bpf, x86: small optimization in alu ops with imm

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For the BPF_REG_0 (BPF_REG_A in cBPF, respectively), we can use
the short form of the opcode as dst mapping is on eax/rax and
thus save a byte per such operation. Added to add/sub/and/or/xor
for 32/64 bit when K immediate is used. There may be more such
low-hanging fruit to add in future as well.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Daniel Borkmann 2018-01-20 01:24:35 +01:00 • committed by Alexei Starovoitov

parent 2e4a30983b

commit de0a444dda

1 changed files with 30 additions and 5 deletions

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arch/x86/net/bpf_jit_comp.c

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