[llvm] r300171 - [APInt] Reorder fields to avoid a hole in the middle of the class

[Davide Italiano via llvm-commits]

On Wed, Apr 12, 2017 at 9:59 PM, Craig Topper via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: ctopper
> Date: Wed Apr 12 23:59:11 2017
> New Revision: 300171
>
> URL: http://llvm.org/viewvc/llvm-project?rev=300171&view=rev
> Log:
> [APInt] Reorder fields to avoid a hole in the middle of the class
>
> Summary:
> APInt is currently implemented with an unsigned BitWidth field first and then a uint_64/pointer union. Due to the 64-bit size of the union there is a hole after the bitwidth.
>
> Putting the union first allows the class to be packed. Making it 12 bytes instead of 16 bytes. An APSInt goes from 20 bytes to 16 bytes.
>
> This shows a 4k reduction on the size of the opt binary on my local x86-64 build. So this enables some other improvement to the code as well.
>

As mentioned in the review, can you please try to write an unittest to
make sure this doesn't break in future?

Thanks,

-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare