1@***********************************************************
2@ Function:    SynthMasterGain
3@ Processor:   ARM-E
4@ Description: Copies 32-bit synth output to 16-bit buffer
5@              with saturated gain control
6@              C-callable.
7@
8@ Usage:
9@	SynthMasterGain(
10@			pInputBuffer
11@			pOutputBuffer,
12@			nGain,
13@			nNumLoopSamples
14@	);
15@
16@ Copyright Sonic Network Inc. 2004
17@****************************************************************
18@ Revision Control:
19@   $Revision: 496 $
20@   $Date: 2006-12-11 14:33:26 -0800 (Mon, 11 Dec 2006) $
21@****************************************************************
22@
23@   where:
24@	long *pInputBuffer
25@	PASSED IN: r0
26@
27@	EAS_PCM *pOutputBuffer
28@	PASSED IN: r1
29@
30@	short nGain
31@	PASSED IN: r2
32@
33@	EAS_U16	nNumLoopSamples
34@	PASSED IN: r3
35@
36@****************************************************************
37
38	#include	"ARM_synth_constants_gnu.inc"
39
40	.arm
41	.text
42
43SynthMasterGain:
44
45	.global	SynthMasterGain	@ allow other files to use this function
46
47
48
49
50
51@ Stack frame
52@ -----------
53	.equ	RET_ADDR_SZ, 0			@return address
54	.equ	REG_SAVE_SZ, 0			@save-on-entry registers saved
55	.equ	FRAME_SZ, (8)			@local variables
56	.equ	ARG_BLK_SZ, 0			@argument block
57
58	.equ	PARAM_OFFSET, (ARG_BLK_SZ + FRAME_SZ + REG_SAVE_SZ + RET_ADDR_SZ)
59
60@ Register usage
61@ --------------
62pnInputBuffer	.req	r0
63pnOutputBuffer	.req	r1
64nGain	.req	r2
65nNumLoopSamples	.req	r3
66
67	STMFD	sp!,{r4-r6,r14}					@Save any save-on-entry registers that are used
68
69	LDR		r6, =0x7fff						@constant for saturation tests
70
71loop:
72	LDR		r4, [pnInputBuffer], #4			@fetch 1st output sample
73
74	LDR		r5, [pnInputBuffer], #4			@fetch 2nd output sample
75
76	SMULWB	r4, r4, nGain					@output = gain * input
77
78	CMP		r4, r6							@check for positive saturation
79	MOVGT	r4, r6							@saturate
80	CMN		r4, r6							@check for negative saturation
81	MVNLT	r4, r6							@saturate
82
83	SMULWB	r5, r5, nGain					@output = gain * input
84
85	STRH	r4, [pnOutputBuffer], #NEXT_OUTPUT_PCM	@save 1st output sample
86
87	CMP		r5, r6							@check for positive saturation
88	MOVGT	r5, r6							@saturate
89	CMN		r5, r6							@check for negative saturation
90	MVNLT	r5, r6							@saturate
91	STRH	r5, [pnOutputBuffer], #NEXT_OUTPUT_PCM	@save 2nd output sample
92
93	SUBS	nNumLoopSamples, nNumLoopSamples, #2
94	BGT		loop
95
96@
97@ Return to calling function
98@----------------------------------------------------------------
99
100	LDMFD	sp!,{r4-r6, lr}				@ return to calling function
101	BX		lr
102
103@*****************************************************************************
104
105	.end		@ end of assembly code
106
107