Enable concurrent sweep on MIPS and ARM64.

runtime/vm/simulator_mips.cc

Index: runtime/vm/simulator_mips.cc
diff --git a/runtime/vm/simulator_mips.cc b/runtime/vm/simulator_mips.cc
index 2b03da8d0d0d0d626cab4e06f37b98280806b314..93fae367943e89531cfc96537d5cc3050c639903 100644
--- a/runtime/vm/simulator_mips.cc
+++ b/runtime/vm/simulator_mips.cc
@@ -1173,9 +1173,9 @@ intptr_t Simulator::WriteExclusiveW(uword addr, intptr_t value, Instr* instr) {
   bool write_allowed = HasExclusiveAccessAndOpen(addr);
   if (write_allowed) {
     WriteW(addr, value, instr);
-    return 0;  // Success.
+    return 1;  // Success.
   }
-  return 1;  // Failure.
+  return 0;  // Failure.
 }
 
 
@@ -2169,6 +2169,19 @@ void Simulator::InstructionDecode(Instr* instr) {
       set_register(instr->RtField(), instr->UImmField() << 16);
       break;
     }
+    case LL: {
+      // Format(instr, "ll 'rt, 'imms('rs)");
+      int32_t base_val = get_register(instr->RsField());
+      int32_t imm_val = instr->SImmField();
+      uword addr = base_val + imm_val;
+      if (Simulator::IsIllegalAddress(addr)) {
+        HandleIllegalAccess(addr, instr);
+      } else {
+        int32_t res = ReadExclusiveW(addr, instr);
+        set_register(instr->RtField(), res);
+      }
+      break;
+    }
     case LW: {
       // Format(instr, "lw 'rt, 'imms('rs)");
       int32_t base_val = get_register(instr->RsField());
@@ -2214,6 +2227,20 @@ void Simulator::InstructionDecode(Instr* instr) {
       }
       break;
     }
+    case SC: {
+      // Format(instr, "sc 'rt, 'imms('rs)");
+      int32_t rt_val = get_register(instr->RtField());
+      int32_t base_val = get_register(instr->RsField());
+      int32_t imm_val = instr->SImmField();
+      uword addr = base_val + imm_val;
+      if (Simulator::IsIllegalAddress(addr)) {
+        HandleIllegalAccess(addr, instr);
+      } else {
+        intptr_t status = WriteExclusiveW(addr, rt_val, instr);
+        set_register(instr->RtField(), status);
+      }
+      break;
+    }
     case SLTI: {
       // Format(instr, "slti 'rt, 'rs, 'imms");
       int32_t rs_val = get_register(instr->RsField());