__fetch_and_add, __builtin_ppc_fetch_and_add, __fetch_and_addlp, __builtin_ppc_fetch_and_addlp

Purpose

Clears and sets bits in the word or doubleword specified by addr by ADD-ing that value with the value specified by val, in a single atomic operation, and returns the original value of addr.

Prototype

int __builtin_ppc_fetch_and_add (volatile int* addr, int val);

long __builtin_ppc_fetch_and_addlp (volatile long* addr, long val);

int __fetch_and_add (volatile int* addr, int val);

long __fetch_and_addlp (volatile long* addr, long val);

Note:

The built-in function in the form of __name is a synonym of the built-in function in the form of __builtin_ppc_name.
The built-in function in the form of __name is provided for compatibility with IBM® XL C/C++ for AIX® 16.1.0 or earlier releases. This built-in function form might be deprecated in the future.

Parameters

addr: The address of the variable to be ADDed. Must be aligned on a 4-byte boundary for a single word and on an 8-byte boundary for a doubleword.
value: The value by which the value in addr is to be ADDed.

Usage

This operation is useful when a variable containing bit flags is shared between several threads or processes.

__fetch_and_addlp is valid only in 64-bit mode.

Note:

This function generates the hardware instruction but does not act as an instruction movement barrier within the compiler. If that is needed, you must also use the __fence function.