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arm64: bpf: optimize modulo operation 

Optimize modulo operation instruction generation by
using single MSUB instruction vs MUL followed by SUB
instruction scheme.

Signed-off-by: Jerin Jacob <jerinj@marvell.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Jerin Jacob 2019-09-02 11:44:48 +05:30 committed by Daniel Borkmann
parent 53092f7e07
commit 504792e07a
2 changed files with 5 additions and 4 deletions
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3
arch/arm64/net/bpf_jit.h
View File

@ -171,6 +171,9 @@
/* Rd = Ra + Rn * Rm */
#define A64_MADD(sf, Rd, Ra, Rn, Rm) aarch64_insn_gen_data3(Rd, Ra, Rn, Rm, \
A64_VARIANT(sf), AARCH64_INSN_DATA3_MADD)
/* Rd = Ra - Rn * Rm */
#define A64_MSUB(sf, Rd, Ra, Rn, Rm) aarch64_insn_gen_data3(Rd, Ra, Rn, Rm, \
A64_VARIANT(sf), AARCH64_INSN_DATA3_MSUB)
/* Rd = Rn * Rm */
#define A64_MUL(sf, Rd, Rn, Rm) A64_MADD(sf, Rd, A64_ZR, Rn, Rm)

6
arch/arm64/net/bpf_jit_comp.c
View File

@ -409,8 +409,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
break;
case BPF_MOD:
emit(A64_UDIV(is64, tmp, dst, src), ctx);
emit(A64_MUL(is64, tmp, tmp, src), ctx);
emit(A64_SUB(is64, dst, dst, tmp), ctx);
emit(A64_MSUB(is64, dst, dst, tmp, src), ctx);
break;
}
break;
@ -516,8 +515,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
case BPF_ALU64 | BPF_MOD | BPF_K:
emit_a64_mov_i(is64, tmp2, imm, ctx);
emit(A64_UDIV(is64, tmp, dst, tmp2), ctx);
emit(A64_MUL(is64, tmp, tmp, tmp2), ctx);
emit(A64_SUB(is64, dst, dst, tmp), ctx);
emit(A64_MSUB(is64, dst, dst, tmp, tmp2), ctx);
break;
case BPF_ALU | BPF_LSH | BPF_K:
case BPF_ALU64 | BPF_LSH | BPF_K: