Problems with addibne Instruction in GCC 2025.02 (xxlcz)

[bigmagic123]

Two issues have been identified with the addibne instruction in the xxlcz extension in GCC 2025.02:

Incorrect behavior when -flto (Link-Time Optimization) is enabled – addibne generates wrong code under LTO.
Jump range violation – The addibne instruction may exceed its legal jump range (>1024 bytes).
Workaround & Fix:

Use -mno-addibne to disable addibne generation explicitly.
GCC now automatically disables addibne when -flto is enabled.
Fixed Version: 2025.10

Details:
LTO Compatibility Issue

When -flto is enabled, the generated addibne behaves incorrectly. The fix ensures it defaults to not generating addibne under LTO.

Jump Range Limit

addibne’s jump offset must be constrained to 1024 bytes, but the current implementation may violate this. The fix enforces the range limit.

Impact:

Projects relying on addibne with -flto need to either:
a) Disable it via -mno-addibne, or
b) Upgrade to 2025.10 where the issues are resolved.
Affected Versions: GCC 2025.02

Fixed Version: 2025.10

[bigmagic123]

If you are using the xxlcz extension together with flto (link-time optimization), please check for potential issues as follows:

Disassemble your firmware using:

Text
riscv64-unknown-elf-objdump -rd xxx.elf

Search for the presence of the addibne instruction.

If addibne is found, it is highly likely that a logic error exists.

Solutions:

Please update your toolchain to 2025.10 or the latest released version.

If you must continue using the 2025.02 version, you can resolve the issue by:

Disabling either xxlcz or flto, or
disabling the _xxlczbri sub-extension by passing the complete xxlcz sub-extensions list without it.
The current xxlcz sub-extensions are:

Text
-xxlcz=_xxlczabs_xxlczbitop_xxlczbitrev_xxlczbmrk_xxlczbri_xxlczgp_xxlczmac_xxlczpstinc_xxlczslet

Simply remove _xxlczbri when passing the xxlcz extended options to resolve this problem.