RealView Compilation Tools Compiler Reference Guide - ARM ...

Compiler-specific Features
4.7.3 __builtin_constant_p
This builtin function determines if a value is known to be constant at compile-time.
Note
This builtin function is a GNU compiler extension that is supported by the ARM
compiler.
Mode
Supported in GNU mode only.
Syntax
int __builtin_constant_p(...)
Where:
... is the argument whose value is to be tested.
Return value
__builtin_constant_p returns the integer 1 if the argument is known to be a
compile-time constant and 0 if it is not known to be a compile-time constant.
Restrictions
A return value of 0 does not indicate that the value is not a constant, but that the
compiler cannot prove it is a constant with the specified value of the -O option.
See also
• -Onum on page 2-66.
4.7.4 __builtin_expect
This intrinsic provides the compiler with branch prediction information. Calling
__builtin_expect(expr, c) informs the compiler that it is expected that expr == c.
Note
This builtin function is a GNU compiler extension that is supported by the ARM
compiler.
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