From af7a0cf9b65d6fee20029fe67c95c494f4b402a7 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Thu, 24 Jul 2025 03:41:39 -0400
Subject: oasm: Add encoding for MRO type instructions

This commit introduces encoding logic for 4 additional instructions:

- MROB (Mask Register Over [byte])
- MROW (Mask Register Over [word])
- MROD (Mask Register Over [dword])
- MROQ (Mask Register Over [qword])

This instruction is used to fill a register with a specific length of
zeros or ones. For example, to fill a register (e.g., x2) with 16-bits
of 1s:

--
!!
!! Clear bits x2[7:0]... Mrrp,,
!! mrow!!
!!
mrow x2, #1
--

Similarly, an operand of zero sets it to zero. For example, to clear an
entire 64-bit register with zeros. Something like this can be done:

--
mroq x1, #0
--

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 usr.bin/oasm/parse.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

(limited to 'usr.bin/oasm/parse.c')

diff --git a/usr.bin/oasm/parse.c b/usr.bin/oasm/parse.c
index 4651b55..ff3c9d2 100644
--- a/usr.bin/oasm/parse.c
+++ b/usr.bin/oasm/parse.c
@@ -51,6 +51,12 @@ static const char *tokstr[] = {
     [ TT_IMM ]  = "<imm>",
     [ TT_LABEL] = "<label>",
 
+    /* Bitwise */
+    [ TT_MROB ] = "mrob",
+    [ TT_MROW ] = "mrow",
+    [ TT_MROD ] = "mrod",
+    [ TT_MROQ ] = "mroq",
+
 
     /* X<n> registers */
     [ TT_X0 ]  = "x0",
@@ -119,6 +125,11 @@ parse_reg(struct oasm_state *state, struct oasm_token *tok)
         state->last = tok->type;
         break;
     default:
+        if (lex_is_mro(state->last)) {
+            state->last = tok->type;
+            break;
+        }
+
         p = tokstr[state->last];
         oasm_err("bad instruction '%s' for regop\n", p);
         return -1;
@@ -187,6 +198,12 @@ parse_tok(struct oasm_state *state, struct oasm_token *tok)
         emit_osmx64(&emit_state, tok);
         break;
     default:
+        if (lex_is_mro(tok->type)) {
+            state->last = tok->type;
+            emit_osmx64(&emit_state, tok);
+            return 0;
+        }
+
         if (!tok->is_reg) {
             oasm_err("syntax error\n");
             return -1;
-- 
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