Datasheet

ARM Compiler Reference

real_num

Is the value passed in r12 to the SWI handler. You

can use this feature to implement indirect SWIs.

The SWI handler can use r12 to determine the

function to perform.

For example:

int __swi_indirect(0) ioctl(int swino, int fn,

void *argp);

This SWI can be called as follows:

ioctl(IOCTL+4, RESET, NULL);

It compiles to a SWI 0 with IOCTL+4 in r12.

To use the indirect SWI mechanism, your system SWI handlers must

make use of the r12 value to select the required operation.

__value_in_regs

This instructs the compiler to return a structure of up to four integer

words in integer registers or up to four floats or doubles in floating-point

registers rather than using memory, for example:

typedef struct int64_struct {

unsigned int lo;

unsigned int hi;

} int64_struct;

__value_in_regs extern

int64_struct mul64(unsigned a, unsigned b);

Declaring a function

__value_in_regs

can be useful when calling

assembler functions that return more than one result. See the AXD and

armsd Debuggers Guide for information on the default method of passing

and returning structures.

Note

A C++ function cannot return a

__value_in_regs

structure if the structure

requires copy constructing.

Function storage class modifiers

A storage class modifier is a subset of function declaration keywords, however they do

not affect the type of the function.

__inline

This instructs the compiler to compile a C function inline if it is sensible

to do so. The semantics of

__inline

are exactly the same as those of the

C++

inline

keyword: