Category
Purpose
Specifies registers that may be altered by functions specified by #pragma mc_func.
Ordinarily, code generated for functions specified by #pragma mc_func may alter any or all volatile registers available on your system. You can use #pragma reg_killed_by to explicitly list a specific set of volatile registers to be altered by such functions. Registers not in this list will not be altered.
Syntax
.-,------------------------------. V | >>-#--pragma--reg_killed_by--function----+----------------------------+-+->< '-register -+--------------+-' '- ---register-'
Parameters
- function
- The name of a function previously defined using the #pragma mc_func directive.
- register
- The symbolic name(s) of either a single register or a range of
registers to be altered by the named function. The symbolic
name must be a valid register name on the target platform. Valid registers
are:
- cr0, cr1, and cr5 to cr7
- Condition registers
- ctr
- Count register
- gr0 and gr3 to gr12
- General purpose registers
- fp0 to fp13
- Floating-point registers
- fsr
- Floating-point and status control register
- lr
- Link register
- vr0 to vr31
- Vector registers (on selected processors only)
- xer
- Fixed-point exception register
You can identify a range of registers by providing the symbolic names of both starting and ending registers, separated by a dash.
If no register is specified, no volatile registers will be killed by the named function.
Examples
The following example shows how
to use #pragma reg_killed_by to list a specific set of volatile
registers to be used by the function defined by #pragma mc_func.
int add_logical(int, int);
#pragma mc_func add_logical {"7c632014" "7c630194"}
/* addc r3 <- r3, r4 */
/* addze r3 <- r3, carry bit */
#pragma reg_killed_by add_logical gr3, xer
/* only gpr3 and the xer are altered by this function */
main() {
int i,j,k;
i = 4;
k = -4;
j = add_logical(i,k);
printf("\n\nresult = %d\n\n",j);
}