diff --git a/src/imagination/rogue/rogue.h b/src/imagination/rogue/rogue.h
index 32b536986a7..cd78bacde8e 100644
--- a/src/imagination/rogue/rogue.h
+++ b/src/imagination/rogue/rogue.h
@@ -508,6 +508,9 @@ enum rogue_io {
    /* Predicate register. */
    ROGUE_IO_P0,
 
+   /* For optional instruction arguments. */
+   ROGUE_IO_NONE,
+
    ROGUE_IO_COUNT,
 };
 
@@ -531,6 +534,11 @@ static inline bool rogue_io_is_ft(enum rogue_io io)
    return (io >= ROGUE_IO_FT0 && io <= ROGUE_IO_FTE);
 }
 
+static inline bool rogue_io_is_none(enum rogue_io io)
+{
+   return io == ROGUE_IO_NONE;
+}
+
 typedef struct rogue_io_info {
    const char *str;
 } rogue_io_info;
diff --git a/src/imagination/rogue/rogue_info.c b/src/imagination/rogue/rogue_info.c
index 9aa7989bf5c..8ee93d9a4c2 100644
--- a/src/imagination/rogue/rogue_info.c
+++ b/src/imagination/rogue/rogue_info.c
@@ -288,6 +288,7 @@ const rogue_io_info rogue_io_infos[ROGUE_IO_COUNT] = {
 	[ROGUE_IO_FT4] = { .str = "ft4", },
 	[ROGUE_IO_FT5] = { .str = "ft5", },
 	[ROGUE_IO_P0] = { .str = "p0", },
+	[ROGUE_IO_NONE] = { .str = "_", },
 };
 
 #define SM(src_mod) BITFIELD64_BIT(ROGUE_ALU_SRC_MOD_##src_mod)