From: Jason Merrill <jason@redhat.com>
To: Patrick Palka <ppalka@redhat.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] c++: non-dependent .* folding [PR112427]
Date: Tue, 14 Nov 2023 17:29:22 -0500 [thread overview]
Message-ID: <d24ec53f-702d-483b-9b80-599b5ada8596@redhat.com> (raw)
In-Reply-To: <d8c2b4e5-63f0-4ba1-9b74-85a8d7bec025@idea>
On 11/14/23 10:43, Patrick Palka wrote:
> On Fri, 10 Nov 2023, Jason Merrill wrote:
>
>> On 11/10/23 10:28, Patrick Palka wrote:
>>> On Fri, 10 Nov 2023, Patrick Palka wrote:
>>>
>>>> On Thu, 9 Nov 2023, Jason Merrill wrote:
>>>>
>>>>> On 11/8/23 16:59, Patrick Palka wrote:
>>>>>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK
>>>>>> for
>>>>>> trunk?
>>>>>>
>>>>>> -- >8 --
>>>>>>
>>>>>> Here when building up the non-dependent .* expression, we crash from
>>>>>> fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
>>>>>> IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
>>>>>> expect. Like in r14-4899-gd80a26cca02587, this patch fixes this by
>>>>>> replacing the problematic piecemeal folding with a single call to
>>>>>> cp_fully_fold.
>>>>>>
>>>>>> PR c++/112427
>>>>>>
>>>>>> gcc/cp/ChangeLog:
>>>>>>
>>>>>> * typeck2.cc (build_m_component_ref): Use cp_convert, build2
>>>>>> and
>>>>>> cp_fully_fold instead of fold_build_pointer_plus and
>>>>>> fold_convert.
>>>>>
>>>>>> gcc/testsuite/ChangeLog:
>>>>>>
>>>>>> * g++.dg/template/non-dependent29.C: New test.
>>>>>> ---
>>>>>> gcc/cp/typeck2.cc | 5 ++++-
>>>>>> gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
>>>>>> 2 files changed, 17 insertions(+), 1 deletion(-)
>>>>>> create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
>>>>>>
>>>>>> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
>>>>>> index 309903afed8..208004221da 100644
>>>>>> --- a/gcc/cp/typeck2.cc
>>>>>> +++ b/gcc/cp/typeck2.cc
>>>>>> @@ -2378,7 +2378,10 @@ build_m_component_ref (tree datum, tree
>>>>>> component,
>>>>>> tsubst_flags_t complain)
>>>>>> /* Build an expression for "object + offset" where offset is
>>>>>> the
>>>>>> value stored in the pointer-to-data-member. */
>>>>>> ptype = build_pointer_type (type);
>>>>>> - datum = fold_build_pointer_plus (fold_convert (ptype, datum),
>>>>>> component);
>>>>>> + datum = cp_convert (ptype, datum, complain);
>>>>>> + datum = build2 (POINTER_PLUS_EXPR, ptype,
>>>>>> + datum, convert_to_ptrofftype (component));
>>>>>
>>>>> We shouldn't need to build the POINTER_PLUS_EXPR at all in template
>>>>> context.
>>>>> OK with that change.
>>>>
>>>> Hmm, that seems harmless at first glance, but I noticed
>>>> build_min_non_dep (called from build_x_binary_op in this case) is
>>>> careful to propagate TREE_SIDE_EFFECTS of the given tree, and so eliding
>>>> POINTER_PLUS_EXPR here could potentially mean that the tree we
>>>> ultimately return from build_x_binary_op when in a template context has
>>>> TREE_SIDE_EFFECTS not set when it used to. Shall we still elide the
>>>> POINTER_PLUS_EXPR in a template context despite this?
>>
>> True, we would need build_min_non_dep to also get TREE_SIDE_EFFECTS from the
>> operands. That might be useful in general for similar situations?
>>
>> I also note that convert_to_ptrofftype uses fold_convert, so the new code
>> could have the same problem if the pointer to member operand is also a
>> COMPONENT_REF.
>
> Ah, makes sense... How does the following look then? I'm not sure if
> we still want to replace fold_build_pointer_plus with build2 if we're
> not going to use that code path in a template context? Bootstrapped and
> regtested on x86_64-pc-linux-gnu.
We probably do, since we now aren't folding the thing before it. OK.
> -- >8 --
> -
> Subject: [PATCH] c++: non-dependent .* operand folding [PR112427]
>
> Here when building up the non-dependent .* expression, we crash from
> fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
> IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
> expect. Like in r14-4899-gd80a26cca02587, this patch fixes this by
> replacing the problematic piecemeal folding with a single call to
> cp_fully_fold. Additionally, don't bother building POINTER_PLUS_EXPR
> in a template context. This means the returned non-dependent tree might
> not have TREE_SIDE_EFFECTS set when it used to, so we need to make
> build_min_non_dep compensate for this by propagating TREE_SIDE_EFFECTS
> from the original arguments like buildN and build_min do, which seems
> like a generally desirable thing to do anyway.
>
> PR c++/112427
>
> gcc/cp/ChangeLog:
>
> * tree.cc (build_min_non_dep): Propagate TREE_SIDE_EFFECTS from
> the original arguments.
> (build_min_non_dep_call_vec): Likewise.
> * typeck2.cc (build_m_component_ref): Use cp_convert, build2 and
> cp_fully_fold instead of fold_build_pointer_plus and fold_convert.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/template/non-dependent29.C: New test.
> ---
> gcc/cp/tree.cc | 11 ++++++++++-
> gcc/cp/typeck2.cc | 6 +++++-
> gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
> 3 files changed, 28 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
>
> diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
> index 417c92ba76f..dc4126f935c 100644
> --- a/gcc/cp/tree.cc
> +++ b/gcc/cp/tree.cc
> @@ -3601,7 +3601,12 @@ build_min_non_dep (enum tree_code code, tree non_dep, ...)
> TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (non_dep);
>
> for (i = 0; i < length; i++)
> - TREE_OPERAND (t, i) = va_arg (p, tree);
> + {
> + tree x = va_arg (p, tree);
> + TREE_OPERAND (t, i) = x;
> + if (x && !TYPE_P (x))
> + TREE_SIDE_EFFECTS (t) |= TREE_SIDE_EFFECTS (x);
> + }
>
> va_end (p);
> return convert_from_reference (t);
> @@ -3636,6 +3641,10 @@ build_min_non_dep_call_vec (tree non_dep, tree fn, vec<tree, va_gc> *argvec)
> non_dep = TREE_OPERAND (non_dep, 0);
> TREE_TYPE (t) = TREE_TYPE (non_dep);
> TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (non_dep);
> + if (argvec)
> + for (tree x : *argvec)
> + if (x && !TYPE_P (x))
> + TREE_SIDE_EFFECTS (t) |= TREE_SIDE_EFFECTS (x);
> return convert_from_reference (t);
> }
>
> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
> index 309903afed8..a75f4f8c2d2 100644
> --- a/gcc/cp/typeck2.cc
> +++ b/gcc/cp/typeck2.cc
> @@ -2378,7 +2378,11 @@ build_m_component_ref (tree datum, tree component, tsubst_flags_t complain)
> /* Build an expression for "object + offset" where offset is the
> value stored in the pointer-to-data-member. */
> ptype = build_pointer_type (type);
> - datum = fold_build_pointer_plus (fold_convert (ptype, datum), component);
> + datum = cp_convert (ptype, datum, complain);
> + if (!processing_template_decl)
> + datum = build2 (POINTER_PLUS_EXPR, ptype,
> + datum, convert_to_ptrofftype (component));
> + datum = cp_fully_fold (datum);
> datum = cp_build_fold_indirect_ref (datum);
> if (datum == error_mark_node)
> return error_mark_node;
> diff --git a/gcc/testsuite/g++.dg/template/non-dependent29.C b/gcc/testsuite/g++.dg/template/non-dependent29.C
> new file mode 100644
> index 00000000000..41bd11ae6b4
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/non-dependent29.C
> @@ -0,0 +1,13 @@
> +// PR c++/112427
> +
> +struct A { int m; void f(); };
> +struct B { A a; };
> +
> +template<class T>
> +void f(B b) {
> + int A::*pd = &A::m;
> + b.a.*pd;
> +
> + void (A::*pf)() = &A::f;
> + (b.a.*pf)();
> +}
prev parent reply other threads:[~2023-11-14 22:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-08 21:59 Patrick Palka
2023-11-10 0:28 ` Jason Merrill
2023-11-10 15:12 ` Patrick Palka
2023-11-10 15:28 ` Patrick Palka
2023-11-10 21:36 ` Jason Merrill
2023-11-14 15:43 ` Patrick Palka
2023-11-14 22:29 ` Jason Merrill [this message]
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