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Compiler-specific Features
4.1.18 __value_in_regs
The __value_in_regs qualifier 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.
__value_in_regs is a function qualifier. It affects the type of a function.
Syntax
__value_in_regs return-type function-name([argument-list]);
Where:
return-type
is the type of a structure of up to four words in size.
Usage
Declaring a function __value_in_regs can be useful when calling functions that return
more than one result.
Restrictions
A C++ function cannot return a __value_in_regs structure if the structure requires copy
constructing.
If a virtual function declared as __value_in_regs is to be overridden, the overriding
function must also be declared as __value_in_regs. If the functions do not match, the
compiler generates an error.
Errors
Where the structure returned in a function qualified by __value_in_regs is too big, a
warning is produced and the __value_in_regs structure is then ignored.
Example
typedef struct int64_struct
{
unsigned int lo;
unsigned int hi;
} int64_struct;
__value_in_regs extern
int64_struct mul64(unsigned a, unsigned b);
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