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.
-- >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)();
+}
--
2.43.0.rc1
