On LoongArch, the regitsters $r4 - $r7 (EH_RETURN_DATA_REGNO) will be saved and restored in the function prologue and epilogue if the given function calls __builtin_eh_return. This causes the return value to be overwritten on normal return paths and breaks a rare case of libgcc's _Unwind_RaiseException.
gcc/ChangeLog: * config/loongarch/loongarch.cc: Do not restore the saved eh_return data registers ($r4-$r7) for a normal return of a function that calls __builtin_eh_return elsewhere. * config/loongarch/loongarch-protos.h: Same. * config/loongarch/loongarch.md: Same. gcc/testsuite/ChangeLog: * gcc.target/eh_return-normal-return.c: New test. --- gcc/config/loongarch/loongarch-protos.h | 2 +- gcc/config/loongarch/loongarch.cc | 41 ++++++++++++------- gcc/config/loongarch/loongarch.md | 18 +++++++- .../gcc.target/eh_return-normal-return.c | 31 ++++++++++++++ 4 files changed, 75 insertions(+), 17 deletions(-) create mode 100644 gcc/testsuite/gcc.target/eh_return-normal-return.c diff --git a/gcc/config/loongarch/loongarch-protos.h b/gcc/config/loongarch/loongarch-protos.h index cb8fc36b086..af20b5d7132 100644 --- a/gcc/config/loongarch/loongarch-protos.h +++ b/gcc/config/loongarch/loongarch-protos.h @@ -60,7 +60,7 @@ enum loongarch_symbol_type { extern rtx loongarch_emit_move (rtx, rtx); extern HOST_WIDE_INT loongarch_initial_elimination_offset (int, int); extern void loongarch_expand_prologue (void); -extern void loongarch_expand_epilogue (bool); +extern void loongarch_expand_epilogue (int); extern bool loongarch_can_use_return_insn (void); extern bool loongarch_symbolic_constant_p (rtx, enum loongarch_symbol_type *); diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc index 3545e66a10e..9c0e0dd1b73 100644 --- a/gcc/config/loongarch/loongarch.cc +++ b/gcc/config/loongarch/loongarch.cc @@ -1015,20 +1015,30 @@ loongarch_save_restore_reg (machine_mode mode, int regno, HOST_WIDE_INT offset, static void loongarch_for_each_saved_reg (HOST_WIDE_INT sp_offset, - loongarch_save_restore_fn fn) + loongarch_save_restore_fn fn, + bool skip_eh_data_regs_p) { HOST_WIDE_INT offset; /* Save the link register and s-registers. */ offset = cfun->machine->frame.gp_sp_offset - sp_offset; for (int regno = GP_REG_FIRST; regno <= GP_REG_LAST; regno++) - if (BITSET_P (cfun->machine->frame.mask, regno - GP_REG_FIRST)) - { - if (!cfun->machine->reg_is_wrapped_separately[regno]) - loongarch_save_restore_reg (word_mode, regno, offset, fn); + { + /* Special care needs to be taken for $r4-$r7 (EH_RETURN_DATA_REGNO) + when returning normally from a function that calls __builtin_eh_return. + In this case, these registers are saved but should not be restored, + or the return value may be clobbered. */ - offset -= UNITS_PER_WORD; - } + if (BITSET_P (cfun->machine->frame.mask, regno - GP_REG_FIRST)) + { + if (!(cfun->machine->reg_is_wrapped_separately[regno] + || (skip_eh_data_regs_p + && GP_ARG_FIRST <= regno && regno < GP_ARG_FIRST + 4))) + loongarch_save_restore_reg (word_mode, regno, offset, fn); + + offset -= UNITS_PER_WORD; + } + } /* This loop must iterate over the same space as its companion in loongarch_compute_frame_info. */ @@ -1297,7 +1307,7 @@ loongarch_expand_prologue (void) GEN_INT (-step1)); RTX_FRAME_RELATED_P (emit_insn (insn)) = 1; size -= step1; - loongarch_for_each_saved_reg (size, loongarch_save_reg); + loongarch_for_each_saved_reg (size, loongarch_save_reg, false); } /* Set up the frame pointer, if we're using one. */ @@ -1382,11 +1392,11 @@ loongarch_can_use_return_insn (void) return reload_completed && cfun->machine->frame.total_size == 0; } -/* Expand an "epilogue" or "sibcall_epilogue" pattern; SIBCALL_P - says which. */ +/* Expand function epilogue for the following insn patterns: + "epilogue" (style == 0) / "sibcall_epilogue" (1) / "eh_return" (2). */ void -loongarch_expand_epilogue (bool sibcall_p) +loongarch_expand_epilogue (int style) { /* Split the frame into two. STEP1 is the amount of stack we should deallocate before restoring the registers. STEP2 is the amount we @@ -1403,7 +1413,8 @@ loongarch_expand_epilogue (bool sibcall_p) bool need_barrier_p = (get_frame_size () + cfun->machine->frame.arg_pointer_offset) != 0; - if (!sibcall_p && loongarch_can_use_return_insn ()) + /* Handle simple returns. */ + if (style == 0 && loongarch_can_use_return_insn ()) { emit_jump_insn (gen_return ()); return; @@ -1479,7 +1490,8 @@ loongarch_expand_epilogue (bool sibcall_p) /* Restore the registers. */ loongarch_for_each_saved_reg (frame->total_size - step2, - loongarch_restore_reg); + loongarch_restore_reg, + crtl->calls_eh_return && style != 2); if (need_barrier_p) loongarch_emit_stack_tie (); @@ -1504,7 +1516,8 @@ loongarch_expand_epilogue (bool sibcall_p) emit_insn (gen_add3_insn (stack_pointer_rtx, stack_pointer_rtx, EH_RETURN_STACKADJ_RTX)); - if (!sibcall_p) + /* Emit return unless doing sibcall. */ + if (style != 1) emit_jump_insn (gen_simple_return_internal (ra)); } diff --git a/gcc/config/loongarch/loongarch.md b/gcc/config/loongarch/loongarch.md index 7a101dd64b7..61b27293489 100644 --- a/gcc/config/loongarch/loongarch.md +++ b/gcc/config/loongarch/loongarch.md @@ -3197,7 +3197,7 @@ (define_expand "epilogue" [(const_int 2)] "" { - loongarch_expand_epilogue (false); + loongarch_expand_epilogue (0); DONE; }) @@ -3205,7 +3205,7 @@ (define_expand "sibcall_epilogue" [(const_int 2)] "" { - loongarch_expand_epilogue (true); + loongarch_expand_epilogue (1); DONE; }) @@ -3262,6 +3262,20 @@ (define_expand "eh_return" emit_insn (gen_eh_set_ra_di (operands[0])); else emit_insn (gen_eh_set_ra_si (operands[0])); + + emit_jump_insn (gen_eh_return_internal ()); + emit_barrier (); + DONE; +}) + +(define_insn_and_split "eh_return_internal" + [(eh_return)] + "" + "#" + "epilogue_completed" + [(const_int 0)] +{ + loongarch_expand_epilogue (2); DONE; }) diff --git a/gcc/testsuite/gcc.target/eh_return-normal-return.c b/gcc/testsuite/gcc.target/eh_return-normal-return.c new file mode 100644 index 00000000000..ad53699f197 --- /dev/null +++ b/gcc/testsuite/gcc.target/eh_return-normal-return.c @@ -0,0 +1,31 @@ +/* { dg-do run } */ +/* { dg-options "-O2" } */ + +#include <stdlib.h> + +int foo() __attribute__((noinline)); +int main (void); + +int foo () +{ + int t; + + /* prevent optimization using asm */ + asm ("" : "=r" (t) : "0" (-1)); + asm ("" : "=r" (t) : "0" (t ? 1 : 0)); + + if (t == 0) + /* never reached */ + __builtin_eh_return (0, __builtin_return_address (0)); + else + return 202312; +} + + +int main (void) +{ + if (foo() == 202312) + return 0; + else + abort (); +} -- 2.43.0