From ee1b3cc0312d7b812345682e07039b02364bb550 Mon Sep 17 00:00:00 2001
From: uvok
Date: Sun, 4 Jan 2026 16:56:30 +0100
Subject: disas: lowercase ops, arg decode

main
---
 nandgame/assembler/disas.py | 113 ++++++++++++++++++++++++++++++--------------
 1 file changed, 78 insertions(+), 35 deletions(-)

(limited to 'nandgame/assembler')

diff --git a/nandgame/assembler/disas.py b/nandgame/assembler/disas.py
index 402df5c..42c681a 100755
--- a/nandgame/assembler/disas.py
+++ b/nandgame/assembler/disas.py
@@ -30,49 +30,92 @@ def decode_jump(ins: int) -> str:
 
     return "; <unknown>"
 
-
-def decode_ins(ins: int) -> str:
+# return op, and whether it's a one-op or two-op
+def decode_ins(ins: int) -> (str, bool):
     opcode = (ins >> 8) & 0x03
     ar_n_log = (ins & (1<<10)) != 0
     opcode |= (ar_n_log << 2)
 
-    if opcode == 0b000: return "AND"
-    if opcode == 0b001: return "OR"
-    if opcode == 0b010: return "XOR"
-    if opcode == 0b011: return "NEG"
-    if opcode == 0b100: return "ADD"
-    if opcode == 0b101: return "INC"
-    if opcode == 0b110: return "SUB"
-    if opcode == 0b111: return "DEC"
+    if opcode == 0b000: return "and", True
+    if opcode == 0b001: return "or", True
+    if opcode == 0b010: return "xor", True
+    if opcode == 0b011: return "neg", False
+    if opcode == 0b100: return "add", True
+    if opcode == 0b101: return "inc", False
+    if opcode == 0b110: return "sub", True
+    if opcode == 0b111: return "dec", False
 
     return "<?>"
 
+# normally, X = arg1 = D
+def decode_arg1(ins: int) -> str:
+    use_mem = (ins & (1<<12)) != 0
+    zx = (ins & (1<<7)) != 0
+    sw = (ins & (1<<6)) != 0
+
+    if zx: return "0"
+# and not sw?
+# zx and swap: don't care, other arg is zeroed
+
+    if not zx and not sw and not use_mem: return "A"
+    if not zx and not sw and use_mem: return "M"
+
+    return "?"
+
+# normally, Y = arg2 = A
+def decode_arg2(ins: int) -> str:
+    use_mem = (ins & (1<<12)) != 0
+    zx = (ins & (1<<7)) != 0
+    sw = (ins & (1<<6)) != 0
+
+    if zx and sw: return "0"
+    # zx and not swap: don't care, other arg is zeroed
+
+    # zx ???
+    if sw and not use_mem: return "A"
+    if sw and use_mem: return "M"
+
+    return "?"
+
+def decode_dest(ins: int) -> str:
+    dA = (ins & (1<<5)) != 0
+    dD = (ins & (1<<4)) != 0
+    dM = (ins & (1<<3)) != 0
+    dest_s = ""
+    if dA: dest_s += "A "
+    if dD: dest_s += "D "
+    if dM: dest_s += "M"
+    if dest_s: dest_s += ", "
+    return dest_s
+
 def decode(ins: int) -> str:
     if (ins & 0x8000 == 0):
         # mov? ldr? ldi? aaaaaaaaaaa....
-        return f"mov A, #{ins}"
+        return f"mov  A, #{ins}"
     else:
-        use_mem = (ins & (1<<12)) != 0
-        zx = (ins & (1<<7)) != 0
-        sw = (ins & (1<<6)) != 0
-        dA = (ins & (1<<5)) != 0
-        dD = (ins & (1<<4)) != 0
-        dM = (ins & (1<<3)) != 0
-
-        codename = decode_ins(ins)
-        return f"{codename:<5}<unknown>{decode_jump(ins)}"
-
-try:
-    with open(sys.argv[1], "rb") as f:
-        while True:
-            insb = f.read(2)
-            if not insb: break
-            ins = int.from_bytes(insb)
-            print(f"\t{insb[0]:02x} {insb[1]:02x}\t{decode(ins)}")
-
-except FileNotFoundError:
-    print(f"File not found.")
-    sys.exit(1)
-# head, tail...
-except BrokenPipeError:
-    sys.exit(0)
+        dest_s = decode_dest(ins)
+        codename, two_op = decode_ins(ins)
+        op1 = decode_arg1(ins)
+        op2 = decode_arg2(ins)
+
+        op2_s = f", {op2}" if two_op else ""
+        return f"{codename:<5}{dest_s:<8}{op1:<3}{op2_s:<5}{decode_jump(ins)}"
+
+def main():
+    try:
+        with open(sys.argv[1], "rb") as f:
+            while True:
+                insb = f.read(2)
+                if not insb: break
+                ins = int.from_bytes(insb)
+                print(f"\t{insb[0]:02x} {insb[1]:02x}\t{decode(ins)}")
+
+    except FileNotFoundError:
+        print(f"File not found.")
+        sys.exit(1)
+    # head, tail...
+    except BrokenPipeError:
+        sys.exit(0)
+
+if __name__ == "__main__":
+    main()
-- 
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