src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.asm.amd64/src/org/graalvm/compiler/asm/amd64/AMD64Assembler.java

*** 3001,3010 ****
--- 3001,3022 ----
      public final void cdqq() {
          rexw();
          emitByte(0x99);
      }
  
+     public final void repStosb() {
+         emitByte(0xf3);
+         rexw();
+         emitByte(0xaa);
+     }
+ 
+     public final void repStosq() {
+         emitByte(0xf3);
+         rexw();
+         emitByte(0xab);
+     }
+ 
      public final void cmovq(ConditionFlag cc, Register dst, Register src) {
          prefixq(dst, src);
          emitByte(0x0F);
          emitByte(0x40 | cc.getValue());
          emitModRM(dst, src);