Added separate 8x8=>16 multiplication routine as start of the multiplication

and division stuff cleanup.

git-svn-id: svn://svn.cc65.org/cc65/trunk@4431 b7a2c559-68d2-44c3-8de9-860c34a00d81

diff --git a/libsrc/runtime/Makefile b/libsrc/runtime/Makefile
index 19cda62daf8ed994c53af0b8761358a61caa9318..34052761cc77fcf3749de210b10d351b82c4108b 100644 (file)
--- a/libsrc/runtime/Makefile
+++ b/libsrc/runtime/Makefile
@@ -153,6 +153,7 @@ OBJS =      add.o           \
                mod.o           \
                mul.o           \
         mul8.o          \
+        mul8x8r16.o     \
        mulax3.o        \
        mulax5.o        \
        mulax6.o        \

diff --git a/libsrc/runtime/mul8x8r16.s b/libsrc/runtime/mul8x8r16.s
new file mode 100644 (file)
index 0000000..b1e679f
--- /dev/null
+++ b/libsrc/runtime/mul8x8r16.s
@@ -0,0 +1,35 @@
+;
+; Ullrich von Bassewitz, 2010-11-02
+;
+; CC65 runtime: 8x8 => 16 multiplication
+;
+
+               .export         mul8x8r16, umul8x8r16
+       .importzp       ptr1, ptr3
+
+
+;---------------------------------------------------------------------------
+; 8x8 => 16 multiplication routine.
+;
+;   lhs         rhs           result          result also in
+; -------------------------------------------------------------
+;   ptr1-lo     ptr3-lo         a/x             ptr1
+;
+
+mul8x8r16:
+umul8x8r16:
+       lda     #0              ; Clear byte 1
+               ldy     #8              ; Number of bits
+        lsr     ptr1            ; Get first bit of lhs into carry
+@L0:    bcc     @L1
+        clc
+        adc     ptr3
+@L1:    ror
+        ror     ptr1
+        dey
+        bne     @L0
+        tax         
+        stx     ptr1+1          ; Result in a/x and ptr1
+       lda     ptr1            ; Load the result
+       rts                     ; Done
+