[llvm] r256302 - Disable use list order on the gold plugin.

[Rafael Espíndola via llvm-commits]

On 12 January 2016 at 17:15, Mehdi Amini <mehdi.amini at apple.com> wrote:
>
>> On Dec 22, 2015, at 3:45 PM, Rafael Espindola via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: rafael
>> Date: Tue Dec 22 17:45:49 2015
>> New Revision: 256302
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=256302&view=rev
>> Log:
>> Disable use list order on the gold plugin.
>>
>> It turns out that his is *really* slow. With this change the link of
>> clang with plugin-opt=emit-llvm goes from 41 to 26 seconds.
>
> plugin-opt=emit-llvm is a debug option, I’m not sure it is a good idea to “optimize” for this case and losing some reproducibility?

I have mixed feeling about it.

I honestly don't remember the specifics, but I noticed that creating a
.bc for all of clang was noticeably slower than what it used to be.

If this option had a small impact or if use order problems were very
common, I would agree that we should leave it enabled. But the option
costs more than a third of the total time. I also only remember
hitting a use list order issue once.

So if there is strong preferences I can put it back, if possible
behind a plugin option.

Cheers,
Rafael