i#1569: Fix AArch64 build broken by 914d4df.

Avoid "unused variable" warnings and define XINST_CREATE_store_1byte.

Review-URL: https://codereview.appspot.com/304390043

core/arch/aarch64/instr_create.h

@@ -88,6 +88,16 @@
  */
 #define XINST_CREATE_store(dc, m, r) INSTR_CREATE_str((dc), (m), (r))
 
+/**
+ * This platform-independent macro creates an instr_t for a 1-byte
+ * memory store instruction.
+ * \param dc  The void * dcontext used to allocate memory for the instr_t.
+ * \param m   The destination memory opnd.
+ * \param r   The source register opnd.
+ */
+#define XINST_CREATE_store_1byte(dc, m, r) \
+  ((void)(m), (void)(r), INSTR_CREATE_xx((dc), 0x25865b)) /* FIXME i#1569 */
+
 /**
  * This platform-independent macro creates an instr_t for a 2-byte
  * memory store instruction.

ext/drx/drx_buf.c

@@ -453,6 +453,10 @@ drx_buf_insert_buf_store_1byte(void *drcontext, drx_buf_t *buf, instrlist_t *ili
             (drcontext,
              OPND_CREATE_MEM8(buf_ptr, offset),
              opnd_create_reg(scratch));
+#else
+        /* FIXME i#1569: NYI */
+        DR_ASSERT(false);
+        instr = NULL;
 #endif
     } else {
         instr = XINST_CREATE_store_1byte
@@ -487,6 +491,10 @@ drx_buf_insert_buf_store_2bytes(void *drcontext, drx_buf_t *buf, instrlist_t *il
             (drcontext,
              OPND_CREATE_MEM16(buf_ptr, offset),
              opnd_create_reg(scratch));
+#else
+        /* FIXME i#1569: NYI */
+        DR_ASSERT(false);
+        instr = NULL;
 #endif
     } else {
         instr = XINST_CREATE_store_2bytes
@@ -566,6 +574,12 @@ drx_buf_insert_buf_store_ptrsz(void *drcontext, drx_buf_t *buf, instrlist_t *ili
                  opnd_create_reg(scratch));
         INSTR_XL8(instr, instr_get_app_pc(where));
         MINSERT(ilist, where, instr);
+#else
+        /* FIXME i#1569: NYI */
+        DR_ASSERT(false);
+        first = NULL;
+        last = NULL;
+        immed = 0;
 #endif
     } else {
         instr_t *instr = XINST_CREATE_store