[RFC 2/2] Implement call0 ABI for xtensa

[augustine.sterling@gmail.com]

On Sat, Feb 28, 2015 at 10:14 AM, Max Filippov <jcmvbkbc@gmail.com> wrote:
> call0 is an ABI that doesn't use register windows.
>
> 2015-02-28  Max Filippov  <jcmvbkbc@gmail.com>
>
> gcc/
>         * config/xtensa/constraints.md ("a" constraint): Include stack
>         pointer in case of call0 ABI.
>         ("q" constraint): Make empty in case of call0 ABI.
>         ("D" constraint): Include stack pointer in case of call0 ABI.
>
>         * config/xtensa/xtensa-protos.h (xtensa_set_return_address,
>         xtensa_expand_epilogue, xtensa_regno_to_class): Add new function
>         prototypes.
>
>         * config/xtensa/xtensa.c (xtensa_callee_save_size): New
>         variable.
>         (xtensa_regno_to_class): Make it a local variable in the
>         function xtensa_regno_to_class.
>         (xtensa_function_epilogue, TARGET_ASM_FUNCTION_EPILOGUE): Remove
>         macro, function prototype and implementation.
>         (reg_nonleaf_alloc_order): Make it a local variable in the
>         function order_regs_for_local_alloc.
>         (xtensa_conditional_register_usage): New function.
>         (TARGET_CONDITIONAL_REGISTER_USAGE): Define macro.
>         (xtensa_valid_move): Allow direct moves to stack pointer
>         register in call0 ABI.
>         (xtensa_setup_frame_addresses): Only spill register windows in
>         windowed ABI.
>         (xtensa_emit_call): Emit call(x)8 or call(x)0 in windowed and
>         call0 ABI respectively.
>         (xtensa_function_arg_1): Only mark a7 register for copying in
>         windowed ABI.
>         (xtensa_call_save_reg): New function.
>         (compute_frame_size): Add space for callee saved register
>         storage to the frame size in call0 ABI.
>         (xtensa_expand_prologue): Generate code to set up stack frame
>         and save callee-saved registers in call0 ABI.
>         (xtensa_expand_epilogue): New function.
>         (xtensa_set_return_address): New function.
>         (xtensa_return_addr): Calculate return address in call0 ABI.
>         (xtensa_builtin_saveregs): Only mark a7 register for copying and
>         emit copying code in windowed ABI.
>         (order_regs_for_local_alloc): Add preferred register allocation
>         order for non-leaf function in call0 ABI.
>         (xtensa_static_chain): Add atatic chain passing for call0 ABI.
>         (xtensa_asm_trampoline_template): Add trampoline generation for
>         call0 ABI.
>         (xtensa_trampoline_init): Add trampoline initialization for
>         call0 ABI.
>         (xtensa_conditional_register_usage, xtensa_regno_to_class): New
>         functions.
>
>         * config/xtensa/xtensa.h (TARGET_WINDOWED_ABI): New macro.
>         (TARGET_CPU_CPP_BUILTINS): Add built-in define for call0 ABI.
>         (CALL_USED_REGISTERS): Modify to encode both windowed and call0
>         ABI call-used registers.
>         (HARD_FRAME_POINTER_REGNUM): Add frame pointer for call0 ABI.
>         (INCOMING_REGNO, OUTGOING_REGNO): Use argument unchanged in
>         call0 ABI.
>         (REG_CLASS_CONTENTS): Include all registers into the preferred
>         reload registers set, adjust the set in the
>         xtensa_conditional_register_usage.
>         (xtensa_regno_to_class): Drop variable declaration.
>         (REGNO_REG_CLASS): Redefine to use xtensa_regno_to_class
>         function.
>         (WINDOW_SIZE): Define as 8 or 0 for windowed and call0 ABI
>         respectively.
>         (FUNCTION_PROFILER): Add _mcount call for call0 ABI.
>         (TRAMPOLINE_SIZE): Define trampoline size for call0 ABI.
>         (RETURN_ADDR_IN_PREVIOUS_FRAME): Define to 0 in call0 ABI.
>         (ASM_OUTPUT_POOL_PROLOGUE): Always generate literal pool
>         location in call0 ABI.
>         (EH_RETURN_STACKADJ_RTX): New definition, use a10 for passing
>         stack adjustment size when handling exception.
>         (CRT_CALL_STATIC_FUNCTION): Add definition for call0 ABI.
>
>         * config/xtensa/xtensa.md (A9_REG, UNSPECV_BLOCKAGE): New
>         definitions.
>         ("return" pattern): Generate ret.n/ret in call0 ABI.
>         ("epilogue" pattern): Expand epilogue.
>         ("nonlocal_goto" pattern): Use default in call0 ABI.
>         ("eh_return" pattern): Move implementation to eh_set_a0_windowed,
>         emit eh_set_a0_* depending on ABI.
>         ("eh_set_a0_windowed" pattern): Former eh_return pattern.
>         ("eh_set_a0_call0", "blockage"): New patterns.
>
> libgcc/
>         * config/xtensa/lib2funcs.S (__xtensa_libgcc_window_spill,
>         __xtensa_nonlocal_goto): Don't compile for call0 ABI.
>         (__xtensa_sync_caches): Only use entry and retw in windowed ABI,
>         use ret in call0 ABI.
>
>         * config/xtensa/t-windowed: New file.
>
>         * libgcc/config/xtensa/t-xtensa (LIB2ADDEH): Move to t-windowed.
>
>         * libgcc/configure: Regenerated.
>
>         * libgcc/configure.ac: Check if xtensa target is configured for
>         windowed ABI and thus needs to use custom unwind code.


This is OK for xtensa.