__align(n)

Where:

__align(n) is useful when the normal alignment of the variable being declared is less than n. Eight-byte alignment can give a significant performance advantage with VFP instructions.

__align can be used in conjunction with extern and static.

Because __align is a storage class modifier, it cannot be used on:

You can only overalign. That is, you can make a two-byte object four-byte aligned but you cannot align a four-byte object at 2 bytes.

__align(8) char buffer[128];  // buffer starts on eight-byte boundary

void foo(void)
{
    ...
    __align(16) int i; // this alignment value is not permitted for
                       // a local variable
    ...
}

__align(16) int i; // permitted as a global variable.