Hi!
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).
Bootstrapped/regtested on powerpc64le-linux, bootstrapped on powerpc64-linux
where regtest is still pending, but homogeneous aggregates are an ELFv2
thing, so I don't expect it to change anything (and so far no such messages
appear in the testsuite log files).
Ok for trunk?
2020-04-22 Jakub Jelinek <ja...@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.
--- gcc/config/rs6000/rs6000-call.c.jj 2020-03-30 22:53:40.746640328 +0200
+++ gcc/config/rs6000/rs6000-call.c 2020-04-22 13:05:07.947809888 +0200
@@ -5528,7 +5528,8 @@ const struct altivec_builtin_types altiv
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 t
|| 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 t
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 t
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 (m
&& 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 +5737,17 @@ rs6000_discover_homogeneous_aggregate (m
*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,
+ "prior to GCC 10, parameters of type "
+ "%qT were passed incorrectly for C++17", type);
+ last_reported_type = type;
+ }
+ }
return true;
}
}
--- gcc/testsuite/g++.dg/tree-ssa/pr27830.C.jj 2020-01-11 16:31:54.844296359
+0100
+++ gcc/testsuite/g++.dg/tree-ssa/pr27830.C 2020-04-22 15:01:37.949881630
+0200
@@ -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
Jakub
