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Replace assert with assume for release build optimization (#1390)

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Sylvie
2024-04-02 11:09:31 -04:00
committed by GitHub
parent 1d39e5ed56
commit a234da42a6
26 changed files with 158 additions and 147 deletions
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32
include/helpers.hpp
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@@ -3,12 +3,12 @@
#ifndef HELPERS_H
#define HELPERS_H
// Ideally, we'd use `__has_attribute` and `__has_builtin`, but these were only introduced in GCC 9
// Ideally we'd use `std::unreachable`, but it has insufficient compiler support
#ifdef __GNUC__ // GCC or compatible
// In release builds, define "unreachable" as such, but trap in debug builds
#ifdef NDEBUG
#define unreachable_ __builtin_unreachable
#else
// In release builds, define "unreachable" as such, but trap in debug builds
#define unreachable_ __builtin_trap
#endif
#else
@@ -18,32 +18,52 @@
}
#endif
// Use builtins whenever possible, and shim them otherwise
// Ideally we'd use `[[assume()]]`, but it has insufficient compiler support
#ifdef NDEBUG
#ifdef _MSC_VER
#define assume(x) __assume(x)
#else
// `[[gnu::assume()]]` for GCC or compatible also has insufficient support (GCC 13+ only)
#define assume(x) \
do { \
if (!(x)) \
unreachable_(); \
} while (0)
#endif
#else
// In release builds, define "assume" as such, but `assert` in debug builds
#include <assert.h>
#define assume assert
#endif
// Ideally we'd use `std::bit_width`, but it has insufficient compiler support
#ifdef __GNUC__ // GCC or compatible
#define ctz __builtin_ctz
#define clz __builtin_clz
#elif defined(_MSC_VER)
#include <assert.h>
#include <intrin.h>
#pragma intrinsic(_BitScanReverse, _BitScanForward)
static inline int ctz(unsigned int x) {
unsigned long cnt;
assert(x != 0);
assume(x != 0);
_BitScanForward(&cnt, x);
return cnt;
}
static inline int clz(unsigned int x) {
unsigned long cnt;
assert(x != 0);
assume(x != 0);
_BitScanReverse(&cnt, x);
return 31 - cnt;
}
#else
#include <limits.h>
static inline int ctz(unsigned int x) {
int cnt = 0;