annotate core/FormatConvert.S @ 511:633ade85e798 prerelease

Cleared build_pd_heavy

@
@ FormatConvert.S
@
@ NEON-based vector functions for converting data between int
@ and float with clipping and optional level scaling. 
@ Written in assembly for performance reasons.
@
@ Bela: http://bela.io
@
@ (c) 2016 Andrew McPherson
@ Centre for Digital Music
@ Queen Mary University of London
@

	.syntax unified
	.arch armv7-a
	.fpu neon

@	void int16_to_float_audio(int numSamples, int16_t *inBuffer, float *outBuffer);
@
@	Convert 16-bit signed ints to floats between -1.0 and 1.0. Used for audio input.
@
@	numSamples should be a multiple of 4 (i.e. with stereo audio, frames should be even)
@	inBuffer should be aligned on an 8-byte boundary.
@ 	outBuffer should be aligned on a 16-byte boundary.

@ Registers:
@    r0: numSamples            How many frames to convert
@    r1: inBuffer              Buffer for input samples from ADC
@    r2: outBuffer             Buffer to store output samples for render function

dIFAu_Input		.dn		D0.S16
qIFAu_Expanded	.qn		Q1.S32
qIFAu_Output	.qn		Q2.F32
dIFAu_Output_0	.dn		D4.F32
dIFAu_Output_1	.dn		D5.F32

	.align	2
	.global	int16_to_float_audio
	.thumb
	.thumb_func
	.type	int16_to_float_audio, %function
int16_to_float_audio:
	lsr r0, r0, #2
	lsl r0, r0, #2				@ Clip off the last two bits of numSamples (only multiples of 4 allowed)
	cmp r0, #0					@ Check for trivial case: zero samples
	it eq
	bxeq lr						@ Return if that's the case

	@ ---- loop: iterate over the number of samples ----
int16_to_float_audio_loop:
	vld1 {dIFAu_Input}, [r1]!						@ Load four 16-bit signed ints from inBuffer++
	vmovl qIFAu_Expanded, dIFAu_Input				@ Convert four 16-bit signed ints to 32-bit signed ints
	vcvt qIFAu_Output, qIFAu_Expanded, #15			@ Convert four Q17.15 fixed points to floats (equiv. to / 32768)
	vst1 {dIFAu_Output_0, dIFAu_Output_1}, [r2]!	@ Store floats back into memory

	subs r0, r0, #4							@ numSamples -= 4
	it gt
	bgt int16_to_float_audio_loop			@ Loop if numSamples > 0

	bx lr
	


@	void int16_to_float_analog(int numSamples, uint16_t *inBuffer, float *outBuffer);
@
@	Convert 16-bit unsigned ints to floats between 0.0 and 1.0. Used for analog input.
@
@	numSamples should be a multiple of 4 (i.e. integer numFrames at 4 channels)
@	inBuffer should be aligned on an 8-byte boundary.
@ 	outBuffer should be aligned on a 16-byte boundary.

@ Registers:
@    r0: numSamples            How many frames to convert
@    r1: inBuffer              Buffer for input samples from ADC
@    r2: outBuffer             Buffer to store output samples for render function

dIFAn_Input		.dn		D0.U16
qIFAn_Expanded	.qn		Q1.U32
qIFAn_Output	.qn		Q2.F32
dIFAn_Output_0	.dn		D4.F32
dIFAn_Output_1	.dn		D5.F32

	.align	2
	.global	int16_to_float_analog
	.thumb
	.thumb_func
	.type	int16_to_float_analog, %function
int16_to_float_analog:
	lsr r0, r0, #2
	lsl r0, r0, #2				@ Clip off the last two bits of numSamples (only multiples of 4 allowed)
	cmp r0, #0					@ Check for trivial case: zero samples
	it eq
	bxeq lr						@ Return if that's the case

	@ ---- loop: iterate over the number of samples ----
int16_to_float_analog_loop:
	vld1 {dIFAn_Input}, [r1]!						@ Load four 16-bit signed ints from inBuffer++
	vmovl qIFAn_Expanded, dIFAn_Input				@ Convert four 16-bit signed ints to 32-bit signed ints
	vcvt qIFAn_Output, qIFAn_Expanded, #16			@ Convert four Q16.16 fixed points to floats (equiv. to / 65536)
	vst1 {dIFAn_Output_0, dIFAn_Output_1}, [r2]!	@ Store floats back into memory

	subs r0, r0, #4							@ numSamples -= 4
	it gt
	bgt int16_to_float_analog_loop			@ Loop if numSamples > 0

	bx lr
	

@	void float_to_int16_audio(int numSamples, float *inBuffer, int16_t *outBuffer);
@
@	Convert floats between -1.0 and 1.0 to 16-bit signed ints, with saturation.
@	Used for audio output.
@
@	numSamples should be a multiple of 4 (i.e. with stereo audio, frames should be even)
@	inBuffer should be aligned on a 16-byte boundary.
@ 	outBuffer should be aligned on an 8-byte boundary.

@ Registers:
@    r0: numSamples            How many frames to convert
@    r1: inBuffer              Buffer for input samples from render function
@    r2: outBuffer             Buffer to store output samples for DAC

qFIAu_Input		.qn		Q0.F32
dFIAu_Input_0	.dn		D0.F32
dFIAu_Input_1,	.dn		D1.F32
qFIAu_Converted	.qn		Q1.S32
dFIAu_Narrowed	.dn		D4.S16	

	.align	2
	.global	float_to_int16_audio
	.thumb
	.thumb_func
	.type	float_to_int16_audio, %function
	
float_to_int16_audio:
	lsr r0, r0, #2
	lsl r0, r0, #2				@ Clip off the last two bits of numSamples (only multiples of 4 allowed)
	cmp r0, #0					@ Check for trivial case: zero samples
	it eq
	bxeq lr						@ Return if that's the case

	@ ---- loop: iterate over the number of samples ----
float_to_int16_audio_loop:
	vld1 {dFIAu_Input_0, dFIAu_Input_1}, [r1]!		@ Load four floats from inBuffer++
	vcvt qFIAu_Converted, qFIAu_Input, #15			@ Convert four floats into four Q17.15 fixed points (equiv. to * 32768)
													@ This will truncate the result to a 32-bit representable value
	vqmovn dFIAu_Narrowed, qFIAu_Converted			@ Convert four 32-bit signed ints to 16-bit signed ints, with saturation
	vst1 {dFIAu_Narrowed}, [r2]!					@ Store ints back into memory

	subs r0, r0, #4							@ numSamples -= 4
	it gt
	bgt float_to_int16_audio_loop			@ Loop if numSamples > 0

	bx lr
	

@	void float_to_int16_analog(int numSamples, float *inBuffer, uint16_t *outBuffer);
@
@	Convert floats between 0.0 and 1.0 to 16-bit unsigned ints, with saturation.
@	Used for analog output.
@
@	numSamples should be a multiple of 4 (i.e. with stereo audio, frames should be even)
@	inBuffer should be aligned on a 16-byte boundary.
@ 	outBuffer should be aligned on an 8-byte boundary.

@ Registers:
@    r0: numSamples            How many frames to convert
@    r1: inBuffer              Buffer for input samples from render function
@    r2: outBuffer             Buffer to store output samples for DAC

qFIAn_Input		.qn		Q0.F32
dFIAn_Input_0	.dn		D0.F32
dFIAn_Input_1,	.dn		D1.F32
qFIAn_Converted	.qn		Q1.U32
dFIAn_Narrowed	.dn		D4.U16	

	.align	2
	.global	float_to_int16_analog
	.thumb
	.thumb_func
	.type	float_to_int16_analog, %function
	
float_to_int16_analog:
	lsr r0, r0, #2
	lsl r0, r0, #2				@ Clip off the last two bits of numSamples (only multiples of 4 allowed)
	cmp r0, #0					@ Check for trivial case: zero samples
	it eq
	bxeq lr						@ Return if that's the case

	@ ---- loop: iterate over the number of samples ----
float_to_int16_analog_loop:
	vld1 {dFIAn_Input_0, dFIAn_Input_1}, [r1]!		@ Load four floats from inBuffer++
	vcvt qFIAn_Converted, qFIAn_Input, #16			@ Convert four floats into four Q16.16 fixed points (equiv. to * 65536)
													@ This will truncate the result to a 32-bit representable value
	vqmovn dFIAn_Narrowed, qFIAn_Converted			@ Convert four 32-bit unsigned ints to 16-bit unsigned ints, with saturation
	vst1 {dFIAn_Narrowed}, [r2]!					@ Store ints back into memory

	subs r0, r0, #4							@ numSamples -= 4
	it gt
	bgt float_to_int16_analog_loop			@ Loop if numSamples > 0

	bx lr