naga raj <gnuuser.raj@xxxxxxxxx> writes:
> I am using Gcc-4.6.0 and I have used bswap RTL pattern for both SI
> and HI modes to generate swapb & swaph instructions respectively.
>
> (define_insn "bswapsi2"
> [(set (match_operand:SI 0 "register_operand" "=r")
> (bswap:SI (match_operand:SI 1 "register_operand" "r")))]
> ""
> "swapb %0, %1"
> )
>
> (define_insn "bswaphi2"
> [(set (match_operand:HI 0 "register_operand" "=r")
> (bswap:HI (match_operand:HI 1 "register_operand" "r")))]
> ""
> "swaph %0, %1"
> )
>
>
>
> I have written a sample example to generate these instructions..
> int swapb(int n)
> {
> return ((((n) & 0xff000000) >> 24)
> | (((n) & 0x00ff0000) >> 8)
> | (((n) & 0x0000ff00) << 8)
> | (((n) & 0x000000ff) << 24));
>
> }
> short int swaph(short int n)
> {
> return ((((n) & 0xff00) >> 8)
> | (((n) & 0xff) << 8));
> }
> int main()
> {
> volatile int a=0x12345678;
> volatile short int b=0x1234;
> a=swapb(a);
> b=swaph(b);
> return 0;
> }
>
> with this example "swapb" instruction has generated but I am unable to
> generate "swaph"(HI mode of bswap RTL pattern) instruction
>
> I have tried all possibilities that I know.
> Am I missing something or this approach is wrong.
> Please guide me to generate swaph instruction.
I'm surprised that you even get swapb when using a volatile variable. I
would remove the volatile. Just make them global variables or function
arguments or something.
Also you should make b an unsigned short, so that gcc doesn't have to
worry about sign extending the result when the expression is implicitly
calculated in type int.
Good luck.
Ian
