[gcc(refs/vendors/ARM/heads/arm-perf-staging)] rs6000: Fix C++14 vs. C++17 ABI bug on powerpc64le [PR94707]
Tamar Christina
tnfchris@gcc.gnu.org
Fri Jul 17 14:52:52 GMT 2020
https://gcc.gnu.org/g:a39ed81b8a0b46320a7c6ece3f7ad4c3f8519609
commit a39ed81b8a0b46320a7c6ece3f7ad4c3f8519609
Author: Jakub Jelinek <jakub@redhat.com>
Date: Thu Apr 23 09:59:57 2020 +0200
rs6000: Fix C++14 vs. C++17 ABI bug on powerpc64le [PR94707]
As mentioned in the PR and on IRC, the recently added struct-layout-1.exp
new tests FAIL on powerpc64le-linux (among other targets).
FAIL: tmpdir-g++.dg-struct-layout-1/t032 cp_compat_x_tst.o-cp_compat_y_tst.o execute
FAIL: tmpdir-g++.dg-struct-layout-1/t058 cp_compat_x_tst.o-cp_compat_y_tst.o execute
FAIL: tmpdir-g++.dg-struct-layout-1/t059 cp_compat_x_tst.o-cp_compat_y_tst.o execute
in particular. The problem is that the presence or absence of the C++17
artificial empty base fields, which have non-zero TYPE_SIZE, but zero
DECL_SIZE, change the ABI decisions, if it is present (-std=c++17), the type
might not be considered homogeneous, while if it is absent (-std=c++14), it
can be.
The following patch fixes that and emits a -Wpsabi inform; perhaps more
often than it could, because the fact that rs6000_discover_homogeneous_aggregate
returns true when it didn't in in GCC 7/8/9 with -std=c++17 doesn't still
mean it will make a different ABI decision, but the warning triggered only
on the test I've changed (the struct-layout-1.exp tests use -w -Wno-psabi
already).
2020-04-23 Jakub Jelinek <jakub@redhat.com>
PR target/94707
* config/rs6000/rs6000-call.c (rs6000_aggregate_candidate): Add
cxx17_empty_base_seen argument. Pass it to recursive calls.
Ignore cxx17_empty_base_field_p fields after setting
*cxx17_empty_base_seen to true.
(rs6000_discover_homogeneous_aggregate): Adjust
rs6000_aggregate_candidate caller. With -Wpsabi, diagnose homogeneous
aggregates with C++17 empty base fields.
* g++.dg/tree-ssa/pr27830.C: Use -Wpsabi -w for -std=c++17 and higher.
Diff:
---
gcc/ChangeLog | 13 +++++++++++++
gcc/config/rs6000/rs6000-call.c | 34 ++++++++++++++++++++++++++++-----
gcc/testsuite/ChangeLog | 3 +++
gcc/testsuite/g++.dg/tree-ssa/pr27830.C | 2 ++
4 files changed, 47 insertions(+), 5 deletions(-)
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 06f7eda0033..93c3076eb86 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,18 @@
2020-04-23 Jakub Jelinek <jakub@redhat.com>
+ PR target/94707
+ * config/rs6000/rs6000-call.c (rs6000_aggregate_candidate): Add
+ cxx17_empty_base_seen argument. Pass it to recursive calls.
+ Ignore cxx17_empty_base_field_p fields after setting
+ *cxx17_empty_base_seen to true.
+ (rs6000_discover_homogeneous_aggregate): Adjust
+ rs6000_aggregate_candidate caller. With -Wpsabi, diagnose homogeneous
+ aggregates with C++17 empty base fields.
+
+ PR c/94705
+ * attribs.c (decl_attribute): Don't diagnose attribute exclusions
+ if last_decl is error_mark_node or has such a TREE_TYPE.
+
PR c/94705
* attribs.c (decl_attribute): Don't diagnose attribute exclusions
if last_decl is error_mark_node or has such a TREE_TYPE.
diff --git a/gcc/config/rs6000/rs6000-call.c b/gcc/config/rs6000/rs6000-call.c
index e08621ace27..a9ae7ab70ca 100644
--- a/gcc/config/rs6000/rs6000-call.c
+++ b/gcc/config/rs6000/rs6000-call.c
@@ -5528,7 +5528,8 @@ const struct altivec_builtin_types altivec_overloaded_builtins[] = {
sub-tree. */
static int
-rs6000_aggregate_candidate (const_tree type, machine_mode *modep)
+rs6000_aggregate_candidate (const_tree type, machine_mode *modep,
+ bool *cxx17_empty_base_seen)
{
machine_mode mode;
HOST_WIDE_INT size;
@@ -5598,7 +5599,8 @@ rs6000_aggregate_candidate (const_tree type, machine_mode *modep)
|| TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
return -1;
- count = rs6000_aggregate_candidate (TREE_TYPE (type), modep);
+ count = rs6000_aggregate_candidate (TREE_TYPE (type), modep,
+ cxx17_empty_base_seen);
if (count == -1
|| !index
|| !TYPE_MAX_VALUE (index)
@@ -5636,7 +5638,14 @@ rs6000_aggregate_candidate (const_tree type, machine_mode *modep)
if (TREE_CODE (field) != FIELD_DECL)
continue;
- sub_count = rs6000_aggregate_candidate (TREE_TYPE (field), modep);
+ if (cxx17_empty_base_field_p (field))
+ {
+ *cxx17_empty_base_seen = true;
+ continue;
+ }
+
+ sub_count = rs6000_aggregate_candidate (TREE_TYPE (field), modep,
+ cxx17_empty_base_seen);
if (sub_count < 0)
return -1;
count += sub_count;
@@ -5669,7 +5678,8 @@ rs6000_aggregate_candidate (const_tree type, machine_mode *modep)
if (TREE_CODE (field) != FIELD_DECL)
continue;
- sub_count = rs6000_aggregate_candidate (TREE_TYPE (field), modep);
+ sub_count = rs6000_aggregate_candidate (TREE_TYPE (field), modep,
+ cxx17_empty_base_seen);
if (sub_count < 0)
return -1;
count = count > sub_count ? count : sub_count;
@@ -5710,7 +5720,9 @@ rs6000_discover_homogeneous_aggregate (machine_mode mode, const_tree type,
&& AGGREGATE_TYPE_P (type))
{
machine_mode field_mode = VOIDmode;
- int field_count = rs6000_aggregate_candidate (type, &field_mode);
+ bool cxx17_empty_base_seen = false;
+ int field_count = rs6000_aggregate_candidate (type, &field_mode,
+ &cxx17_empty_base_seen);
if (field_count > 0)
{
@@ -5725,6 +5737,18 @@ rs6000_discover_homogeneous_aggregate (machine_mode mode, const_tree type,
*elt_mode = field_mode;
if (n_elts)
*n_elts = field_count;
+ if (cxx17_empty_base_seen && warn_psabi)
+ {
+ static const_tree last_reported_type;
+ if (type != last_reported_type)
+ {
+ inform (input_location,
+ "parameter passing for argument of type %qT "
+ "when C++17 is enabled changed to match C++14 "
+ "in GCC 10.1", type);
+ last_reported_type = type;
+ }
+ }
return true;
}
}
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 684e408c1a5..245c1512c76 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
2020-04-23 Jakub Jelinek <jakub@redhat.com>
+ PR target/94707
+ * g++.dg/tree-ssa/pr27830.C: Use -Wpsabi -w for -std=c++17 and higher.
+
PR c/94705
* gcc.dg/pr94705.c: New test.
diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr27830.C b/gcc/testsuite/g++.dg/tree-ssa/pr27830.C
index 01c7fc18783..551ebc428cd 100644
--- a/gcc/testsuite/g++.dg/tree-ssa/pr27830.C
+++ b/gcc/testsuite/g++.dg/tree-ssa/pr27830.C
@@ -1,5 +1,7 @@
/* { dg-do compile } */
/* { dg-options "-O" } */
+/* Ignore ABI warnings for C++17 and later. */
+/* { dg-additional-options "-Wno-psabi -w" { target c++17 } } */
struct gc{};
struct transform:public gc
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