Hi, on 2021/6/21 下午9:41, Chris S via Gcc-help wrote: > Are the capabilities and/or limitations of GCC10 LTO documented anywhere? > I understand it only at a high level but not with details, and am having > trouble finding any current information that describes it very clearly. > Some questions came up recently that I'd like to be able to answer, but it > boils down to this: > > Is it possible to build static libraries that have LTO optimizations > applied to the object code they contain (that is, all the code in that > library is optimized together with LTO), but when built together into a > final binary, no additional LTO is performed? We have several large, > static libraries that are mostly unrelated, and are looking for ways to > reduce a massive increase in build times after moving to g++10, where > almost 80% of the time is spent in LTO. If the compiling time is the concern, maybe it's worth to trying with LTO parallel build, such as -flto=auto or -flto=n. https://gcc.gnu.org/onlinedocs/gcc-10.3.0/gcc/Optimize-Options.html#Optimize-Options BR, Kewen > Having optimized individual > libraries but not a global optimized binary might be a reasonable > tradeoff. Is this possible? > > I don't have a good mental model of when "extra information" (GIMPLE) is > merely included in the code for later use, and when that GIMPLE information > is actually used to perform LTO optimizations. (My suspicion is that it's > only when building the final binary.) However, if we can build static > libraries that are already optimized within themselves, a hint of what > command line options to use would also be very appreciated. > > Thanks. > Chris >
