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From: "Björn Töpel" <bjorn.topel@gmail.com>
To: daniel@iogearbox.net, ast@kernel.org, netdev@vger.kernel.org
Cc: "Björn Töpel" <bjorn.topel@gmail.com>,
	linux-riscv@lists.infradead.org, bpf@vger.kernel.org
Subject: [PATCH bpf-next v2 5/9] riscv, bpf: optimize BPF tail calls
Date: Mon, 16 Dec 2019 10:13:39 +0100
Message-ID: <20191216091343.23260-6-bjorn.topel@gmail.com> (raw)
In-Reply-To: <20191216091343.23260-1-bjorn.topel@gmail.com>

Remove one addi, and instead use the offset part of jalr.

Signed-off-by: Björn Töpel <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)
-- 
2.20.1



  parent reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-16  9:13 [PATCH bpf-next v2 0/9] riscv: BPF JIT fix, optimizations and far jumps support Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 1/9] riscv, bpf: fix broken BPF tail calls Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 2/9] riscv, bpf: add support for far branching Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 3/9] riscv, bpf: add support for far branching when emitting tail call Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 4/9] riscv, bpf: add support for far jumps and exits Björn Töpel
2019-12-16  9:13 ` Björn Töpel [this message]
2019-12-16  9:13 ` [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free Björn Töpel
2019-12-16 15:09   ` Daniel Borkmann
2019-12-18  6:23     ` Björn Töpel
2020-01-04  1:32       ` Paul Walmsley
2020-01-07 10:24         ` Björn Töpel
2020-01-07 10:47           ` Paul Walmsley
2020-02-02 13:37   ` Alex Ghiti
2020-02-03 12:28     ` Björn Töpel
2020-02-03 20:57       ` Alex Ghiti
2019-12-16  9:13 ` [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 8/9] riscv, bpf: add missing uapi header for BPF_PROG_TYPE_PERF_EVENT programs Björn Töpel
2019-12-16  9:13 ` [PATCH bpf-next v2 9/9] riscv, perf: add arch specific perf_arch_bpf_user_pt_regs Björn Töpel
2019-12-19 15:07 ` [PATCH bpf-next v2 0/9] riscv: BPF JIT fix, optimizations and far jumps support Daniel Borkmann
2019-12-19 22:02 ` [PATCH bpf-next v2 1/9] riscv, bpf: fix broken BPF tail calls Palmer Dabbelt
2019-12-23 18:03 ` [PATCH bpf-next v2 2/9] riscv, bpf: add support for far branching Palmer Dabbelt
2020-01-07  8:13   ` Björn Töpel
2020-01-23  2:08   ` Palmer Dabbelt
2019-12-23 18:18 ` [PATCH bpf-next v2 3/9] riscv, bpf: add support for far branching when emitting tail call Palmer Dabbelt
2019-12-23 18:18 ` [PATCH bpf-next v2 4/9] riscv, bpf: add support for far jumps and exits Palmer Dabbelt
2019-12-23 18:29 ` [PATCH bpf-next v2 5/9] riscv, bpf: optimize BPF tail calls Palmer Dabbelt
2019-12-23 18:30 ` [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free Palmer Dabbelt
2019-12-23 18:58 ` [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls Palmer Dabbelt
2020-01-07 10:14   ` Björn Töpel
2020-01-28  2:15   ` Palmer Dabbelt
2020-02-03 12:11     ` Björn Töpel
2019-12-23 18:58 ` [PATCH bpf-next v2 8/9] riscv, bpf: add missing uapi header for BPF_PROG_TYPE_PERF_EVENT programs Palmer Dabbelt
2019-12-23 18:58 ` [PATCH bpf-next v2 9/9] riscv, perf: add arch specific perf_arch_bpf_user_pt_regs Palmer Dabbelt

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