v2: Add psABI warning and test.
--
This fixes tmpdir-g++.dg-struct-layout-1/{t032,t059} failure. Clang++
also ignores C++17 empty bases in return values.
gcc/
* config/mips/mips.cc (mips_fpr_return_fields): Ignore
cxx17_empty_base_field_p fields and set an indicator.
(mips_return_in_msb): Adjust for mips_fpr_return_fields change.
(mips_function_value_1): Inform psABI change about C++ 17 empty
bases.
gcc/testsuite/
* g++.target/mips/cxx17_empty_base.C: New test.
---
gcc/config/mips/mips.cc | 58 +++++++++++++++++--
.../g++.target/mips/cxx17_empty_base.C | 20 +++++++
2 files changed, 73 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/g++.target/mips/cxx17_empty_base.C
diff --git a/gcc/config/mips/mips.cc b/gcc/config/mips/mips.cc
index 079bb03968a..57ce0884951 100644
--- a/gcc/config/mips/mips.cc
+++ b/gcc/config/mips/mips.cc
@@ -6346,12 +6346,21 @@ mips_callee_copies (cumulative_args_t, const
function_arg_info &arg)
The C++ FE used to remove zero-width bit-fields in GCC 11 and earlier.
To make a proper diagnostic, this function will set
HAS_CXX_ZERO_WIDTH_BF to true once a C++ zero-width bit-field shows up,
- and then ignore it. Then the caller can determine if this zero-width
- bit-field will make a difference and emit a -Wpsabi inform. */
+ and then ignore it.
+
+ We had failed to ignore C++ 17 empty bases in GCC 7, 8, 9, 10, and 11.
+ This caused an ABI incompatibility between C++ 14 and C++ 17. This is
+ fixed now and to make a proper diagnostic, this function will set
+ HAS_CXX17_EMPTY_BASE to true once a C++ 17 empty base shows up, and
+ then ignore it.
+
+ The caller should use the value of HAS_CXX17_EMPTY_BASE and/or
+ HAS_CXX_ZERO_WIDTH_BF to emit a proper -Wpsabi inform. */
static int
mips_fpr_return_fields (const_tree valtype, tree *fields,
- bool *has_cxx_zero_width_bf)
+ bool *has_cxx_zero_width_bf,
+ bool *has_cxx17_empty_base)
{
tree field;
int i;
@@ -6368,6 +6377,12 @@ mips_fpr_return_fields (const_tree valtype, tree *fields,
if (TREE_CODE (field) != FIELD_DECL)
continue;
+ if (cxx17_empty_base_field_p (field))
+ {
+ *has_cxx17_empty_base = true;
+ continue;
+ }
+
if (DECL_FIELD_CXX_ZERO_WIDTH_BIT_FIELD (field))
{
*has_cxx_zero_width_bf = true;
@@ -6403,8 +6418,13 @@ mips_return_in_msb (const_tree valtype)
tree fields[2];
bool has_cxx_zero_width_bf = false;
+
+ /* Its value is not used. */
+ bool has_cxx17_empty_base = false;
+
return (mips_fpr_return_fields (valtype, fields,
- &has_cxx_zero_width_bf) == 0
+ &has_cxx_zero_width_bf,
+ &has_cxx17_empty_base) == 0
|| has_cxx_zero_width_bf);
}
@@ -6501,11 +6521,18 @@ mips_function_value_1 (const_tree valtype, const_tree
fn_decl_or_type,
mode = promote_function_mode (valtype, mode, &unsigned_p, func, 1);
bool has_cxx_zero_width_bf = false;
+ bool has_cxx17_empty_base = false;
int use_fpr = mips_fpr_return_fields (valtype, fields,
- &has_cxx_zero_width_bf);
+ &has_cxx_zero_width_bf,
+ &has_cxx17_empty_base);
+
+ /* If has_cxx_zero_width_bf and has_cxx17_empty_base are both
+ true, it *happens* that there is no ABI change. So we won't
+ inform in this case. */
if (TARGET_HARD_FLOAT
&& warn_psabi
&& has_cxx_zero_width_bf
+ && !has_cxx17_empty_base
&& use_fpr != 0)
{
static unsigned last_reported_type_uid;
@@ -6527,6 +6554,27 @@ mips_function_value_1 (const_tree valtype, const_tree
fn_decl_or_type,
if (has_cxx_zero_width_bf)
use_fpr = 0;
+ if (TARGET_HARD_FLOAT
+ && warn_psabi
+ && use_fpr != 0
+ && has_cxx17_empty_base)
+ {
+ static unsigned last_reported_type_uid;
+ unsigned uid = TYPE_UID (TYPE_MAIN_VARIANT (valtype));
+ if (uid != last_reported_type_uid)
+ {
+ static const char *url
+ = CHANGES_ROOT_URL
+ "gcc-12/changes.html#mips_cxx17_empty_bases";
+ inform (input_location,
+ "the ABI for returning a value with C++ 17 empty "
+ "bases but otherwise an aggregate with only one or "
+ "two floating-point fields was changed in GCC "
+ "%{12.1%}", url);
+ last_reported_type_uid = uid;
+ }
+ }
+
/* Handle structures whose fields are returned in $f0/$f2. */
switch (use_fpr)
{
diff --git a/gcc/testsuite/g++.target/mips/cxx17_empty_base.C
b/gcc/testsuite/g++.target/mips/cxx17_empty_base.C
new file mode 100644
index 00000000000..da6d54b95d9
--- /dev/null
+++ b/gcc/testsuite/g++.target/mips/cxx17_empty_base.C
@@ -0,0 +1,20 @@
+// { dg-do compile }
+// { dg-options "-O2 -std=c++17 -mabi=64 -mhard-float" }
+// { dg-final { scan-assembler "\\\$f0" } }
+
+struct empty {};
+
+struct foo : empty
+{
+ double a;
+ double b;
+};
+
+struct foo
+make_foo(void) // { dg-message "the ABI for returning a value with C\\\+\\\+
17 empty bases but otherwise an aggregate with only one or two floating-point
fields was changed in GCC 12.1" }
+{
+ struct foo ret;
+ ret.a = 114;
+ ret.b = 514;
+ return ret;
+}
--
2.35.1
