On Mon, Sep 14, 2020 at 07:06:29PM +0100, Matthew Wilcox wrote: > $ objdump -d test.o > 0000000000000000 <a>: > 0: 89 f8 mov %edi,%eax > 2: 83 e0 03 and $0x3,%eax > 5: c3 retq > > Please stop submitting uglifying patches without checking they actually > improve anything. GCC is smarter than you think it is.
His main point isn't that - it's reshuffling LOOKUP_... bits to make that kind of optimisation possible. However, doing that sets us up for PITA down the road (e.g. reshuffling LOOKUP_... bits becomes forbidden, etc.) and I'd rather not go there unless we have a real-world evidence that it does buy us anything.
