pcat: make find compare strings

find is the biggest chunk of logic of the boot code. The 8086 version
is significantly terser than the z80 one. REP/CMPS helps...

blk/812

@@ -5,7 +5,7 @@ JMPn, 0 A,,   ( 00, main )     JMPn, 0 A,,   ( 03, find )
 0 A,          ( 0a, unused )   JMPn, 0 A,,   ( 0b, cellWord )
 JMPn, 0 A,, ( 0e compiledWord ) JMPn, 0 A,,  ( 11, pushRS )
 JMPn, 0 A,,   ( 14, popRS )
-BX JMPr,      ( 17, nativeWord ) 0 A,
+DI JMPr,      ( 17, nativeWord ) 0 A,
 JMPn, 0 A,,   ( 1a, next )     JMPn, 0 A,,   ( 1d, unused )
 0 A, 0 A,     ( 20, numberWord ) 0 A, 0 A,   ( 22, litWord )
 0 A, 0 A,     ( 24, addrWord ) 0 A, 0 A,     ( 26, unused )

blk/813

@@ -9,5 +9,5 @@ H@ XCURRENT !        ( set current tip of dict, 0x42 )
 ;CODE
 CODE FOO
     AH 0x0e MOVri, ( print char ) AL 'X' MOVri, 0x10 INT,
-    L2 BSET JMPs, L2 @ RPCs,
+    BEGIN, JMPs, AGAIN,
 ;CODE

blk/814

@@ -1,5 +1,5 @@
-L1 BSET PC 3 - ORG @ 0x34 + ! ( execute -- BX -> wordref )
+L1 BSET PC 3 - ORG @ 0x34 + ! ( execute -- DI -> wordref )
     AH AH XORrr,
-    AL [BX] MOVr[],
-    BX INCx, ( PFA )
+    AL [DI] MOVr[],
+    DI INCx, ( PFA )
     AX JMPr,

blk/815

@@ -1,14 +1,16 @@
 L4 BSET PC 3 - ORG @ 4 + ! ( find )
 ( find word the same name as str in SI starting from tip in
-  BX. Returns wordref in BX. Z if found, NZ if not. )
+  DI. Returns wordref in BX. Z if found, NZ if not. )
     CH CH XORrr, CL [SI] MOVr[], ( CX -> strlen )
-    SI INCx,
-    AX AX XORxx, ( initial prev )
-    BEGIN, ( inner )
-        BX AX SUBxx, ( jump to prev wordref )
-        BX DECx, AL [BX] MOVr[], ( strlen )
-        CL AL CMPrr, IFZ, BX INCx, RETn, THEN,
-        BX DECx, BX DECx, AX [BX] MOVx[], ( prev )
-        AX AX ORxx,
-    JNZ, AGAIN,
-    BEGIN, JMPs, AGAIN,
+    SI INCx, ( first char ) AX AX XORxx, ( initial prev )
+    BEGIN, ( loop )
+        DI AX SUBxx, ( jump to prev wordref )
+        DI DECx, AL [DI] 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,
+            REPZ, CMPSB,
+            CX POPx, DI POPx, SI POPx, ( <-- lvl 3 )
+            IFZ, DI INCx, AL AL XORrr, ( Z ) RETn, THEN,
+        THEN,
+                                                      ( cont. )

blk/816

@@ -1,6 +1,6 @@
-L3 BSET 3 A, 'F' A, 'O' A, 'O' A,
-PC 3 - ORG @ 1+ ! ( main )
-    BX 0x08 MOVxm, ( LATEST )
-    SI L3 @ MOVxi,
-    CALLn, L4 @ RPCn, ( find )
-    JMPs, L1 @ RPCs, ( execute )
+( find cont. )
+        DI DECx, DI DECx, AX [DI] MOVx[], ( prev )
+        AX AX ORxx,
+    JNZ, AGAIN, ( loop )
+    AX INCx, ( NZ ) RETn,
+

blk/817

@@ -0,0 +1,8 @@
+L3 BSET 3 A, 'F' A, 'O' A, 'O' A,
+PC 3 - ORG @ 1+ ! ( main )
+    DI 0x08 MOVxm, ( LATEST )
+    SI L3 @ MOVxi,
+    CALLn, L4 @ RPCn, ( find )
+    IFZ, JMPs, L1 @ RPCs, ( execute ) THEN,
+    AH 0x0e MOVri, ( print char ) AL '!' MOVri, 0x10 INT,
+    BEGIN, JMPs, AGAIN,

recipes/pcat/xcomp.fs

@@ -1,7 +1,7 @@
 750 LOAD  ( 8086 asm )
 262 LOAD  ( xcomp )
 270 LOAD  ( xcomp overrides )
-812 816 LOADR
+812 817 LOADR
 (entry) _
 ( Update LATEST )
 PC ORG @ 8 + !