Revert of [Atomics] Implement ldaxr/stlxr instructions in ARM64 simulator...

Revert of [Atomics] Implement ldaxr/stlxr instructions in ARM64 simulator (patchset #8 id:140001 of https://codereview.chromium.org/2711473002/ )

Reason for revert:
The tree is closed due to an msan violation (use of uninitialized value) in the arm64 simulator soon after this patch landed; this seems related

https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20arm64%20-%20sim%20-%20MSAN/builds/13607/steps/Check/logs/simulator_invalidate_..

Original issue's description:
> [Atomics] Implement ldaxr/stlxr instructions in ARM64 simulator
>
> BUG=v8:4614
> R=binji@chromium.org
>
> Review-Url: https://codereview.chromium.org/2711473002
> Cr-Commit-Position: refs/heads/master@{#43461}
> Committed: https://chromium.googlesource.com/v8/v8/+/a2a2c1b9eeccd86e77f2c7e6eda3e1b09bb5306c

TBR=binji@chromium.org,jarin@chromium.org,jacob.bramley@arm.com,aseemgarg@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4614

Review-Url: https://codereview.chromium.org/2720133003
Cr-Commit-Position: refs/heads/master@{#43463}

src/arm64/constants-arm64.h

@@ -199,14 +199,7 @@ const unsigned kFloatExponentBits = 8;
   V_(SysOp1, 18, 16, Bits)                              \
   V_(SysOp2, 7, 5, Bits)                                \
   V_(CRn, 15, 12, Bits)                                 \
-  V_(CRm, 11, 8, Bits)                                  \
-                                                        \
-  /* Load-/store-exclusive */                           \
-  V_(LoadStoreXLoad, 22, 22, Bits)                      \
-  V_(LoadStoreXNotExclusive, 23, 23, Bits)              \
-  V_(LoadStoreXAcquireRelease, 15, 15, Bits)            \
-  V_(LoadStoreXSizeLog2, 31, 30, Bits)                  \
-  V_(LoadStoreXPair, 21, 21, Bits)
+  V_(CRm, 11, 8, Bits)
 
 #define SYSTEM_REGISTER_FIELDS_LIST(V_, M_)                                    \
 /* NZCV */                                                                     \

src/arm64/simulator-arm64.h

@@ -865,97 +865,6 @@ class Simulator : public DecoderVisitor {
   char* last_debugger_input() { return last_debugger_input_; }
   char* last_debugger_input_;
 
-  // Synchronization primitives. See ARM DDI 0487A.a, B2.10. Pair types not
-  // implemented.
-  enum class MonitorAccess {
-    Open,
-    Exclusive,
-  };
-
-  enum class TransactionSize {
-    None = 0,
-    Byte = 1,
-    HalfWord = 2,
-    Word = 4,
-  };
-
-  TransactionSize get_transaction_size(unsigned size);
-
-  // The least-significant bits of the address are ignored. The number of bits
-  // is implementation-defined, between 3 and 11. See ARM DDI 0487A.a, B2.10.3.
-  static const uintptr_t kExclusiveTaggedAddrMask = ~((1 << 11) - 1);
-
-  class LocalMonitor {
-   public:
-    LocalMonitor();
-
-    // These functions manage the state machine for the local monitor, but do
-    // not actually perform loads and stores. NotifyStoreExcl only returns
-    // true if the exclusive store is allowed; the global monitor will still
-    // have to be checked to see whether the memory should be updated.
-    void NotifyLoad(uintptr_t addr);
-    void NotifyLoadExcl(uintptr_t addr, TransactionSize size);
-    void NotifyStore(uintptr_t addr);
-    bool NotifyStoreExcl(uintptr_t addr, TransactionSize size);
-
-   private:
-    void Clear();
-
-    MonitorAccess access_state_;
-    uintptr_t tagged_addr_;
-    TransactionSize size_;
-  };
-
-  class GlobalMonitor {
-   public:
-    GlobalMonitor();
-
-    class Processor {
-     public:
-      Processor();
-
-     private:
-      friend class GlobalMonitor;
-      // These functions manage the state machine for the global monitor, but do
-      // not actually perform loads and stores.
-      void Clear_Locked();
-      void NotifyLoadExcl_Locked(uintptr_t addr);
-      void NotifyStore_Locked(uintptr_t addr, bool is_requesting_processor);
-      bool NotifyStoreExcl_Locked(uintptr_t addr, bool is_requesting_processor);
-
-      MonitorAccess access_state_;
-      uintptr_t tagged_addr_;
-      Processor* next_;
-      Processor* prev_;
-      // A stxr can fail due to background cache evictions. Rather than
-      // simulating this, we'll just occasionally introduce cases where an
-      // exclusive store fails. This will happen once after every
-      // kMaxFailureCounter exclusive stores.
-      static const int kMaxFailureCounter = 5;
-      int failure_counter_;
-    };
-
-    // Exposed so it can be accessed by Simulator::{Read,Write}Ex*.
-    base::Mutex mutex;
-
-    void NotifyLoadExcl_Locked(uintptr_t addr, Processor* processor);
-    void NotifyStore_Locked(uintptr_t addr, Processor* processor);
-    bool NotifyStoreExcl_Locked(uintptr_t addr, Processor* processor);
-
-    // Called when the simulator is destroyed.
-    void RemoveProcessor(Processor* processor);
-
-   private:
-    bool IsProcessorInLinkedList_Locked(Processor* processor) const;
-    void PrependProcessor_Locked(Processor* processor);
-
-    Processor* head_;
-  };
-
-  LocalMonitor local_monitor_;
-  GlobalMonitor::Processor global_monitor_processor_;
-  static base::LazyInstance<GlobalMonitor>::type global_monitor_;
-
  private:
   void Init(FILE* stream);
 

test/cctest/BUILD.gn

@@ -224,7 +224,6 @@ v8_executable("cctest") {
       "test-javascript-arm64.cc",
       "test-js-arm64-variables.cc",
       "test-run-wasm-relocation-arm64.cc",
-      "test-simulator-arm64.cc",
       "test-utils-arm64.cc",
       "test-utils-arm64.h",
       "wasm/test-run-wasm-simd-lowering.cc",

test/cctest/cctest.gyp

@@ -266,7 +266,6 @@
       'test-javascript-arm64.cc',
       'test-js-arm64-variables.cc',
       'test-run-wasm-relocation-arm64.cc',
-      'test-simulator-arm64.cc',
       'wasm/test-run-wasm-simd-lowering.cc'
     ],
     'cctest_sources_s390': [  ### gcmole(arch:s390) ###