On Fri, 30 Mar 2012, Martin Jambor wrote:
> Hi,
>
> when testing a patch of mine on sparc64-linux, I came across an Ada
> bootstrap failure due to a structure DECL which was marked addressable
> but had a register DECL_RTL (and therefore mem_ref_refers_to_non_mem_p
> failed to trigger on it).
>
> Mode of the structure was TI (16 bytes int) and it was mistakenly
> marked as addressable during expansion of an assignment statement in
> which a 12 byte portion of it was copied to another structure with
> BLKmode. Specifically, this happened because expand_assignment called
> store_expr which loaded the required portion to temporary 12 byte
> BLKmode MEM_P variable and then called emit_block_move from the
> temporary to the destination. emit_block_move_hints then marked
> MEM_EXPR of the temp as addressable because it handled the copy by
> emitting a library call. And MEM_EXPR pointed to the DECL of the
> source of the assignment which I believe is the bug, thus this patch
> re-sets MEM_EXPR of temp in these cases.
>
> However, if anybody believes the main issue is elsewhere and another
> component of this chain of events needs to be fixed, I'll be happy to
> come up with another patch. so far this patch has passed bootstrap
> and testing on x86_64-linux and helped my patch which uncovered this
> issue to reach stage 3 of bootstrap.
>
> What do you think, is it OK for trunk?
Hmm, I think this should be done at the point we create the mem - where
does that happen?
Richard.
> Thanks,
>
> Martin
>
>
> 2012-03-30 Martin Jambor <mjam...@suse.cz>
>
> * expr.c (non_mem_decl_p): New function with half of previous
> functionality of...
> (mem_ref_refers_to_non_mem_p): ...this one.
> (store_expr): Reset MEM_EXPR of temp if it refers to memory but the
> original expression is based on a non-memory based declaration.
>
> Index: src/gcc/expr.c
> ===================================================================
> --- src.orig/gcc/expr.c
> +++ src/gcc/expr.c
> @@ -4479,6 +4479,24 @@ get_bit_range (unsigned HOST_WIDE_INT *b
> *bitend = *bitstart + tree_low_cst (DECL_SIZE (repr), 1) - 1;
> }
>
> +/* Returns true if T is a DECL that does not reside in a memory and has a
> + non-BLK mode. */
> +
> +static bool
> +non_mem_decl_p (tree t)
> +{
> + if (!DECL_P (t))
> + return false;
> + gcc_checking_assert (!TREE_ADDRESSABLE (t)
> + || !DECL_RTL_SET_P (t)
> + || MEM_P (DECL_RTL (t)));
> + return (!TREE_ADDRESSABLE (t)
> + && DECL_MODE (t) != BLKmode
> + && DECL_RTL_SET_P (t)
> + && !MEM_P (DECL_RTL (t)));
> +}
> +
> +
> /* Returns true if the MEM_REF REF refers to an object that does not
> reside in memory and has non-BLKmode. */
>
> @@ -4489,11 +4507,7 @@ mem_ref_refers_to_non_mem_p (tree ref)
> if (TREE_CODE (base) != ADDR_EXPR)
> return false;
> base = TREE_OPERAND (base, 0);
> - return (DECL_P (base)
> - && !TREE_ADDRESSABLE (base)
> - && DECL_MODE (base) != BLKmode
> - && DECL_RTL_SET_P (base)
> - && !MEM_P (DECL_RTL (base)));
> + return non_mem_decl_p (base);
> }
>
> /* Expand an assignment that stores the value of FROM into TO. If
> NONTEMPORAL
> @@ -5105,6 +5119,16 @@ store_expr (tree exp, rtx target, int ca
> &alt_rtl);
> }
>
> + /* When the original expression is a declaration not residing in memory but
> + temp is a MEM RTX, we must dissociate it from the original expression or
> + emit_block_move might mark it as addressable. */
> + if (MEM_P (temp))
> + {
> + tree base = get_base_address (exp);
> + if (base && non_mem_decl_p (base))
> + set_mem_expr (temp, NULL_TREE);
> + }
> +
> /* If TEMP is a VOIDmode constant and the mode of the type of EXP is not
> the same as that of TARGET, adjust the constant. This is needed, for
> example, in case it is a CONST_DOUBLE and we want only a word-sized
>
>
--
Richard Guenther <rguent...@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer
