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. 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
