8086asm: add 8-bit JMP, MOVrI, INT,

Verified against nasm with equivalent code.

blk/731

@@ -1,2 +1,9 @@
+H@ ORG !
+JMP8, L1 FWR8 ( start )
+L2 BSET ( msg )
+," Hello, World!" 0 A,
+L1 FSET ( start )
 AH 0x42 MOVri,
-8 H@ 2 - DUMP
+0x10 INT,
+SI L2 @ ( msg ) MOVrI,
+PC ORG @ DUMP

blk/750

@@ -1 +1 @@
-1 3 LOADR+
+1 5 LOADR+

blk/751

@@ -1,4 +1,5 @@
 VARIABLE ORG
+VARIABLE L1 VARIABLE L2 VARIABLE L3 VARIABLE L4
 : AL 0 ; : CL 1 ; : DL 2 ; : BL 3 ;
 : AH 4 ; : CH 5 ; : DH 6 ; : BH 7 ;
 : AX 8 ; : CX 9 ; : DX 10 ; : BX 11 ;

blk/753

@@ -1 +1,6 @@
 : MOVri, SWAP 0xb0 OR A, A, ;
+: MOVrI, SWAP 0xb0 OR A, 256 /MOD A, A, ;
+: INT, 0xcd A, A, ;
+( no argument, flow ops are special )
+: JMP8, 0xeb A, ;
+: JMP16, 0xe9 A, ;

blk/754

@@ -0,0 +1,17 @@
+( Place BEGIN, where you want to jump back and AGAIN after
+  a relative jump operator. Just like BSET and BWR. )
+: BEGIN, PC ;
+: BSET PC SWAP ! ;
+( same as BSET, but we need to write a placeholder )
+( : FJR, PC 0 A, ;
+: IFZ, JRNZ, FJR, ;
+: IFNZ, JRZ, FJR, ;
+: IFC, JRNC, FJR, ;
+: IFNC, JRC, FJR, ; )
+: THEN,
+    DUP PC          ( l l pc )
+    -^              ( l off )
+    ( warning: l is a PC offset, not a mem addr! )
+    SWAP ORG @ + ( BIN( @ - ) ( off addr )
+    C! ;
+

blk/755

@@ -0,0 +1,9 @@
+: FWR8 BSET 0 A, ;
+: FSET @ THEN, ;
+( : BREAK, FJR, 0x8000 OR ;
+: BREAK?, DUP 0x8000 AND IF
+        0x7fff AND 1 ALLOT THEN, -1 ALLOT
+    THEN ;
+: AGAIN, BREAK?, PC - 1- A, ; )
+( : BWR @ AGAIN, ; )
+