[LLVMdev] How to not zeroinitialize array

[Tim Northover]

Hi Russel,

On 21 July 2015 at 13:31, Russell Hadley <rhadley at microsoft.com> wrote:
> My question is where is this transform happening – it looks like it’s a
> byproduct of parsing the ll file which was super surprising to me.

It's not even a transformation. It's just a shorthand used for
printing out (and reading in) a constant 0. What you want to do (well,
what you think you want to do) is prevent LLVM from putting any 0 data
in a special section when compiling.

> And second is there a know what to circumvent this?  For my app I just want the
> zero’d space in the section so I can copy it into memory.

This is probably better handled at the linker level, but for hacking
purposes there does seem to be an llc option to override the choice to
use automatic zero-fill: -nozero-initialized-in-bss. I've never used
it, but it may help for some quick tests.

Cheers.

Tim.