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Changes due to code review.

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IrgendwerA8
2019-03-21 20:43:07 +01:00
committed by Oliver Schmidt
parent 399250a105
commit db8bd84a82
12 changed files with 39 additions and 40 deletions
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libsrc/common/_mul20.s
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; mul20.s
;
; This file is part of
; cc65 - a freeware C compiler for 6502 based systems
;
; https://github.com/cc65/cc65
;
; See "LICENSE" file for legal information.
;
;
; unsigned int __fastcall__ _mul20(unsigned char value);
;
; REMARKS: Function is defined to return with carry-flag cleared
.importzp tmp4
.export __mul20
.proc __mul20 ; = 30 bytes, 41/46 cycles
sta tmp4 ; remember value for later addition...
ldx #0 ; clear high-byte
asl a ; * 2
bcc mul4 ; high-byte affected?
ldx #2 ; this will be the 1st high-bit soon...
mul4: asl a ; * 4
bcc mul5 ; high-byte affected?
inx ; => yes, apply to 0 high-bit
clc ; prepare addition
mul5: adc tmp4 ; * 5
bcc mul10 ; high-byte affected?
inx ; yes, correct...
mul10: stx tmp4 ; continue with classic shifting...
asl a ; * 10
rol tmp4
asl a ; * 20
rol tmp4
ldx tmp4 ; deliver high-byte in X
rts
.endproc
libsrc/common/_mul40.s
+50
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; mul40.s
;
; This file is part of
; cc65 - a freeware C compiler for 6502 based systems
;
; https://github.com/cc65/cc65
;
; See "LICENSE" file for legal information.
;
;
; unsigned int __fastcall__ _mul40(unsigned char value);
;
; REMARKS: Function is defined to return with carry-flag cleared
.importzp tmp4
.export __mul40
.proc __mul40 ; = 33 bytes, 48/53 cycles
sta tmp4 ; remember value for later addition...
ldx #0 ; clear high-byte
asl a ; * 2
bcc mul4 ; high-byte affected?
ldx #2 ; this will be the 1st high-bit soon...
mul4: asl a ; * 4
bcc mul5 ; high-byte affected?
inx ; => yes, apply to 0 high-bit
clc ; prepare addition
mul5: adc tmp4 ; * 5
bcc mul10 ; high-byte affected?
inx ; yes, correct...
mul10: stx tmp4 ; continue with classic shifting...
asl a ; * 10
rol tmp4
asl a ; * 20
rol tmp4
asl a ; * 40
rol tmp4
ldx tmp4 ; deliver high-byte in X
rts
.endproc