8086asm: add support for modrm 8-bit displacement

blk/730

@@ -6,7 +6,7 @@ Mnemonics are followed by argument types. For example, MOVri,
 moves 8-bit immediate to 8-bit register.
 
 'r' = 8-bit register           'x' = 16-bit register
-'i' = immediate, size depends on other operand.
+'i' = 8-bit immediate          'I' = 16-bit immediate
 's' = SREG register
 
 Mnemonics that only have one signature (for example INT,) don't

blk/755

@@ -1,11 +1,16 @@
 : OPrm CREATE C, DOES> C@ A, SWAP 3 LSHIFT OR A, ;
 0x8a OPrm MOVr[],    0x8b OPrm MOVx[],
 
+: OPrm+ ( r m off ) CREATE C, DOES>
+    C@ A, ROT 3 LSHIFT ROT OR 0x40 OR A, A, ;
+0x8a OPrm+ MOVr[]+,    0x8b OPrm+ MOVx[]+,
+
 : MOVri, SWAP 0xb0 OR A, A, ;
-: MOVxi, SWAP 0xb8 OR A, A,, ;
+: MOVxI, SWAP 0xb8 OR A, A,, ;
 : MOVsx, 0x8e A, SWAP 3 LSHIFT OR 0xc0 OR A, ;
 : MOVxm, 0x8b A, SWAP 3 LSHIFT 0x6 OR A, A,, ;
 : INT, 0xcd A, A, ;
-: ADDAXi, 0x05 A, A,, ; : ADDALi, 0x04 A, A, ;
+: ADDAXI, 0x05 A, A,, ; : ADDALi, 0x04 A, A, ;
+: SUBxi, 0x83 A, SWAP 0xe8 OR A, A, ;
 : JMPr, 0xff A, 7 AND 0xe0 OR A, ;
 : JMPf, ( seg off ) 0xea A, SPLITB A, A, A,, ;

blk/811

@@ -2,9 +2,9 @@ H@ ORG ! 0x7c00 BIN( ! ( BIOS loads boot bin at 0x7c00 )
 JMPs, L1 FWRs ( start )
 ORG @ 0x25 + HERE ! ( bypass BPB )
 L1 FSET ( start )
-CLI, CLD, AX 0x800 MOVxi, DS AX MOVsx, ES AX MOVsx,
-SS AX MOVsx, SP 0xffff MOVxi, STI,
-AH 2 MOVri, DX 0 MOVxi, CH 0 MOVri, CL 2 MOVri, AL 1 MOVri,
-BX 0 MOVxi, 0x13 INT, ( read 2nd sector of boot floppy )
+CLI, CLD, AX 0x800 MOVxI, DS AX MOVsx, ES AX MOVsx,
+SS AX MOVsx, SP 0xffff MOVxI, STI,
+AH 2 MOVri, DX 0 MOVxI, CH 0 MOVri, CL 2 MOVri, AL 1 MOVri,
+BX 0 MOVxI, 0x13 INT, ( read 2nd sector of boot floppy )
 0x800 0 JMPf,
 ORG @ 0x1fe + HERE ! 0x55 A, 0xaa A,

blk/815

@@ -5,12 +5,12 @@ L4 BSET PC 3 - ORG @ 4 + ! ( find )
     SI INCx, ( first char ) AX AX XORxx, ( initial prev )
     BEGIN, ( loop )
         DI AX SUBxx, ( jump to prev wordref )
-        DI DECx, AL [DI] MOVr[], ( strlen )
+        AL [DI] -1 MOVr[]+, ( strlen )
         CL AL CMPrr, IFZ, ( same len )
             SI PUSHx, DI PUSHx, CX PUSHx, ( --> lvl 3 )
-            2 ADDALi, ( prev ) AH AH XORrr, DI AX SUBxx,
+            3 ADDALi, ( header ) AH AH XORrr, DI AX SUBxx,
             REPZ, CMPSB,
             CX POPx, DI POPx, SI POPx, ( <-- lvl 3 )
-            IFZ, DI INCx, AL AL XORrr, ( Z ) RETn, THEN,
+            IFZ, AL AL XORrr, ( Z ) RETn, THEN,
         THEN,
                                                       ( cont. )

blk/816

@@ -1,5 +1,5 @@
 ( find cont. )
-        DI DECx, DI DECx, AX [DI] MOVx[], ( prev )
+        DI 3 SUBxi, AX [DI] MOVx[], ( prev )
         AX AX ORxx,
     JNZ, AGAIN, ( loop )
     AX INCx, ( NZ ) RETn,

blk/817

@@ -1,7 +1,7 @@
 L3 BSET 3 A, 'F' A, 'O' A, 'O' A,
 PC 3 - ORG @ 1+ ! ( main )
     DI 0x08 MOVxm, ( LATEST )
-    SI L3 @ MOVxi,
+    SI L3 @ MOVxI,
     CALLn, L4 @ RPCn, ( find )
     IFZ, JMPs, L1 @ RPCs, ( execute ) THEN,
     AH 0x0e MOVri, ( print char ) AL '!' MOVri, 0x10 INT,