
void bt(const Operand& dst, Register src);
void bts(const Operand& dst, Register src);
Modified: branches/bleeding_edge/src/ia32/ic-ia32.cc
==============================================================================
--- branches/bleeding_edge/src/ia32/ic-ia32.cc (original)
+++ branches/bleeding_edge/src/ia32/ic-ia32.cc Thu Jul 16 05:56:50 2009
@@ -97,15 +97,20 @@
// Generate an unrolled loop that performs a few probes before
// giving up. Measurements done on Gmail indicate that 2 probes
// cover ~93% of loads from dictionaries.
- static const int kProbes = 4;
const int kElementsStartOffset =
Array::kHeaderSize + StringDictionary::kElementsStartIndex *
kPointerSize;
- for (int i = 0; i < kProbes; i++) {
- // Compute the masked index: (hash + i + i * i) & mask.
+
+ static const uint32_t kProbes =
+ HashTable<StringDictionaryShape, String*>::kNofFastProbes;
+ static const uint32_t kShift =
+ HashTable<StringDictionaryShape, String*>::kHashRotateShift;
+
+ for (uint32_t i = 0; i < kProbes; i++) {
+ // Compute the masked index.
__ mov(r1, FieldOperand(name, String::kLengthOffset));
__ shr(r1, String::kHashShift);
if (i > 0) {
- __ add(Operand(r1), Immediate(StringDictionary::GetProbeOffset(i)));
+ __ ror(r1, (kShift * i) % kBitsPerInt);
}
__ and_(r1, Operand(r2));
Modified: branches/bleeding_edge/src/objects.cc
==============================================================================
--- branches/bleeding_edge/src/objects.cc (original)
+++ branches/bleeding_edge/src/objects.cc Thu Jul 16 05:56:50 2009
@@ -6502,7 +6502,8 @@
Object* HashTable<Shape, Key>::Allocate(
int at_least_space_for) {
int capacity = RoundUpToPowerOf2(at_least_space_for);
- if (capacity < 4) capacity = 4; // Guarantee min capacity.
+ static const int kMinCapacity = 16;
+ if (capacity < kMinCapacity) capacity = kMinCapacity;
Object* obj = Heap::AllocateHashTable(EntryToIndex(capacity));
if (!obj->IsFailure()) {
HashTable::cast(obj)->SetNumberOfElements(0);
@@ -6516,26 +6517,25 @@
// Find entry for key otherwise return -1.
template<typename Shape, typename Key>
int HashTable<Shape, Key>::FindEntry(Key key) {
- uint32_t nof = NumberOfElements();
- if (nof == 0) return kNotFound; // Bail out if empty.
-
- uint32_t capacity = Capacity();
+ uint32_t mask = Capacity() - 1;
uint32_t hash = Shape::Hash(key);
- uint32_t entry = GetProbe(hash, 0, capacity);
- Object* element = KeyAt(entry);
- uint32_t passed_elements = 0;
- if (!element->IsNull()) {
- if (!element->IsUndefined() && Shape::IsMatch(key, element)) return
entry;
- if (++passed_elements == nof) return kNotFound;
+ // For the first probes rotate the hash to ensure a proper spread.
+ for (uint32_t i = 0; i < kNofFastProbes; i++) {
+ int entry = hash & mask;
+ Object* element = KeyAt(entry);
+ if (element->IsUndefined()) return kNotFound;
+ if (!element->IsNull() && Shape::IsMatch(key, element)) return entry;
+ hash = RotateRight(hash, kHashRotateShift);
}
- for (uint32_t i = 1; !element->IsUndefined(); i++) {
- entry = GetProbe(hash, i, capacity);
- element = KeyAt(entry);
- if (!element->IsNull()) {
- if (!element->IsUndefined() && Shape::IsMatch(key, element)) return
entry;
- if (++passed_elements == nof) return kNotFound;
- }
+
+
+ // In this unlikely event, do a linear scan.
+ for (uint32_t i = 1; i <= mask; i++) {
+ int entry = ++hash & mask;
+ Object* element = KeyAt(entry);
+ if (element->IsUndefined()) return kNotFound;
+ if (!element->IsNull() && Shape::IsMatch(key, element)) return entry;
}
return kNotFound;
}
@@ -6579,15 +6579,23 @@
template<typename Shape, typename Key>
uint32_t HashTable<Shape, Key>::FindInsertionEntry(uint32_t hash) {
- uint32_t capacity = Capacity();
- uint32_t entry = GetProbe(hash, 0, capacity);
- Object* element = KeyAt(entry);
-
- for (uint32_t i = 1; !(element->IsUndefined() || element->IsNull());
i++) {
- entry = GetProbe(hash, i, capacity);
+ uint32_t mask = Capacity() - 1;
+ int entry;
+ Object* element;
+
+ // For the first probes rotate the hash to ensure a proper spread.
+ for (uint32_t i = 0; i < kNofFastProbes; i++) {
+ entry = hash & mask;
element = KeyAt(entry);
+ if (element->IsUndefined() || element->IsNull()) return entry;
+ hash = RotateRight(hash, kHashRotateShift);
}
+ do {
+ entry = ++hash & mask;
+ element = KeyAt(entry);
+ } while(!(element->IsUndefined() || element->IsNull()));
+
return entry;
}
@@ -6666,6 +6674,10 @@
template
int Dictionary<StringDictionaryShape, String*>::NumberOfEnumElements();
+template
+int HashTable<NumberDictionaryShape, uint32_t>::FindEntry(uint32_t key);
+
+
// Collates undefined and unexisting elements below limit from position
// zero of the elements. The object stays in Dictionary mode.
Object* JSObject::PrepareSlowElementsForSort(uint32_t limit) {
@@ -7021,7 +7033,7 @@
uint32_t HashForObject(Object* obj) {
FixedArray* symbols = FixedArray::cast(obj);
int len = symbols->length();
- uint32_t hash = 0;
+ uint32_t hash = 40617523; // In case the array is empty.
for (int i = 0; i < len; i++) {
hash ^= String::cast(symbols->get(i))->Hash();
}
Modified: branches/bleeding_edge/src/objects.h
==============================================================================
--- branches/bleeding_edge/src/objects.h (original)
+++ branches/bleeding_edge/src/objects.h Thu Jul 16 05:56:50 2009
@@ -2051,11 +2051,6 @@
// Casting.
static inline HashTable* cast(Object* obj);
- // Compute the probe offset (quadratic probing).
- INLINE(static uint32_t GetProbeOffset(uint32_t n)) {
- return (n + n * n) >> 1;
- }
-
static const int kNumberOfElementsIndex = 0;
static const int kCapacityIndex = 1;
static const int kPrefixStartIndex = 2;
@@ -2071,6 +2066,9 @@
// Find entry for key otherwise return -1.
int FindEntry(Key key);
+ static const uint32_t kNofFastProbes = 4;
+ static const uint32_t kHashRotateShift = 3;
+
protected:
// Find the entry at which to insert element with the given key that
@@ -2094,13 +2092,6 @@
// and non-zero.
ASSERT(capacity > 0);
fast_set(this, kCapacityIndex, Smi::FromInt(capacity));
- }
-
-
- // Returns probe entry.
- static uint32_t GetProbe(uint32_t hash, uint32_t number, uint32_t size) {
- ASSERT(IsPowerOf2(size));
- return (hash + GetProbeOffset(number)) & (size - 1);
}
// Ensure enough space for n additional elements.
Modified: branches/bleeding_edge/src/utils.h
==============================================================================
--- branches/bleeding_edge/src/utils.h (original)
+++ branches/bleeding_edge/src/utils.h Thu Jul 16 05:56:50 2009
@@ -212,6 +212,21 @@
//
----------------------------------------------------------------------------
+// Bitwise rotate word
+
+inline uint32_t RotateRight(uint32_t value, uint32_t n) {
+ ASSERT(n < 31);
+ return (value >> n) | (value << (32-n));
+}
+
+
+inline uint32_t RotateLeft(uint32_t value, uint32_t n) {
+ ASSERT(n < 31);
+ return (value << n) | (value >> (32-n));
+}
+
+
+//
----------------------------------------------------------------------------
// I/O support.
// Our version of printf(). Avoids compilation errors that we get
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