netdev - [PATCH net-next 09/13] ARM: net: bpf: use ldr instructions with shifted rm register

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Date:   Tue, 10 Jul 2018 13:36:49 +0100
From:   Russell King <rmk+kernel@...linux.org.uk>
To:     netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH net-next 09/13] ARM: net: bpf: use ldr instructions with
 shifted rm register

Rather than pre-shifting the rm register for the ldr in the tail call,
shift it in the load instruction.  This eliminates one unnecessary
instruction.

Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
---
 arch/arm/net/bpf_jit_32.c | 3 +--
 arch/arm/net/bpf_jit_32.h | 4 ++++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index c7591877c350..a375eb33ac69 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -1047,8 +1047,7 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
 	r_array = arm_bpf_get_reg32(r2[1], tmp2[1], ctx);
 	emit(ARM_ADD_I(tmp[1], r_array, off), ctx);
 	r_index = arm_bpf_get_reg32(r3[1], tmp2[1], ctx);
-	emit(ARM_MOV_SI(tmp[0], r_index, SRTYPE_ASL, 2), ctx);
-	emit(ARM_LDR_R(tmp[1], tmp[1], tmp[0]), ctx);
+	emit(ARM_LDR_R_SI(tmp[1], tmp[1], r_index, SRTYPE_ASL, 2), ctx);
 	emit(ARM_CMP_I(tmp[1], 0), ctx);
 	_emit(ARM_COND_EQ, ARM_B(jmp_offset), ctx);
 
diff --git a/arch/arm/net/bpf_jit_32.h b/arch/arm/net/bpf_jit_32.h
index ca9f1f5589f4..9d605e7a8309 100644
--- a/arch/arm/net/bpf_jit_32.h
+++ b/arch/arm/net/bpf_jit_32.h
@@ -190,6 +190,10 @@
 #define ARM_LDR_R(rt, rn, rm)	(ARM_INST_LDR_R | ARM_INST_LDST__U \
 				 | (rt) << 12 | (rn) << 16 \
 				 | (rm))
+#define ARM_LDR_R_SI(rt, rn, rm, type, imm) \
+				(ARM_INST_LDR_R | ARM_INST_LDST__U \
+				 | (rt) << 12 | (rn) << 16 \
+				 | (imm) << 7 | (type) << 5 | (rm))
 #define ARM_LDRB_R(rt, rn, rm)	(ARM_INST_LDRB_R | ARM_INST_LDST__U \
 				 | (rt) << 12 | (rn) << 16 \
 				 | (rm))
-- 
2.7.4