linux-kernel - [PATCH] lib/raid6: use vdupq_n_u8 to avoid endianness warnings

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Message-Id: <20190226040345.202047-1-ndesaulniers@google.com>
Date:   Mon, 25 Feb 2019 20:03:42 -0800
From:   ndesaulniers@...gle.com
To:     catalin.marinas@....com, will.deacon@....com
Cc:     ard.biesheuvel@...aro.org, arnd@...db.de, broonie@...nel.org,
        linux@...linux.org.uk, linux-arm-kernel@...ts.infradead.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] lib/raid6: use vdupq_n_u8 to avoid endianness warnings

Clang warns: vector initializers are not compatible with NEON intrinsics
in big endian mode [-Wnonportable-vector-initialization]

While this is usually the case, it's not an issue for this case since
we're initializing the uint8x16_t (16x uint8_t's) with the same value.

Instead, use vdupq_n_u8 which both compilers lower into a single movi
instruction: https://godbolt.org/z/vBrgzt

This avoids the static storage for a constant value.

Link: https://github.com/ClangBuiltLinux/linux/issues/214
Suggested-by: Nathan Chancellor <natechancellor@...il.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 lib/raid6/neon.uc            | 5 ++---
 lib/raid6/recov_neon_inner.c | 7 ++-----
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/lib/raid6/neon.uc b/lib/raid6/neon.uc
index d5242f544551..b7c68030da4f 100644
--- a/lib/raid6/neon.uc
+++ b/lib/raid6/neon.uc
@@ -28,7 +28,6 @@
 
 typedef uint8x16_t unative_t;
 
-#define NBYTES(x) ((unative_t){x,x,x,x, x,x,x,x, x,x,x,x, x,x,x,x})
 #define NSIZE	sizeof(unative_t)
 
 /*
@@ -61,7 +60,7 @@ void raid6_neon$#_gen_syndrome_real(int disks, unsigned long bytes, void **ptrs)
 	int d, z, z0;
 
 	register unative_t wd$$, wq$$, wp$$, w1$$, w2$$;
-	const unative_t x1d = NBYTES(0x1d);
+	const unative_t x1d = vdupq_n_u8(0x1d);
 
 	z0 = disks - 3;		/* Highest data disk */
 	p = dptr[z0+1];		/* XOR parity */
@@ -92,7 +91,7 @@ void raid6_neon$#_xor_syndrome_real(int disks, int start, int stop,
 	int d, z, z0;
 
 	register unative_t wd$$, wq$$, wp$$, w1$$, w2$$;
-	const unative_t x1d = NBYTES(0x1d);
+	const unative_t x1d = vdupq_n_u8(0x1d);
 
 	z0 = stop;		/* P/Q right side optimization */
 	p = dptr[disks-2];	/* XOR parity */
diff --git a/lib/raid6/recov_neon_inner.c b/lib/raid6/recov_neon_inner.c
index 8cd20c9f834a..7d00c31a6547 100644
--- a/lib/raid6/recov_neon_inner.c
+++ b/lib/raid6/recov_neon_inner.c
@@ -10,11 +10,6 @@
 
 #include <arm_neon.h>
 
-static const uint8x16_t x0f = {
-	0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f,
-	0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f,
-};
-
 #ifdef CONFIG_ARM
 /*
  * AArch32 does not provide this intrinsic natively because it does not
@@ -41,6 +36,7 @@ void __raid6_2data_recov_neon(int bytes, uint8_t *p, uint8_t *q, uint8_t *dp,
 	uint8x16_t pm1 = vld1q_u8(pbmul + 16);
 	uint8x16_t qm0 = vld1q_u8(qmul);
 	uint8x16_t qm1 = vld1q_u8(qmul + 16);
+	uint8x16_t x0f = vdupq_n_u8(0x0f);
 
 	/*
 	 * while ( bytes-- ) {
@@ -87,6 +83,7 @@ void __raid6_datap_recov_neon(int bytes, uint8_t *p, uint8_t *q, uint8_t *dq,
 {
 	uint8x16_t qm0 = vld1q_u8(qmul);
 	uint8x16_t qm1 = vld1q_u8(qmul + 16);
+	uint8x16_t x0f = vdupq_n_u8(0x0f);
 
 	/*
 	 * while (bytes--) {
-- 
2.21.0.rc2.261.ga7da99ff1b-goog