Parted out F_SUB_B to alu_sub.

1 files changed, 18 insertions, 0 deletions

diff --git a/alu.asm b/alu.asm
index 18f5260..22217bb 100644
--- a/alu.asm
+++ b/alu.asm
@@ -19,3 +19,21 @@ alu_sbc:
 	move.w	#$0202,(flag_byte-flag_storage)(a3)
 	pop.l	d2
 	rts
+
+alu_sub:
+	;; SUB instruction
+	;; SUB d1,d0
+	;; d1 - d0 -> d1
+	;; sets flags
+
+	;; XXX use lea and then d(an) if you have a spare register.
+	;; preserve operands for flagging
+
+	move.b	d0,(f_tmp_src_b-flag_storage)(a3)
+	move.b	d1,(f_tmp_dst_b-flag_storage)(a3)
+	move.b	#1,(f_tmp_byte-flag_storage)(a3)
+	andi.b	#%00000010,(flag_valid-flag_storage)(a3)
+	move.b	#%00000010,(flag_byte-flag_storage)(a3)
+	sub	d0,d1
+	move	sr,(f_host_sr-flag_storage)(a3)
+	rts