mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 02:39:48 +00:00
bpf, riscv: Optimize BPF_JSET BPF_K using andi on RV64
This patch optimizes BPF_JSET BPF_K by using a RISC-V andi instruction when the BPF immediate fits in 12 bits, instead of first loading the immediate to a temporary register. Examples of generated code with and without this optimization: BPF_JMP_IMM(BPF_JSET, R1, 2, 1) without optimization: 20: li t1,2 24: and t1,a0,t1 28: bnez t1,0x30 BPF_JMP_IMM(BPF_JSET, R1, 2, 1) with optimization: 20: andi t1,a0,2 24: bnez t1,0x2c BPF_JMP32_IMM(BPF_JSET, R1, 2, 1) without optimization: 20: li t1,2 24: mv t2,a0 28: slli t2,t2,0x20 2c: srli t2,t2,0x20 30: slli t1,t1,0x20 34: srli t1,t1,0x20 38: and t1,t2,t1 3c: bnez t1,0x44 BPF_JMP32_IMM(BPF_JSET, R1, 2, 1) with optimization: 20: andi t1,a0,2 24: bnez t1,0x2c In these examples, because the upper 32 bits of the sign-extended immediate are 0, BPF_JMP BPF_JSET and BPF_JMP32 BPF_JSET are equivalent and therefore the JIT produces identical code for them. Co-developed-by: Xi Wang <xi.wang@gmail.com> Signed-off-by: Xi Wang <xi.wang@gmail.com> Signed-off-by: Luke Nelson <luke.r.nels@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Björn Töpel <bjorn.topel@gmail.com> Acked-by: Björn Töpel <bjorn.topel@gmail.com> Link: https://lore.kernel.org/bpf/20200506000320.28965-5-luke.r.nels@gmail.com
This commit is contained in:
parent
ca349a6a10
commit
073ca6a036
1 changed files with 19 additions and 8 deletions
|
@ -792,8 +792,6 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
|
|||
case BPF_JMP32 | BPF_JSGE | BPF_K:
|
||||
case BPF_JMP | BPF_JSLE | BPF_K:
|
||||
case BPF_JMP32 | BPF_JSLE | BPF_K:
|
||||
case BPF_JMP | BPF_JSET | BPF_K:
|
||||
case BPF_JMP32 | BPF_JSET | BPF_K:
|
||||
rvoff = rv_offset(i, off, ctx);
|
||||
s = ctx->ninsns;
|
||||
if (imm) {
|
||||
|
@ -813,15 +811,28 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
|
|||
|
||||
/* Adjust for extra insns */
|
||||
rvoff -= (e - s) << 2;
|
||||
emit_branch(BPF_OP(code), rd, rs, rvoff, ctx);
|
||||
break;
|
||||
|
||||
if (BPF_OP(code) == BPF_JSET) {
|
||||
/* Adjust for and */
|
||||
rvoff -= 4;
|
||||
emit(rv_and(rs, rd, rs), ctx);
|
||||
emit_branch(BPF_JNE, rs, RV_REG_ZERO, rvoff, ctx);
|
||||
case BPF_JMP | BPF_JSET | BPF_K:
|
||||
case BPF_JMP32 | BPF_JSET | BPF_K:
|
||||
rvoff = rv_offset(i, off, ctx);
|
||||
s = ctx->ninsns;
|
||||
if (is_12b_int(imm)) {
|
||||
emit(rv_andi(RV_REG_T1, rd, imm), ctx);
|
||||
} else {
|
||||
emit_branch(BPF_OP(code), rd, rs, rvoff, ctx);
|
||||
emit_imm(RV_REG_T1, imm, ctx);
|
||||
emit(rv_and(RV_REG_T1, rd, RV_REG_T1), ctx);
|
||||
}
|
||||
/* For jset32, we should clear the upper 32 bits of t1, but
|
||||
* sign-extension is sufficient here and saves one instruction,
|
||||
* as t1 is used only in comparison against zero.
|
||||
*/
|
||||
if (!is64 && imm < 0)
|
||||
emit(rv_addiw(RV_REG_T1, RV_REG_T1, 0), ctx);
|
||||
e = ctx->ninsns;
|
||||
rvoff -= (e - s) << 2;
|
||||
emit_branch(BPF_JNE, RV_REG_T1, RV_REG_ZERO, rvoff, ctx);
|
||||
break;
|
||||
|
||||
/* function call */
|
||||
|
|
Loading…
Reference in a new issue