On Wed, 27 Jul 2022, juzhe.zh...@rivai.ai wrote:
> From: zhongjuzhe <juzhe.zh...@rivai.ai>
>
> gcc/ChangeLog:
>
> * expr.cc (expand_assignment): Change GET_MODE_PRECISION to
> GET_MODE_BITSIZE
>
> ---
> gcc/expr.cc | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/expr.cc b/gcc/expr.cc
> index 80bb1b8a4c5..ac2b3c07df6 100644
> --- a/gcc/expr.cc
> +++ b/gcc/expr.cc
> @@ -5574,7 +5574,7 @@ expand_assignment (tree to, tree from, bool nontemporal)
> code contains an out-of-bounds access to a small array. */
> if (!MEM_P (to_rtx)
> && GET_MODE (to_rtx) != BLKmode
> - && known_ge (bitpos, GET_MODE_PRECISION (GET_MODE (to_rtx))))
> + && known_ge (bitpos, GET_MODE_BITSIZE (GET_MODE (to_rtx))))
I think this has the chance to go wrong with regard to endianess.
Consider to_rtx with 32bit mode size but 12bit mode precision. bitpos
is relative to the start of to_rtx as if it were in memory and bitsize
determines the contiguous region affected. But since we are actually
storing into a non-memory endianess comes into play.
So no, I don't think the patch is correct, it would be way more
complicated to get the desired improvement.
Richard.
> {
> expand_normal (from);
> result = NULL;
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)
