Inline instance object hash code into object header on 64 bit.

runtime/vm/assembler_arm64.h

 // 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.
 
 #ifndef RUNTIME_VM_ASSEMBLER_ARM64_H_
 #define RUNTIME_VM_ASSEMBLER_ARM64_H_
 
 #ifndef RUNTIME_VM_ASSEMBLER_H_
 #error Do not include assembler_arm64.h directly; use assembler.h instead.
 #endif
@@ skipping 724 matching lines @@
            (a.type() == Address::PairPreIndex));
     EmitLoadStoreRegPair(LDP, rt, rt2, a, sz);
   }
   void stp(Register rt, Register rt2, Address a, OperandSize sz = kDoubleWord) {
     ASSERT((a.type() == Address::PairOffset) ||
            (a.type() == Address::PairPostIndex) ||
            (a.type() == Address::PairPreIndex));
     EmitLoadStoreRegPair(STP, rt, rt2, a, sz);
   }
 
-  void ldxr(Register rt, Register rn) {
+  void ldxr(Register rt, Register rn, OperandSize size = kDoubleWord) {

[rmacnak, 2017/06/19 18:12:21]

Please copy the ldxr/stxr tests in assembler_arm64_test.cc to try both access
sizes.

[erikcorry, 2017/06/21 12:12:12]

Done.

     // rt = value
     // rn = address
-    EmitLoadStoreExclusive(LDXR, R31, rn, rt, kDoubleWord);
+    EmitLoadStoreExclusive(LDXR, R31, rn, rt, size);
   }
-  void stxr(Register rs, Register rt, Register rn) {
+  void stxr(Register rs,
+            Register rt,
+            Register rn,
+            OperandSize size = kDoubleWord) {
     // rs = status (1 = failure, 0 = success)
     // rt = value
     // rn = address
-    EmitLoadStoreExclusive(STXR, rs, rn, rt, kDoubleWord);
+    EmitLoadStoreExclusive(STXR, rs, rn, rt, size);
   }
   void clrex() {
     const int32_t encoding = static_cast<int32_t>(CLREX);
     Emit(encoding);
   }
 
   // Conditional select.
   void csel(Register rd, Register rn, Register rm, Condition cond) {
     EmitConditionalSelect(CSEL, rd, rn, rm, cond, kDoubleWord);
   }
@@ skipping 917 matching lines @@
         (static_cast<int32_t>(hw_idx) << kHWShift) |
         (static_cast<int32_t>(imm.value() & 0xffff) << kImm16Shift);
     Emit(encoding);
   }
 
   void EmitLoadStoreExclusive(LoadStoreExclusiveOp op,
                               Register rs,
                               Register rn,
                               Register rt,
                               OperandSize sz = kDoubleWord) {
-    ASSERT(sz == kDoubleWord);
-    const int32_t size = B31 | B30;
+    ASSERT(sz == kDoubleWord || sz == kWord);
+    const int32_t size = B31 | (sz == kDoubleWord ? B30 : 0);
 
     ASSERT((rs != kNoRegister) && (rs != ZR));
     ASSERT((rn != kNoRegister) && (rn != ZR));
     ASSERT((rt != kNoRegister) && (rt != ZR));
 
     const int32_t encoding =
         op | size | (static_cast<int32_t>(ConcreteRegister(rs)) << kRsShift) |
         (static_cast<int32_t>(ConcreteRegister(rn)) << kRnShift) |
         (static_cast<int32_t>(ConcreteRegister(rt)) << kRtShift);
 
@@ skipping 218 matching lines @@
                                   Register value,
                                   Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_ASSEMBLER_ARM64_H_