MATLAB: [Fixed Point Converter] 1000 bit fraction length at 2^x if x is loaded from .mat file

fixed-point converterFixed-Point DesignerHDL Coder

I got a problem with code like this in the fixed-point converter:
dut_tb.m
dut(8);
dut.m
function out = dut(in)
    S = coder.load('constants.mat');
    out = in+2^S.exponent;
end
storeConstants.m
function [] = storeConstants()
    exponent = 8;
    save('constants.mat');
end
convert.m
exArgs = {8};
fc = coder.config('fixpt');
fc.TestBenchName = 'dut_tb';
codegen -float2fixed fc -args exArgs dut
Reproduction steps:
run storeConstants and then convert.
The fixed-point converter automatically uses a fraction length of 1000 for the power of two operation.
As this is just a simple bitshift in hardware, I cannot see the purpose of this high precision. How can
I disable this huge fraction length?

Best Answer

A temporary fix is using bitsll as recommended here:
For efficient HDL code generation, use the Fixed-Point Designer functions bitsll, bitsrl, or bitsra instead of bitshift.
So i exchanged 
out = in+2^S.exponent;
to
out = in+bitsll(uint8(1),S.exponent);
Uint8 being used, because I want the result to be unsigned, because it needs to be used in a divider.
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