[PATCH bpf-next v2 1/3] bpf, arm64: Simplify if logic in emit_lse_atomic()

[PATCH bpf-next v2 1/3] bpf, arm64: Simplify if logic in emit_lse_atomic()

[Peilin Ye]

Delete that unnecessary outer if clause.  No functional change.

Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 arch/arm64/net/bpf_jit_comp.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 66708b95493a..9040033eb1ea 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -648,16 +648,14 @@ static int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
 	const s16 off = insn->off;
 	u8 reg = dst;
 
-	if (off || arena) {
-		if (off) {
-			emit_a64_mov_i(1, tmp, off, ctx);
-			emit(A64_ADD(1, tmp, tmp, dst), ctx);
-			reg = tmp;
-		}
-		if (arena) {
-			emit(A64_ADD(1, tmp, reg, arena_vm_base), ctx);
-			reg = tmp;
-		}
+	if (off) {
+		emit_a64_mov_i(1, tmp, off, ctx);
+		emit(A64_ADD(1, tmp, tmp, dst), ctx);
+		reg = tmp;
+	}
+	if (arena) {
+		emit(A64_ADD(1, tmp, reg, arena_vm_base), ctx);
+		reg = tmp;
 	}
 
 	switch (insn->imm) {
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH bpf-next v2 2/3] bpf, arm64: Factor out emit_a64_add_i()

[Peilin Ye]

As suggested by Xu, factor out emit_a64_add_i() for later use.  No
functional change.

Suggested-by: Xu Kuohai <xukuohai@huaweicloud.com>
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 arch/arm64/net/bpf_jit_comp.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 9040033eb1ea..8ee9528d8795 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -267,6 +267,19 @@ static bool is_addsub_imm(u32 imm)
 	return !(imm & ~0xfff) || !(imm & ~0xfff000);
 }
 
+static inline void emit_a64_add_i(const bool is64, const int dst, const int src,
+				  const int tmp, const s32 imm, struct jit_ctx *ctx)
+{
+	if (is_addsub_imm(imm)) {
+		emit(A64_ADD_I(is64, dst, src, imm), ctx);
+	} else if (is_addsub_imm(-imm)) {
+		emit(A64_SUB_I(is64, dst, src, -imm), ctx);
+	} else {
+		emit_a64_mov_i(is64, tmp, imm, ctx);
+		emit(A64_ADD(is64, dst, src, tmp), ctx);
+	}
+}
+
 /*
  * There are 3 types of AArch64 LDR/STR (immediate) instruction:
  * Post-index, Pre-index, Unsigned offset.
@@ -1144,14 +1157,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 	/* dst = dst OP imm */
 	case BPF_ALU | BPF_ADD | BPF_K:
 	case BPF_ALU64 | BPF_ADD | BPF_K:
-		if (is_addsub_imm(imm)) {
-			emit(A64_ADD_I(is64, dst, dst, imm), ctx);
-		} else if (is_addsub_imm(-imm)) {
-			emit(A64_SUB_I(is64, dst, dst, -imm), ctx);
-		} else {
-			emit_a64_mov_i(is64, tmp, imm, ctx);
-			emit(A64_ADD(is64, dst, dst, tmp), ctx);
-		}
+		emit_a64_add_i(is64, dst, dst, tmp, imm, ctx);
 		break;
 	case BPF_ALU | BPF_SUB | BPF_K:
 	case BPF_ALU64 | BPF_SUB | BPF_K:
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH bpf-next v2 3/3] bpf, arm64: Emit A64_{ADD,SUB}_I when possible in emit_{lse,ll_sc}_atomic()

[Peilin Ye]

Currently in emit_{lse,ll_sc}_atomic(), if there is an offset, we add it
to the base address by doing e.g.:

  if (off) {
          emit_a64_mov_i(1, tmp, off, ctx);
          emit(A64_ADD(1, tmp, tmp, dst), ctx);
  ...

As pointed out by Xu, we can use emit_a64_add_i() (added in the previous
patch) instead, which tries to combine the above into a single A64_ADD_I
or A64_SUB_I when possible.

Suggested-by: Xu Kuohai <xukuohai@huaweicloud.com>
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
change in v2:
  * move the logic into a helper (added in v2 2/3) and use it (Xu)

v1: https://lore.kernel.org/bpf/953c7241e82496cb7a8b5a8724028ad646cd0896.1735342016.git.yepeilin@google.com/

 arch/arm64/net/bpf_jit_comp.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 8ee9528d8795..8446848edddb 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -662,8 +662,7 @@ static int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
 	u8 reg = dst;
 
 	if (off) {
-		emit_a64_mov_i(1, tmp, off, ctx);
-		emit(A64_ADD(1, tmp, tmp, dst), ctx);
+		emit_a64_add_i(1, tmp, reg, tmp, off, ctx);
 		reg = tmp;
 	}
 	if (arena) {
@@ -734,7 +733,7 @@ static int emit_ll_sc_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
 	const s32 imm = insn->imm;
 	const s16 off = insn->off;
 	const bool isdw = BPF_SIZE(code) == BPF_DW;
-	u8 reg;
+	u8 reg = dst;
 	s32 jmp_offset;
 
 	if (BPF_MODE(code) == BPF_PROBE_ATOMIC) {
@@ -743,11 +742,8 @@ static int emit_ll_sc_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
 		return -EINVAL;
 	}
 
-	if (!off) {
-		reg = dst;
-	} else {
-		emit_a64_mov_i(1, tmp, off, ctx);
-		emit(A64_ADD(1, tmp, tmp, dst), ctx);
+	if (off) {
+		emit_a64_add_i(1, tmp, reg, tmp, off, ctx);
 		reg = tmp;
 	}
 
-- 
2.47.1.613.gc27f4b7a9f-goog

Re: [PATCH bpf-next v2 1/3] bpf, arm64: Simplify if logic in emit_lse_atomic()

[Xu Kuohai]

On 1/3/2025 10:02 AM, Peilin Ye wrote:
> Delete that unnecessary outer if clause.  No functional change.
> 
> Signed-off-by: Peilin Ye <yepeilin@google.com>
> ---
>   arch/arm64/net/bpf_jit_comp.c | 18 ++++++++----------
>   1 file changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 66708b95493a..9040033eb1ea 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -648,16 +648,14 @@ static int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
>   	const s16 off = insn->off;
>   	u8 reg = dst;
>   
> -	if (off || arena) {
> -		if (off) {
> -			emit_a64_mov_i(1, tmp, off, ctx);
> -			emit(A64_ADD(1, tmp, tmp, dst), ctx);
> -			reg = tmp;
> -		}
> -		if (arena) {
> -			emit(A64_ADD(1, tmp, reg, arena_vm_base), ctx);
> -			reg = tmp;
> -		}
> +	if (off) {
> +		emit_a64_mov_i(1, tmp, off, ctx);
> +		emit(A64_ADD(1, tmp, tmp, dst), ctx);
> +		reg = tmp;
> +	}
> +	if (arena) {
> +		emit(A64_ADD(1, tmp, reg, arena_vm_base), ctx);
> +		reg = tmp;
>   	}
>   
>   	switch (insn->imm) {

Thanks for the improvements.

For the series:

Acked-by: Xu Kuohai <xukuohai@huawei.com>

Re: [PATCH bpf-next v2 1/3] bpf, arm64: Simplify if logic in emit_lse_atomic()

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Fri,  3 Jan 2025 02:02:53 +0000 you wrote:
> Delete that unnecessary outer if clause.  No functional change.
> 
> Signed-off-by: Peilin Ye <yepeilin@google.com>
> ---
>  arch/arm64/net/bpf_jit_comp.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)

Here is the summary with links:
  - [bpf-next,v2,1/3] bpf, arm64: Simplify if logic in emit_lse_atomic()
    https://git.kernel.org/bpf/bpf-next/c/0a5807219a86
  - [bpf-next,v2,2/3] bpf, arm64: Factor out emit_a64_add_i()
    https://git.kernel.org/bpf/bpf-next/c/66bb58ac06c2
  - [bpf-next,v2,3/3] bpf, arm64: Emit A64_{ADD,SUB}_I when possible in emit_{lse,ll_sc}_atomic()
    https://git.kernel.org/bpf/bpf-next/c/8c21f88407d2

You are awesome, thank you!
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