In-object double fields unboxing (for 64-bit only).

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 886d9ad9d71ec8a0b36190ab299e835559627b69..9b9b5f93ed13602e788a15c5d8aed931d21a1a56 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -488,8 +488,12 @@ void StoreStubCompiler::GenerateStoreTransition(MacroAssembler* masm,
       __ bind(&do_store);
     }
   } else if (representation.IsDouble()) {
+    FieldIndex index = FieldIndex::ForDescriptor(*transition, descriptor);
+
     Label do_store, heap_number;
-    __ AllocateHeapNumber(storage_reg, scratch1, slow, MUTABLE);
+    if (!FLAG_unbox_double_fields || !index.is_inobject()) {
+      __ AllocateHeapNumber(storage_reg, scratch1, slow, MUTABLE);
+    }
 
     __ JumpIfNotSmi(value_reg, &heap_number);
     __ SmiToInteger32(scratch1, value_reg);
@@ -502,7 +506,9 @@ void StoreStubCompiler::GenerateStoreTransition(MacroAssembler* masm,
     __ movsd(xmm0, FieldOperand(value_reg, HeapNumber::kValueOffset));
 
     __ bind(&do_store);
-    __ movsd(FieldOperand(storage_reg, HeapNumber::kValueOffset), xmm0);
+    if (!FLAG_unbox_double_fields || !index.is_inobject()) {
+      __ movsd(FieldOperand(storage_reg, HeapNumber::kValueOffset), xmm0);
+    }
   }
 
   // Stub never generated for non-global objects that require access
@@ -546,44 +552,38 @@ void StoreStubCompiler::GenerateStoreTransition(MacroAssembler* masm,
     return;
   }
 
-  int index = transition->instance_descriptors()->GetFieldIndex(
-      transition->LastAdded());
-
-  // Adjust for the number of properties stored in the object. Even in the
-  // face of a transition we can use the old map here because the size of the
-  // object and the number of in-object properties is not going to change.
-  index -= object->map()->inobject_properties();
+  FieldIndex index = FieldIndex::ForDescriptor(*transition, descriptor);

[Toon Verwaest, 2014/07/29 15:02:09]

Nice cleanup. What about porting this to other platforms as well?

[Igor Sheludko, 2014/10/30 14:23:44]

Done.

 
   // TODO(verwaest): Share this code as a code stub.
   SmiCheck smi_check = representation.IsTagged()
       ? INLINE_SMI_CHECK : OMIT_SMI_CHECK;
-  if (index < 0) {
+  if (index.is_inobject()) {
     // Set the property straight into the object.
-    int offset = object->map()->instance_size() + (index * kPointerSize);
-    if (representation.IsDouble()) {
-      __ movp(FieldOperand(receiver_reg, offset), storage_reg);
+    if (FLAG_unbox_double_fields && representation.IsDouble()) {
+      __ movsd(FieldOperand(receiver_reg, index.offset()), xmm0);
+    } else if (representation.IsDouble()) {
+      __ movp(FieldOperand(receiver_reg, index.offset()), storage_reg);
     } else {
-      __ movp(FieldOperand(receiver_reg, offset), value_reg);
+      __ movp(FieldOperand(receiver_reg, index.offset()), value_reg);
     }
 
-    if (!representation.IsSmi()) {
+    if ((!FLAG_unbox_double_fields || !representation.IsDouble()) &&
+        !representation.IsSmi()) {
       // Update the write barrier for the array address.
       if (!representation.IsDouble()) {
         __ movp(storage_reg, value_reg);
       }
-      __ RecordWriteField(
-          receiver_reg, offset, storage_reg, scratch1, kDontSaveFPRegs,
-          EMIT_REMEMBERED_SET, smi_check);
+      __ RecordWriteField(receiver_reg, index.offset(), storage_reg, scratch1,
+                          kDontSaveFPRegs, EMIT_REMEMBERED_SET, smi_check);
     }
   } else {
     // Write to the properties array.
-    int offset = index * kPointerSize + FixedArray::kHeaderSize;
     // Get the properties array (optimistically).
     __ movp(scratch1, FieldOperand(receiver_reg, JSObject::kPropertiesOffset));
     if (representation.IsDouble()) {
-      __ movp(FieldOperand(scratch1, offset), storage_reg);
+      __ movp(FieldOperand(scratch1, index.offset()), storage_reg);
     } else {
-      __ movp(FieldOperand(scratch1, offset), value_reg);
+      __ movp(FieldOperand(scratch1, index.offset()), value_reg);
     }
 
     if (!representation.IsSmi()) {
@@ -591,9 +591,8 @@ void StoreStubCompiler::GenerateStoreTransition(MacroAssembler* masm,
       if (!representation.IsDouble()) {
         __ movp(storage_reg, value_reg);
       }
-      __ RecordWriteField(
-          scratch1, offset, storage_reg, receiver_reg, kDontSaveFPRegs,
-          EMIT_REMEMBERED_SET, smi_check);
+      __ RecordWriteField(scratch1, index.offset(), storage_reg, receiver_reg,
+                          kDontSaveFPRegs, EMIT_REMEMBERED_SET, smi_check);
     }
   }
 
@@ -642,28 +641,33 @@ void StoreStubCompiler::GenerateStoreField(MacroAssembler* masm,
       __ bind(&do_store);
     }
   } else if (representation.IsDouble()) {
-    // Load the double storage.
-    if (index.is_inobject()) {
-      __ movp(scratch1, FieldOperand(receiver_reg, index.offset()));
-    } else {
-      __ movp(scratch1,
-              FieldOperand(receiver_reg, JSObject::kPropertiesOffset));
-      __ movp(scratch1, FieldOperand(scratch1, index.offset()));
-    }
-
-    // Store the value into the storage.
+    // Prepare value for storing.
     Label do_store, heap_number;
     __ JumpIfNotSmi(value_reg, &heap_number);
-    __ SmiToInteger32(scratch2, value_reg);
-    __ Cvtlsi2sd(xmm0, scratch2);
+    __ SmiToInteger32(scratch1, value_reg);
+    __ Cvtlsi2sd(xmm0, scratch1);
     __ jmp(&do_store);
 
     __ bind(&heap_number);
     __ CheckMap(value_reg, masm->isolate()->factory()->heap_number_map(),
                 miss_label, DONT_DO_SMI_CHECK);
     __ movsd(xmm0, FieldOperand(value_reg, HeapNumber::kValueOffset));
+
     __ bind(&do_store);
-    __ movsd(FieldOperand(scratch1, HeapNumber::kValueOffset), xmm0);
+    // Store it either to respective mutable box or directly to in-object field.
+    Operand operand = FieldOperand(scratch1, HeapNumber::kValueOffset);

[Toon Verwaest, 2014/07/29 15:02:09]

Arg this code is confusing. Can you please just set up Operand after loading
values into scratch1? e.g.:

Operand operand = FLAG_unbox_double_fields && index.is_inobject()
    ? FieldOperand(receiver_reg, index.offset()
    : FieldOperand(scratch1, HeapNumber::kValueOffset);

I know it doesn't really matter, but it's a bit confusing that you "load
something from scratch1", and only then set up "scratch1".

[Igor Sheludko, 2014/10/30 14:23:44]

Done.

+    if (index.is_inobject()) {
+      if (FLAG_unbox_double_fields) {
+        operand = FieldOperand(receiver_reg, index.offset());
+      } else {
+        __ movp(scratch1, FieldOperand(receiver_reg, index.offset()));
+      }
+    } else {
+      __ movp(scratch1,
+              FieldOperand(receiver_reg, JSObject::kPropertiesOffset));
+      __ movp(scratch1, FieldOperand(scratch1, index.offset()));
+    }
+    __ movsd(operand, xmm0);
     // Return the value (register rax).
     ASSERT(value_reg.is(rax));
     __ ret(0);