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bpf, riscv: Optimize FROM_LE using verifier_zext on RV64
This patch adds two optimizations for BPF_ALU BPF_END BPF_FROM_LE in the RV64 BPF JIT. First, it enables the verifier zero-extension optimization to avoid zero extension when imm == 32. Second, it avoids generating code for imm == 64, since it is equivalent to a no-op. 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/20200506000320.28965-3-luke.r.nels@gmail.com
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1 changed files with 14 additions and 6 deletions
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@ -542,13 +542,21 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
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/* dst = BSWAP##imm(dst) */
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case BPF_ALU | BPF_END | BPF_FROM_LE:
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{
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int shift = 64 - imm;
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emit(rv_slli(rd, rd, shift), ctx);
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emit(rv_srli(rd, rd, shift), ctx);
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switch (imm) {
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case 16:
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emit(rv_slli(rd, rd, 48), ctx);
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emit(rv_srli(rd, rd, 48), ctx);
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break;
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case 32:
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if (!aux->verifier_zext)
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emit_zext_32(rd, ctx);
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break;
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case 64:
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/* Do nothing */
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break;
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}
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break;
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}
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case BPF_ALU | BPF_END | BPF_FROM_BE:
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emit(rv_addi(RV_REG_T2, RV_REG_ZERO, 0), ctx);
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