[LLVMdev] -Os

[Renato Golin]

On 23 July 2013 19:36, Jim Grosbach <grosbach at apple.com> wrote:

> 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.
>

Jim,

A while ago I proposed that we annotated the options the front-end passed
to the back-end on the IR with named metadata, but it didn't catch on.

Would it make sense to have some call-back mechanism while setting back-end
flags to keep a tab on what's called and have a dump as metadata, so that
you can just write it to the IR file at the end? More or less what we have
for functions, currently.

This would hint llc, lli and others to what flags it must set itself
(architecture, optimizations, etc) and would minimize the impact of split
compilation. Those tools are free to ignore any option it doesn't
recognize, of course, as with any metadata.

Another way would be to teach llc, lli and others all command line options
of all supported front-ends, but that wouldn't be very productive, I think.

cheers,
--renato
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