[factory] Make NewByteArray return canonical empty byte array

... for length = 0, analogously to what e.g. NewFixedArray does.

Simplify some call sites that had special handling for this case
(there are others that didn't).

Change-Id: Ib3de5506300e967aca072fad53df7ab04ef68839
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3009225
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75629}

src/baseline/baseline-compiler.cc

@@ -60,7 +60,6 @@ namespace baseline {
 template <typename IsolateT>
 Handle<ByteArray> BytecodeOffsetTableBuilder::ToBytecodeOffsetTable(
     IsolateT* isolate) {
-  if (bytes_.empty()) return isolate->factory()->empty_byte_array();
   Handle<ByteArray> table = isolate->factory()->NewByteArray(
       static_cast<int>(bytes_.size()), AllocationType::kOld);
   MemCopy(table->GetDataStartAddress(), bytes_.data(), bytes_.size());

src/codegen/source-position-table.cc

@@ -173,9 +173,7 @@ void SourcePositionTableBuilder::AddEntry(const PositionTableEntry& entry) {
 template <typename IsolateT>
 Handle<ByteArray> SourcePositionTableBuilder::ToSourcePositionTable(
     IsolateT* isolate) {
-  if (bytes_.empty()) return isolate->factory()->empty_byte_array();
   DCHECK(!Omit());
-
   Handle<ByteArray> table = isolate->factory()->NewByteArray(
       static_cast<int>(bytes_.size()), AllocationType::kOld);
   MemCopy(table->GetDataStartAddress(), bytes_.data(), bytes_.size());

src/compiler/backend/code-generator.cc

@@ -983,10 +983,6 @@ Handle<PodArray<InliningPosition>> CreateInliningPositions(
     OptimizedCompilationInfo* info, Isolate* isolate) {
   const OptimizedCompilationInfo::InlinedFunctionList& inlined_functions =
       info->inlined_functions();
-  if (inlined_functions.size() == 0) {
-    return Handle<PodArray<InliningPosition>>::cast(
-        isolate->factory()->empty_byte_array());
-  }
   Handle<PodArray<InliningPosition>> inl_positions =
       PodArray<InliningPosition>::New(
           isolate, static_cast<int>(inlined_functions.size()),

src/heap/factory-base.cc

@@ -170,6 +170,7 @@ Handle<ByteArray> FactoryBase<Impl>::NewByteArray(int length,
     FATAL("Fatal JavaScript invalid size error %d", length);
     UNREACHABLE();
   }
+  if (length == 0) return impl()->empty_byte_array();
   int size = ByteArray::SizeFor(length);
   HeapObject result = AllocateRawWithImmortalMap(
       size, allocation, read_only_roots().byte_array_map());

src/heap/factory-base.h

@@ -115,15 +115,17 @@ class EXPORT_TEMPLATE_DECLARE(V8_EXPORT_PRIVATE) FactoryBase
       int length, AllocationType allocation = AllocationType::kYoung);
 
   // Allocates a weak fixed array-like object with given map and initialized
-  // with undefined values.
+  // with undefined values. Length must be > 0.
   Handle<WeakFixedArray> NewWeakFixedArrayWithMap(
       Map map, int length, AllocationType allocation = AllocationType::kYoung);
 
   // Allocates a fixed array which may contain in-place weak references. The
   // array is initialized with undefined values
+  // The function returns a pre-allocated empty weak fixed array for length = 0.
   Handle<WeakFixedArray> NewWeakFixedArray(
       int length, AllocationType allocation = AllocationType::kYoung);
 
+  // The function returns a pre-allocated empty byte array for length = 0.
   Handle<ByteArray> NewByteArray(
       int length, AllocationType allocation = AllocationType::kYoung);
 

src/utils/memcopy.h

@@ -89,6 +89,7 @@ inline void MemCopy(void* dest, const void* src, size_t size) {
   case N:                 \
     memcpy(dest, src, N); \
     return;
+    CASE(0)
     CASE(1)
     CASE(2)
     CASE(3)