[LLVMdev] Bitcode parsing performance

Rafael EspĂ­ndola rafael.espindola at gmail.com
Fri Jan 10 06:05:44 PST 2014

On 10 January 2014 03:09, Sean Silva <chisophugis at gmail.com> wrote:
> This Summer I was working on LTO and Rafael mentioned to me that debug info
> is not lazy loaded, which was the cause for the insane resource usage I was
> seeing when doing LTO with debug info. This is likely the reason that the
> lazy loading was so ineffective for your debug build.
> Rafael, am I remembering this right/can you give more information? I expect
> that this will have to get fixed before pitching LLD as a turnkey LTO
> solution (not sure where in the priority list it is).

In the case of LTO, there were two main issues.

* Duplicate type debug information.
* All metadata (including debug info) is loaded eagerly.

As Eric mentioned, we can now merge type debug info from multiple
translation units, which results in a smaller total size. Kevin, what
llvm version are you using? Do you get a smaller combined bitcode with

The issue of loading all of the debug info ahead of time is still
there. We will need to fix that at some point or reduce its size
further so that the impact is small enough.


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