[libcxx-dev] libcxx performance issue

[Yan Yichen via libcxx-dev]

I’m using trunk version of both libstdc++ and libc++.


From: Marshall Clow <mclow.lists at gmail.com>
Sent: Tuesday, August 27, 2019 12:37 AM
To: Yan Yichen <yichen.yan at inf.ethz.ch>
Cc: libcxx-dev at lists.llvm.org
Subject: Re: [libcxx-dev] libcxx performance issue



On Mon, Aug 26, 2019 at 3:36 PM Marshall Clow <mclow.lists at gmail.com<mailto:mclow.lists at gmail.com>> wrote:


On Sat, Aug 24, 2019 at 11:28 AM Yan Yichen via libcxx-dev <libcxx-dev at lists.llvm.org<mailto:libcxx-dev at lists.llvm.org>> wrote:
Dear developers,
  Sorry to bother you, but I’ve met a wired problem using clang with libcxx.
  I’ve built clang and libcxx with clang, and trying to compile c++ program with libc++, but compilation is extremely slow when using libcxx, as below:

$ time clang++ -o /dev/null -std=c++11 -stdlib=libc++ test.cc
clang++ -o /dev/null -std=c++11 -stdlib=libc++ test.cc  4.29s user 0.06s system 97% cpu 4.476 total
$ time clang++ -o /dev/null -std=c++11 test.cc
clang++ -o /dev/null -std=c++11 test.cc  1.41s user 0.06s system 92% cpu 1.582 total

  I wonder if you have any idea where should I start to address this issue, or anything I probably configured wrong? Thanks in advanced.


I'm afraid I have no idea what you're comparing *with*.

Or rather, comparing *against*.
What are you using when you're not using libc++?

-- Marshall

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