Song Liu wrote: > On Wed, Oct 2, 2019 at 5:30 PM Daniel Borkmann <dan...@iogearbox.net> wrote: > > > > Replace 'cmp reg, 0' with 'test reg, reg' for comparisons against > > zero. Saves 1 byte of instruction encoding per occurrence. The flag > > results of test 'reg, reg' are identical to 'cmp reg, 0' in all > > cases except for AF which we don't use/care about. In terms of > > macro-fusibility in combination with a subsequent conditional jump > > instruction, both have the same properties for the jumps used in > > the JIT translation. For example, same JITed Cilium program can > > shrink a bit from e.g. 12,455 to 12,317 bytes as tests with 0 are > > used quite frequently. > > > > Signed-off-by: Daniel Borkmann <dan...@iogearbox.net> > > Acked-by: Song Liu <songliubrav...@fb.com>
Bonus points for causing me to spend the morning remembering the differences between cmd, and, or, and test. Also wonder if at some point we should clean up the jit a bit and add some defines/helpers for all the open coded opcodes and such. Acked-by: John Fastabend <john.fastab...@gmail.com>
