Enable concurrent sweep on MIPS and ARM64.

runtime/vm/disassembler_arm64.cc

Index: runtime/vm/disassembler_arm64.cc
diff --git a/runtime/vm/disassembler_arm64.cc b/runtime/vm/disassembler_arm64.cc
index bf0787718f28639e8e1d616a963e2c553b89830d..a43925a33185cb7aca8d5872d14772919328000f 100644
--- a/runtime/vm/disassembler_arm64.cc
+++ b/runtime/vm/disassembler_arm64.cc
@@ -334,6 +334,10 @@ int ARM64Decoder::FormatRegister(Instr* instr, const char* format) {
     int reg = instr->RaField();
     PrintRegister(reg, R31IsZR);
     return 2;
+  } else if (format[1] == 's') {  // 'rs: Rs register
+    int reg = instr->RsField();
+    PrintRegister(reg, R31IsZR);
+    return 2;
   }
   UNREACHABLE();
   return -1;
@@ -742,6 +746,26 @@ void ARM64Decoder::DecodeLoadRegLiteral(Instr* instr) {
 }
 
 
+void ARM64Decoder::DecodeLoadStoreExclusive(Instr* instr) {
+  if ((instr->Bit(23) != 0) ||
+      (instr->Bit(21) != 0) ||
+      (instr->Bit(15) != 0)) {
+    Unknown(instr);
+  }
+  const int32_t size = instr->Bits(30, 2);
+  if (size != 3) {
+    Unknown(instr);
+  }
+
+  const bool is_load = instr->Bit(22) == 1;
+  if (is_load) {
+    Format(instr, "ldxr 'rt, 'rn");
+  } else {
+    Format(instr, "stxr 'rs, 'rt, 'rn");
+  }
+}
+
+
 void ARM64Decoder::DecodeAddSubImm(Instr* instr) {
   switch (instr->Bit(30)) {
     case 0: {
@@ -950,6 +974,8 @@ void ARM64Decoder::DecodeLoadStore(Instr* instr) {
     DecodeLoadStoreRegPair(instr);
   } else if (instr->IsLoadRegLiteralOp()) {
     DecodeLoadRegLiteral(instr);
+  } else if (instr->IsLoadStoreExclusiveOp()) {
+    DecodeLoadStoreExclusive(instr);
   } else {
     Unknown(instr);
   }