https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125795
Bug ID: 125795
Summary: Code generation broken with -funroll-loops when
targeting armv8-a.
Product: gcc
Version: 15.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: nick at appletonaudio dot com
Target Milestone: ---
Created attachment 64740
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64740&action=edit
The .s file output of building a small test-case with -save-temps
I did some bisection using godbolt and found this issue started appearing
between version 13.4.0 and 14.1.0. I listed the affected version as 15.2.0
because that is what I am using. The code generation is fine when targeting
amd64 which is why I have listed the component as "target" but this is just my
best guess.
Thank you for all your great work and let me know if there is more information
needed.
---
* the exact version of GCC;
* the options given when GCC was configured/built;
Follows is the output from `gcc -v`
> COLLECT_GCC=gcc
> COLLECT_LTO_WRAPPER=/usr/libexec/gcc/aarch64-linux-gnu/15/lto-wrapper
> OFFLOAD_TARGET_NAMES=nvptx-none
> OFFLOAD_TARGET_DEFAULT=1
> Target: aarch64-linux-gnu
> Configured with: ../src/configure -v --with-pkgversion='Ubuntu
> 15.2.0-16ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-15/README.Bugs
> --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2,rust,cobol,algol68
> --prefix=/usr --with-gcc-major-version-only --program-suffix=-15
> --program-prefix=aarch64-linux-gnu- --enable-shared --enable-linker-build-id
> --libexecdir=/usr/libexec --without-included-gettext --enable-threads=posix
> --libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu
> --enable-libstdcxx-debug --enable-libstdcxx-time=yes
> --with-default-libstdcxx-abi=new --enable-libstdcxx-backtrace
> --enable-gnu-unique-object --disable-libquadmath
> --disable-libquadmath-support --enable-plugin --enable-default-pie
> --with-system-zlib --enable-libphobos-checking=release
> --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch
> --enable-fix-cortex-a53-843419 --disable-werror
> --enable-offload-targets=nvptx-none=/build/gcc-15-BXQoGT/gcc-15-15.2.0/debian/tmp-nvptx/usr
> --enable-offload-defaulted --without-cuda-driver --enable-checking=release
> --build=aarch64-linux-gnu --host=aarch64-linux-gnu --target=aarch64-linux-gnu
> --with-build-config=bootstrap-lto-lean --enable-link-serialization=4
> Thread model: posix
> Supported LTO compression algorithms: zlib zstd
> gcc version 15.2.0 (Ubuntu 15.2.0-16ubuntu1)
* the system type;
> Linux {redacted} 7.0.0-22-generic #22-Ubuntu SMP PREEMPT_DYNAMIC Mon May 25
> 15:37:49 UTC 2026 aarch64 GNU/Linux
* the complete command line that triggers the bug;
> gcc -funroll-loops -O2 ~/repromain.c
> ./a.out
(`abort()` will be called on failure.)
* the compiler output (error messages, warnings, etc.); and
No output messages with -Wall, -Wextra and -pedantic
* the preprocessed file (*.i*) that triggers the bug ...
The .s file produced by the following command is attached:
> gcc -funroll-loops -O2 repromain.c -save-temps
