[ovs-dev] [PATCH] hash: Convert macros to inline functions.

Ethan Jackson ethan at nicira.com
Wed Feb 1 17:38:28 PST 2012


Looks good,

Ethan

On Wed, Jan 18, 2012 at 11:30, Ben Pfaff <blp at nicira.com> wrote:
> I always assumed that macros would generate better code.  I was wrong.  The
> generated code was identical with inline functions, with GCC version 4.4.5.
>
> Signed-off-by: Ben Pfaff <blp at nicira.com>
> ---
>  lib/hash.c |   12 ++++++------
>  lib/hash.h |   50 ++++++++++++++++++++++++++++----------------------
>  2 files changed, 34 insertions(+), 28 deletions(-)
>
> diff --git a/lib/hash.c b/lib/hash.c
> index 61e17b2..b3d9156 100644
> --- a/lib/hash.c
> +++ b/lib/hash.c
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (c) 2008, 2009, 2010 Nicira Networks.
> + * Copyright (c) 2008, 2009, 2010, 2012 Nicira Networks.
>  *
>  * Licensed under the Apache License, Version 2.0 (the "License");
>  * you may not use this file except in compliance with the License.
> @@ -30,7 +30,7 @@ hash_words(const uint32_t *p, size_t n, uint32_t basis)
>         a += p[0];
>         b += p[1];
>         c += p[2];
> -        HASH_MIX(a, b, c);
> +        hash_mix(&a, &b, &c);
>         n -= 3;
>         p += 3;
>     }
> @@ -44,7 +44,7 @@ hash_words(const uint32_t *p, size_t n, uint32_t basis)
>         /* fall through */
>     case 1:
>         a += p[0];
> -        HASH_FINAL(a, b, c);
> +        hash_final(&a, &b, &c);
>         /* fall through */
>     case 0:
>         break;
> @@ -59,7 +59,7 @@ hash_3words(uint32_t a, uint32_t b, uint32_t c)
>     a += 0xdeadbeef;
>     b += 0xdeadbeef;
>     c += 0xdeadbeef;
> -    HASH_FINAL(a, b, c);
> +    hash_final(&a, &b, &c);
>     return c;
>  }
>
> @@ -85,7 +85,7 @@ hash_bytes(const void *p_, size_t n, uint32_t basis)
>         a += tmp[0];
>         b += tmp[1];
>         c += tmp[2];
> -        HASH_MIX(a, b, c);
> +        hash_mix(&a, &b, &c);
>         n -= sizeof tmp;
>         p += sizeof tmp;
>     }
> @@ -96,7 +96,7 @@ hash_bytes(const void *p_, size_t n, uint32_t basis)
>         a += tmp[0];
>         b += tmp[1];
>         c += tmp[2];
> -        HASH_FINAL(a, b, c);
> +        hash_final(&a, &b, &c);
>     }
>
>     return c;
> diff --git a/lib/hash.h b/lib/hash.h
> index 026eeda..05799b2 100644
> --- a/lib/hash.h
> +++ b/lib/hash.h
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (c) 2008, 2009, 2010 Nicira Networks.
> + * Copyright (c) 2008, 2009, 2010, 2012 Nicira Networks.
>  *
>  * Licensed under the Apache License, Version 2.0 (the "License");
>  * you may not use this file except in compliance with the License.
> @@ -29,28 +29,34 @@ extern "C" {
>  /* This is the public domain lookup3 hash by Bob Jenkins from
>  * http://burtleburtle.net/bob/c/lookup3.c, modified for style. */
>
> -#define HASH_ROT(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
> +static inline uint32_t
> +hash_rot(uint32_t x, int k)
> +{
> +    return (x << k) | (x >> (32 - k));
> +}
>
> -#define HASH_MIX(a, b, c)                       \
> -    do {                                        \
> -      a -= c; a ^= HASH_ROT(c,  4); c += b;     \
> -      b -= a; b ^= HASH_ROT(a,  6); a += c;     \
> -      c -= b; c ^= HASH_ROT(b,  8); b += a;     \
> -      a -= c; a ^= HASH_ROT(c, 16); c += b;     \
> -      b -= a; b ^= HASH_ROT(a, 19); a += c;     \
> -      c -= b; c ^= HASH_ROT(b,  4); b += a;     \
> -    } while (0)
> +static inline void
> +hash_mix(uint32_t *a, uint32_t *b, uint32_t *c)
> +{
> +      *a -= *c; *a ^= hash_rot(*c,  4); *c += *b;
> +      *b -= *a; *b ^= hash_rot(*a,  6); *a += *c;
> +      *c -= *b; *c ^= hash_rot(*b,  8); *b += *a;
> +      *a -= *c; *a ^= hash_rot(*c, 16); *c += *b;
> +      *b -= *a; *b ^= hash_rot(*a, 19); *a += *c;
> +      *c -= *b; *c ^= hash_rot(*b,  4); *b += *a;
> +}
>
> -#define HASH_FINAL(a, b, c)                     \
> -    do {                                        \
> -      c ^= b; c -= HASH_ROT(b, 14);             \
> -      a ^= c; a -= HASH_ROT(c, 11);             \
> -      b ^= a; b -= HASH_ROT(a, 25);             \
> -      c ^= b; c -= HASH_ROT(b, 16);             \
> -      a ^= c; a -= HASH_ROT(c,  4);             \
> -      b ^= a; b -= HASH_ROT(a, 14);             \
> -      c ^= b; c -= HASH_ROT(b, 24);             \
> -    } while (0)
> +static inline void
> +hash_final(uint32_t *a, uint32_t *b, uint32_t *c)
> +{
> +      *c ^= *b; *c -= hash_rot(*b, 14);
> +      *a ^= *c; *a -= hash_rot(*c, 11);
> +      *b ^= *a; *b -= hash_rot(*a, 25);
> +      *c ^= *b; *c -= hash_rot(*b, 16);
> +      *a ^= *c; *a -= hash_rot(*c,  4);
> +      *b ^= *a; *b -= hash_rot(*a, 14);
> +      *c ^= *b; *c -= hash_rot(*b, 24);
> +}
>
>  uint32_t hash_words(const uint32_t *, size_t n_word, uint32_t basis);
>  uint32_t hash_2words(uint32_t, uint32_t);
> @@ -87,7 +93,7 @@ static inline uint32_t hash_boolean(bool x, uint32_t basis)
>  {
>     const uint32_t P0 = 0xc2b73583;   /* This is hash_int(1, 0). */
>     const uint32_t P1 = 0xe90f1258;   /* This is hash_int(2, 0). */
> -    return (x ? P0 : P1) ^ HASH_ROT(basis, 1);
> +    return (x ? P0 : P1) ^ hash_rot(basis, 1);
>  }
>
>  static inline uint32_t hash_double(double x, uint32_t basis)
> --
> 1.7.2.5
>
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