https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116497
--- Comment #16 from Andi Kleen <andi-gcc at firstfloor dot org> --- Created attachment 59013 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59013&action=edit test case This test case using Pinski's clobber trick shows the benefit. If you compile with -O2 -mgeneral-regs-only the inc/dec opcodes don't save any extra registers and generate nearly optimal code. If you make the SAVE_REGS/DONT_SAVE_REGS macros empty they have a lot of extra push/pop, which would ruin the interpreter loop. -mgeneral-regs-only works for this case, but breaks SSE.
