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https://github.com/gbdev/rgbds.git
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94 lines
2.3 KiB
C++
94 lines
2.3 KiB
C++
/* SPDX-License-Identifier: MIT */
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#ifndef HELPERS_H
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#define HELPERS_H
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// Ideally, we'd use `__has_attribute` and `__has_builtin`, but these were only introduced in GCC 9
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#ifdef __GNUC__ // GCC or compatible
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#define format_(archetype, str_index, first_arg) \
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__attribute__((format(archetype, str_index, first_arg)))
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#define attr_(...) __attribute__((__VA_ARGS__))
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// In release builds, define "unreachable" as such, but trap in debug builds
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#ifdef NDEBUG
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#define unreachable_ __builtin_unreachable
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#else
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#define unreachable_ __builtin_trap
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#endif
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#else
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// Unsupported, but no need to throw a fit
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#define format_(archetype, str_index, first_arg)
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#define attr_(...)
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// This seems to generate similar code to __builtin_unreachable, despite different semantics
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// Note that executing this is undefined behavior (declared [[noreturn]], but does return)
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[[noreturn]] static inline void unreachable_() {
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}
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#endif
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// Use builtins whenever possible, and shim them otherwise
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#ifdef __GNUC__ // GCC or compatible
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#define ctz __builtin_ctz
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#define clz __builtin_clz
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#elif defined(_MSC_VER)
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#include <assert.h>
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#include <intrin.h>
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#pragma intrinsic(_BitScanReverse, _BitScanForward)
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static inline int ctz(unsigned int x) {
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unsigned long cnt;
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assert(x != 0);
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_BitScanForward(&cnt, x);
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return cnt;
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}
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static inline int clz(unsigned int x) {
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unsigned long cnt;
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assert(x != 0);
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_BitScanReverse(&cnt, x);
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return 31 - cnt;
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}
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#else
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#include <limits.h>
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static inline int ctz(unsigned int x) {
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int cnt = 0;
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while (!(x & 1)) {
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x >>= 1;
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cnt++;
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}
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return cnt;
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}
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static inline int clz(unsigned int x) {
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int cnt = 0;
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while (x <= UINT_MAX / 2) {
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x <<= 1;
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cnt++;
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}
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return cnt;
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}
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#endif
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// Macros for stringification
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#define STR(x) #x
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#define EXPAND_AND_STR(x) STR(x)
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// Obtaining the size of an array; `arr` must be an expression, not a type!
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// (Having two instances of `arr` is OK because the contents of `sizeof` are not evaluated.)
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#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof *(arr))
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// For lack of <ranges>, this adds some more brevity
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#define RANGE(s) std::begin(s), std::end(s)
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// Convenience feature for visiting variants.
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template<typename... Ts>
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struct Visitor : Ts... {
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using Ts::operator()...;
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};
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template<typename... Ts>
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Visitor(Ts...) -> Visitor<Ts...>;
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#endif // HELPERS_H
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