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/* Licensed under LGPLv2.1+ - see LICENSE file for details */
#ifndef CCAN_LIKELY_H
#define CCAN_LIKELY_H
#include "config.h"
#include <ccan/str/str.h>
#include <stdbool.h>
#ifndef CCAN_LIKELY_DEBUG
#if HAVE_BUILTIN_EXPECT
/**
* likely - indicate that a condition is likely to be true.
* @cond: the condition
*
* This uses a compiler extension where available to indicate a likely
* code path and optimize appropriately; it's also useful for readers
* to quickly identify exceptional paths through functions. The
* threshold for "likely" is usually considered to be between 90 and
* 99%; marginal cases should not be marked either way.
*
* See Also:
* unlikely(), likely_stats()
*
* Example:
* // Returns false if we overflow.
* static inline bool inc_int(unsigned int *val)
* {
* (*val)++;
* if (likely(*val))
* return true;
* return false;
* }
*/
#define likely(cond) __builtin_expect(!!(cond), 1)
/**
* unlikely - indicate that a condition is unlikely to be true.
* @cond: the condition
*
* This uses a compiler extension where available to indicate an unlikely
* code path and optimize appropriately; see likely() above.
*
* See Also:
* likely(), likely_stats(), COLD (compiler.h)
*
* Example:
* // Prints a warning if we overflow.
* static inline void inc_int(unsigned int *val)
* {
* (*val)++;
* if (unlikely(*val == 0))
* fprintf(stderr, "Overflow!");
* }
*/
#define unlikely(cond) __builtin_expect(!!(cond), 0)
#else
#define likely(cond) (!!(cond))
#define unlikely(cond) (!!(cond))
#endif
#else /* CCAN_LIKELY_DEBUG versions */
#define likely(cond) \
(_likely_trace(!!(cond), 1, stringify(cond), __FILE__, __LINE__))
#define unlikely(cond) \
(_likely_trace(!!(cond), 0, stringify(cond), __FILE__, __LINE__))
long _likely_trace(bool cond, bool expect,
const char *condstr,
const char *file, unsigned int line);
#endif
#ifdef CCAN_LIKELY_DEBUG
/**
* likely_stats - return description of abused likely()/unlikely()
* @min_hits: minimum number of hits
* @percent: maximum percentage correct
*
* When CCAN_LIKELY_DEBUG is defined, likely() and unlikely() trace their
* results: this causes a significant slowdown, but allows analysis of
* whether the branches are labelled correctly.
*
* This function returns a malloc'ed description of the least-correct
* usage of likely() or unlikely(). It ignores places which have been
* called less than @min_hits times, and those which were predicted
* correctly more than @percent of the time. It returns NULL when
* nothing meets those criteria.
*
* Note that this call is destructive; the returned offender is
* removed from the trace so that the next call to likely_stats() will
* return the next-worst likely()/unlikely() usage.
*
* Example:
* // Print every place hit more than twice which was wrong > 5%.
* static void report_stats(void)
* {
* #ifdef CCAN_LIKELY_DEBUG
* const char *bad;
*
* while ((bad = likely_stats(2, 95)) != NULL) {
* printf("Suspicious likely: %s", bad);
* free(bad);
* }
* #endif
* }
*/
const char *likely_stats(unsigned int min_hits, unsigned int percent);
#endif /* CCAN_LIKELY_DEBUG */
#endif /* CCAN_LIKELY_H */
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