https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109253
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jose E. Marchesi <jema...@gcc.gnu.org>: https://gcc.gnu.org/g:f31a019d1161ec78846473da743aedf49cca8c27 commit r14-5930-gf31a019d1161ec78846473da743aedf49cca8c27 Author: Jose E. Marchesi <jose.march...@oracle.com> Date: Fri Nov 24 06:30:28 2023 +0100 Emit funcall external declarations only if actually used. There are many places in GCC where alternative local sequences are tried in order to determine what is the cheapest or best alternative to use in the current target. When any of these sequences involve a libcall, the current implementation of emit_library_call_value_1 introduce a side-effect consisting on emitting an external declaration for the funcall (such as __divdi3) which is thus emitted even if the sequence that does the libcall is not retained. This is problematic in targets such as BPF, because the kernel loader chokes on the spurious symbol __divdi3 and makes the resulting BPF object unloadable. Note that BPF objects are not linked before being loaded. This patch changes asssemble_external_libcall to defer emitting declarations of external libcall symbols, by saving the call tree nodes in a temporary list pending_libcall_symbols and letting process_pending_assembly_externals to emit them only if they have been referenced. Solution suggested and sketched by Richard Sandiford. Regtested in x86_64-linux-gnu. Tested with host x86_64-linux-gnu with target bpf-unknown-none. gcc/ChangeLog PR target/109253 * varasm.cc (pending_libcall_symbols): New variable. (process_pending_assemble_externals): Process pending_libcall_symbols. (assemble_external_libcall): Defer emitting external libcall symbols to process_pending_assemble_externals. gcc/testsuite/ChangeLog PR target/109253 * gcc.target/bpf/divmod-libcall-1.c: New test. * gcc.target/bpf/divmod-libcall-2.c: Likewise. * gcc.c-torture/compile/libcall-2.c: Likewise.
