diff options
Diffstat (limited to 'gen/bits/intconf.c')
| -rw-r--r-- | gen/bits/intconf.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/gen/bits/intconf.c b/gen/bits/intconf.c index 7e48fce..5a52d12 100644 --- a/gen/bits/intconf.c +++ b/gen/bits/intconf.c @@ -21,7 +21,18 @@ +/** + * Used to determine the signness of `char`. + */ volatile char nul = 0; + +/** + * Used to determine the signness of `wchar_t`. + * + * Note that `wchar_t` is set implicitly by the + * help of the compiler so that our libc does + * not taint the result. + */ volatile typeof(L'\0') wnul = 0; @@ -35,6 +46,15 @@ volatile typeof(L'\0') wnul = 0; */ +/** + * Measure the performance of a intrinsic integer type, + * and if it is faster than the previous candidate (or + * is the first candidate,) store it as the, yet, most + * performant candidate. + * + * @param VAR A volatile register variable of the + * type that shall be tested. + */ #define FAST_TEST(VAR) \ n = 0, *VAR##p = 0; \ if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &start)) \ @@ -65,10 +85,26 @@ volatile typeof(L'\0') wnul = 0; last = this +/** + * Determine whether the performance of `typeof(VAR)` should be determined, + * when finding the most performant, compatiable intrinsic type of a `int_fastN_t`. + * + * @param VAR An variable of the type (or the type itself) that is a candidate. + * @return Determine whether the type shall be tested. + */ #define TEST(VAR) (this = 8 * (int)sizeof(VAR), ((this >= bits) && (this > last))) + #if defined(__GNUC__) __attribute__((optimize("-O0"))) #endif +/** + * Find the (in general) fastest intrinsic integer type, + * that has at least a specified number of bits. + * + * @param bits The minimum number of bits the type may have. + * @return The number of bits the most performance + * compatible integer type has. + */ static int fast(int bits) { int last = 0, this = 0, best = 0, n, m; @@ -103,11 +139,26 @@ static int fast(int bits) #undef TEST +/** + * @param argc The number of command line arguments, should + * be either 1 (print integer width information) + * or 2 (otherwise). + * @param argv Command line arguments, if `argc == 2`, `argv[2]` + * is interpreted as follows: + * - "fast8" Print the number of bits in `int_fast8_t` and `uint_fast8_t`. + * - "fast16" Print the number of bits in `int_fast16_t` and `uint_fast16_t`. + * - "fast32" Print the number of bits in `int_fast32_t` and `uint_fast32_t`. + * - "fast64" Print the number of bits in `int_fast64_t` and `uint_fast64_t`. + * - "char-signed" Print 1 if `char` is signed, and `0` if it is unsigned. + * - "wchar-signed" Print 1 if `wchar_t` is signed, and `0` if it is unsigned. + * @return 0 on success, 1 on error (including printing error.) + */ int main(int argc, char* argv[]) { int r = 0; if (argc < 2) { + /* Print the number of bits in the intrinsic integers types. */ r |= printf("CHAR_BIT %zu\n", 8 * sizeof(char)); r |= printf("SHORT_BIT %zu\n", 8 * sizeof(short int)); r |= printf("INT_BIT %zu\n", 8 * sizeof(int)); @@ -116,6 +167,7 @@ int main(int argc, char* argv[]) r |= printf("PTR_BIT %zu\n", 8 * sizeof(void*)); r |= printf("WCHAR_BIT %zu\n", 8 * sizeof(L'\0')); + /* Print the intrinsic type for specific numbers of bits. */ r |= printf("INT%zu %s\n", 8 * sizeof(char), "char"); r |= printf("INT%zu %s\n", 8 * sizeof(short int), "short int"); r |= printf("INT%zu %s\n", 8 * sizeof(int), "int"); |