https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84521
--- Comment #29 from Wilco ---
Author: wilco
Date: Wed Jun 19 12:52:43 2019
New Revision: 272473
URL: https://gcc.gnu.org/viewcvs?rev=272473=gcc=rev
Log:
Simplify setjmp and non-local goto implementation (PR84521)
This fixes and simplifies the setjmp and non-local goto implementation.
Currently the virtual frame pointer is saved when using __builtin_setjmp or
a non-local goto. Depending on whether a frame pointer is used, this may
either save SP or FP with an immediate offset. However the goto or longjmp
always updates the hard frame pointer.
A receiver veneer in the original function then assigns the hard frame pointer
to the virtual frame pointer, which should, if it works correctly, again assign
SP or FP. However the special elimination code in eliminate_regs_in_insn
doesn't do this correctly unless the frame pointer is used, and even if it
worked by writing SP, the frame pointer would still be corrupted.
A much simpler implementation is to always save and restore the hard frame
pointer. This avoids 2 redundant instructions which add/subtract the virtual
frame offset. A large amount of code can be removed as a result, including all
implementations of TARGET_BUILTIN_SETJMP_FRAME_VALUE (all of which already use
the hard frame pointer). The expansion of nonlocal_goto on PA can be simplied
to just restore the hard frame pointer.
This fixes the most obvious issues, however there are still issues on targets
which define HARD_FRAME_POINTER_IS_FRAME_POINTER (arm, mips).
Each function could have a different hard frame pointer, so a non-local goto
may restore the wrong frame pointer (TARGET_BUILTIN_SETJMP_FRAME_VALUE could
be useful for this).
The i386 TARGET_BUILTIN_SETJMP_FRAME_VALUE was incorrect: if stack_realign_fp
is true, it would save the hard frame pointer value but restore the virtual
frame pointer which according to ix86_initial_elimination_offset can have a
non-zero offset from the hard frame pointer.
The ia64 implementation of nonlocal_goto seems incorrect since the helper
function moves the the frame pointer value into the static chain register
(so this patch does nothing to make it better or worse).
AArch64 + x86-64 bootstrap OK, new test passes on AArch64, x86-64 and Arm.
gcc/
PR middle-end/84521
* builtins.c (expand_builtin_setjmp_setup): Save
hard_frame_pointer_rtx.
(expand_builtin_setjmp_receiver): Do not emit sfp = fp move since we
restore fp.
* function.c (expand_function_start): Save hard_frame_pointer_rtx for
non-local goto.
* lra-eliminations.c (eliminate_regs_in_insn): Remove sfp = fp
elimination code.
(remove_reg_equal_offset_note): Remove unused function.
* reload1.c (eliminate_regs_in_insn): Remove sfp = hfp elimination
code.
* config/arc/arc.c (TARGET_BUILTIN_SETJMP_FRAME_VALUE): Remove.
(arc_builtin_setjmp_frame_value): Remove function.
* config/avr/avr.c (TARGET_BUILTIN_SETJMP_FRAME_VALUE): Remove.
(avr_builtin_setjmp_frame_value): Remove function.
* config/i386/i386.c (TARGET_BUILTIN_SETJMP_FRAME_VALUE): Remove.
(ix86_builtin_setjmp_frame_value): Remove function.
* config/pa/pa.md (nonlocal_goto): Remove FP adjustment.
* config/sparc/sparc.c (TARGET_BUILTIN_SETJMP_FRAME_VALUE): Remove.
(sparc_builtin_setjmp_frame_value): Remove function.
* config/vax/vax.c (TARGET_BUILTIN_SETJMP_FRAME_VALUE): Remove.
(vax_builtin_setjmp_frame_value): Remove function.
* config/xtensa/xtensa.c (xtensa_frame_pointer_required): Force frame
pointer if has_nonlocal_label.
testsuite/
PR middle-end/84521
* gcc.c-torture/execute/pr84521.c: New test.
Added:
trunk/gcc/testsuite/gcc.c-torture/execute/pr84521.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/builtins.c
trunk/gcc/config/arc/arc.c
trunk/gcc/config/avr/avr.c
trunk/gcc/config/i386/i386.c
trunk/gcc/config/pa/pa.md
trunk/gcc/config/sparc/sparc.c
trunk/gcc/config/vax/vax.c
trunk/gcc/config/xtensa/xtensa.c
trunk/gcc/function.c
trunk/gcc/lra-eliminations.c
trunk/gcc/reload1.c
trunk/gcc/testsuite/ChangeLog
