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riscv, bpf: Optimize BPF tail calls

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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
This commit is contained in:
Björn Töpel 2019-12-16 10:13:39 +01:00 committed by Daniel Borkmann
parent 33203c02f2
commit fe8322b866
1 changed files with 7 additions and 6 deletions
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13
arch/riscv/net/bpf_jit_comp.c
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@ -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)