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/emit.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

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

diff --git a/usr.bin/oasm/emit.c b/usr.bin/oasm/emit.c
index eb38779..3261522 100644
--- a/usr.bin/oasm/emit.c
+++ b/usr.bin/oasm/emit.c
@@ -296,6 +296,67 @@ emit_encode_br(struct emit_state *state, struct oasm_token *tok)
     return TAILQ_NEXT(tok, link);
 }
 
+/*
+ * Encode the MRO type instructions
+ *
+ * mrob x1[7:0]
+ * mrow x1[15:0]   ! Mrowwww :3333
+ * mrod x1[31:0]
+ * mroq x[63:0]
+ *
+ * Returns the next token on success,
+ * otherwise NULL.
+ */
+static struct oasm_token *
+emit_encode_mro(struct emit_state *state, struct oasm_token *tok)
+{
+    inst_t curinst;
+    reg_t rd;
+    uint8_t opcode = OSMX64_MROB;
+    char *inst_str = "mrob";
+
+    switch (tok->type) {
+    case TT_MROW:
+        opcode = OSMX64_MROW;
+        inst_str = "mrow";
+        break;
+    case TT_MROD:
+        opcode = OSMX64_MROD;
+        inst_str = "mrod";
+        break;
+    case TT_MROQ:
+        opcode = OSMX64_MROQ;
+        inst_str = "mroq";
+        break;
+    }
+
+    /* Next token should be a register */
+    tok = TAILQ_NEXT(tok, link);
+    if (!tok_is_xreg(tok->type)) {
+        oasm_err("[emit error]: expected register in '%s'\n", inst_str);
+        return NULL;
+    }
+
+    rd = ir_to_reg(tok->type);
+    if (rd == OSMX64_R_BAD) {
+        oasm_err("[emit error]: got bad register in '%s'\n", inst_str);
+        return NULL;
+    }
+
+    /* Next token should be an IMM */
+    tok = TAILQ_NEXT(tok, link);
+    if (tok->type != TT_IMM) {
+        oasm_err("[emit error]: expected <imm> after reg in '%s'\n", inst_str);
+        return NULL;
+    }
+
+    curinst.opcode = opcode;
+    curinst.rd = rd;
+    curinst.imm = tok->imm;
+    emit_bytes(state, &curinst, sizeof(curinst));
+    return TAILQ_NEXT(tok, link);
+}
+
 int
 emit_osmx64(struct emit_state *state, struct oasm_token *tp)
 {
@@ -387,6 +448,10 @@ emit_process(struct oasm_state *oasm, struct emit_state *emit)
             curtok = emit_encode_hlt(emit, curtok);
             break;
         default:
+            if (lex_is_mro(curtok->type)) {
+                curtok = emit_encode_mro(emit, curtok);
+                break;
+            }
             curtok = TAILQ_NEXT(curtok, link);
             break;
         }
-- 
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