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

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and division stuff cleanup.


git-svn-id: svn://svn.cc65.org/cc65/trunk@4431 b7a2c559-68d2-44c3-8de9-860c34a00d81
This commit is contained in:
uz 2009-11-02 22:28:02 +00:00
parent 9fa0acfefc
commit fdc7604d8f
2 changed files with 36 additions and 0 deletions
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1
libsrc/runtime/Makefile
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@ -153,6 +153,7 @@ OBJS = add.o \
mod.o \
mul.o \
mul8.o \
mul8x8r16.o \
mulax3.o \
mulax5.o \
mulax6.o \

35
libsrc/runtime/mul8x8r16.s Normal file
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@ -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