sdcc-3.9.0 fork implementing GNU assembler syntax

This fork aims to provide better support for stm8-binutils

1 files changed, 143 insertions, 0 deletions

diff --git a/device/lib/z80/divunsigned.s b/device/lib/z80/divunsigned.s
new file mode 100644
index 0000000..15f209a
--- /dev/null
+++ b/device/lib/z80/divunsigned.s
@@ -0,0 +1,143 @@
+;--------------------------------------------------------------------------
+;  divunsigned.s
+;
+;  Copyright (C) 2000-2012, Michael Hope, Philipp Klaus Krause, Marco Bodrato
+;
+;  This library is free software; you can redistribute it and/or modify it
+;  under the terms of the GNU General Public License as published by the
+;  Free Software Foundation; either version 2, or (at your option) any
+;  later version.
+;
+;  This library is distributed in the hope that it will be useful,
+;  but WITHOUT ANY WARRANTY; without even the implied warranty of
+;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;  GNU General Public License for more details.
+;
+;  You should have received a copy of the GNU General Public License 
+;  along with this library; see the file COPYING. If not, write to the
+;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
+;   MA 02110-1301, USA.
+;
+;  As a special exception, if you link this library with other files,
+;  some of which are compiled with SDCC, to produce an executable,
+;  this library does not by itself cause the resulting executable to
+;  be covered by the GNU General Public License. This exception does
+;  not however invalidate any other reasons why the executable file
+;   might be covered by the GNU General Public License.
+;--------------------------------------------------------------------------
+
+        ;; Originally from GBDK by Pascal Felber.
+
+.area   _CODE
+
+.globl	__divuint
+.globl	__divuchar
+
+__divuint:
+        pop     af
+        pop     hl
+        pop     de
+        push    de
+        push    hl
+        push    af
+
+        jr      __divu16
+
+__divuchar:
+        ld      hl,#2+1
+        add     hl,sp
+
+        ld      e,(hl)
+        dec     hl
+        ld      l,(hl)
+
+        ;; Fall through
+__divu8::
+        ld      h,#0x00
+        ld      d,h
+        ; Fall through to __divu16
+
+        ;; unsigned 16-bit division
+        ;;
+        ;; Entry conditions
+        ;;   HL = dividend
+        ;;   DE = divisor
+        ;;
+        ;; Exit conditions
+        ;;   HL = quotient
+        ;;   DE = remainder
+        ;;   carry = 0
+        ;;   If divisor is 0, quotient is set to "infinity", i.e HL = 0xFFFF.
+        ;;
+        ;; Register used: AF,B,DE,HL
+__divu16::
+        ;; Two algorithms: one assumes divisor <2^7, the second
+        ;; assumes divisor >=2^7; choose the applicable one.
+        ld      a,e
+        and     a,#0x80
+        or      a,d
+        jr      NZ,.morethan7bits
+        ;; Both algorithms "rotate" 24 bits (H,L,A) but roles change.
+
+        ;; unsigned 16/7-bit division
+.atmost7bits:
+        ld      b,#16           ; bits in dividend and possible quotient
+        ;; Carry cleared by AND/OR, this "0" bit will pass trough HL.[*]
+        adc     hl,hl
+.dvloop7:
+        ;; HL holds both dividend and quotient. While we shift a bit from
+        ;;  MSB of dividend, we shift next bit of quotient in from carry.
+        ;; A holds remainder.
+        rla
+
+        ;; If remainder is >= divisor, next bit of quotient is 1.  We try
+        ;;  to compute the difference.
+        sub     a,e
+        jr      NC,.nodrop7     ; Jump if remainder is >= dividend
+        add     a,e             ; Otherwise, restore remainder
+        ;; The add above sets the carry, because sbc a,e did set it.
+.nodrop7:
+        ccf                     ; Complement borrow so 1 indicates a
+                                ;  successful substraction (this is the
+                                ;  next bit of quotient)
+        adc     hl,hl
+        djnz    .dvloop7
+        ;; Carry now contains the same value it contained before
+        ;; entering .dvloop7[*]: "0" = valid result.
+        ld      e,a             ; DE = remainder, HL = quotient
+        ret
+
+.morethan7bits:
+        ld      b,#9            ; at most 9 bits in quotient.
+        ld      a,l             ; precompute the first 7 shifts, by
+        ld      l,h             ;  doing 8
+        ld      h,#0
+        rr      l               ;  undoing 1
+.dvloop:
+        ;; Shift next bit of quotient into bit 0 of dividend
+        ;; Shift next MSB of dividend into LSB of remainder
+        ;; A holds both dividend and quotient. While we shift a bit from
+        ;;  MSB of dividend, we shift next bit of quotient in from carry
+        ;; HL holds remainder
+        adc     hl,hl           ; HL < 2^(7+9), no carry, ever.
+
+        ;; If remainder is >= divisor, next bit of quotient is 1. We try
+        ;;  to compute the difference.
+        sbc     hl,de
+        jr      NC,.nodrop      ; Jump if remainder is >= dividend
+        add     hl,de           ; Otherwise, restore remainder
+	;; The add above sets the carry, because sbc hl,de did set it.
+.nodrop:
+        ccf                     ; Complement borrow so 1 indicates a
+                                ;  successful substraction (this is the
+                                ;  next bit of quotient)
+        rla
+        djnz    .dvloop
+        ;; Take care of the ninth quotient bit! after the loop B=0.
+        rl      b               ; BA = quotient
+        ;; Carry now contains "0" = valid result.
+        ld      d,b
+        ld      e,a             ; DE = quotient, HL = remainder
+        ex      de,hl           ; HL = quotient, DE = remainder
+        ret
+