[Bug target/124778] New: [15/16 Regression] [SH] ICE in decompose_multiword_subregs, at lower-subreg.cc:1728

[glaubitz at physik dot fu-berlin.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124778

            Bug ID: 124778
           Summary: [15/16 Regression] [SH] ICE in
                    decompose_multiword_subregs, at lower-subreg.cc:1728
           Product: gcc
           Version: 15.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: glaubitz at physik dot fu-berlin.de
                CC: olegendo at gcc dot gnu.org, sjames at gcc dot gnu.org
  Target Milestone: ---
            Target: sh*-*-*

Trying to build util-linux with GCC 15 or 16 on Debian unstable sh4 fails with:

(unstable-sh4-sbuild)root@esk:/build/reproducible-path/util-linux-2.42# gcc-16
-DHAVE_CONFIG_H -I. -include config.h -I./include
-DLOCALEDIR=\"/usr/share/locale\" -D_PATH_RUNSTATEDIR=\"/run\"
-D_PATH_LOCALSTATEDIR=\"/var\" -D_PATH_SYSCONFDIR=\"/etc\"
-D_PATH_SYSCONFSTATICDIR=\"/usr/lib\" -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64 -Wdate-time -D_FORTIFY_SOURCE=2
-fsigned-char -fno-common -Wall -Wextra -Waddress-of-packed-member
-Wdiscarded-qualifiers -Wimplicit-function-declaration -Wmissing-declarations
-Wmissing-parameter-type -Wmissing-prototypes -Wnested-externs
-Wno-missing-field-initializers -Wold-style-definition -Wpointer-arith
-Wredundant-decls -Wsign-compare -Wstrict-prototypes -Wtype-limits
-Wuninitialized -Wunused-but-set-parameter -Wunused-but-set-variable
-Wunused-parameter -Wunused-result -Wunused-variable -Wvla -Walloca
-Werror=sequence-point -I./libblkid/src -I./libblkid/src -g -O2
-Werror=implicit-function-declaration
-ffile-prefix-map=/build/reproducible-path/util-linux-2.42=.
-fstack-protector-strong -Wformat -Werror=format-security -c
libblkid/src/superblocks/linux_raid.c  -fPIC -DPIC -o
libblkid/src/superblocks/.libs/la-linux_raid.o
during RTL pass: subreg3
libblkid/src/superblocks/linux_raid.c: In function 'probe_raid1':
libblkid/src/superblocks/linux_raid.c:240:1: internal compiler error: in
decompose_multiword_subregs, at lower-subreg.cc:1728
  240 | }
      | ^
0x1ac7d39 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag*, diagnostics::kind)
        ???:0
0x1abeb81 internal_error(char const*, ...)
        ???:0
0x672fcf fancy_abort(char const*, int, char const*)
        ???:0
/usr/libexec/gcc/sh4-linux-gnu/16/cc1 -quiet -I . -I ./include -I
./libblkid/src -I ./libblkid/src -imultiarch sh4-linux-gnu -D HAVE_CONFIG_H -D
LOCALEDIR="/usr/share/locale" -D _PATH_RUNSTATEDIR="/run" -D
_PATH_LOCALSTATEDIR="/var" -D _PATH_SYSCONFDIR="/etc" -D
_PATH_SYSCONFSTATICDIR="/usr/lib" -D _LARGEFILE_SOURCE -D _FILE_OFFSET_BITS=64
-D _TIME_BITS=64 -D _FORTIFY_SOURCE=2 -D PIC -include config.h
libblkid/src/superblocks/linux_raid.c -quiet -dumpdir
libblkid/src/superblocks/.libs/ -dumpbase la-linux_raid.c -dumpbase-ext .c -g
-O2 -Wdate-time -Wall -Wextra -Waddress-of-packed-member -Wdiscarded-qualifiers
-Wimplicit-function-declaration -Wmissing-declarations -Wmissing-parameter-type
-Wmissing-prototypes -Wnested-externs -Wno-missing-field-initializers
-Wold-style-definition -Wpointer-arith -Wredundant-decls -Wsign-compare
-Wstrict-prototypes -Wtype-limits -Wuninitialized -Wunused-but-set-parameter=3
-Wunused-but-set-variable=3 -Wunused-parameter -Wunused-result
-Wunused-variable -Wvla -Walloca -Werror=sequence-point
-Werror=implicit-function-declaration -Wformat=1 -Werror=format-security
-fsigned-char -fno-common
-ffile-prefix-map=/build/reproducible-path/util-linux-2.42=.
-fstack-protector-strong -fPIC -o /tmp/ccCmDExw.s
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-16/README.Bugs> for instructions.
(unstable-sh4-sbuild)root@esk:/build/reproducible-path/util-linux-2.42#

Compiling the exact same source file with GCC 14 works:

(unstable-sh4-sbuild)root@esk:/build/reproducible-path/util-linux-2.42# gcc-14
-DHAVE_CONFIG_H -I. -include config.h -I./include
-DLOCALEDIR=\"/usr/share/locale\" -D_PATH_RUNSTATEDIR=\"/run\"
-D_PATH_LOCALSTATEDIR=\"/var\" -D_PATH_SYSCONFDIR=\"/etc\"
-D_PATH_SYSCONFSTATICDIR=\"/usr/lib\" -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64 -Wdate-time -D_FORTIFY_SOURCE=2
-fsigned-char -fno-common -Wall -Wextra -Waddress-of-packed-member
-Wdiscarded-qualifiers -Wimplicit-function-declaration -Wmissing-declarations
-Wmissing-parameter-type -Wmissing-prototypes -Wnested-externs
-Wno-missing-field-initializers -Wold-style-definition -Wpointer-arith
-Wredundant-decls -Wsign-compare -Wstrict-prototypes -Wtype-limits
-Wuninitialized -Wunused-but-set-parameter -Wunused-but-set-variable
-Wunused-parameter -Wunused-result -Wunused-variable -Wvla -Walloca
-Werror=sequence-point -I./libblkid/src -I./libblkid/src -g -O2
-Werror=implicit-function-declaration
-ffile-prefix-map=/build/reproducible-path/util-linux-2.42=.
-fstack-protector-strong -Wformat -Werror=format-security -c
libblkid/src/superblocks/linux_raid.c  -fPIC -DPIC -o
libblkid/src/superblocks/.libs/la-linux_raid.o
(unstable-sh4-sbuild)root@esk:/build/reproducible-path/util-linux-2.42#

Please note that both Debian's gcc-15 and gcc-16 packages are LRA-enabled with
the patches from PR target/55212, so this might be an LRA-related regression.
Will try to test with reload later.

I will attach the preprocessed source shortly.