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.

0 files changed, 0 insertions, 0 deletions