diff options
Diffstat (limited to 'tools/include/linux')
| -rw-r--r-- | tools/include/linux/bits.h | 5 | ||||
| -rw-r--r-- | tools/include/linux/compiler.h | 22 |
2 files changed, 24 insertions, 3 deletions
diff --git a/tools/include/linux/bits.h b/tools/include/linux/bits.h index 8de2914e6510..14fd0ca9a6cd 100644 --- a/tools/include/linux/bits.h +++ b/tools/include/linux/bits.h @@ -20,9 +20,8 @@ */ #if !defined(__ASSEMBLY__) #include <linux/build_bug.h> -#define GENMASK_INPUT_CHECK(h, l) \ - (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ - __is_constexpr((l) > (h)), (l) > (h), 0))) +#include <linux/compiler.h> +#define GENMASK_INPUT_CHECK(h, l) BUILD_BUG_ON_ZERO(const_true((l) > (h))) #else /* * BUILD_BUG_ON_ZERO is not available in h files included from asm files, diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h index 9c05a59f0184..d627e66a04a6 100644 --- a/tools/include/linux/compiler.h +++ b/tools/include/linux/compiler.h @@ -81,6 +81,28 @@ #define __is_constexpr(x) \ (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) +/* + * Similar to statically_true() but produces a constant expression + * + * To be used in conjunction with macros, such as BUILD_BUG_ON_ZERO(), + * which require their input to be a constant expression and for which + * statically_true() would otherwise fail. + * + * This is a trade-off: const_true() requires all its operands to be + * compile time constants. Else, it would always returns false even on + * the most trivial cases like: + * + * true || non_const_var + * + * On the opposite, statically_true() is able to fold more complex + * tautologies and will return true on expressions such as: + * + * !(non_const_var * 8 % 4) + * + * For the general case, statically_true() is better. + */ +#define const_true(x) __builtin_choose_expr(__is_constexpr(x), x, false) + #ifdef __ANDROID__ /* * FIXME: Big hammer to get rid of tons of: |