[llvm-dev] llvm and clang are getting slower

[Jonas Paulsson via llvm-dev]

Hi,

There is a possibility that r259673 could play a role here.

For the buildSchedGraph() method, there is the -dag-maps-huge-region 
that has the default value of 1000. When I commited the patch, I was 
expecting people to lower this value as needed and also suggested this, 
but this has not happened. 1000 is very high, basically "unlimited".

It would be interesting to see what results you get with e.g.-mllvm 
-dag-maps-huge-region=50. Of course, since this is a trade-off between 
compile time and scheduler freedom, some care should be taken before 
lowering this in trunk.

Just a thought,

Jonas


On 2016-03-08 17:13, Rafael Espíndola via llvm-dev wrote:
> I have just benchmarked building trunk llvm and clang in Debug,
> Release and LTO modes (see the attached scrip for the cmake lines).
>
> The compilers used were clang 3.5, 3.6, 3.7, 3.8 and trunk. In all
> cases I used the system libgcc and libstdc++.
>
> For release builds there is a monotonic increase in each version. From
> 163 minutes with 3.5 to 212 minutes with trunk. For comparison, gcc
> 5.3.2 takes 205 minutes.
>
> Debug and LTO show an improvement in 3.7, but have regressed again in 3.8.
>
> Cheers,
> Rafael
>
>
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