From fe8322b866d560a3b3535ed9aa49df59809decbe Mon Sep 17 00:00:00 2001 From: =?utf8?q?Bj=C3=B6rn=20T=C3=B6pel?= Date: Mon, 16 Dec 2019 10:13:39 +0100 Subject: [PATCH] riscv, bpf: Optimize BPF tail calls MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Remove one addi, and instead use the offset part of jalr. Signed-off-by: Björn Töpel Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20191216091343.23260-6-bjorn.topel@gmail.com --- arch/riscv/net/bpf_jit_comp.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c index 2fc0f24ad30f..8aa19c846881 100644 --- a/arch/riscv/net/bpf_jit_comp.c +++ b/arch/riscv/net/bpf_jit_comp.c @@ -552,7 +552,7 @@ static int epilogue_offset(struct rv_jit_context *ctx) return (to - from) << 2; } -static void __build_epilogue(u8 reg, struct rv_jit_context *ctx) +static void __build_epilogue(bool is_tail_call, struct rv_jit_context *ctx) { int stack_adjust = ctx->stack_size, store_offset = stack_adjust - 8; @@ -589,9 +589,11 @@ static void __build_epilogue(u8 reg, struct rv_jit_context *ctx) emit(rv_addi(RV_REG_SP, RV_REG_SP, stack_adjust), ctx); /* Set return value. */ - if (reg == RV_REG_RA) + if (!is_tail_call) emit(rv_addi(RV_REG_A0, RV_REG_A5, 0), ctx); - emit(rv_jalr(RV_REG_ZERO, reg, 0), ctx); + emit(rv_jalr(RV_REG_ZERO, is_tail_call ? RV_REG_T3 : RV_REG_RA, + is_tail_call ? 4 : 0), /* skip TCC init */ + ctx); } /* return -1 or inverted cond */ @@ -751,9 +753,8 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx) if (is_12b_check(off, insn)) return -1; emit(rv_ld(RV_REG_T3, off, RV_REG_T2), ctx); - emit(rv_addi(RV_REG_T3, RV_REG_T3, 4), ctx); emit(rv_addi(RV_REG_TCC, RV_REG_T1, 0), ctx); - __build_epilogue(RV_REG_T3, ctx); + __build_epilogue(true, ctx); return 0; } @@ -1504,7 +1505,7 @@ static void build_prologue(struct rv_jit_context *ctx) static void build_epilogue(struct rv_jit_context *ctx) { - __build_epilogue(RV_REG_RA, ctx); + __build_epilogue(false, ctx); } static int build_body(struct rv_jit_context *ctx, bool extra_pass) -- 2.30.2