[Bug middle-end/101062] [10/11/12 Regression] wrong code with "-O2 -fno-toplevel-reorder -frename-registers"
cvs-commit at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Fri Jun 18 09:23:27 GMT 2021
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
<jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:c63b440cda7449fb6079831db3911ab3dde7c9f0
commit r11-8614-gc63b440cda7449fb6079831db3911ab3dde7c9f0
Author: Jakub Jelinek <jakub@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 <jakub@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)
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