[Atomics] Add dmb/dsb/isb instructions to ARM

src/arm/assembler-arm.h

Index: src/arm/assembler-arm.h
diff --git a/src/arm/assembler-arm.h b/src/arm/assembler-arm.h
index 6c38d7d33dad97f54a63885e7253f2f392878807..d308b886bd0b4fb36cd17f7ee7fec26e03723265 100644
--- a/src/arm/assembler-arm.h
+++ b/src/arm/assembler-arm.h
@@ -989,6 +989,11 @@ class Assembler : public AssemblerBase {
   void bkpt(uint32_t imm16);  // v5 and above
   void svc(uint32_t imm24, Condition cond = al);
 
+  // Synchronization instructions
+  void dmb(BarrierOption option);
+  void dsb(BarrierOption option);
+  void isb(BarrierOption option);
+
   // Coprocessor instructions
 
   void cdp(Coprocessor coproc, int opcode_1,