Loop unrolling functions

Overview

These functions allow users to explicitly unroll the body of a loop.

The simplest way to use them is to provide a lambda expression with the loop body. For example:

aie::vector<int, 16> a;
aie::unroll_for<int, 0, 16>([](int i) __aie_inline {
   a.push(i);
});

It is recommended that any functions or function-like objects used are marked with the always_inline attribute. There are different ways you can specify this:

1. Preprocessor macro: __aie_inline
2. GNU attribute syntax: __attribute__((always_inline))
3. C++11 attribute syntax: the attribute is not C++ standard but it is supported in most common compilers: [[gnu::always_inline]], [[clang::always_inline]].

References:

• https://clang.llvm.org/docs/AttributeReference.html#always-inline-force-inline
• https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute

Functions
template<typename T , T Start, T End, T Step = 1, typename Fn >
void	aie::unroll_for (Fn &&fn)
	Invokes a function object as many times as specified by a linear index sequence.
template<typename T , T StartY, T EndY, T StepY, T StartX, T EndX, T StepX, typename Fn >
void	aie::unroll_for_2d (Fn &&fn)
	Invokes a function object as many times as defined by a 2D index sequence.
template<unsigned Times, typename Fn >
void	aie::unroll_times (Fn &&fn)
	Invokes a function object a given number of times.
template<unsigned TimesY, unsigned TimesX, typename Fn >
void	aie::unroll_times_2d (Fn &&fn)
	Invokes a function object as many times as defined by a 2D index sequence.

Function Documentation

unroll_for()

template<typename T , T Start, T End, T Step = 1, typename Fn >

void aie::unroll_for

(

Fn &&

fn

)

Invokes a function object as many times as specified by a linear index sequence.

Template Parameters

T	Type of the sequence values passed to the function.
Start	First value in the sequence.
End	Upper limit of the sequence.
Step	Distance between two consecutive values in the sequence.

Parameters

fn	A function object that takes a sequence value by argument. The signature of the function should be equivalent to one of the following: void fun(const Type &i); void fun(); The signature does not need to have const & and the type Type must be either T or implicitly convertible from T.

unroll_for_2d()

template<typename T , T StartY, T EndY, T StepY, T StartX, T EndX, T StepX, typename Fn >

void aie::unroll_for_2d

(

Fn &&

fn

)

Invokes a function object as many times as defined by a 2D index sequence.

Template Parameters

T	Type of the sequence values passed to the function.
StartY	First value in the sequence (y-axis).
EndY	Upper limit of the sequence(y-axis).
StepY	Distance between two consecutive values in the sequence (y-axis).
StartX	First value in the sequence (x-axis).
EndX	Upper limit of the sequence (x-axis).
StepX	Distance between two consecutive values in the sequence (x-axis).

Parameters

fn

A function object that takes two values of type T by argument, one per dimension. The signature of the function should be equivalent to one the following: void fun(const Type &x, const Type &y); void fun(); The signature does not need to have const & and the type Type must be either T or implicitly convertible from T.

unroll_times()

template<unsigned Times, typename Fn >

void aie::unroll_times

(

Fn &&

fn

)

Invokes a function object a given number of times.

The function takes the current count by argument.

Template Parameters

Times

Total number of function calls.

Parameters

fn	A function object that takes the current count by argument. The signature of the function should be equivalent to one of the following: void fun(const Type &i); void fun(); The signature does not need to have const & and the type Type must be either unsigned or implicitly convertible from it.

unroll_times_2d()

template<unsigned TimesY, unsigned TimesX, typename Fn >

void aie::unroll_times_2d

(

Fn &&

fn

)

Invokes a function object as many times as defined by a 2D index sequence.

Template Parameters

TimesY	Total number of function calls (y-axis).
TimesX	Total number of function calls (x-axis).

Parameters

fn

A function object that takes two values by argument, representing the current count for each of the dimensions. The signature of the function should be equivalent to one of the following: void fun(const Type &x, const Type &y); void fun(); The signature does not need to have const & and the type Type must be either unsigned or implicitly convertible from it.