set_directive_bind_op - 2023.1 English

Description

Vitis HLS implements the operations in the code using specific implementations. The set_directive_bind_op command specifies that for a specified variable, an operation (mul, add, sub) should be mapped to a specific device resource for implementation (impl) in the RTL. If this command is not specified, Vitis HLS automatically determines the resource to use.

For example, to indicate that a specific multiplier operation (mul) is implemented in the device fabric rather than a DSP, you can use the set_directive_bind_op command.

You can also specify the latency of the operation using the -latency option.

Syntax

set_directive_bind_op [OPTIONS] <location> <variable>

• <location> is the location (in the format function[/label]) which contains the variable.
• <variable> is the variable to be assigned. The variable in this case is one that is assigned the result of the operation that is the target of this directive.

Options

-op <value>

Defines the operation to bind to a specific implementation resource. Supported functional operations include: mul, add, sub

Supported floating point operations include: fadd, fsub, fdiv, fexp, flog, fmul, frsqrt, frecip, fsqrt, dadd, dsub, ddiv, dexp, dlog, dmul, drsqrt, drecip, dsqrt, hadd, hsub, hdiv, hmul, and hsqrt

Tip: Floating-point operations include single precision (f), double-precision (d), and half-precision (h).

-impl <value>

Defines the implementation to use for the specified operation.

Supported implementations for functional operations include fabric and dsp.

Supported implementations for floating point operations include: fabric, meddsp, fulldsp, maxdsp, and primitivedsp.

Note: primitivedsp is only available on Versal devices.

-latency <int>

Defines the default latency for the implementation of the operation. The valid latency varies according to the specified op and impl. The default is -1, which lets Vitis HLS choose the latency.

The tables below reflect the supported combinations of operation, implementation, and latency.

Examples

In the following example, a two-stage pipelined multiplier using fabric logic is specified to implement the multiplication for variable <c> of the function foo.

int foo (int a, int b) {
int c, d;
c = a*b;
d = a*c;
return d;
}

set_directive_bind_op -op mul -impl fabric -latency 2 "foo" c

See Also

• pragma HLS bind_op
• set_directive_bind_storage