Test for sign bit.
int signbit(float ); intn signbit(floatn ); int signbit(double ); longn signbit(doublen );
| int signbit (half) // if half extension enabled shortn signbit (halfn) // if half extension enabled |
|---|
The built-in function signbit tests for sign bit. The scalar version of the function returns a 1 if the sign bit in the float is set else returns 0. The vector version of the function returns the following for each component in floatn: -1 (i.e. all bits set) if the sign bit in the float is set else returns 0.
If an implementation extends this specification to support IEEE-754 flags or exceptions, then all built-in relational functions shall proceed without raising the invalid floating-point exception when one or more of the operands are NaNs.
The built-in relational functions are extended with cl_khr_fp16(3clc) to include appropriate versions of functions that take half, and half{2|3|4|8|16} as arguments and return values.
The function returns a 0 if the specified relation is false and a 1 if the specified relation is true for scalar argument types. These functions shall return a 0 if the specified relation is false and a - 1 (i.e. all bits set) if the specified relation is true for vector argument types.
\m[blue]OpenCL Specification\m[]\s-2\u[1]\d\s+2
relationalFunctions(3clc)
The Khronos Group
Copyright © 2007-2011 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.
OpenCL Specification
page 264, section 6.12.6 - Relational Functions