SPRUI04 User guide

SPRUI04F july 2015 – april 2023

.return

Return a Value to a C callable Procedure

Syntax

.return [argument]

Description

The .return directive function is equivalent to the return statement in C/C++ code. It places the optional argument in the appropriate register for a return value as per the C/C++ calling conventions (see Section 8.4).

The optional argument can have the following meanings:

Zero arguments implies a .cproc region that has no return value, similar to a void function in C/C++ code.
An argument implies a .cproc region that has a 32-bit return value, similar to an int function in C/C++ code.
A register pair of the format hi:lo implies a .cproc region that has a 40-bit long, a 64-bit long long, or a 64-bit type double return value; similar to a long/long long/double function in C/C++ code.

Arguments to the .return directive can be either symbolic register names or machine-register names.

All return statements in a .cproc region must be consistent in the type of the return value. It is not legal to mix a .return arg with a .return hi:lo in the same .cproc region.

The .return directive is unconditional. To perform a conditional .return, simply use a conditional branch around a .return. The assembly optimizer removes the branch and generates the appropriate conditional code. For example, to return if condition cc is true, code the return as:

[!cc]  B   around
       .return
around:

Example

This example uses a symbolic register, tmp, and a machine-register, A5, as .return arguments:

     .cproc ...
     .reg tmp
     ...
     .return tmp= legal symbolic name
     ...
     .return a5 = legal actual name