[Bug target/78118] xtensa: ICE in gcc-6.1.0/libgcc/libgcc2.c:1992:1: error: unrecognizable insn

[jcmvbkbc at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78118

--- Comment #4 from jcmvbkbc at gcc dot gnu.org ---
Author: jcmvbkbc
Date: Tue Nov  1 17:16:33 2016
New Revision: 241748

URL: https://gcc.gnu.org/viewcvs?rev=241748&root=gcc&view=rev
Log:
xtensa: Fix PR target/78118

It started failing after the following commit: 32e90dc6a0cda45 ("PR
rtl-optimization/61047").

The change that made xtensa backend go ICE looks completely unrelated,
and indeed, the issue is caused by the side effect of
compute_frame_size() function call hidden in the
INITIAL_ELIMINATION_OFFSET macro. This call updates the value of the
xtensa_current_frame_size static variable, used in "return" instruction
predicate. Prior to the change the value of xtensa_current_frame_size was
set to 0 after the end of epilogue generation, which enabled the "return"
instruction for the CALL0 ABI, but after the change the additional
INITIAL_ELIMINATION_OFFSET calls make xtensa_current_frame_size non-zero
and "return" pattern unavailable.

Get rid of the global xtensa_current_frame_size and
xtensa_callee_save_size variables by moving them into the
machine_function structure. Implement predicate for the "return" pattern
as a function. Don't communicate completion of epilogue generation
through zeroing of xtensa_current_frame_size, add explicit epilogue_done
variable to the machine_function structure. Don't update stack frame
layout after the completion of reload.

2016-11-01  Max Filippov  <jcmvbkbc@gmail.com>
gcc/
        * config/xtensa/xtensa-protos.h
        (xtensa_use_return_instruction_p): New prototype.
        * config/xtensa/xtensa.c (xtensa_current_frame_size,
        xtensa_callee_save_size): Remove.
        (struct machine_function): Add new fields: current_frame_size,
        callee_save_size, frame_laid_out and epilogue_done.
        (compute_frame_size, xtensa_expand_prologue,
        xtensa_expand_epilogue): Replace xtensa_callee_save_size with
        cfun->machine->callee_save_size and xtensa_current_frame_size
        with cfun->machine->current_frame_size.
        (compute_frame_size): Update cfun->machine->frame_laid_out and
        don't update frame layout after reload completion.
        (xtensa_expand_epilogue): Set cfun->machine->epilogue_done
        instead of zeroing xtensa_current_frame_size.
        (xtensa_use_return_instruction_p): New function.
        * config/xtensa/xtensa.h (xtensa_current_frame_size): Remove
        declaration.
        (INITIAL_ELIMINATION_OFFSET): Use return value of
        compute_frame_size instead of xtensa_current_frame_size value.
        * config/xtensa/xtensa.md ("return" pattern): Use new predicate
        function xtensa_use_return_instruction_p instead of inline code.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/xtensa/xtensa-protos.h
    trunk/gcc/config/xtensa/xtensa.c
    trunk/gcc/config/xtensa/xtensa.h
    trunk/gcc/config/xtensa/xtensa.md