Adds load/store from signed unscaled 9-bit offset w/ no writeback.

runtime/vm/assembler_arm64.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/longjump.h"
@@ skipping 250 matching lines @@
   const intptr_t object_pool_pc_dist =
     Instructions::HeaderSize() - Instructions::object_pool_offset() +
     CodeSize();
   // PP <- Read(PC - object_pool_pc_dist).
   ldr(pp, Address::PC(-object_pool_pc_dist));
 
   // When in the PP register, the pool pointer is untagged. When we
   // push it on the stack with PushPP it is tagged again. PopPP then untags
   // when restoring from the stack. This will make loading from the object
   // pool only one instruction for the first 4096 entries. Otherwise, because
-  // the offset wouldn't be aligned, it would always be at least two
-  // instructions.
+  // the offset wouldn't be aligned, it would be only one instruction for the
+  // first 64 entries.
   sub(pp, pp, Operand(kHeapObjectTag));
 }
 
 void Assembler::LoadWordFromPoolOffset(Register dst, Register pp,
                                        uint32_t offset) {
   ASSERT(dst != pp);
   if (Address::CanHoldOffset(offset)) {
     ldr(dst, Address(pp, offset));
   } else {
     const uint16_t offset_low = Utils::Low16Bits(offset);
@@ skipping 269 matching lines @@
     LoadImmediate(TMP2, imm, pp);
     cmp(rn, Operand(TMP2));
   }
 }
 
 
 void Assembler::LoadFromOffset(Register dest, Register base, int32_t offset) {
   ASSERT(base != TMP2);
   if (Address::CanHoldOffset(offset)) {
     ldr(dest, Address(base, offset));
-  } else if (Address::CanHoldOffset(offset, Address::PreIndex)) {
-    mov(TMP2, base);
-    ldr(dest, Address(TMP2, offset, Address::PreIndex));
   } else {
     // Since offset is 32-bits, it won't be loaded from the pool.
     AddImmediate(TMP2, base, offset, kNoRegister);
     ldr(dest, Address(TMP2));
   }
 }
 
 
 void Assembler::StoreToOffset(Register src, Register base, int32_t offset) {
   ASSERT(src != TMP2);
@@ skipping 67 matching lines @@
 
 
 void Assembler::CallRuntime(const RuntimeEntry& entry,
                             intptr_t argument_count) {
   entry.Call(this, argument_count);
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64