netdev - [PATCH RFC bpf-next 09/10] arm: include: asm: swab: mask rev16 instruction for clang

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Date:   Fri, 30 Aug 2019 03:50:36 +0300
From:   Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:     linux@...linux.org.uk, ast@...nel.org, daniel@...earbox.net,
        yhs@...com, davem@...emloft.net, jakub.kicinski@...ronome.com,
        hawk@...nel.org, john.fastabend@...il.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
Subject: [PATCH RFC bpf-next 09/10] arm: include: asm: swab: mask rev16 instruction for clang

The samples/bpf with clang -emit-llvm reuses linux headers to build
bpf samples, and this w/a only for samples (samples/bpf/Makefile
CLANG-bpf).

It allows to build samples/bpf for arm bpf using clang.
In another way clang -emit-llvm generates errors like:

CLANG-bpf  samples/bpf/tc_l2_redirect_kern.o
<inline asm>:1:2: error: invalid register/token name
rev16 r3, r0

This decision is arguable, probably there is another way, but
it doesn't have impact on samples/bpf, so it's easier just ignore
it for clang, at least for now.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
---
 arch/arm/include/asm/swab.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/include/asm/swab.h b/arch/arm/include/asm/swab.h
index c6051823048b..a9fd9cd33d5e 100644
--- a/arch/arm/include/asm/swab.h
+++ b/arch/arm/include/asm/swab.h
@@ -25,8 +25,11 @@ static inline __attribute_const__ __u32 __arch_swahb32(__u32 x)
 	__asm__ ("rev16 %0, %1" : "=r" (x) : "r" (x));
 	return x;
 }
+
+#ifndef __clang__
 #define __arch_swahb32 __arch_swahb32
 #define __arch_swab16(x) ((__u16)__arch_swahb32(x))
+#endif
 
 static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
 {
-- 
2.17.1