bdiff: don't check border condition in loop
This is pretty much a copy of d500ddae7494, just to a different loop.
The condition `p == plast` (`plast == a + len - 1`) was only true on
the final iteration of the loop. So it was wasteful to check for it
on every iteration. We decrease the iteration count by 1 and add an
explicit check for `p == plast` after the loop.
Again, we see modest wins.
From the mozilla-unified repository:
$ perfbdiff -m 3041e4d59df2
! wall 0.035502 comb 0.040000 user 0.040000 sys 0.000000 (best of 100)
! wall 0.030480 comb 0.030000 user 0.030000 sys 0.000000 (best of 100)
$ perfbdiff 0e9928989e9c --alldata --count 100
! wall 4.097394 comb 4.100000 user 4.100000 sys 0.000000 (best of 3)
! wall 3.597798 comb 3.600000 user 3.600000 sys 0.000000 (best of 3)
The 2nd example throws a total of ~3.3GB of data at bdiff. This
change increases the throughput from ~811 MB/s to ~924 MB/s.
/**
* Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
/* Note : this module is expected to remain private, do not expose it */
#ifndef ERROR_H_MODULE
#define ERROR_H_MODULE
#if defined (__cplusplus)
extern "C" {
#endif
/* ****************************************
* Dependencies
******************************************/
#include <stddef.h> /* size_t */
#include "zstd_errors.h" /* enum list */
/* ****************************************
* Compiler-specific
******************************************/
#if defined(__GNUC__)
# define ERR_STATIC static __attribute__((unused))
#elif defined (__cplusplus) || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */)
# define ERR_STATIC static inline
#elif defined(_MSC_VER)
# define ERR_STATIC static __inline
#else
# define ERR_STATIC static /* this version may generate warnings for unused static functions; disable the relevant warning */
#endif
/*-****************************************
* Customization (error_public.h)
******************************************/
typedef ZSTD_ErrorCode ERR_enum;
#define PREFIX(name) ZSTD_error_##name
/*-****************************************
* Error codes handling
******************************************/
#ifdef ERROR
# undef ERROR /* reported already defined on VS 2015 (Rich Geldreich) */
#endif
#define ERROR(name) ((size_t)-PREFIX(name))
ERR_STATIC unsigned ERR_isError(size_t code) { return (code > ERROR(maxCode)); }
ERR_STATIC ERR_enum ERR_getErrorCode(size_t code) { if (!ERR_isError(code)) return (ERR_enum)0; return (ERR_enum) (0-code); }
/*-****************************************
* Error Strings
******************************************/
const char* ERR_getErrorString(ERR_enum code); /* error_private.c */
ERR_STATIC const char* ERR_getErrorName(size_t code)
{
return ERR_getErrorString(ERR_getErrorCode(code));
}
#if defined (__cplusplus)
}
#endif
#endif /* ERROR_H_MODULE */