linux-kernel - Re: [PATCH 1/2] lib: Add lz4 compressor module

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Date:	Thu, 18 Apr 2013 11:50:08 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Chanho Min <chanho.min@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Darrick J. Wong" <djwong@...ibm.com>,
	Bob Pearson <rpearson@...temfabricworks.com>,
	Richard Weinberger <richard@....at>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-crypto@...r.kernel.org,
	Yann Collet <yann.collet.73@...il.com>,
	Kyungsik Lee <kyungsik.lee@....com>,
	Chanho Min <chanho0207@...il.com>,
	"Linux/m68k" <linux-m68k@...r.kernel.org>,
	sparclinux <sparclinux@...r.kernel.org>,
	Linux-Next <linux-next@...r.kernel.org>
Subject: Re: [PATCH 1/2] lib: Add lz4 compressor module

On Thu, Mar 14, 2013 at 10:48 AM, Chanho Min <chanho.min@....com> wrote:
> +#ifdef __BIG_ENDIAN
> +#define LZ4_NBCOMMONBYTES(val) (__builtin_clzll(val) >> 3)
> +#else
> +#define LZ4_NBCOMMONBYTES(val) (__builtin_ctzll(val) >> 3)
> +#endif
>
>  #else  /* 32-bit */
>  #define STEPSIZE 4
> @@ -83,6 +130,14 @@ typedef struct _U64_S { u64 v; } U64_S;
>         } while (0)
>
>  #define LZ4_SECURECOPY LZ4_WILDCOPY
> +#define HTYPE const u8*
> +
> +#ifdef __BIG_ENDIAN
> +#define LZ4_NBCOMMONBYTES(val) (__builtin_clz(val) >> 3)
> +#else
> +#define LZ4_NBCOMMONBYTES(val) (__builtin_ctz(val) >> 3)
> +#endif

It seems at least m68k and sparc don't have the __builtin_clz() functions:

m68k-allmodconfig (http://kisskb.ellerman.id.au/kisskb/buildresult/8572593/):

ERROR: "__clzsi2" [lib/lz4/lz4hc_compress.ko] undefined!
ERROR: "__clzsi2" [lib/lz4/lz4_compress.ko] undefined!

sparc64-allmodconfig (http://kisskb.ellerman.id.au/kisskb/buildresult/8572790/):

ERROR: "__clzdi2" [lib/lz4/lz4hc_compress.ko] undefined!
ERROR: "__clzdi2" [lib/lz4/lz4_compress.ko] undefined!

sparc-allmodconfig (http://kisskb.ellerman.id.au/kisskb/buildresult/8572795/):

ERROR: "__clzdi2" [lib/lz4/lz4hc_compress.ko] undefined!
ERROR: "__clzdi2" [lib/lz4/lz4_compress.ko] undefined!

There may be more, hidden by build errors before reaching the link or modpost
phases.

The gmail-whitespace-damaged patch below fixes the m68k and sparc builds
for me, does this look acceptable?

diff --git a/lib/lz4/lz4defs.h b/lib/lz4/lz4defs.h
index abcecdc..81d3251 100644
--- a/lib/lz4/lz4defs.h
+++ b/lib/lz4/lz4defs.h
@@ -107,12 +107,6 @@ typedef struct _U64_S { u64 v; } U64_S;
  } while (0)
 #define HTYPE u32

-#ifdef __BIG_ENDIAN
-#define LZ4_NBCOMMONBYTES(val) (__builtin_clzll(val) >> 3)
-#else
-#define LZ4_NBCOMMONBYTES(val) (__builtin_ctzll(val) >> 3)
-#endif
-
 #else /* 32-bit */
 #define STEPSIZE 4

@@ -132,12 +126,12 @@ typedef struct _U64_S { u64 v; } U64_S;
 #define LZ4_SECURECOPY LZ4_WILDCOPY
 #define HTYPE const u8*

-#ifdef __BIG_ENDIAN
-#define LZ4_NBCOMMONBYTES(val) (__builtin_clz(val) >> 3)
-#else
-#define LZ4_NBCOMMONBYTES(val) (__builtin_ctz(val) >> 3)
 #endif

+#ifdef __BIG_ENDIAN
+#define LZ4_NBCOMMONBYTES(val) (((STEPSIZE * 8) - 1 - __fls(val)) >> 3)
+#else
+#define LZ4_NBCOMMONBYTES(val) (__ffs(val) >> 3)
 #endif

 #define LZ4_READ_LITTLEENDIAN_16(d, s, p) \

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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