[arm] Allow immediate-index write barriers.

src/compiler/arm/instruction-selector-arm.cc

 // Copyright 2014 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/base/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 337 matching lines @@
   Node* base = node->InputAt(0);
   Node* index = node->InputAt(1);
   Node* value = node->InputAt(2);
 
   StoreRepresentation store_rep = StoreRepresentationOf(node->op());
   WriteBarrierKind write_barrier_kind = store_rep.write_barrier_kind();
   MachineRepresentation rep = store_rep.representation();
 
   if (write_barrier_kind != kNoWriteBarrier) {
     DCHECK_EQ(MachineRepresentation::kTagged, rep);
+    AddressingMode addressing_mode;
     InstructionOperand inputs[3];
     size_t input_count = 0;
     inputs[input_count++] = g.UseUniqueRegister(base);
-    inputs[input_count++] = g.UseUniqueRegister(index);
+    // OutOfLineRecordWrite uses the index in an 'add' instruction as well as
+    // for the store itself, so we must check compatibility with both.
+    if (g.CanBeImmediate(index, kArmAdd) && g.CanBeImmediate(index, kArmStr)) {
+      inputs[input_count++] = g.UseImmediate(index);
+      addressing_mode = kMode_Offset_RI;
+    } else {
+      inputs[input_count++] = g.UseUniqueRegister(index);
+      addressing_mode = kMode_Offset_RR;
+    }
     inputs[input_count++] = (write_barrier_kind == kMapWriteBarrier)
                                 ? g.UseRegister(value)
                                 : g.UseUniqueRegister(value);
     RecordWriteMode record_write_mode = RecordWriteMode::kValueIsAny;
     switch (write_barrier_kind) {
       case kNoWriteBarrier:
         UNREACHABLE();
         break;
       case kMapWriteBarrier:
         record_write_mode = RecordWriteMode::kValueIsMap;
         break;
       case kPointerWriteBarrier:
         record_write_mode = RecordWriteMode::kValueIsPointer;
         break;
       case kFullWriteBarrier:
         record_write_mode = RecordWriteMode::kValueIsAny;
         break;
     }
     InstructionOperand temps[] = {g.TempRegister(), g.TempRegister()};
     size_t const temp_count = arraysize(temps);
     InstructionCode code = kArchStoreWithWriteBarrier;
+    code |= AddressingModeField::encode(addressing_mode);
     code |= MiscField::encode(static_cast<int>(record_write_mode));
     Emit(code, 0, nullptr, input_count, inputs, temp_count, temps);
   } else {
     ArchOpcode opcode = kArchNop;
     switch (rep) {
       case MachineRepresentation::kFloat32:
         opcode = kArmVstrF32;
         break;
       case MachineRepresentation::kFloat64:
         opcode = kArmVstrF64;
@@ skipping 1228 matching lines @@
              MachineOperatorBuilder::kFloat64RoundTiesAway |
              MachineOperatorBuilder::kFloat32RoundTiesEven |
              MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8