What makes a difference in the resulting compiler's speed when building gcc?

[Sven C. Dack]

On 27/10/16 18:15, Markus Trippelsdorf wrote:
> On 2016.10.27 at 18:08 +0100, Sven C. Dack wrote:
>> On 27/10/16 17:30, Marc Glisse wrote:
>>> On Thu, 27 Oct 2016, Sven C. Dack wrote:
>>>
>>>> I've been installing private copies of gcc for a while now, but only
>>>> recently did I notice that my distro's gcc (Debian testing) is doing
>>>> much better when comparing compile times than any of my copies. For
>>>> instance does it take 230s for my copy to compile a linux kernel,
>>>> but only 163s for my distro's gcc, which is almost a minute in
>>>> difference for something that doesn't take more than 3-4 minutes to
>>>> compile.
>>>>
>>>> What makes this noteworthy for me is that I've compiled my copy with
>>>> profiledbootstrap and LTO enabled and also optimized it for my CPU,
>>>> whereas the distro's compiler won't have been optimized quite that
>>>> much, but yet is it so much faster in speed. I don't know how
>>>> exactly my distro's gcc has been set up, because the Debian build
>>>> rules are rather complex and include their own set of patches. So I
>>>> thought I start with asking here first.
>>>>
>>>> What is that can make such a huge difference in compile speed for
>>>> two copies of gcc, both version 6.2, using the same options, on the
>>>> same source? Or are any of the configure options know to have a huge
>>>> impact on the resulting compiler's speed?
>>> --enable-checking=release would be the first thing to check.
>>>
>> Thank you, will do.
>>
>> I can already say that I am using "yes", because I'm using the latest git
>> versions and have always favoured a reasonable amount of checks. If this is
>> already the cause for the difference then I might actually keep it this way.
> Yes, this is the cause. You can use -fno-checking to switch some checks
> off at compile time.
>
I've compared it now... It is 231s (155%) with "--enable-checking=yes" and 149s 
(100%) with "--enable-checking=release".

Thanks again!