Vector-ICs - speed towards the monomorphic exit as quickly as possible.

src/arm/code-stubs-arm.cc

 // 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/v8.h"
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 4351 matching lines @@
 }
 
 
 void VectorRawLoadStub::GenerateForTrampoline(MacroAssembler* masm) {
   GenerateImpl(masm, true);
 }
 
 
 static void HandleArrayCases(MacroAssembler* masm, Register receiver,
                              Register key, Register vector, Register slot,
-                             Register feedback, Register scratch1,
-                             Register scratch2, Register scratch3,
+                             Register feedback, Register receiver_map,
+                             Register scratch1, Register scratch2,
                              bool is_polymorphic, Label* miss) {
   // feedback initially contains the feedback array
   Label next_loop, prepare_next;
-  Label load_smi_map, compare_map;
   Label start_polymorphic;
 
-  Register receiver_map = scratch1;
-  Register cached_map = scratch2;
+  Register cached_map = scratch1;
 
-  // Receiver might not be a heap object.
-  __ JumpIfSmi(receiver, &load_smi_map);
-  __ ldr(receiver_map, FieldMemOperand(receiver, HeapObject::kMapOffset));
-  __ bind(&compare_map);
   __ ldr(cached_map,
          FieldMemOperand(feedback, FixedArray::OffsetOfElementAt(0)));
   __ ldr(cached_map, FieldMemOperand(cached_map, WeakCell::kValueOffset));
   __ cmp(receiver_map, cached_map);
   __ b(ne, &start_polymorphic);
   // found, now call handler.
   Register handler = feedback;
   __ ldr(handler, FieldMemOperand(feedback, FixedArray::OffsetOfElementAt(1)));
   __ add(pc, handler, Operand(Code::kHeaderSize - kHeapObjectTag));
 
 
-  Register length = scratch3;
+  Register length = scratch2;
   __ bind(&start_polymorphic);
   __ ldr(length, FieldMemOperand(feedback, FixedArray::kLengthOffset));
   if (!is_polymorphic) {
     // If the IC could be monomorphic we have to make sure we don't go past the
     // end of the feedback array.
     __ cmp(length, Operand(Smi::FromInt(2)));
     __ b(eq, miss);
   }
 
   Register too_far = length;
   Register pointer_reg = feedback;
 
   // +-----+------+------+-----+-----+ ... ----+
   // | map | len  | wm0  | h0  | wm1 |      hN |
   // +-----+------+------+-----+-----+ ... ----+
   //                 0      1     2        len-1
   //                              ^              ^
   //                              |              |
   //                         pointer_reg      too_far
-  //                         aka feedback     scratch3
-  // also need receiver_map (aka scratch1)
-  // use cached_map (scratch2) to look in the weak map values.
+  //                         aka feedback     scratch2
+  // also need receiver_map
+  // use cached_map (scratch1) to look in the weak map values.
   __ add(too_far, feedback, Operand::PointerOffsetFromSmiKey(length));
   __ add(too_far, too_far, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
   __ add(pointer_reg, feedback,
          Operand(FixedArray::OffsetOfElementAt(2) - kHeapObjectTag));
 
   __ bind(&next_loop);
   __ ldr(cached_map, MemOperand(pointer_reg));
   __ ldr(cached_map, FieldMemOperand(cached_map, WeakCell::kValueOffset));
   __ cmp(receiver_map, cached_map);
   __ b(ne, &prepare_next);
   __ ldr(handler, MemOperand(pointer_reg, kPointerSize));
   __ add(pc, handler, Operand(Code::kHeaderSize - kHeapObjectTag));
 
   __ bind(&prepare_next);
   __ add(pointer_reg, pointer_reg, Operand(kPointerSize * 2));
   __ cmp(pointer_reg, too_far);
   __ b(lt, &next_loop);
 
   // We exhausted our array of map handler pairs.
   __ jmp(miss);
-
-  __ bind(&load_smi_map);
-  __ LoadRoot(receiver_map, Heap::kHeapNumberMapRootIndex);
-  __ jmp(&compare_map);
 }
 
 
 static void HandleMonomorphicCase(MacroAssembler* masm, Register receiver,
-                                  Register key, Register vector, Register slot,
-                                  Register weak_cell, Register scratch,
-                                  Label* miss) {
-  // feedback initially contains the feedback array
-  Label compare_smi_map;
-  Register receiver_map = scratch;
-  Register cached_map = weak_cell;
-
+                                  Register receiver_map, Register feedback,
+                                  Register vector, Register slot,
+                                  Register scratch, Label* compare_map,
+                                  Label* load_smi_map, Label* try_array) {
+  __ JumpIfSmi(receiver, load_smi_map);
+  __ ldr(receiver_map, FieldMemOperand(receiver, HeapObject::kMapOffset));
+  __ bind(compare_map);
+  Register cached_map = scratch;
   // Move the weak map into the weak_cell register.
-  __ ldr(cached_map, FieldMemOperand(weak_cell, WeakCell::kValueOffset));
-
-  // Receiver might not be a heap object.
-  __ JumpIfSmi(receiver, &compare_smi_map);
-  __ ldr(receiver_map, FieldMemOperand(receiver, HeapObject::kMapOffset));
+  __ ldr(cached_map, FieldMemOperand(feedback, WeakCell::kValueOffset));
   __ cmp(cached_map, receiver_map);
-  __ b(ne, miss);
-
-  Register handler = weak_cell;
+  __ b(ne, try_array);
+  Register handler = feedback;
   __ add(handler, vector, Operand::PointerOffsetFromSmiKey(slot));
   __ ldr(handler,
          FieldMemOperand(handler, FixedArray::kHeaderSize + kPointerSize));
-  __ add(pc, handler, Operand(Code::kHeaderSize - kHeapObjectTag));
-
-  // In microbenchmarks, it made sense to unroll this code so that the call to
-  // the handler is duplicated for a HeapObject receiver and a Smi receiver.
-  __ bind(&compare_smi_map);
-  __ CompareRoot(weak_cell, Heap::kHeapNumberMapRootIndex);
-  __ b(ne, miss);
-  __ add(handler, vector, Operand::PointerOffsetFromSmiKey(slot));
-  __ ldr(handler,
-         FieldMemOperand(handler, FixedArray::kHeaderSize + kPointerSize));
   __ add(pc, handler, Operand(Code::kHeaderSize - kHeapObjectTag));
 }
 
 
 void VectorRawLoadStub::GenerateImpl(MacroAssembler* masm, bool in_frame) {
   Register receiver = VectorLoadICDescriptor::ReceiverRegister();  // r1
   Register name = VectorLoadICDescriptor::NameRegister();          // r2
   Register vector = VectorLoadICDescriptor::VectorRegister();      // r3
   Register slot = VectorLoadICDescriptor::SlotRegister();          // r0
   Register feedback = r4;
-  Register scratch1 = r5;
+  Register receiver_map = r5;
+  Register scratch1 = r8;
 
   __ add(feedback, vector, Operand::PointerOffsetFromSmiKey(slot));
   __ ldr(feedback, FieldMemOperand(feedback, FixedArray::kHeaderSize));
 
-  // Is it a weak cell?
-  Label try_array;
-  Label not_array, smi_key, key_okay, miss;
-  __ ldr(scratch1, FieldMemOperand(feedback, HeapObject::kMapOffset));
-  __ CompareRoot(scratch1, Heap::kWeakCellMapRootIndex);
-  __ b(ne, &try_array);
-  HandleMonomorphicCase(masm, receiver, name, vector, slot, feedback, scratch1,
-                        &miss);
+  // Try to quickly handle the monomorphic case without knowing for sure
+  // if we have a weak cell in feedback. We do know it's safe to look
+  // at WeakCell::kValueOffset.
+  Label try_array, load_smi_map, compare_map;
+  Label not_array, miss;
+  HandleMonomorphicCase(masm, receiver, receiver_map, feedback, vector, slot,
+                        scratch1, &compare_map, &load_smi_map, &try_array);
 
   // Is it a fixed array?
   __ bind(&try_array);
+  __ ldr(scratch1, FieldMemOperand(feedback, HeapObject::kMapOffset));
   __ CompareRoot(scratch1, Heap::kFixedArrayMapRootIndex);
   __ b(ne, &not_array);
-  HandleArrayCases(masm, receiver, name, vector, slot, feedback, scratch1, r8,
-                   r9, true, &miss);
+  HandleArrayCases(masm, receiver, name, vector, slot, feedback, receiver_map,
+                   scratch1, r9, true, &miss);
 
   __ bind(&not_array);
   __ CompareRoot(feedback, Heap::kmegamorphic_symbolRootIndex);
   __ b(ne, &miss);
   Code::Flags code_flags = Code::RemoveTypeAndHolderFromFlags(
       Code::ComputeHandlerFlags(Code::LOAD_IC));
   masm->isolate()->stub_cache()->GenerateProbe(masm, Code::LOAD_IC, code_flags,
                                                false, receiver, name, feedback,
-                                               scratch1, r8, r9);
+                                               receiver_map, scratch1, r9);
 
   __ bind(&miss);
   LoadIC::GenerateMiss(masm);
+
+
+  __ bind(&load_smi_map);
+  __ LoadRoot(receiver_map, Heap::kHeapNumberMapRootIndex);
+  __ jmp(&compare_map);
 }
 
 
 void VectorRawKeyedLoadStub::Generate(MacroAssembler* masm) {
   GenerateImpl(masm, false);
 }
 
 
 void VectorRawKeyedLoadStub::GenerateForTrampoline(MacroAssembler* masm) {
   GenerateImpl(masm, true);
 }
 
 
 void VectorRawKeyedLoadStub::GenerateImpl(MacroAssembler* masm, bool in_frame) {
   Register receiver = VectorLoadICDescriptor::ReceiverRegister();  // r1
   Register key = VectorLoadICDescriptor::NameRegister();           // r2
   Register vector = VectorLoadICDescriptor::VectorRegister();      // r3
   Register slot = VectorLoadICDescriptor::SlotRegister();          // r0
   Register feedback = r4;
-  Register scratch1 = r5;
+  Register receiver_map = r5;
+  Register scratch1 = r8;
 
   __ add(feedback, vector, Operand::PointerOffsetFromSmiKey(slot));
   __ ldr(feedback, FieldMemOperand(feedback, FixedArray::kHeaderSize));
 
-  // Is it a weak cell?
-  Label try_array;
-  Label not_array, smi_key, key_okay, miss;
-  __ ldr(scratch1, FieldMemOperand(feedback, HeapObject::kMapOffset));
-  __ CompareRoot(scratch1, Heap::kWeakCellMapRootIndex);
-  __ b(ne, &try_array);
-  HandleMonomorphicCase(masm, receiver, key, vector, slot, feedback, scratch1,
-                        &miss);
+  // Try to quickly handle the monomorphic case without knowing for sure
+  // if we have a weak cell in feedback. We do know it's safe to look
+  // at WeakCell::kValueOffset.
+  Label try_array, load_smi_map, compare_map;
+  Label not_array, miss;
+  HandleMonomorphicCase(masm, receiver, receiver_map, feedback, vector, slot,
+                        scratch1, &compare_map, &load_smi_map, &try_array);
 
   __ bind(&try_array);
   // Is it a fixed array?
+  __ ldr(scratch1, FieldMemOperand(feedback, HeapObject::kMapOffset));
   __ CompareRoot(scratch1, Heap::kFixedArrayMapRootIndex);
   __ b(ne, &not_array);
 
   // We have a polymorphic element handler.
   Label polymorphic, try_poly_name;
   __ bind(&polymorphic);
-  HandleArrayCases(masm, receiver, key, vector, slot, feedback, scratch1, r8,
-                   r9, true, &miss);
+  HandleArrayCases(masm, receiver, key, vector, slot, feedback, receiver_map,
+                   scratch1, r9, true, &miss);
 
   __ bind(&not_array);
   // Is it generic?
   __ CompareRoot(feedback, Heap::kmegamorphic_symbolRootIndex);
   __ b(ne, &try_poly_name);
   Handle<Code> megamorphic_stub =
       KeyedLoadIC::ChooseMegamorphicStub(masm->isolate());
   __ Jump(megamorphic_stub, RelocInfo::CODE_TARGET);
 
   __ bind(&try_poly_name);
   // We might have a name in feedback, and a fixed array in the next slot.
   __ cmp(key, feedback);
   __ b(ne, &miss);
   // If the name comparison succeeded, we know we have a fixed array with
   // at least one map/handler pair.
   __ add(feedback, vector, Operand::PointerOffsetFromSmiKey(slot));
   __ ldr(feedback,
          FieldMemOperand(feedback, FixedArray::kHeaderSize + kPointerSize));
-  HandleArrayCases(masm, receiver, key, vector, slot, feedback, scratch1, r8,
-                   r9, false, &miss);
+  HandleArrayCases(masm, receiver, key, vector, slot, feedback, receiver_map,
+                   scratch1, r9, false, &miss);
 
   __ bind(&miss);
   KeyedLoadIC::GenerateMiss(masm);
+
+  __ bind(&load_smi_map);
+  __ LoadRoot(receiver_map, Heap::kHeapNumberMapRootIndex);
+  __ jmp(&compare_map);
 }
 
 
 void ProfileEntryHookStub::MaybeCallEntryHook(MacroAssembler* masm) {
   if (masm->isolate()->function_entry_hook() != NULL) {
     ProfileEntryHookStub stub(masm->isolate());
     int code_size = masm->CallStubSize(&stub) + 2 * Assembler::kInstrSize;
     PredictableCodeSizeScope predictable(masm, code_size);
     __ push(lr);
     __ CallStub(&stub);
@@ skipping 691 matching lines @@
                            kStackUnwindSpace, NULL,
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM