[arm64] Use exclusive instructions in exchange

src/arm64/decoder-arm64-inl.h

 // 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.
 
 #ifndef V8_ARM64_DECODER_ARM64_INL_H_
 #define V8_ARM64_DECODER_ARM64_INL_H_
 
 #include "src/arm64/decoder-arm64.h"
 #include "src/globals.h"
 #include "src/utils.h"
@@ skipping 195 matching lines @@
 }
 
 
 template<typename V>
 void Decoder<V>::DecodeLoadStore(Instruction* instr) {
   DCHECK((instr->Bits(27, 24) == 0x8) ||
          (instr->Bits(27, 24) == 0x9) ||
          (instr->Bits(27, 24) == 0xC) ||
          (instr->Bits(27, 24) == 0xD) );
 
+  if ((instr->Bit(28) == 0) && (instr->Bit(29) == 0) && (instr->Bit(26) == 1)) {

[binji, 2017/03/15 22:17:35]

Not necessary to check for instr->Bit(24) here?

+    DecodeAdvSIMDLoadStore(instr);
+    return;
+  }
+
   if (instr->Bit(24) == 0) {
     if (instr->Bit(28) == 0) {
       if (instr->Bit(29) == 0) {
         if (instr->Bit(26) == 0) {
           if (instr->Mask(0xA08000) == 0x800000 ||
               instr->Mask(0xA00000) == 0xA00000) {
             V::VisitUnallocated(instr);
           } else if (instr->Mask(0x808000) == 0) {
-            // Load/Store exclusive without acquire/release are unimplemented.
-            V::VisitUnimplemented(instr);
+            V::VisitLoadStoreExclusive(instr);
           } else {
             V::VisitLoadStoreAcquireRelease(instr);
           }
-        } else {
-          DecodeAdvSIMDLoadStore(instr);
         }
       } else {
         if ((instr->Bits(31, 30) == 0x3) ||
             (instr->Mask(0xC4400000) == 0x40000000)) {
           V::VisitUnallocated(instr);
         } else {
           if (instr->Bit(23) == 0) {
             if (instr->Mask(0xC4400000) == 0xC0400000) {
               V::VisitUnallocated(instr);
             } else {
@@ skipping 407 matching lines @@
   // TODO(all): Implement Advanced SIMD data processing instruction decode.
   DCHECK(instr->Bits(27, 25) == 0x7);
   V::VisitUnimplemented(instr);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ARM64_DECODER_ARM64_INL_H_