math64.s

来自「symbian 下的helix player源代码」· S 代码 · 共 114 行

; ***** BEGIN LICENSE BLOCK *****
; Source last modified: $Id: math64.s,v 1.2.46.1 2004/07/09 02:00:51 hubbe Exp $
; 
; * Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved.
; 
; The contents of this file, and the files included with this file,
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; Source License (the "RPSL") available at
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; the file under the current version of the RealNetworks Community
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; will apply. You may also obtain the license terms directly from
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; This file is part of the Helix DNA Technology. RealNetworks is the
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; ***** END LICENSE BLOCK *****

;/* assembly.s
; * 
; * the assembly routines are written in this separate .s file because EVC++ won't inline...
; *
; * Notes on APCS (ARM procedure call standard):
; *  - first four arguments are in r0-r3
; *  - additional argumets are pushed onto stack in reverse order
; *  - return value goes in r0
; *  - routines can overwrite r0-r3, r12 without saving
; *  - other registers must be preserved with stm/ldm commands
; * 
; * Equivalent register names:
; *
; * r0  r1  r2  r3  r4  r5  r6  r7  r8  r9  r10 r11 r12 r13 r14 r15
; * ---------------------------------------------------------------
; * a1  a2  a3  a4  v1  v2  v3  v4  v5  v6  sl  fp  ip  sp  lr  pc
; */

	INCLUDE kxarm.h
	TEXTAREA

; int MULSHIFT32(int x, int y)
	LEAF_ENTRY MulShift32

	smull r2,r0,r1,r0
	mov   pc, lr			

	ENTRY_END MulShift32

; int MulShift31(int x, int y)
	LEAF_ENTRY MulShift31

	smull r2,r0,r1,r0
	mov   r2,r2,lsr #31
	orr   r0,r2,r0,lsl #1

	mov   pc, lr			

	ENTRY_END MulShift31

; int MULSHIFT30(int x, int y)
	LEAF_ENTRY MulShift30

	smull r2,r0,r1,r0
	mov   r2,r2,lsr #30
	orr   r0,r2,r0,lsl #2

	mov   pc, lr			

	ENTRY_END MulShift30

; int MulShiftN(int x, int y, int n)
	LEAF_ENTRY MulShiftN

	smull r3,r0,r1,r0  ; r0 hi, h3 lo
	mov   r3,r3,lsr r2 ; shift lo right by r2 
	rsb   r2,r2,#32
	orr   r0,r3,r0,lsl r2 ; shift hi left by 32-r2, and or in

	mov   pc, lr			

	ENTRY_END MulShiftN

	END