https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120795
Bug ID: 120795
Summary: [16 regression] ICE when building folly-2025.04.14.00
(df_refs_verify, at df-scan.cc:4029)
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: sjames at gcc dot gnu.org
Target Milestone: ---
Originally reported downstream in Gentoo at
https://bugs.gentoo.org/show_bug.cgi?id=958958.
This started in the last day or so. I think it's Jeff's ext-dce commit (and
-fno-ext-dce works).
```
$ g++ -c
./CMakeFiles/folly_base.dir/folly/executors/CPUThreadPoolExecutor.cpp.ii -O2
-march=znver2 -std=gnu++20
during RTL pass: combine
In file included from
/var/tmp/portage/dev-cpp/folly-2025.04.14.00-r1/work/folly-2025.04.14.00/folly/container/detail/F14Policy.h:29,
from
/var/tmp/portage/dev-cpp/folly-2025.04.14.00-r1/work/folly-2025.04.14.00/folly/container/F14Map.h:41,
from
/var/tmp/portage/dev-cpp/folly-2025.04.14.00-r1/work/folly-2025.04.14.00/folly/io/async/Request.h:29,
from
/var/tmp/portage/dev-cpp/folly-2025.04.14.00-r1/work/folly-2025.04.14.00/folly/executors/ThreadPoolExecutor.h:31,
from
/var/tmp/portage/dev-cpp/folly-2025.04.14.00-r1/work/folly-2025.04.14.00/folly/executors/CPUThreadPoolExecutor.h:24,
from
/var/tmp/portage/dev-cpp/folly-2025.04.14.00-r1/work/folly-2025.04.14.00/folly/executors/CPUThreadPoolExecutor.cpp:18:
/var/tmp/portage/dev-cpp/folly-2025.04.14.00-r1/work/folly-2025.04.14.00/folly/container/detail/F14Table.h:
In member function ‘void
folly::f14::detail::F14Table<Policy>::rehashImpl(std::size_t, std::size_t,
std::size_t, std::size_t, std::size_t) [with Policy =
folly::f14::detail::ValueContainerPolicy<const void*, void, void, void,
void>]’:
/var/tmp/portage/dev-cpp/folly-2025.04.14.00-r1/work/folly-2025.04.14.00/folly/container/detail/F14Table.h:2370:3:
internal compiler error: in df_refs_verify, at df-scan.cc:4029
2370 | }
| ^
0x55ff2668de55 internal_error(char const*, ...)
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/diagnostic-global-context.cc:517
0x55ff266807da fancy_abort(char const*, int, char const*)
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/diagnostic.cc:1803
0x55ff2530c0bf df_refs_verify
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/df-scan.cc:4029
0x55ff2530c0bf df_insn_refs_verify
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/df-scan.cc:4091
0x55ff2530c0bf df_bb_verify
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/df-scan.cc:4128
0x55ff26f76027 df_scan_verify()
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/df-scan.cc:4249
0x55ff26f6f4ce df_verify()
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/df-core.cc:1864
0x55ff26f6f4ce df_analyze_1
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/df-core.cc:1251
0x55ff26f6f4ce df_analyze()
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/df-core.cc:1335
0x55ff27091395 rest_of_handle_combine
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/combine.cc:15225
0x55ff27091395 execute
/usr/src/debug/sys-devel/gcc-16.0.9999/gcc-16.0.9999/gcc/combine.cc:15275
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://bugs.gentoo.org/> for instructions.
```
---
```
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/16/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-16.0.9999/work/gcc-16.0.9999/configure
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr
--bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/16
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/16/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/16
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/16/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/16/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/16/include/g++-v16
--disable-silent-rules --disable-dependency-tracking
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/16/python
--enable-libphobos --enable-objc-gc
--enable-languages=c,c++,d,objc,obj-c++,fortran,ada,rust --enable-obsolete
--enable-secureplt --disable-werror --with-system-zlib --enable-nls
--without-included-gettext --disable-libunwind-exceptions
--enable-checking=yes,extra,rtl,df --with-bugurl=https://bugs.gentoo.org/
--with-pkgversion='Gentoo 16.0.9999 p, commit
127aabd4d9cabfe7f6af572bade472d481a5bb67' --with-gcc-major-version-only
--enable-libstdcxx-time --enable-lto --disable-libstdcxx-pch --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
--enable-multilib --with-multilib-list=m32,m64 --disable-fixed-point
--enable-targets=all --enable-offload-defaulted
--enable-offload-targets=nvptx-none --enable-libgomp --disable-libssp
--enable-libada --enable-cet --disable-systemtap --enable-valgrind-annotations
--disable-vtable-verify --disable-libvtv --with-zstd --without-isl
--enable-default-pie --enable-host-pie --enable-host-bind-now
--enable-default-ssp --disable-fixincludes
--with-gxx-libcxx-include-dir=/usr/include/c++/v1
--with-build-config='bootstrap-O3 bootstrap-lto bootstrap-cet'
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 16.0.0 20250623 (experimental)
2334d30cd8feac28831ffef857cd09753a3ca3d3 (Gentoo 16.0.9999 p, commit
127aabd4d9cabfe7f6af572bade472d481a5bb67)
```
