57a610f1c5
Instead of unconditionally performing push/pop on %rax/%rdx in case of division/modulo, we can save a few bytes in case of destination register being either BPF r0 (%rax) or r3 (%rdx) since the result is written in there anyway. Also, we do not need to copy the source to %r11 unless the source is either %rax, %rdx or an immediate. For example, before the patch: 22: push %rax 23: push %rdx 24: mov %rsi,%r11 27: xor %edx,%edx 29: div %r11 2c: mov %rax,%r11 2f: pop %rdx 30: pop %rax 31: mov %r11,%rax After: 22: push %rdx 23: xor %edx,%edx 25: div %rsi 28: pop %rdx Signed-off-by: Jie Meng <jmeng@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Tested-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20211002035626.2041910-1-jmeng@fb.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.