https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #27 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by H.J. Lu <h...@gcc.gnu.org>: https://gcc.gnu.org/g:a96549dce7636edfc693bf758ef27fcd8adc6161 commit r14-8469-ga96549dce7636edfc693bf758ef27fcd8adc6161 Author: H.J. Lu <hjl.to...@gmail.com> Date: Tue Jan 23 06:59:50 2024 -0800 x86: Add no_callee_saved_registers function attribute When an interrupt handler is implemented by an assembly stub which does: 1. Save all registers. 2. Call a C function. 3. Restore all registers. 4. Return from interrupt. it is completely unnecessary to save and restore any registers in the C function called by the assembly stub, even if they would normally be callee-saved. Add no_callee_saved_registers function attribute, which is complementary to no_caller_saved_registers function attribute, to mark a function which doesn't have any callee-saved registers. Such a function won't save and restore any registers. Classify function call-saved register handling type with: 1. Default call-saved registers. 2. No caller-saved registers with no_caller_saved_registers attribute. 3. No callee-saved registers with no_callee_saved_registers attribute. Disallow sibcall if callee is a no_callee_saved_registers function and caller isn't a no_callee_saved_registers function. Otherwise, callee-saved registers won't be preserved. After a no_callee_saved_registers function is called, all registers may be clobbered. If the calling function isn't a no_callee_saved_registers function, we need to preserve all registers which aren't used by function calls. gcc/ PR target/103503 PR target/113312 * config/i386/i386-expand.cc (ix86_expand_call): Replace no_caller_saved_registers check with call_saved_registers check. Clobber all registers that are not used by the callee with no_callee_saved_registers attribute. * config/i386/i386-options.cc (ix86_set_func_type): Set call_saved_registers to TYPE_NO_CALLEE_SAVED_REGISTERS for noreturn function. Disallow no_callee_saved_registers with interrupt or no_caller_saved_registers attributes together. (ix86_set_current_function): Replace no_caller_saved_registers check with call_saved_registers check. (ix86_handle_no_caller_saved_registers_attribute): Renamed to ... (ix86_handle_call_saved_registers_attribute): This. (ix86_gnu_attributes): Add ix86_handle_call_saved_registers_attribute. * config/i386/i386.cc (ix86_conditional_register_usage): Replace no_caller_saved_registers check with call_saved_registers check. (ix86_function_ok_for_sibcall): Don't allow callee with no_callee_saved_registers attribute when the calling function has callee-saved registers. (ix86_comp_type_attributes): Also check no_callee_saved_registers. (ix86_epilogue_uses): Replace no_caller_saved_registers check with call_saved_registers check. (ix86_hard_regno_scratch_ok): Likewise. (ix86_save_reg): Replace no_caller_saved_registers check with call_saved_registers check. Don't save any registers for TYPE_NO_CALLEE_SAVED_REGISTERS. Save all registers with TYPE_DEFAULT_CALL_SAVED_REGISTERS if function with no_callee_saved_registers attribute is called. (find_drap_reg): Replace no_caller_saved_registers check with call_saved_registers check. * config/i386/i386.h (call_saved_registers_type): New enum. (machine_function): Replace no_caller_saved_registers with call_saved_registers. * doc/extend.texi: Document no_callee_saved_registers attribute. gcc/testsuite/ PR target/103503 PR target/113312 * gcc.dg/torture/no-callee-saved-run-1a.c: New file. * gcc.dg/torture/no-callee-saved-run-1b.c: Likewise. * gcc.target/i386/no-callee-saved-1.c: Likewise. * gcc.target/i386/no-callee-saved-2.c: Likewise. * gcc.target/i386/no-callee-saved-3.c: Likewise. * gcc.target/i386/no-callee-saved-4.c: Likewise. * gcc.target/i386/no-callee-saved-5.c: Likewise. * gcc.target/i386/no-callee-saved-6.c: Likewise. * gcc.target/i386/no-callee-saved-7.c: Likewise. * gcc.target/i386/no-callee-saved-8.c: Likewise. * gcc.target/i386/no-callee-saved-9.c: Likewise. * gcc.target/i386/no-callee-saved-10.c: Likewise. * gcc.target/i386/no-callee-saved-11.c: Likewise. * gcc.target/i386/no-callee-saved-12.c: Likewise. * gcc.target/i386/no-callee-saved-13.c: Likewise. * gcc.target/i386/no-callee-saved-14.c: Likewise. * gcc.target/i386/no-callee-saved-15.c: Likewise. * gcc.target/i386/no-callee-saved-16.c: Likewise. * gcc.target/i386/no-callee-saved-17.c: Likewise. * gcc.target/i386/no-callee-saved-18.c: Likewise.
