8086asm: begin adding MODRM-enabled ops

blk/731

@@ -3,7 +3,12 @@ JMP8, L1 FWR8 ( start )
 L2 BSET ( msg )
 ," Hello, World!" 0 A,
 L1 FSET ( start )
-AH 0x42 MOVri,
+CLI,
+AH 0 MOVri,
+AL 2 MOVri,
 0x10 INT,
 SI L2 @ ( msg ) MOVrI,
+AH 0x0e MOVri,
+LODSB,
+AL AL ORrr,
 PC ORG @ DUMP

blk/752

@@ -1,2 +1,8 @@
+( Splits word into msb/lsb, lsb being on TOS )
+: SPLITB
+    256 /MOD SWAP
+;
 : PC H@ ORG @ - ;
 : A, C, ;
+( dst8 src8 -- modrm )
+: MODRMrr 0x7 AND 3 LSHIFT SWAP 0x7 AND OR 0xc0 OR ;

blk/753

@@ -1,6 +1,9 @@
 : MOVri, SWAP 0xb0 OR A, A, ;
-: MOVrI, SWAP 0xb0 OR A, 256 /MOD A, A, ;
+: MOVrI, SWAP 0xb0 OR A, SPLITB A, A, ;
 : INT, 0xcd A, A, ;
 ( no argument, flow ops are special )
 : JMP8, 0xeb A, ;
 : JMP16, 0xe9 A, ;
+: LODSB, 0xac A, ;
+: CLI, 0xfa A, ;
+: ORrr, 0x08 A, MODRMrr A, ;

blk/754

@@ -10,8 +10,7 @@
 : IFNC, JRC, FJR, ; )
 : THEN,
     DUP PC          ( l l pc )
-    -^              ( l off )
+    -^ 1-           ( l off )
     ( warning: l is a PC offset, not a mem addr! )
     SWAP ORG @ + ( BIN( @ - ) ( off addr )
     C! ;
-