FFT Addressing

Overview

FFT addressing intrinsics .

Data pointer increment functions
v2cint32 *	fft_data_incr (v2cint32 *ptr, int range, v2cint32 *&target, umod_t &cntwrap)
	Increment the FFT data pointer.
v8cint16 *	fft_data_incr (v8cint16 *ptr, int range, v8cint16 *&target, umod_t &cntwrap)
	Increment the FFT data pointer.
v4cint16 *	fft_data_incr (v4cint16 *ptr, int range, v4cint16 *&target, umod_t &cntwrap)
	Increment the FFT data pointer.
v4cfloat *	fft_data_incr (v4cfloat *ptr, int range, v4cfloat *&target, umod_t &cntwrap)
	Increment the FFT data pointer.
v2cfloat *	fft_data_incr (v2cfloat *ptr, int range, v2cfloat *&target, umod_t &cntwrap)
	Increment the FFT data pointer.

Data pointer increment functions without cntwrap return value
v4cint32 *	fft_data_incr (v4cint32 *ptr, int range, v4cint32 *&target)
	Iterate over the FFT input values.
v2cint32 *	fft_data_incr (v2cint32 *ptr, int range, v2cint32 *&target)
	Iterate over the FFT input values.
v8cint16 *	fft_data_incr (v8cint16 *ptr, int range, v8cint16 *&target)
	Iterate over the FFT input values.
v4cint16 *	fft_data_incr (v4cint16 *ptr, int range, v4cint16 *&target)
	Iterate over the FFT input values.
v4cfloat *	fft_data_incr (v4cfloat *ptr, int range, v4cfloat *&target)
	Iterate over the FFT input values.
v2cfloat *	fft_data_incr (v2cfloat *ptr, int range, v2cfloat *&target)
	Iterate over the FFT input values.

Twiddle factor increment functions
void *	fft_twiddle_incr_inl (void *ptr, int bytes, umod_t cntwrap, int step)
	Increment the twiddle factor pointer.
#define	fft_twiddle_incr(ptr, cntwrap, step)   fft_twiddle_incr_inl((ptr), 1, (cntwrap), (step))
	Increment the twiddle factor pointer.

Macro Definition Documentation

#define fft_twiddle_incr	(		ptr,
			cntwrap,
			step
	)		fft_twiddle_incr_inl((ptr), 1, (cntwrap), (step))

Increment the twiddle factor pointer.

Parameters

[in]	cntwrap	Contains the block wrap (cntwrap[19]) and the count of previous wraps (cntwrap[2:0])
[in,out]	ptr	Pointer to the current twiddle vector.
[in]	step	Binary logarithm of the number of wraps per pointer increment. Must be a compile-time constant.

This function is called within every stage of the Stockham FFT algorithm in order to get a new set of twiddle values.

The internal logic of this function can be thought of as the following:

bool wrap = cntwrap >> 19;
bool cntzero = (cntwrap & ((1 << step) - 1)) == 0;
if(wrap && cntzero)
  ++ptw;

Function Documentation

v2cint32* fft_data_incr	(	v2cint32 *	ptr,
		int	range,
		v2cint32 *&	target,
		umod_t &	cntwrap
	)

Increment the FFT data pointer.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block
[in,out]	cntwrap	Wrap bit (cntwrap[19]) and wrap counter (cntwrap[2:0])

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

cnt = cntwrap & 0x7;
if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
  wrap    = 1;
  cnt     = (cnt+1) & 0x7;
}
else
  wrap    = 0;

cntwrap = (wrap << 19) | cnt;

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

v8cint16* fft_data_incr	(	v8cint16 *	ptr,
		int	range,
		v8cint16 *&	target,
		umod_t &	cntwrap
	)

Increment the FFT data pointer.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block
[in,out]	cntwrap	Wrap bit (cntwrap[19]) and wrap counter (cntwrap[2:0])

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

cnt = cntwrap & 0x7;
if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
  wrap    = 1;
  cnt     = (cnt+1) & 0x7;
}
else
  wrap    = 0;

cntwrap = (wrap << 19) | cnt;

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

v4cint16* fft_data_incr	(	v4cint16 *	ptr,
		int	range,
		v4cint16 *&	target,
		umod_t &	cntwrap
	)

Increment the FFT data pointer.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block
[in,out]	cntwrap	Wrap bit (cntwrap[19]) and wrap counter (cntwrap[2:0])

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

cnt = cntwrap & 0x7;
if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
  wrap    = 1;
  cnt     = (cnt+1) & 0x7;
}
else
  wrap    = 0;

cntwrap = (wrap << 19) | cnt;

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

v4cfloat* fft_data_incr	(	v4cfloat *	ptr,
		int	range,
		v4cfloat *&	target,
		umod_t &	cntwrap
	)

Increment the FFT data pointer.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block
[in,out]	cntwrap	Wrap bit (cntwrap[19]) and wrap counter (cntwrap[2:0])

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

cnt = cntwrap & 0x7;
if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
  wrap    = 1;
  cnt     = (cnt+1) & 0x7;
}
else
  wrap    = 0;

cntwrap = (wrap << 19) | cnt;

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

v2cfloat* fft_data_incr	(	v2cfloat *	ptr,
		int	range,
		v2cfloat *&	target,
		umod_t &	cntwrap
	)

Increment the FFT data pointer.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block
[in,out]	cntwrap	Wrap bit (cntwrap[19]) and wrap counter (cntwrap[2:0])

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

cnt = cntwrap & 0x7;
if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
  wrap    = 1;
  cnt     = (cnt+1) & 0x7;
}
else
  wrap    = 0;

cntwrap = (wrap << 19) | cnt;

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

v4cint32* fft_data_incr	(	v4cint32 *	ptr,
		int	range,
		v4cint32 *&	target
	)

Iterate over the FFT input values.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
}

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

See Also

fft_data_incr()

v2cint32* fft_data_incr	(	v2cint32 *	ptr,
		int	range,
		v2cint32 *&	target
	)

Iterate over the FFT input values.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
}

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

See Also

fft_data_incr()

v8cint16* fft_data_incr	(	v8cint16 *	ptr,
		int	range,
		v8cint16 *&	target
	)

Iterate over the FFT input values.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
}

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

See Also

fft_data_incr()

v4cint16* fft_data_incr	(	v4cint16 *	ptr,
		int	range,
		v4cint16 *&	target
	)

Iterate over the FFT input values.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
}

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

See Also

fft_data_incr()

v4cfloat* fft_data_incr	(	v4cfloat *	ptr,
		int	range,
		v4cfloat *&	target
	)

Iterate over the FFT input values.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
}

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

See Also

fft_data_incr()

v2cfloat* fft_data_incr	(	v2cfloat *	ptr,
		int	range,
		v2cfloat *&	target
	)

Iterate over the FFT input values.

Parameters

[in,out]	ptr	Pointer to the input vector
[in]	range	Size of the block of vectors to iterate over between jumps
[in,out]	target	Pointer to the end of the consecutive block

This function enables the iteration of the pointer that is the current target of the butterfly operation. If this pointer becomes equal to the target i.e. reaches the end of the wrap, it skips the appropriate distance (the range) and begins to iterate towards a newly assigned target. The pseudocode showing this logic can be seen below:

if(++ptr == target)
{
  ptr    += (radix-1) * range;
  target +=  radix    * range;
}

Note

The radix value must be set statically with set_rdx(). Allowed values for the radix are 2,3,4,5 and 7.

See Also

fft_data_incr()

void* fft_twiddle_incr_inl	(	void *	ptr,
		int	bytes,
		umod_t	cntwrap,
		int	step
	)

Increment the twiddle factor pointer.

Parameters

[in]	cntwrap	Contains the block wrap (cntwrap[19]) and the count of previous wraps (cntwrap[2:0])
[in,out]	ptr	Pointer to the current twiddle vector.
[in]	step	Binary logarithm of the number of wraps per pointer increment. Must be a compile-time constant.

This function is called within every stage of the Stockham FFT algorithm in order to get a new set of twiddle values.

The internal logic of this function can be thought of as the following:

bool wrap = cntwrap >> 19;
bool cntzero = (cntwrap & ((1 << step) - 1)) == 0;
if(wrap && cntzero)
  ++ptw;