Use a better hash function in IdentityMap.

Reduces time for ConstantArrayBuilderTest.AllocateAllEntries from 21000ms to 106ms in
debug mode.

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1696363002

Cr-Commit-Position: refs/heads/master@{#34038}

src/identity-map.cc

@@ -4,7 +4,7 @@
 
 #include "src/identity-map.h"
 
-#include "src/heap/heap.h"
+#include "src/base/functional.h"
 #include "src/heap/heap-inl.h"
 #include "src/zone-containers.h"
 
@@ -42,8 +42,7 @@ IdentityMapBase::RawEntry IdentityMapBase::Insert(Object* key) {
 int IdentityMapBase::Hash(Object* address) {
   CHECK_NE(address, heap_->not_mapped_symbol());
   uintptr_t raw_address = reinterpret_cast<uintptr_t>(address);
-  // Xor some of the upper bits, since the lower 2 or 3 are usually aligned.
-  return static_cast<int>((raw_address >> 11) ^ raw_address);
+  return static_cast<int>(hasher_(raw_address));
 }
 
 

src/identity-map.h

@@ -5,6 +5,7 @@
 #ifndef V8_IDENTITY_MAP_H_
 #define V8_IDENTITY_MAP_H_
 
+#include "src/base/functional.h"
 #include "src/handles.h"
 
 namespace v8 {
@@ -48,6 +49,7 @@ class IdentityMapBase {
   RawEntry Insert(Object* key);
   int Hash(Object* address);
 
+  base::hash<uintptr_t> hasher_;
   Heap* heap_;
   Zone* zone_;
   int gc_counter_;

test/unittests/interpreter/constant-array-builder-unittest.cc

@@ -33,13 +33,11 @@ STATIC_CONST_MEMBER_DEFINITION const size_t
 TEST_F(ConstantArrayBuilderTest, AllocateAllEntries) {
   ConstantArrayBuilder builder(isolate(), zone());
   for (size_t i = 0; i < kMaxCapacity; i++) {
-    Handle<Object> object = isolate()->factory()->NewNumberFromSize(i);
-    builder.Insert(object);
-    CHECK_EQ(builder.size(), i + 1);
-    CHECK(builder.At(i)->SameValue(*object));
+    builder.Insert(handle(Smi::FromInt(static_cast<int>(i)), isolate()));
   }
+  CHECK_EQ(builder.size(), kMaxCapacity);
   for (size_t i = 0; i < kMaxCapacity; i++) {
-    CHECK_EQ(Handle<Smi>::cast(builder.At(i))->value(), static_cast<double>(i));
+    CHECK_EQ(Handle<Smi>::cast(builder.At(i))->value(), i);
   }
 }