[LLVMdev] -Os

Jim Grosbach grosbach at apple.com
Tue Jul 23 11:36:08 PDT 2013

On Jul 23, 2013, at 5:22 AM, reed kotler <rkotler at mips.com> wrote:

> On 07/23/2013 05:19 AM, Konstantin Tokarev wrote:
>> 23.07.2013, 16:05, "reed kotler" <rkotler at mips.com>:
>>> When I use -Os with a clang that implicitly calls llc, I get much
>>> different code than when call clang first with -Os and then call llc.
>> clang does NOT call llc internally.
> I understand. It's invoking that functionality is what I meant to say but not technically
> running that command.

This isn’t just a nitpick. This is exactly why you’re seeing differences. The pass managers aren’t always set up the same, for example.

FWIW, I feel your pain. This is a long-standing weakness of our infrastructure.


>>> How do I get these two paths to generate the same code?
>> Call llc with -Os?
> You can't pass -Os to llc.
> -Os is a clang only option. It's reflected in the IR used by llc in the function attributes.
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