Implemented RFE #1914256

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

diff --git a/device/lib/z80/memmove.s b/device/lib/z80/memmove.s
new file mode 100644 (file)
index 0000000..55462ef
--- /dev/null
+++ b/device/lib/z80/memmove.s
@@ -0,0 +1,44 @@
+        .area   _CODE
+
+       .globl _memmove
+
+; The Z80 has the ldir and lddr instructions, which are perfect for implementing memmove().
+
+_memmove:
+       push    ix
+       ld      ix,#0
+       add     ix,sp
+       ld      c, 8(ix)
+       ld      b, 9(ix)
+       ld      a, c
+       or      a, b
+       jr      Z, memmove_end
+       ld      e, 4(ix)
+       ld      d, 5(ix)
+       ld      l, 6(ix)
+       ld      h, 7(ix)
+       ld      a, l
+       sbc     hl, de  ; or above cleared carry.
+       ld      l, a
+       ld      h, 7(ix)
+       jr      NC, memmove_up
+memmove_down:
+       add     hl, bc
+       dec     hl
+       ld      a, e
+       add     a, c
+       ld      e, a
+       ld      a, d
+       adc     a, b
+       ld      d, a
+       dec     de
+       lddr
+       jr      memmove_end
+memmove_up:
+       ldir
+memmove_end:
+       ld      l, 4(ix)
+       ld      h, 5(ix)
+       pop     ix
+       ret
+