| // Copyright 2012 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/ic/stub-cache.h" |
| |
| #include "src/ast/ast.h" |
| #include "src/base/bits.h" |
| #include "src/counters.h" |
| #include "src/heap/heap.h" |
| #include "src/ic/ic-inl.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| StubCache::StubCache(Isolate* isolate) : isolate_(isolate) { |
| // Ensure the nullptr (aka Smi::kZero) which StubCache::Get() returns |
| // when the entry is not found is not considered as a handler. |
| DCHECK(!IC::IsHandler(MaybeObject())); |
| } |
| |
| void StubCache::Initialize() { |
| DCHECK(base::bits::IsPowerOfTwo(kPrimaryTableSize)); |
| DCHECK(base::bits::IsPowerOfTwo(kSecondaryTableSize)); |
| Clear(); |
| } |
| |
| // Hash algorithm for the primary table. This algorithm is replicated in |
| // assembler for every architecture. Returns an index into the table that |
| // is scaled by 1 << kCacheIndexShift. |
| int StubCache::PrimaryOffset(Name name, Map map) { |
| STATIC_ASSERT(kCacheIndexShift == Name::kHashShift); |
| // Compute the hash of the name (use entire hash field). |
| DCHECK(name->HasHashCode()); |
| uint32_t field = name->hash_field(); |
| // Using only the low bits in 64-bit mode is unlikely to increase the |
| // risk of collision even if the heap is spread over an area larger than |
| // 4Gb (and not at all if it isn't). |
| uint32_t map_low32bits = static_cast<uint32_t>(map.ptr()); |
| // Base the offset on a simple combination of name and map. |
| uint32_t key = map_low32bits + field; |
| return key & ((kPrimaryTableSize - 1) << kCacheIndexShift); |
| } |
| |
| // Hash algorithm for the secondary table. This algorithm is replicated in |
| // assembler for every architecture. Returns an index into the table that |
| // is scaled by 1 << kCacheIndexShift. |
| int StubCache::SecondaryOffset(Name name, int seed) { |
| // Use the seed from the primary cache in the secondary cache. |
| uint32_t name_low32bits = static_cast<uint32_t>(name.ptr()); |
| uint32_t key = (seed - name_low32bits) + kSecondaryMagic; |
| return key & ((kSecondaryTableSize - 1) << kCacheIndexShift); |
| } |
| |
| int StubCache::PrimaryOffsetForTesting(Name name, Map map) { |
| return PrimaryOffset(name, map); |
| } |
| |
| int StubCache::SecondaryOffsetForTesting(Name name, int seed) { |
| return SecondaryOffset(name, seed); |
| } |
| |
| #ifdef DEBUG |
| namespace { |
| |
| bool CommonStubCacheChecks(StubCache* stub_cache, Name name, Map map, |
| MaybeObject handler) { |
| // Validate that the name and handler do not move on scavenge, and that we |
| // can use identity checks instead of structural equality checks. |
| DCHECK(!Heap::InNewSpace(name)); |
| DCHECK(!Heap::InNewSpace(handler)); |
| DCHECK(name->IsUniqueName()); |
| DCHECK(name->HasHashCode()); |
| if (handler->ptr() != kNullAddress) DCHECK(IC::IsHandler(handler)); |
| return true; |
| } |
| |
| } // namespace |
| #endif |
| |
| void StubCache::Set(Name name, Map map, MaybeObject handler) { |
| DCHECK(CommonStubCacheChecks(this, name, map, handler)); |
| |
| // Compute the primary entry. |
| int primary_offset = PrimaryOffset(name, map); |
| Entry* primary = entry(primary_, primary_offset); |
| MaybeObject old_handler(primary->value); |
| |
| // If the primary entry has useful data in it, we retire it to the |
| // secondary cache before overwriting it. |
| if (old_handler != MaybeObject::FromObject( |
| isolate_->builtins()->builtin(Builtins::kIllegal)) && |
| primary->map != kNullAddress) { |
| Map old_map = Map::cast(Object(primary->map)); |
| int seed = PrimaryOffset(Name::cast(Object(primary->key)), old_map); |
| int secondary_offset = |
| SecondaryOffset(Name::cast(Object(primary->key)), seed); |
| Entry* secondary = entry(secondary_, secondary_offset); |
| *secondary = *primary; |
| } |
| |
| // Update primary cache. |
| primary->key = name.ptr(); |
| primary->value = handler.ptr(); |
| primary->map = map.ptr(); |
| isolate()->counters()->megamorphic_stub_cache_updates()->Increment(); |
| } |
| |
| MaybeObject StubCache::Get(Name name, Map map) { |
| DCHECK(CommonStubCacheChecks(this, name, map, MaybeObject())); |
| int primary_offset = PrimaryOffset(name, map); |
| Entry* primary = entry(primary_, primary_offset); |
| if (primary->key == name.ptr() && primary->map == map.ptr()) { |
| return MaybeObject(primary->value); |
| } |
| int secondary_offset = SecondaryOffset(name, primary_offset); |
| Entry* secondary = entry(secondary_, secondary_offset); |
| if (secondary->key == name.ptr() && secondary->map == map.ptr()) { |
| return MaybeObject(secondary->value); |
| } |
| return MaybeObject(); |
| } |
| |
| void StubCache::Clear() { |
| MaybeObject empty = MaybeObject::FromObject( |
| isolate_->builtins()->builtin(Builtins::kIllegal)); |
| Name empty_string = ReadOnlyRoots(isolate()).empty_string(); |
| for (int i = 0; i < kPrimaryTableSize; i++) { |
| primary_[i].key = empty_string.ptr(); |
| primary_[i].map = kNullAddress; |
| primary_[i].value = empty.ptr(); |
| } |
| for (int j = 0; j < kSecondaryTableSize; j++) { |
| secondary_[j].key = empty_string.ptr(); |
| secondary_[j].map = kNullAddress; |
| secondary_[j].value = empty.ptr(); |
| } |
| } |
| |
| } // namespace internal |
| } // namespace v8 |