Applied patch #2762516

[fw/sdcc] / device / lib / z80 / mul.s

diff --git a/device/lib/z80/mul.s b/device/lib/z80/mul.s
index 9c33ac30aa4054d95e9c6db7958b1a43198630fb..e81ac80040b958cb5be49d3e9b458f748d5900d7 100644 (file)
--- a/device/lib/z80/mul.s
+++ b/device/lib/z80/mul.s
@@ -1,66 +1,53 @@
-       ;; Originally from GBDK by Pascal Felber.
-       
-       .area   _CODE
-       
-__mulschar::
-        ;; Need to sign extend before going in.
-        push    bc
-        ld      c,l
-        
-        ld      a,l
-        rla
-        sbc     a,a
-        ld      b,a
+        .area   _CODE
 
-        ld      a,e
-        rla
-        sbc     a,a
-        ld      d,a
+__mulint_rrx_s::
+        pop     af
+        pop     hl
+        pop     de
+        push    de
+        push    hl
+        push    af
 
-        jp      .mul16
+        ;; Fall through
 
-__muluchar::
-__mulsint::
-__muluint::
+__muluchar_rrx_hds::
+__mulint_rrx_hds::
        ;; Parameters:
-       ;;      HL, DE (left, right irrelivent)
-       ;; Must preserve BC
-       push    bc
+       ;;      hl, de (left, right irrelevant)
        ld      b,h
        ld      c,l
-       
+
        ;; 16-bit multiplication
-       ;; 
+       ;;
        ;; Entry conditions
-       ;;   BC = multiplicand
-       ;;   DE = multiplier
-       ;; 
+       ;; bc = multiplicand
+       ;; de = multiplier
+       ;;
        ;; Exit conditions
-       ;;   DE = less significant word of product
+       ;; hl = less significant word of product
        ;;
        ;; Register used: AF,BC,DE,HL
-.mul16:
-.mulu16:
-       LD      HL,#0x00        ; Product = 0
-       LD      A,#15           ; Count = bit length - 1
-       ;; Shift-and-add algorithm
-       ;; If MSB of multiplier is 1, add multiplicand to partial product
-       ;; Shift partial product, multiplier left 1 bit
-.mlp:
-       SLA     E               ; Shift multiplier left 1 bit
-       RL      D
-       jp      NC,.mlp1        ; Jump if MSB of multiplier = 0
-       ADD     HL,BC           ; Add multiplicand to partial product
-.mlp1:
-       ADD     HL,HL           ; Shift partial product left
-       DEC     A
-       jp      NZ,.mlp         ; Continue until count = 0
-       ;; Add multiplicand one last time if MSB of multiplier is 1
-       BIT     7,D             ; Get MSB of multiplier
-       JR      Z,.mend         ; Exit if MSB of multiplier is 0
-       ADD     HL,BC           ; Add multiplicand to product
-.mend:
-                               ; HL = result
-       pop     bc
-       ret
+__mul16::
+       xor     a,a
+       ld      l,a
+       or      a,b
+       ld      b,#16
+
+        ;; Optimise for the case when this side has 8 bits of data or
+        ;; less.  This is often the case with support address calls.
+        jr      NZ,2$
+        ld      b,#8
+        ld      a,c
+1$:
+        ;; Taken from z88dk, which originally borrowed from the
+        ;; Spectrum rom.
+        add     hl,hl
+2$:
+        rl      c
+        rla                     ;DLE 27/11/98
+        jr      NC,3$
+        add     hl,de
+3$:
+        djnz    1$
+        ret