[Reduction] #467: Far long multiplication

Yeah, the code is identical to the near version, with the only difference
being the PROC directive declaring the function as either near or far. Now, I
could either turn the function body into some kind of macro stored in a
separate file and then instantiate it from both near and far functions... or I
could just copy the original structure. Who cares, anyway.

libs/BorlandC/f_lxmul.asm

@@ -0,0 +1,62 @@
+; *Not* the original file, but an edit to turn it into an includable slice.
+; Changes include:
+; * removal of RULES.ASI to eliminate redundancy
+; * removal of the 'CODE' segment declaration (for obvious reasons)
+; * the @@ prefix on any local labels
+
+;[]-----------------------------------------------------------------[]
+;|      F_LXMUL.ASM -- long multiply routine                         |
+;[]-----------------------------------------------------------------[]
+
+;
+;       C/C++ Run Time Library - Version 5.0
+; 
+;       Copyright (c) 1987, 1992 by Borland International
+;       All Rights Reserved.
+; 
+; calls to this routine are generated by the compiler to perform
+; long multiplications.
+
+; There is no check for overflow.  Consequently, the same routine
+; is used for both signed and unsigned long multiplies.
+
+;
+; in:
+;       (dx:ax) - 32bit arg1
+;       (cx:bx) - 32bit arg2
+; out:
+;       (dx:ax) - 32bit product
+;
+; reg use: bx,cx destroyed, all others preserved or contain result.
+;
+; hi(result) := lo(hi(arg1) * lo(arg2)) +
+;               lo(hi(arg2) * lo(arg1)) +
+;               hi(lo(arg1) * lo(arg2))
+; lo(result) := lo(lo(arg1) * lo(arg2))
+;
+;
+
+        public  LXMUL@
+        public  F_LXMUL@
+
+LXMUL@          PROC    FAR
+F_LXMUL@:
+                push    si
+                xchg    si,ax           ; save lo1
+                xchg    ax,dx
+                test    ax,ax           ; skip mul if hi1==0
+                jz      @@nohi1
+                mul     bx              ; hi1 * lo2
+
+@@nohi1:        ; if we jumped here, ax==0 so the following swap works
+                jcxz    @@nohi2         ; skip mul if hi2==0
+                xchg    cx, ax          ; result <-> hi2
+                mul     si              ; lo1 * hi2
+                add     ax, cx          ; ax = hi1*lo2 + hi2*lo1
+@@nohi2:
+                xchg    ax,si
+                mul     bx              ; lo1 * lo2
+                add     dx,si           ; hi order result += partials
+                pop     si
+                ret
+LXMUL@          ENDP

th01_fuuin.asm

@@ -3465,33 +3465,7 @@ __dos_setfileattr endp
 include libs/BorlandC/dosgdriv.asm
 include libs/BorlandC/errormsg.asm
 include libs/BorlandC/exit.asm
-
-; =============== S U B	R O U T	I N E =======================================
-
-; Attributes: library function
-
-LXMUL@		proc far
-		push	si
-		xchg	ax, si
-		xchg	ax, dx
-		test	ax, ax
-		jz	short loc_1F0F
-		mul	bx
-
-loc_1F0F:
-		jcxz	short loc_1F16
-		xchg	ax, cx
-		mul	si
-		add	ax, cx
-
-loc_1F16:
-		xchg	ax, si
-		mul	bx
-		add	dx, si
-		pop	si
-		retf
-LXMUL@		endp
-
+include libs/BorlandC/f_lxmul.asm
 include libs/BorlandC/f_scopy.asm
 include libs/BorlandC/getvect.asm
 include libs/BorlandC/H_LDIV.ASM

th01_reiiden.asm

@@ -4933,33 +4933,7 @@ __dos_setfileattr endp
 include libs/BorlandC/dosgdriv.asm
 include libs/BorlandC/errormsg.asm
 include libs/BorlandC/exit.asm
-
-; =============== S U B	R O U T	I N E =======================================
-
-; Attributes: library function
-
-LXMUL@		proc far
-		push	si
-		xchg	ax, si
-		xchg	ax, dx
-		test	ax, ax
-		jz	short loc_2749
-		mul	bx
-
-loc_2749:
-		jcxz	short loc_2750
-		xchg	ax, cx
-		mul	si
-		add	ax, cx
-
-loc_2750:
-		xchg	ax, si
-		mul	bx
-		add	dx, si
-		pop	si
-		retf
-LXMUL@		endp
-
+include libs/BorlandC/f_lxmul.asm
 include libs/BorlandC/f_scopy.asm
 include libs/BorlandC/getvect.asm
 include libs/BorlandC/H_LDIV.ASM

th02_op.asm

@@ -695,33 +695,7 @@ include libs/BorlandC/dosenv.asm
 include libs/BorlandC/dosgdriv.asm
 include libs/BorlandC/errormsg.asm
 include libs/BorlandC/exit.asm
-
-; =============== S U B	R O U T	I N E =======================================
-
-; Attributes: library function
-
-LXMUL@		proc far
-		push	si
-		xchg	ax, si
-		xchg	ax, dx
-		test	ax, ax
-		jz	short loc_366B
-		mul	bx
-
-loc_366B:
-		jcxz	short loc_3672
-		xchg	ax, cx
-		mul	si
-		add	ax, cx
-
-loc_3672:
-		xchg	ax, si
-		mul	bx
-		add	dx, si
-		pop	si
-		retf
-LXMUL@		endp
-
+include libs/BorlandC/f_lxmul.asm
 include libs/BorlandC/f_scopy.asm
 include libs/BorlandC/getvect.asm
 include libs/BorlandC/H_LDIV.ASM