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Re: [C++ PATCH 2/4] Fix conversions for built-in operator overloading candidates.
I've reverted this patch for the moment.
On Wed, Sep 18, 2019 at 8:19 PM JiangNing OS
<jiangning@os.amperecomputing.com> wrote:
>
> Hi Jason,
>
> This commit caused boot-strap failure on aarch64. Is it a bug? Can this be fixed ASAP?
>
> ../../gcc/gcc/expmed.c:5602:19: error: ���int_mode��� may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 5602 | scalar_int_mode int_mode;
> | ^~~~~~~~
>
> Thanks,
> -Jiangning
>
> > -----Original Message-----
> > From: gcc-patches-owner@gcc.gnu.org <gcc-patches-owner@gcc.gnu.org>
> > On Behalf Of Jason Merrill
> > Sent: Monday, September 16, 2019 12:33 PM
> > To: gcc-patches@gcc.gnu.org
> > Subject: [C++ PATCH 2/4] Fix conversions for built-in operator overloading
> > candidates.
> >
> > While working on C++20 operator<=>, I noticed that build_new_op_1 was
> > doing too much conversion when a built-in candidate was selected; the
> > standard says it should only perform user-defined conversions, and then
> > leave the normal operator semantics to handle any standard conversions.
> > This is important for operator<=> because a comparison of two different
> > unscoped enums is ill-formed; if we promote the enums to int here,
> > cp_build_binary_op never gets to see the original operand types, so we can't
> > give the error.
> >
> > Tested x86_64-pc-linux-gnu, applying to trunk.
> >
> > * call.c (build_new_op_1): Don't apply any standard conversions to
> > the operands of a built-in operator. Don't suppress conversions in
> > cp_build_unary_op.
> > * typeck.c (cp_build_unary_op): Do integral promotions for enums.
> > ---
> > gcc/cp/call.c | 51 ++++++++++++++++++++++++------------------------
> > gcc/cp/typeck.c | 4 ++--
> > gcc/cp/ChangeLog | 7 +++++++
> > 3 files changed, 34 insertions(+), 28 deletions(-)
> >
> > diff --git a/gcc/cp/call.c b/gcc/cp/call.c index c3045d948c5..457fa6605c2
> > 100644
> > --- a/gcc/cp/call.c
> > +++ b/gcc/cp/call.c
> > @@ -6139,41 +6139,40 @@ build_new_op_1 (const op_location_t &loc,
> > enum tree_code code, int flags,
> > break;
> > }
> >
> > - /* We need to strip any leading REF_BIND so that bitfields
> > - don't cause errors. This should not remove any important
> > - conversions, because builtins don't apply to class
> > - objects directly. */
> > + /* "If a built-in candidate is selected by overload resolution, the
> > + operands of class type are converted to the types of the
> > + corresponding parameters of the selected operation function,
> > + except that the second standard conversion sequence of a
> > + user-defined conversion sequence (12.3.3.1.2) is not applied."
> > +*/
> > conv = cand->convs[0];
> > - if (conv->kind == ck_ref_bind)
> > - conv = next_conversion (conv);
> > - arg1 = convert_like (conv, arg1, complain);
> > + if (conv->user_conv_p)
> > + {
> > + while (conv->kind != ck_user)
> > + conv = next_conversion (conv);
> > + arg1 = convert_like (conv, arg1, complain);
> > + }
> >
> > if (arg2)
> > {
> > conv = cand->convs[1];
> > - if (conv->kind == ck_ref_bind)
> > - conv = next_conversion (conv);
> > - else
> > - arg2 = decay_conversion (arg2, complain);
> > -
> > - /* We need to call warn_logical_operator before
> > - converting arg2 to a boolean_type, but after
> > - decaying an enumerator to its value. */
> > - if (complain & tf_warning)
> > - warn_logical_operator (loc, code, boolean_type_node,
> > - code_orig_arg1, arg1,
> > - code_orig_arg2, arg2);
> > -
> > - arg2 = convert_like (conv, arg2, complain);
> > + if (conv->user_conv_p)
> > + {
> > + while (conv->kind != ck_user)
> > + conv = next_conversion (conv);
> > + arg2 = convert_like (conv, arg2, complain);
> > + }
> > }
> > +
> > if (arg3)
> > {
> > conv = cand->convs[2];
> > - if (conv->kind == ck_ref_bind)
> > - conv = next_conversion (conv);
> > - convert_like (conv, arg3, complain);
> > + if (conv->user_conv_p)
> > + {
> > + while (conv->kind != ck_user)
> > + conv = next_conversion (conv);
> > + arg3 = convert_like (conv, arg3, complain);
> > + }
> > }
> > -
> > }
> > }
> >
> > @@ -6241,7 +6240,7 @@ build_new_op_1 (const op_location_t &loc, enum
> > tree_code code, int flags,
> > case REALPART_EXPR:
> > case IMAGPART_EXPR:
> > case ABS_EXPR:
> > - return cp_build_unary_op (code, arg1, candidates != 0, complain);
> > + return cp_build_unary_op (code, arg1, false, complain);
> >
> > case ARRAY_REF:
> > return cp_build_array_ref (input_location, arg1, arg2, complain); diff --git
> > a/gcc/cp/typeck.c b/gcc/cp/typeck.c index 70094d1b426..620f2c9afdf 100644
> > --- a/gcc/cp/typeck.c
> > +++ b/gcc/cp/typeck.c
> > @@ -6242,7 +6242,7 @@ cp_build_unary_op (enum tree_code code, tree
> > xarg, bool noconvert,
> > : _("wrong type argument to unary plus"));
> > else
> > {
> > - if (!noconvert && CP_INTEGRAL_TYPE_P (TREE_TYPE (arg)))
> > + if (!noconvert && INTEGRAL_OR_ENUMERATION_TYPE_P
> > (TREE_TYPE
> > +(arg)))
> > arg = cp_perform_integral_promotions (arg, complain);
> >
> > /* Make sure the result is not an lvalue: a unary plus or minus @@
> > -6267,7 +6267,7 @@ cp_build_unary_op (enum tree_code code, tree xarg,
> > bool noconvert,
> > |
> > WANT_VECTOR_OR_COMPLEX,
> > arg, true)))
> > errstring = _("wrong type argument to bit-complement");
> > - else if (!noconvert && CP_INTEGRAL_TYPE_P (TREE_TYPE (arg)))
> > + else if (!noconvert && INTEGRAL_OR_ENUMERATION_TYPE_P
> > (TREE_TYPE
> > + (arg)))
> > {
> > /* Warn if the expression has boolean value. */
> > if (TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE diff --git
> > a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index e92d49f1b76..a03a428109b
> > 100644
> > --- a/gcc/cp/ChangeLog
> > +++ b/gcc/cp/ChangeLog
> > @@ -1,3 +1,10 @@
> > +2019-09-15 Jason Merrill <jason@redhat.com>
> > +
> > + * call.c (build_new_op_1): Don't apply any standard conversions to
> > + the operands of a built-in operator. Don't suppress conversions in
> > + cp_build_unary_op.
> > + * typeck.c (cp_build_unary_op): Do integral promotions for enums.
> > +
> > 2019-09-15 Marek Polacek <polacek@redhat.com>
> >
> > PR c++/91740 - ICE with constexpr call and ?: in ARRAY_REF.
> > --
> > 2.21.0
>