Improve performance of stubcode based array allocation moving stub to isolate specific area.

runtime/vm/stub_code_mips.cc

Index: runtime/vm/stub_code_mips.cc
===================================================================
--- runtime/vm/stub_code_mips.cc	(revision 36227)
+++ runtime/vm/stub_code_mips.cc	(working copy)
@@ -682,130 +682,118 @@
 // Called for inline allocation of arrays.
 // Input parameters:
 //   RA: return address.
-//   A1: Array length as Smi.
+//   A1: Array length as Smi (must be preserved).
 //   A0: array element type (either NULL or an instantiated type).
 // NOTE: A1 cannot be clobbered here as the caller relies on it being saved.
 // The newly allocated object is returned in V0.
 void StubCode::GenerateAllocateArrayStub(Assembler* assembler) {
   __ TraceSimMsg("AllocateArrayStub");
   Label slow_case;
-  if (FLAG_inline_alloc) {
-    // Compute the size to be allocated, it is based on the array length
-    // and is computed as:
-    // RoundedAllocationSize((array_length * kwordSize) + sizeof(RawArray)).
-    // Assert that length is a Smi.
-    __ andi(CMPRES1, A1, Immediate(kSmiTagMask));
-    if (FLAG_use_slow_path) {
-      __ b(&slow_case);
-    } else {
-      __ bne(CMPRES1, ZR, &slow_case);
-    }
-    __ bltz(A1, &slow_case);
-    // Check for maximum allowed length.
-    const intptr_t max_len =
-        reinterpret_cast<int32_t>(Smi::New(Array::kMaxElements));
-    __ BranchUnsignedGreater(A1, max_len, &slow_case);
 
-    __ lw(T0, FieldAddress(CTX, Context::isolate_offset()));
-    __ lw(T0, Address(T0, Isolate::heap_offset()));
-    __ lw(T0, Address(T0, Heap::new_space_offset()));
+  // Compute the size to be allocated, it is based on the array length
+  // and is computed as:
+  // RoundedAllocationSize((array_length * kwordSize) + sizeof(RawArray)).
+  __ mov(T3, A1);  // Array length.
 
-    // Calculate and align allocation size.
-    // Load new object start and calculate next object start.
-    // A0: array element type.
-    // A1: Array length as Smi.
-    // T0: Points to new space object.
-    __ lw(V0, Address(T0, Scavenger::top_offset()));
-    intptr_t fixed_size = sizeof(RawArray) + kObjectAlignment - 1;
-    __ LoadImmediate(T3, fixed_size);
-    __ sll(TMP, A1, 1);  // A1 is Smi.
-    __ addu(T3, T3, TMP);
-    ASSERT(kSmiTagShift == 1);
-    __ LoadImmediate(TMP, ~(kObjectAlignment - 1));
-    __ and_(T3, T3, TMP);
+  // Check that length is a positive Smi.
+  __ andi(CMPRES1, T3, Immediate(kSmiTagMask));
+  __ bne(CMPRES1, ZR, &slow_case);
+  __ bltz(T3, &slow_case);
 
-    __ AdduDetectOverflow(T2, T3, V0, CMPRES1);
-    __ bltz(CMPRES1, &slow_case);  // CMPRES1 < 0 on overflow.
+  // Check for maximum allowed length.
+  const intptr_t max_len =
+      reinterpret_cast<int32_t>(Smi::New(Array::kMaxElements));
+  __ BranchUnsignedGreater(T3, max_len, &slow_case);
 
-    // Check if the allocation fits into the remaining space.
-    // V0: potential new object start.
-    // A0: array element type.
-    // A1: array length as Smi.
-    // T0: points to new space object.
-    // T2: potential next object start.
-    // T3: array size.
-    __ lw(CMPRES1, Address(T0, Scavenger::end_offset()));
-    __ BranchUnsignedGreaterEqual(T2, CMPRES1, &slow_case);
+  const intptr_t fixed_size = sizeof(RawArray) + kObjectAlignment - 1;
+  __ LoadImmediate(T2, fixed_size);
+  __ sll(T3, T3, 1);  // T3 is  a Smi.
+  __ addu(T2, T2, T3);
+  ASSERT(kSmiTagShift == 1);
+  __ LoadImmediate(T3, ~(kObjectAlignment - 1));
+  __ and_(T2, T2, T3);
 
-    // Successfully allocated the object(s), now update top to point to
-    // next object start and initialize the object.
-    // V0: potential new object start.
-    // T2: potential next object start.
-    // T0: Points to new space object.
-    __ sw(T2, Address(T0, Scavenger::top_offset()));
-    __ addiu(V0, V0, Immediate(kHeapObjectTag));
-    // T1: Size of allocation in bytes.
-    __ subu(T1, T2, V0);
-    __ UpdateAllocationStatsWithSize(kArrayCid, T1, T5);
+  // T2: Allocation size.
 
-    // V0: new object start as a tagged pointer.
-    // A0: array element type.
-    // A1: Array length as Smi.
-    // T2: new object end address.
+  Isolate* isolate = Isolate::Current();
+  Heap* heap = isolate->heap();
 
-    // Store the type argument field.
-    __ StoreIntoObjectNoBarrier(
-        V0,
-        FieldAddress(V0, Array::type_arguments_offset()),
-        A0);
+  __ LoadImmediate(T3, heap->TopAddress());
+  __ lw(T0, Address(T3, 0));  // Potential new object start.
 
-    // Set the length field.
-    __ StoreIntoObjectNoBarrier(
-        V0,
-        FieldAddress(V0, Array::length_offset()),
-        A1);
+  __ AdduDetectOverflow(T1, T0, T2, CMPRES1);  // Potential next object start.
+  __ bltz(CMPRES1, &slow_case);  // CMPRES1 < 0 on overflow.
 
-    // Calculate the size tag.
-    // V0: new object start as a tagged pointer.
-    // A1: Array length as Smi.
-    // T2: new object end address.
-    // T3: array size.
+  // Check if the allocation fits into the remaining space.
+  // T0: potential new object start.
+  // T1: potential next object start.
+  // T2: allocation size.
+  __ LoadImmediate(T4, heap->EndAddress());
+  __ lw(T4, Address(T4, 0));
+  __ BranchUnsignedGreaterEqual(T1, T4, &slow_case);
+
+  // Successfully allocated the object(s), now update top to point to
+  // next object start and initialize the object.
+  __ sw(T1, Address(T3, 0));
+  __ addiu(T0, T0, Immediate(kHeapObjectTag));
+  __ UpdateAllocationStatsWithSize(kArrayCid, T2, T4);
+
+  // Initialize the tags.
+  // T0: new object start as a tagged pointer.
+  // T1: new object end address.
+  // T2: allocation size.
+  {
+    Label overflow, done;
     const intptr_t shift = RawObject::kSizeTagPos - kObjectAlignmentLog2;
-    // If no size tag overflow, shift T3 left, else set T3 to zero.
-    __ LoadImmediate(T4, RawObject::SizeTag::kMaxSizeTag);
-    __ sltu(CMPRES1, T4, T3);  // CMPRES1 = T4 < T3 ? 1 : 0
-    __ sll(TMP, T3, shift);  // TMP = T3 << shift;
-    __ movz(T3, TMP, CMPRES1);  // T3 = T4 >= T3 ? 0 : T3
-    __ movn(T3, ZR, CMPRES1);  // T3 = T4 < T3 ? TMP : T3
+    const Class& cls = Class::Handle(isolate->object_store()->array_class());
 
+    __ BranchUnsignedGreater(T2, RawObject::SizeTag::kMaxSizeTag, &overflow);
+    __ b(&done);
+    __ delay_slot()->sll(T2, T2, shift);
+    __ Bind(&overflow);
+    __ mov(T2, ZR);
+    __ Bind(&done);
+
     // Get the class index and insert it into the tags.
-    __ LoadImmediate(TMP, RawObject::ClassIdTag::encode(kArrayCid));
-    __ or_(T3, T3, TMP);
-    __ sw(T3, FieldAddress(V0, Array::tags_offset()));
+    // T2: size and bit tags.
+    __ LoadImmediate(TMP, RawObject::ClassIdTag::encode(cls.id()));
+    __ or_(T2, T2, TMP);
+    __ sw(T2, FieldAddress(T0, Array::tags_offset()));  // Store tags.
+  }
 
-    // Initialize all array elements to raw_null.
-    // V0: new object start as a tagged pointer.
-    // T2: new object end address.
-    // A1: Array length as Smi.
-    __ AddImmediate(T3, V0, Array::data_offset() - kHeapObjectTag);
-    // T3: iterator which initially points to the start of the variable
-    // data area to be initialized.
+  // T0: new object start as a tagged pointer.
+  // T1: new object end address.
+  // Store the type argument field.
+  __ StoreIntoObjectNoBarrier(T0,
+                              FieldAddress(T0, Array::type_arguments_offset()),
+                              A0);
 
-    __ LoadImmediate(T7, reinterpret_cast<intptr_t>(Object::null()));
-    Label loop, loop_exit;
-    __ BranchUnsignedGreaterEqual(T3, T2, &loop_exit);
-    __ Bind(&loop);
-    __ addiu(T3, T3, Immediate(kWordSize));
-    __ bne(T3, T2, &loop);
-    __ delay_slot()->sw(T7, Address(T3, -kWordSize));
-    __ Bind(&loop_exit);
+  // Set the length field.
+  __ StoreIntoObjectNoBarrier(T0,
+                              FieldAddress(T0, Array::length_offset()),
+                              A1);
 
-    // Done allocating and initializing the array.
-    // V0: new object.
-    // A1: Array length as Smi (preserved for the caller.)
-    __ Ret();
-  }
+  __ LoadImmediate(T7, reinterpret_cast<int32_t>(Object::null()));
+  // Initialize all array elements to raw_null.
+  // T0: new object start as a tagged pointer.
+  // T1: new object end address.
+  // T2: iterator which initially points to the start of the variable
+  // data area to be initialized.
+  // T7: null.
+  __ AddImmediate(T2, T0, sizeof(RawArray) - kHeapObjectTag);
 
+  Label done;
+  Label init_loop;
+  __ Bind(&init_loop);
+  __ BranchUnsignedGreaterEqual(T2, T1, &done);
+  __ sw(T7, Address(T2, 0));
+  __ b(&init_loop);
+  __ delay_slot()->addiu(T2, T2, Immediate(kWordSize));
+  __ Bind(&done);
+
+  __ Ret();  // Returns the newly allocated object in V0.
+  __ delay_slot()->mov(V0, T0);
+
   // Unable to allocate the array using the fast inline code, just call
   // into the runtime.
   __ Bind(&slow_case);