How to implement the instruction in the back end

[Mohamed Shafi]

On Fri, May 9, 2008 at 12:03 AM, Ian Lance Taylor <iant@google.com> wrote:
> "Mohamed Shafi" <shafitvm@gmail.com> writes:
>
>  > For the 16-bit target that i porting now to gcc 4.1.2 doesn't have any
>  > branch instructions. It only has jump instructions. For comparison
>  > operation it has this instruction:
>  >
>  > if cond Rx Ry
>  >  execute this insn
>  >
>  > So compare and branch is implemented as
>  >
>  > if cond Rx Ry
>  >   jmp Label
>
>  For gcc's purposes this is no different from having a usual
>  conditional branch instruction.  It's just a jump with a condition.
>
>
>  > This instructions has also another form. To check whether a particular
>  > bit in a register is set or not.
>  >
>  > if bs Rx, bitNo
>  >  execute this insn
>  >
>  > My questions is how will i be able to implement this instruction in
>  > the back-end?
>
>  Sure, this is just a conditional instruction where the condition is a
>  ZERO_EXTRACT.
>
>  Look at the ARM backend for examples of how to work with conditional
>  instructions.

thanks for the pointer. In fact many back-ends have this, now that you
have showed me where to look
But it would of great help if you could tell the C statment that
actually invoked this type of pattern .. Maybe wrt some back-end?

Regards,
Shafi