Commit ca349a6a authored by Luke Nelson's avatar Luke Nelson Committed by Daniel Borkmann

bpf, riscv: Optimize BPF_JMP BPF_K when imm == 0 on RV64

This patch adds an optimization to BPF_JMP (32- and 64-bit) BPF_K for
when the BPF immediate is zero.

When the immediate is zero, the code can directly use the RISC-V zero
register instead of loading a zero immediate to a temporary register
first.
Co-developed-by: default avatarXi Wang <xi.wang@gmail.com>
Signed-off-by: default avatarXi Wang <xi.wang@gmail.com>
Signed-off-by: default avatarLuke Nelson <luke.r.nels@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Reviewed-by: default avatarBjörn Töpel <bjorn.topel@gmail.com>
Acked-by: default avatarBjörn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200506000320.28965-4-luke.r.nels@gmail.com
parent 21a099ab
......@@ -796,7 +796,13 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
case BPF_JMP32 | BPF_JSET | BPF_K:
rvoff = rv_offset(i, off, ctx);
s = ctx->ninsns;
emit_imm(RV_REG_T1, imm, ctx);
if (imm) {
emit_imm(RV_REG_T1, imm, ctx);
rs = RV_REG_T1;
} else {
/* If imm is 0, simply use zero register. */
rs = RV_REG_ZERO;
}
if (!is64) {
if (is_signed_bpf_cond(BPF_OP(code)))
emit_sext_32_rd(&rd, ctx);
......@@ -811,11 +817,10 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
if (BPF_OP(code) == BPF_JSET) {
/* Adjust for and */
rvoff -= 4;
emit(rv_and(RV_REG_T1, rd, RV_REG_T1), ctx);
emit_branch(BPF_JNE, RV_REG_T1, RV_REG_ZERO, rvoff,
ctx);
emit(rv_and(rs, rd, rs), ctx);
emit_branch(BPF_JNE, rs, RV_REG_ZERO, rvoff, ctx);
} else {
emit_branch(BPF_OP(code), rd, RV_REG_T1, rvoff, ctx);
emit_branch(BPF_OP(code), rd, rs, rvoff, ctx);
}
break;
......
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