Standard Types - 2023.1 English

The following code example shows some basic arithmetic operations being performed.

#include "types_standard.h"

void types_standard(din_A  inA, din_B  inB, din_C  inC, din_D  inD,
 dout_1 *out1, dout_2 *out2, dout_3 *out3, dout_4 *out4
) {

 // Basic arithmetic operations
 *out1 = inA * inB;
 *out2 = inB + inA;
 *out3 = inC / inA;
 *out4 = inD % inA;

} 

The data types in the example above are defined in the header file types_standard.h shown in the following code example. They show how the following types can be used:

• Standard signed types
• Unsigned types
• Exact-width integer types (with the inclusion of header file stdint.h)

  
  #include <stdio.h>
  #include <stdint.h>
  
  #define N 9
  
  typedef char din_A;
  typedef short din_B;
  typedef int din_C;
  typedef long long din_D;
  
  typedef int dout_1;
  typedef unsigned char dout_2;
  typedef int32_t dout_3;
  typedef int64_t dout_4;
  
  void types_standard(din_A inA,din_B inB,din_C inC,din_D inD,dout_1 
  
  *out1,dout_2 *out2,dout_3 *out3,dout_4 *out4);
  

These different types result in the following operator and port sizes after synthesis:

• The multiplier used to calculate result out1 is a 24-bit multiplier. An 8-bit char type multiplied by a 16-bit short type requires a 24-bit multiplier. The result is sign-extended to 32-bit to match the output port width.
• The adder used for out2 is 8-bit. Because the output is an 8-bit unsigned char type, only the bottom 8-bits of inB (a 16-bit short) are added to 8-bit char type inA.
• For output out3 (32-bit exact width type), 8-bit char type inA is sign-extended to 32-bit value and a 32-bit division operation is performed with the 32-bit (int type) inC input.
• A 64-bit modulus operation is performed using the 64-bit long long type inD and 8-bit char type inA sign-extended to 64-bit, to create a 64-bit output result out4.

As the result of out1 indicates, Vitis HLS uses the smallest operator it can and extends the result to match the required output bit-width. For result out2, even though one of the inputs is 16-bit, an 8-bit adder can be used because only an 8-bit output is required. As the results for out3 and out4 show, if all bits are required, a full sized operator is synthesized.