Re: GCC47 movmem breaks RA, GCC46 RA is fine

[Paulo J. Matos]

On 27/04/12 09:21, Richard Guenther wrote:

This differs from what GCC47 does and seems to work better.
I would like help on how to best handle this situation under GCC47.

Not provide movmem which looks like open-coded and not in any way
"optimized"?


Thanks Richard, however I don't understand your comment.
GCC46 outputs for this problem:
$t25:
        enterl  #H'0002
        st      AL,@H'fff9
        st      AH,@H'fff8
        ld      X,@$XAP_AH
        ld      X,@(0,X)
        ld      AL,#H'0010
        ld      AH,@H'fff9
        bc2
        ld      AL,@H'fff8
        leavel  #H'0002

and GCC47, once movmemqi and setmemqi are disabled:
$t25:
        enterl  #H'0005
        st      AH,@(H'0001,Y)
        ld      X,@$XAP_AH
        ld      X,@(0,X)
        ld      AH,#H'0010
        st      AH,@(0,Y)
        ld      AH,@$XAP_UXL
        bsr     $memcpy
        ld      AL,@(H'0001,Y)
        leavel  #H'0005


It feels to me that GCC46 version is better:
* no branch to subroutine memcpy;
* less stack usage (argument to enterl);

So, using our block copy (bc2) instruction is an optimisation, don't you 
think?

--
PMatos