On Wed, Mar 16, 2016 at 7:25 AM, jps...@gmail.com via cfe-users < cfe-users@lists.llvm.org> wrote:
> Hi, I recently installed "Release" clang (svn r263305) from source on my > OSX machine, and it's compiling a 20 file C++ program about 50% slower than > the natively installed clang 3.7 (that came with xcode, I believe, although > I don't use xcode). I currently have both sets of tools installed and am > able to switch back and forth and verify using time that clang 3.7 takes > about 30 seconds and clang 3.9 takes about 45 seconds, on average (all > flags, settings, etc. are the same for both). I did build with "Release" as > the build type, although I also did set DLLVM_ENABLE_ASSERTIONS=ON (could > this be the problem?). > Yes, the build system should print a warning telling you that an assertions enabled build can be up to ten times slower. Performance comparisons/measurements of an assertions enabled compiler aren't something we really do/tune for. > More details below. Please let me know if you have any ideas about why > this newer clang would be noticable slower. > > Generally, I'm just trying to use clang as a user, not a clang developer, > so if you have general recommendations for how to configure this, please > let me know. > > Thank you, > Jim > > How I configured and installed: > > cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release > -DLLVM_ENABLE_ASSERTIONS=ON ../llvm > make > cmake -DCMAKE_INSTALL_PREFIX=$CLANG_PREFIX -P cmake_install.cmake > > > Here are some specifics: > > $ uname -a > Darwin localhost 15.0.0 Darwin Kernel Version 15.0.0: Wed Aug 26 16:57:32 > PDT 2015; root:xnu-3247.1.106~1/RELEASE_X86_64 x86_64 > > $ clang --version > clang version 3.9.0 (trunk 263305) > Target: x86_64-apple-darwin15.0.0 > Thread model: posix > InstalledDir: /Users/jim/toolchains/llvm/bin > > _______________________________________________ > cfe-users mailing list > cfe-users@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-users > >
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