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Optimize bit counting using __builtin_popcount

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Use the __builtin_popcount intrinsic to optimize the bit counting
function if the compiler supports it. This change replaces the manual
bit counting algorithm with the more efficient built-in function, which
leverages hardware support on compatible processors.

This modification ensures that the code remains backward-compatible by
falling back to the original implementation when __builtin_popcount is
not available.
This commit is contained in:
Kuan-Wei Chiu 2024-06-24 05:51:55 +08:00
parent 540d741df0
commit ac5815d994
2 changed files with 8 additions and 0 deletions
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4
include/afl-fuzz.h
View File

@ -116,6 +116,10 @@
#include <TargetConditionals.h>
#endif
#ifndef __has_builtin
#define __has_builtin(x) 0
#endif
#undef LIST_FOREACH /* clashes with FreeBSD */
#include "list.h"
#ifndef SIMPLE_FILES

4
src/afl-fuzz-bitmap.c
View File

@ -75,9 +75,13 @@ u32 count_bits(afl_state_t *afl, u8 *mem) {
}
#if __has_builtin(__builtin_popcount)
ret += __builtin_popcount(v);
#else
v -= ((v >> 1) & 0x55555555);
v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
ret += (((v + (v >> 4)) & 0xF0F0F0F) * 0x01010101) >> 24;
#endif
}