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riscv, bpf: Optimize BPF tail calls
Remove one addi, and instead use the offset part of jalr. Signed-off-by: Björn Töpel <bjorn.topel@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20191216091343.23260-6-bjorn.topel@gmail.com
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33203c02f2
commit
fe8322b866
1 changed files with 7 additions and 6 deletions
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@ -552,7 +552,7 @@ static int epilogue_offset(struct rv_jit_context *ctx)
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return (to - from) << 2;
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}
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static void __build_epilogue(u8 reg, struct rv_jit_context *ctx)
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static void __build_epilogue(bool is_tail_call, struct rv_jit_context *ctx)
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{
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int stack_adjust = ctx->stack_size, store_offset = stack_adjust - 8;
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@ -589,9 +589,11 @@ static void __build_epilogue(u8 reg, struct rv_jit_context *ctx)
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emit(rv_addi(RV_REG_SP, RV_REG_SP, stack_adjust), ctx);
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/* Set return value. */
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if (reg == RV_REG_RA)
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if (!is_tail_call)
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emit(rv_addi(RV_REG_A0, RV_REG_A5, 0), ctx);
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emit(rv_jalr(RV_REG_ZERO, reg, 0), ctx);
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emit(rv_jalr(RV_REG_ZERO, is_tail_call ? RV_REG_T3 : RV_REG_RA,
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is_tail_call ? 4 : 0), /* skip TCC init */
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ctx);
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}
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/* return -1 or inverted cond */
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@ -751,9 +753,8 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
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if (is_12b_check(off, insn))
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return -1;
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emit(rv_ld(RV_REG_T3, off, RV_REG_T2), ctx);
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emit(rv_addi(RV_REG_T3, RV_REG_T3, 4), ctx);
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emit(rv_addi(RV_REG_TCC, RV_REG_T1, 0), ctx);
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__build_epilogue(RV_REG_T3, ctx);
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__build_epilogue(true, ctx);
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return 0;
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}
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@ -1504,7 +1505,7 @@ static void build_prologue(struct rv_jit_context *ctx)
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static void build_epilogue(struct rv_jit_context *ctx)
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{
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__build_epilogue(RV_REG_RA, ctx);
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__build_epilogue(false, ctx);
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}
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static int build_body(struct rv_jit_context *ctx, bool extra_pass)
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