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nfp: bpf: optimize comparisons to negative constants 

Comparison instruction requires a subtraction.  If the constant
is negative we are more likely to fit it into a NFP instruction
directly if we change the sign and use addition.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Jakub Kicinski 2018-04-24 21:22:39 -07:00 committed by Daniel Borkmann
parent 61dd8f0007
commit 7bdc97be90
2 changed files with 35 additions and 13 deletions
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28
drivers/net/ethernet/netronome/nfp/bpf/jit.c
View File

@ -1247,6 +1247,7 @@ static int cmp_imm(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
const struct bpf_insn *insn = &meta->insn;
u64 imm = insn->imm; /* sign extend */
const struct jmp_code_map *code;
enum alu_op alu_op, carry_op;
u8 reg = insn->dst_reg * 2;
swreg tmp_reg;
@ -1254,19 +1255,22 @@ static int cmp_imm(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
if (!code)
return -EINVAL;
alu_op = meta->jump_neg_op ? ALU_OP_ADD : ALU_OP_SUB;
carry_op = meta->jump_neg_op ? ALU_OP_ADD_C : ALU_OP_SUB_C;
tmp_reg = ur_load_imm_any(nfp_prog, imm & ~0U, imm_b(nfp_prog));
if (!code->swap)
emit_alu(nfp_prog, reg_none(), reg_a(reg), ALU_OP_SUB, tmp_reg);
emit_alu(nfp_prog, reg_none(), reg_a(reg), alu_op, tmp_reg);
else
emit_alu(nfp_prog, reg_none(), tmp_reg, ALU_OP_SUB, reg_a(reg));
emit_alu(nfp_prog, reg_none(), tmp_reg, alu_op, reg_a(reg));
tmp_reg = ur_load_imm_any(nfp_prog, imm >> 32, imm_b(nfp_prog));
if (!code->swap)
emit_alu(nfp_prog, reg_none(),
reg_a(reg + 1), ALU_OP_SUB_C, tmp_reg);
reg_a(reg + 1), carry_op, tmp_reg);
else
emit_alu(nfp_prog, reg_none(),
tmp_reg, ALU_OP_SUB_C, reg_a(reg + 1));
tmp_reg, carry_op, reg_a(reg + 1));
emit_br(nfp_prog, code->br_mask, insn->off, 0);
@ -2745,13 +2749,26 @@ static void nfp_bpf_opt_neg_add_sub(struct nfp_prog *nfp_prog)
continue;
if (BPF_CLASS(insn.code) != BPF_ALU &&
BPF_CLASS(insn.code) != BPF_ALU64)
BPF_CLASS(insn.code) != BPF_ALU64 &&
BPF_CLASS(insn.code) != BPF_JMP)
continue;
if (BPF_SRC(insn.code) != BPF_K)
continue;
if (insn.imm >= 0)
continue;
if (BPF_CLASS(insn.code) == BPF_JMP) {
switch (BPF_OP(insn.code)) {
case BPF_JGE:
case BPF_JSGE:
case BPF_JLT:
case BPF_JSLT:
meta->jump_neg_op = true;
break;
default:
continue;
}
} else {
if (BPF_OP(insn.code) == BPF_ADD)
insn.code = BPF_CLASS(insn.code) | BPF_SUB;
else if (BPF_OP(insn.code) == BPF_SUB)
@ -2760,6 +2777,7 @@ static void nfp_bpf_opt_neg_add_sub(struct nfp_prog *nfp_prog)
continue;
meta->insn.code = insn.code | BPF_K;
}
meta->insn.imm = -insn.imm;
}

4
drivers/net/ethernet/netronome/nfp/bpf/main.h
View File

@ -236,6 +236,7 @@ struct nfp_bpf_reg_state {
* @xadd_over_16bit: 16bit immediate is not guaranteed
* @xadd_maybe_16bit: 16bit immediate is possible
* @jmp_dst: destination info for jump instructions
* @jump_neg_op: jump instruction has inverted immediate, use ADD instead of SUB
* @func_id: function id for call instructions
* @arg1: arg1 for call instructions
* @arg2: arg2 for call instructions
@ -264,7 +265,10 @@ struct nfp_insn_meta {
bool xadd_maybe_16bit;
};
/* jump */
struct {
struct nfp_insn_meta *jmp_dst;
bool jump_neg_op;
};
/* function calls */
struct {
u32 func_id;