> On Feb 8, 2017, at 2:31 PM, David Blaikie <dblai...@gmail.com> wrote: > > > > On Wed, Feb 8, 2017 at 2:25 PM Amjad Aboud via Phabricator > <revi...@reviews.llvm.org <mailto:revi...@reviews.llvm.org>> wrote: > aaboud added a comment. > > > How much does the build directory grow? > > Is there any noticeable compile time regression? > > I build clang in release mode using GCC, then used that build to build clang > in debug mode with "-fstandalone-debug" flag, one time with my changes and > another time without my changes. > > Without my changes > ------------------ > > Clang executable Size: 1,565MB > Build time: 17m57.504s > > Withmy changes > -------------- > > Clang executable Size: 2,043MB > Build time: 17m58.008s > > Do, build time is the same, but binary size was increased about 30%. > However, remember that we are emitting macro debug info in dwarf4 format, > once we support emitting it in dwarf5 format the size should be reduced > significantly.
That sounds like we shouldn't be enabling it by default at -gdwarf-4; and we can revisit that decision for -gdwarf-5 whenever it is ready. > > How are you measuring the build time? Total time for, say "ninja clang" with > full parallelism? That'd be hard to measure the actual impact (since it could > be the link time or other things are dominating, etc). If you have a reliable > way to time (I'm assuming Intel has lots of tools for measuring compiler > performance) the compilation, get a sense of the variance, etc (& link time, > to get a sense of how much the larger inputs affect linker performance) would > be useful. > > But I'm not too fussed if no one else is worried (not sure which, if any > platforms other than your own, are planning to turn this on by default so > people might not be too invested in it). (wouldn't mind some second opinions, > etc) > > > > I'm not sure it makes sense to motivate this feature with > > "-fstandalone-debug" flag. > > Is "-fmacro-debug" flag sounds good? > > Sounds alright to me. Personally I find "-fmacro-debug-info" to be more descriptive, but "-fmacro-debug" mirrors "-fstandalone-debug", so I'm fine with that too. We could also use "-fdebug-macro" for symmetry with "-fdebug-type-section". Does GCC have a command line option for this that we could mirror? Please don't forget to document the new option in the man page and user guide. -- adrian > > Should we extend DebugInfoKind enumeration to support the debug info macro? > Or we should add a new option to CodeGenOptions? > > Separate option - it should be orthogonal to standalone/no-standalone, for > example. > > > > https://reviews.llvm.org/D16135 <https://reviews.llvm.org/D16135>
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