https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81625
--- Comment #5 from Fredrik Hederstierna <fredrik.hederstie...@securitas-direct.com> --- I tried build several AVR toolchains from 3.4.6 to 7.1.0 and I can confirm that code size increases as described. I suspect for AVR this might start already from 3.x -> 4.x Checked Bug 17549 - [4.0 Regression] 10% increase in codesize with C code compared to GCC 3.3: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=17549 If TER pass is disabled adding "-fno-tree-ter", then results get more than -10% smaller. Though results still gets +10% worse than 3.4.6 even with 7.1.0, though adding -mstrict-X also makes its slightly better too..