* [PATCH] c++: -Wdangling-reference tweak to unbreak aarch64
@ 2024-02-01 21:23 Marek Polacek
2024-02-01 22:15 ` Jason Merrill
0 siblings, 1 reply; 2+ messages in thread
From: Marek Polacek @ 2024-02-01 21:23 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
aarch64-unknown-linux-gnu now bootstraps.
-- >8 --
My recent -Wdangling-reference change to not warn on std::span-like classes
unfortunately caused a new warning: extending reference_like_class_p also
opens the door to new warnings since we use reference_like_class_p for
checking the return type of the function: either it must be a reference
or a reference_like_class_p.
We can consider even non-templates as std::span-like to get rid of the
warning here.
gcc/cp/ChangeLog:
* call.cc (reference_like_class_p): Consider even non-templates for
std::span-like classes.
gcc/ChangeLog:
* doc/invoke.texi: Update -Wdangling-reference documentation.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wdangling-reference21.C: New test.
---
gcc/cp/call.cc | 8 ++--
gcc/doc/invoke.texi | 2 +-
.../g++.dg/warn/Wdangling-reference21.C | 44 +++++++++++++++++++
3 files changed, 48 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wdangling-reference21.C
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index 42cbd0da036..1dac1470d3b 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -14082,8 +14082,8 @@ reference_like_class_p (tree ctype)
return true;
}
- /* Avoid warning if CTYPE looks like std::span: it's a class template,
- has a T* member, and a trivial destructor. For example,
+ /* Avoid warning if CTYPE looks like std::span: it has a T* member and
+ a trivial destructor. For example,
template<typename T>
struct Span {
@@ -14092,9 +14092,7 @@ reference_like_class_p (tree ctype)
};
is considered std::span-like. */
- if (NON_UNION_CLASS_TYPE_P (ctype)
- && CLASSTYPE_TEMPLATE_INSTANTIATION (ctype)
- && TYPE_HAS_TRIVIAL_DESTRUCTOR (ctype))
+ if (NON_UNION_CLASS_TYPE_P (ctype) && TYPE_HAS_TRIVIAL_DESTRUCTOR (ctype))
for (tree field = next_aggregate_field (TYPE_FIELDS (ctype));
field; field = next_aggregate_field (DECL_CHAIN (field)))
if (TYPE_PTR_P (TREE_TYPE (field)))
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 14730c0c508..e9c691d63da 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -3929,7 +3929,7 @@ struct Span @{
@};
@end smallexample
-as @code{std::span}-like; that is, the class is a non-union class template
+as @code{std::span}-like; that is, the class is a non-union class
that has a pointer data member and a trivial destructor.
This warning is enabled by @option{-Wall}.
diff --git a/gcc/testsuite/g++.dg/warn/Wdangling-reference21.C b/gcc/testsuite/g++.dg/warn/Wdangling-reference21.C
new file mode 100644
index 00000000000..e1b6e3dd94c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wdangling-reference21.C
@@ -0,0 +1,44 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wdangling-reference" }
+// Reduced from config/aarch64/aarch64-early-ra.cc.
+
+template <typename T> struct array_slice {
+ using iterator = T *;
+ iterator begin();
+ iterator end();
+ iterator m_base;
+};
+
+struct allocno_group_info { };
+
+char recog_data_2;
+int record_constraints_op;
+struct early_ra {
+ using operand_mask = int;
+ struct allocno_info {
+ int is_earlyclobbered;
+ };
+ struct allocno_subgroup {
+ array_slice<allocno_info> allocnos();
+ allocno_group_info *group;
+ };
+ allocno_subgroup get_allocno_subgroup(int);
+ void record_constraints();
+};
+void early_ra::record_constraints() {
+ operand_mask earlyclobber_operands, matched_operands, unmatched_operands,
+ matches_operands, op_mask = operand_mask();
+ auto record_operand = [&](int, int) {
+ operand_mask overlaps;
+ matches_operands |= overlaps;
+ };
+ for (int opno = 0; recog_data_2; ++opno) {
+ operand_mask op_mask = earlyclobber_operands |= op_mask;
+ if (0)
+ record_operand(1, 0);
+ }
+ if (op_mask || (matched_operands & unmatched_operands && 0))
+ for (auto &allocno : get_allocno_subgroup(record_constraints_op).allocnos())
+ allocno.is_earlyclobbered = true;
+}
+
base-commit: 44764984cf24e27cf7756cffd197283b9c62db8b
--
2.43.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] c++: -Wdangling-reference tweak to unbreak aarch64
2024-02-01 21:23 [PATCH] c++: -Wdangling-reference tweak to unbreak aarch64 Marek Polacek
@ 2024-02-01 22:15 ` Jason Merrill
0 siblings, 0 replies; 2+ messages in thread
From: Jason Merrill @ 2024-02-01 22:15 UTC (permalink / raw)
To: Marek Polacek, GCC Patches
On 2/1/24 16:23, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
OK.
> aarch64-unknown-linux-gnu now bootstraps.
>
> -- >8 --
> My recent -Wdangling-reference change to not warn on std::span-like classes
> unfortunately caused a new warning: extending reference_like_class_p also
> opens the door to new warnings since we use reference_like_class_p for
> checking the return type of the function: either it must be a reference
> or a reference_like_class_p.
>
> We can consider even non-templates as std::span-like to get rid of the
> warning here.
>
> gcc/cp/ChangeLog:
>
> * call.cc (reference_like_class_p): Consider even non-templates for
> std::span-like classes.
>
> gcc/ChangeLog:
>
> * doc/invoke.texi: Update -Wdangling-reference documentation.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/warn/Wdangling-reference21.C: New test.
> ---
> gcc/cp/call.cc | 8 ++--
> gcc/doc/invoke.texi | 2 +-
> .../g++.dg/warn/Wdangling-reference21.C | 44 +++++++++++++++++++
> 3 files changed, 48 insertions(+), 6 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/warn/Wdangling-reference21.C
>
> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
> index 42cbd0da036..1dac1470d3b 100644
> --- a/gcc/cp/call.cc
> +++ b/gcc/cp/call.cc
> @@ -14082,8 +14082,8 @@ reference_like_class_p (tree ctype)
> return true;
> }
>
> - /* Avoid warning if CTYPE looks like std::span: it's a class template,
> - has a T* member, and a trivial destructor. For example,
> + /* Avoid warning if CTYPE looks like std::span: it has a T* member and
> + a trivial destructor. For example,
>
> template<typename T>
> struct Span {
> @@ -14092,9 +14092,7 @@ reference_like_class_p (tree ctype)
> };
>
> is considered std::span-like. */
> - if (NON_UNION_CLASS_TYPE_P (ctype)
> - && CLASSTYPE_TEMPLATE_INSTANTIATION (ctype)
> - && TYPE_HAS_TRIVIAL_DESTRUCTOR (ctype))
> + if (NON_UNION_CLASS_TYPE_P (ctype) && TYPE_HAS_TRIVIAL_DESTRUCTOR (ctype))
> for (tree field = next_aggregate_field (TYPE_FIELDS (ctype));
> field; field = next_aggregate_field (DECL_CHAIN (field)))
> if (TYPE_PTR_P (TREE_TYPE (field)))
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 14730c0c508..e9c691d63da 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -3929,7 +3929,7 @@ struct Span @{
> @};
> @end smallexample
>
> -as @code{std::span}-like; that is, the class is a non-union class template
> +as @code{std::span}-like; that is, the class is a non-union class
> that has a pointer data member and a trivial destructor.
>
> This warning is enabled by @option{-Wall}.
> diff --git a/gcc/testsuite/g++.dg/warn/Wdangling-reference21.C b/gcc/testsuite/g++.dg/warn/Wdangling-reference21.C
> new file mode 100644
> index 00000000000..e1b6e3dd94c
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/Wdangling-reference21.C
> @@ -0,0 +1,44 @@
> +// { dg-do compile { target c++11 } }
> +// { dg-options "-Wdangling-reference" }
> +// Reduced from config/aarch64/aarch64-early-ra.cc.
> +
> +template <typename T> struct array_slice {
> + using iterator = T *;
> + iterator begin();
> + iterator end();
> + iterator m_base;
> +};
> +
> +struct allocno_group_info { };
> +
> +char recog_data_2;
> +int record_constraints_op;
> +struct early_ra {
> + using operand_mask = int;
> + struct allocno_info {
> + int is_earlyclobbered;
> + };
> + struct allocno_subgroup {
> + array_slice<allocno_info> allocnos();
> + allocno_group_info *group;
> + };
> + allocno_subgroup get_allocno_subgroup(int);
> + void record_constraints();
> +};
> +void early_ra::record_constraints() {
> + operand_mask earlyclobber_operands, matched_operands, unmatched_operands,
> + matches_operands, op_mask = operand_mask();
> + auto record_operand = [&](int, int) {
> + operand_mask overlaps;
> + matches_operands |= overlaps;
> + };
> + for (int opno = 0; recog_data_2; ++opno) {
> + operand_mask op_mask = earlyclobber_operands |= op_mask;
> + if (0)
> + record_operand(1, 0);
> + }
> + if (op_mask || (matched_operands & unmatched_operands && 0))
> + for (auto &allocno : get_allocno_subgroup(record_constraints_op).allocnos())
> + allocno.is_earlyclobbered = true;
> +}
> +
>
> base-commit: 44764984cf24e27cf7756cffd197283b9c62db8b
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