From: Yang Yujie <yangyu...@loongson.cn>
On LoongArch, the regitsters $r4 - $r7 (EH_RETURN_DATA_REGNO) will be saved
and restored in the function prologue and epilogue if the given function calls
__builtin_eh_return. This causes the return value to be overwritten on normal
return paths and breaks a rare case of libgcc's _Unwind_RaiseException.
gcc/ChangeLog:
PR target/114848
* config/loongarch/loongarch.cc: Do not restore the saved eh_return
data registers ($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/loongarch/eh_return-normal-return.c: New test.
(cherry picked from commit 4b421728289e6f1caa0dfaa953a11698ab95d37d)
---
gcc/config/loongarch/loongarch-protos.h | 2 +-
gcc/config/loongarch/loongarch.cc | 35 ++++++++++++-----
gcc/config/loongarch/loongarch.md | 23 ++++++++++-
.../loongarch/eh_return-normal-return.c | 38 +++++++++++++++++++
4 files changed, 85 insertions(+), 13 deletions(-)
create mode 100644
gcc/testsuite/gcc.target/loongarch/eh_return-normal-return.c
diff --git a/gcc/config/loongarch/loongarch-protos.h
b/gcc/config/loongarch/loongarch-protos.h
index 2144c2421ed..8af82ffaa20 100644
--- a/gcc/config/loongarch/loongarch-protos.h
+++ b/gcc/config/loongarch/loongarch-protos.h
@@ -47,7 +47,7 @@ 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 33b1919e7a3..a0e11f2fc66 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -1008,7 +1008,8 @@ 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;
@@ -1017,7 +1018,15 @@ loongarch_for_each_saved_reg (HOST_WIDE_INT sp_offset,
for (int regno = GP_REG_FIRST; regno <= GP_REG_LAST; regno++)
if (BITSET_P (cfun->machine->frame.mask, regno - GP_REG_FIRST))
{
- 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. */
+
+ if (!(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;
}
@@ -1289,7 +1298,7 @@ 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);
}
@@ -1336,11 +1345,13 @@ 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 using the following insn patterns:
+ "epilogue" (style == NORMAL_RETURN)
+ "sibcall_epilogue" (style == SIBCALL_RETURN)
+ "eh_return" (style == EXCEPTION_RETURN) */
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
@@ -1357,7 +1368,8 @@ 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 == NORMAL_RETURN && loongarch_can_use_return_insn ())
{
emit_jump_insn (gen_return ());
return;
@@ -1433,7 +1445,9 @@ 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 != EXCEPTION_RETURN);
if (need_barrier_p)
loongarch_emit_stack_tie ();
@@ -1454,11 +1468,12 @@ loongarch_expand_epilogue (bool sibcall_p)
}
/* Add in the __builtin_eh_return stack adjustment. */
- if (crtl->calls_eh_return)
+ if (crtl->calls_eh_return && style == EXCEPTION_RETURN)
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 != SIBCALL_RETURN)
emit_jump_insn (gen_simple_return_internal (ra));
}
diff --git a/gcc/config/loongarch/loongarch.md b/gcc/config/loongarch/loongarch.md
index b49e058407c..1361e7ba7bf 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -98,6 +98,11 @@ (define_constants
(T1_REGNUM 13)
(S0_REGNUM 23)
+ ;; Return path styles
+ (NORMAL_RETURN 0)
+ (SIBCALL_RETURN 1)
+ (EXCEPTION_RETURN 2)
+
;; PIC long branch sequences are never longer than 100 bytes.
(MAX_PIC_BRANCH_LENGTH 100)
])
@@ -2715,7 +2720,7 @@ (define_expand "epilogue"
[(const_int 2)]
""
{
- loongarch_expand_epilogue (false);
+ loongarch_expand_epilogue (NORMAL_RETURN);
DONE;
})
@@ -2723,7 +2728,7 @@ (define_expand "sibcall_epilogue"
[(const_int 2)]
""
{
- loongarch_expand_epilogue (true);
+ loongarch_expand_epilogue (SIBCALL_RETURN);
DONE;
})
@@ -2780,6 +2785,20 @@ (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 (EXCEPTION_RETURN);
DONE;
})
diff --git a/gcc/testsuite/gcc.target/loongarch/eh_return-normal-return.c b/gcc/testsuite/gcc.target/loongarch/eh_return-normal-return.c
new file mode 100644
index 00000000000..f8f3965f894
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/eh_return-normal-return.c
@@ -0,0 +1,38 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#include <stdlib.h>
+
+int foo () __attribute__((noinline));
+int main ();
+
+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 if (t == 1)
+ /* return here */
+ return 202312;
+
+ else
+ /* never reached: prevent vrp optimization in main */
+ return 0;
+}
+
+int
+main ()
+{
+ if (foo() == 202312)
+ return 0;
+ else
+ abort ();
+}
