https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71399
--- Comment #10 from Ludovic Courtès <ludo at gnu dot org> --- In fact, the revert only needs to be done on the initial pseudo-cross-compiler that is used to build the native compiler (I'm attaching a PDF of the dependency graph, where the initial pseudo-cross-compiler as described at http://linuxfromscratch.org/lfs/view/stable/chapter05/gcc-pass1.html is marked as "gcc-cross-boot0", and the final native compiler is simply "gcc"). To summarize, if we build 4.9.4 with a cross-4.9.3, that's fine; if we build 4.9.4 with a cross-4.9.4, we get the bootstrap comparison failure. That would suggest a code generation issue that somehow propagates from the initial cross-compiler up to stage2 of the compiler we're building.