https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94707
--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:a39ed81b8a0b46320a7c6ece3f7ad4c3f8519609 commit r10-7907-ga39ed81b8a0b46320a7c6ece3f7ad4c3f8519609 Author: Jakub Jelinek <ja...@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 <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.
