Revert of [Atomics] Remove Atomics code stubs; use TF ops

src/compiler/arm/code-generator-arm.cc

Index: src/compiler/arm/code-generator-arm.cc
diff --git a/src/compiler/arm/code-generator-arm.cc b/src/compiler/arm/code-generator-arm.cc
index 9ac862c6175104054676e95fc1075b053a745065..ecbee760b9ee8470c0a85fd3d5290268c2d6b6a1 100644
--- a/src/compiler/arm/code-generator-arm.cc
+++ b/src/compiler/arm/code-generator-arm.cc
@@ -388,13 +388,6 @@
     DCHECK_EQ(LeaveCC, i.OutputSBit());           \
   } while (0)
 
-#define ASSEMBLE_ATOMIC_LOAD_INTEGER(asm_instr)                       \
-  do {                                                                \
-    __ asm_instr(i.OutputRegister(),                                  \
-                 MemOperand(i.InputRegister(0), i.InputRegister(1))); \
-    __ dmb(ISH);                                                      \
-  } while (0)
-
 void CodeGenerator::AssembleDeconstructFrame() {
   __ LeaveFrame(StackFrame::MANUAL);
 }
@@ -1256,22 +1249,6 @@
     case kCheckedLoadWord64:
     case kCheckedStoreWord64:
       UNREACHABLE();  // currently unsupported checked int64 load/store.
-      break;
-
-    case kAtomicLoadInt8:
-      ASSEMBLE_ATOMIC_LOAD_INTEGER(ldrsb);
-      break;
-    case kAtomicLoadUint8:
-      ASSEMBLE_ATOMIC_LOAD_INTEGER(ldrb);
-      break;
-    case kAtomicLoadInt16:
-      ASSEMBLE_ATOMIC_LOAD_INTEGER(ldrsh);
-      break;
-    case kAtomicLoadUint16:
-      ASSEMBLE_ATOMIC_LOAD_INTEGER(ldrh);
-      break;
-    case kAtomicLoadWord32:
-      ASSEMBLE_ATOMIC_LOAD_INTEGER(ldr);
       break;
   }
 }  // NOLINT(readability/fn_size)