Sorry for the slow review.
Robin Dapp via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> Hi,
>
> while evaluating another patch that introduces more lvalue paradoxical
> subregs I ran into an ICE in combine at
>
> wide_int o = wi::insert (rtx_mode_t (outer, temp_mode),
> rtx_mode_t (inner, dest_mode),
> offset, width);
>
> because width (=GET_MODE_PRECISION (dest_mode)) > GET_MODE_PRECISION
> (temp_mode).
>
> From the comments and the code it looks like we do not want to handle a
> paradoxical subreg here so I quickly added a check for it which prevents
> the ICE. The check could also be added to reg_subword_p () I guess.
Yeah, I think adding it to reg_subword_p would be better, immediately
after the GET_CODE (x) == SUBREG test.
OK with that change, thanks.
Richard
>
> Is this the right thing to do or am I missing something, i.e. my other
> patch might be doing something it should not?
>
> Bootstrap on s390x was successful and testsuite is looking good so far.
>
> Regards
> Robin
>
> --
>
> gcc/ChangeLog:
>
> * combine.c (try_combine): Check for paradoxical subreg.
>
> From 2b74c66f8d97c30c45e99336c9871cccd8cf94e1 Mon Sep 17 00:00:00 2001
> From: Robin Dapp <rd...@linux.ibm.com>
> Date: Tue, 22 Jun 2021 17:35:37 +0200
> Subject: [PATCH 11/11] combine paradoxical subreg fix.
>
> ---
> gcc/combine.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/combine.c b/gcc/combine.c
> index 6476812a212..de04560db21 100644
> --- a/gcc/combine.c
> +++ b/gcc/combine.c
> @@ -2782,7 +2782,8 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
> rtx_insn *i0,
> && CONST_SCALAR_INT_P (SET_SRC (temp_expr))
> && GET_CODE (PATTERN (i3)) == SET
> && CONST_SCALAR_INT_P (SET_SRC (PATTERN (i3)))
> - && reg_subword_p (SET_DEST (PATTERN (i3)), SET_DEST (temp_expr)))
> + && reg_subword_p (SET_DEST (PATTERN (i3)), SET_DEST (temp_expr))
> + && !paradoxical_subreg_p (SET_DEST (PATTERN (i3))))
> {
> rtx dest = SET_DEST (PATTERN (i3));
> rtx temp_dest = SET_DEST (temp_expr);
