Optimised mul, added asm string functions

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

diff --git a/device/lib/z80/mul.s b/device/lib/z80/mul.s
index 4f3e793a2f912db9bfe768f94f640af0d4e3cdf3..7e7cceff85001301ab272b02ff75d16de2300ca8 100644 (file)
--- a/device/lib/z80/mul.s
+++ b/device/lib/z80/mul.s
@@ -79,25 +79,26 @@ __muluint_rrx_hds::
        ;; 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
-       ret
+        ld      hl,#0
+        ld      a,b
+        ; ld c,c
+        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.
+        or      a
+        jp      nz,1$
+        
+        ld      b,#8
+        ld      a,c
+1$:
+        ;; Taken from z88dk, which originally borrowed from the
+        ;; Spectrum rom.
+        add     hl,hl
+        rl      c
+        rla                     ;DLE 27/11/98
+        jr      nc,2$
+        add     hl,de
+2$:     
+        djnz    1$
+        ret