Disaggregate - Disaggregate - 2026.1 English - UG1399

Description

The DISAGGREGATE pragma lets you deconstruct a struct variable into its individual elements. The number and type of elements created are determined by the contents of the struct itself.

Syntax

Place the pragma in the C source within the boundaries of the region, function, or loop.

#pragma HLS disaggregate variable=<variable>

Options

• variable=<variable> : Specifies the struct variable to disaggregate.

Example 1

The following example shows the struct variable a in function top will be disaggregated:

#pragma HLS disaggregate variable=a

Example 2

Disaggregated structs can be addressed in your code by the using standard C/C++ coding style as shown below. Notice the different methods for accessing the pointer element (a) versus the reference element (c);

struct SS
{
  int x[N];
  int y[N];
};
int top(SS *a, int b[4][6], SS &c) {
#pragma HLS disaggregate variable = a
#pragma HLS interface s_axilite port = a->x
#pragma HLS interface s_axilite port = a->y
// Following is now supported
#pragma HLS disaggregate variable = c
#pragma HLS interface ap_memory port = c.x
#pragma HLS interface ap_memory port = c.y

Example 3

The following example shows the Dot struct containing the RGB struct as an element. If you apply the DISAGGREGATE pragma to variable Arr , then only the top-level Dot struct is disaggregated.

struct Pixel {
char R;
char G;
char B;
};
struct Dot {
Pixel RGB;
unsigned Size;
};
#define N 1086
void DUT(Dot Arr[N]) {
#pragma HLS disaggregate variable=Arr
...
}

If you want to disaggregate the whole struct, Dot and RGB , then you can assign the DISAGGREGATE pragma as shown below.

void DUT(Dot Arr[N]) {
#pragma HLS disaggregate variable=Arr->RGB
...
}

void DUT(char Arr_RGB_R[N], char Arr_RGB_G[N], char Arr_RGB_B[N], unsigned Arr_Size[N]) {
#pragma HLS disaggregate variable=Arr->RGB
...
}

See Also

• syn.directive.dependence
• Aggregate