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

@@ -3001,10 +3001,22 @@
     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);