https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101062
--- Comment #17 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-11 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:c63b440cda7449fb6079831db3911ab3dde7c9f0 commit r11-8614-gc63b440cda7449fb6079831db3911ab3dde7c9f0 Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Jun 16 12:17:55 2021 +0200 stor-layout: Create DECL_BIT_FIELD_REPRESENTATIVE even for bitfields in unions [PR101062] The following testcase is miscompiled on x86_64-linux, the bitfield store is implemented as a RMW 64-bit operation at d+24 when the d variable has size of only 28 bytes and scheduling moves in between the R and W part a store to a different variable that happens to be right after the d variable. The reason for this is that we weren't creating DECL_BIT_FIELD_REPRESENTATIVEs for bitfields in unions. The following patch does create them, but treats all such bitfields as if they were in a structure where the particular bitfield is the only field. 2021-06-16 Jakub Jelinek <ja...@redhat.com> PR middle-end/101062 * stor-layout.c (finish_bitfield_representative): For fields in unions assume nextf is always NULL. (finish_bitfield_layout): Compute bit field representatives also in unions, but handle it as if each bitfield was the only field in the aggregate. * gcc.dg/pr101062.c: New test. (cherry picked from commit b4b50bf2864e09f028a39a3f460222632c4d7348)
