Low-level integer routines with gcc: Difference between revisions
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Gcc supports low-level integer routines similar to the FORTRAN routines POPCOUNT, ISHIFT... | Gcc supports low-level integer routines similar to the FORTRAN routines POPCOUNT, ISHIFT... | ||
The examples below are given for ''long long'', the routines name changes for ''long'' and ''int'' | |||
<source lang="cpp"> | <source lang="cpp"> | ||
long long __ashlti3 (long long a, int b ) //These functions return the result of shifting a left by b bits. | long long __ashlti3 (long long a, int b ) //These functions return the result of shifting a left by b bits. |
Revision as of 16:31, 11 April 2012
Gcc supports low-level integer routines similar to the FORTRAN routines POPCOUNT, ISHIFT...
The examples below are given for long long, the routines name changes for long and int <source lang="cpp"> long long __ashlti3 (long long a, int b ) //These functions return the result of shifting a left by b bits. long long __ashrti3 (long long a, int b ) //These functions return the result of arithmetically shifting a right by b bits. long long __divti3 (long long a, long long b ) //These functions return the quotient of the signed division of a and b. long long __lshrti3 (long long a, int b ) //These functions return the result of logically shifting a right by b bits. int __clzti2 (long long a ) //These functions return the number of leading 0-bits in a, starting at the most significant bit position.
//If a is zero, the result is undefined.
int __ctzti2 (long long a ) //These functions return the number of trailing 0-bits in a, starting at the least significant bit position.
//If a is zero, the result is undefined.
int __ffsti2 (long long a ) //These functions return the index of the least significant 1-bit in a, or the value zero if a is zero.
// The least significant bit is index one.
int __parityti2 (long long a ) //These functions return the value zero if the number of bits set in a is even, and the value one otherwise. int __popcountti2 (long long a ) //These functions return the number of bits set in a. int64_t __bswapdi2 (int64 t a ) //These functions return the a byteswapped. </source>