Control Signed Left Shifts in Generated Code

If you have an Embedded Coder^® license, you can control whether MATLAB^® Coder™ replaces multiplications by powers of two with signed left bitwise shifts. Some coding standards, such as MISRA™, do not allow bitwise operations on signed integers.

By default, MATLAB Coder replaces multiplication by powers of two with signed left shifts. Here is an example of generated C code that uses a signed left shift for multiplication by eight.

i <<= 3;

To increase the likelihood of generating MISRA C:2012 compliant code, disable the replacement of multiplication by powers of two with signed left shifts. Here is an example of generated C code that does not use a signed left shift for multiplication by eight:

i = i * 8;

Control Signed Left Shifts Using the MATLAB Coder App

On the Generate Code page, to open the Generate dialog box, click the Generate arrow .
Set Build type to one of the following:
- Source Code
- Static Library (.lib)
- Dynamic Library (.dll)
- Executable (.exe)
Click More Settings.
On the Code Appearance tab, select or clear the Use signed shift left for fixed-point operations and multiplication by powers of 2 check box.

Control Signed Left Shifts Using the Command-Line Interface

Create a code configuration object for 'lib', 'dll', or 'exe'. For example:
```
cfg = coder.config('lib','ecoder',true); % or dll or exe
```
Set the EnableSignedLeftShifts property to true or false. For example:
```
cfg.EnableSignedLeftShifts = false;
```