* [PATCH v5] LoongArch: Fix eh_return epilogue for normal returns.
@ 2023-12-08 10:01 Yang Yujie
2023-12-12 2:03 ` chenglulu
0 siblings, 1 reply; 2+ messages in thread
From: Yang Yujie @ 2023-12-08 10:01 UTC (permalink / raw)
To: gcc-patches; +Cc: xry111, chenglulu, xuchenghua, Yang Yujie
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/loongarch/eh_return-normal-return.c: New test.
---
gcc/config/loongarch/loongarch-protos.h | 2 +-
gcc/config/loongarch/loongarch.cc | 34 ++++++++++++-----
gcc/config/loongarch/loongarch.md | 23 ++++++++++-
.../loongarch/eh_return-normal-return.c | 38 +++++++++++++++++++
4 files changed, 84 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 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);
\f
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..1277c0e9f72 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -1015,7 +1015,8 @@ 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;
@@ -1024,7 +1025,14 @@ 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))
{
- if (!cfun->machine->reg_is_wrapped_separately[regno])
+ /* 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 (!(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;
@@ -1297,7 +1305,7 @@ 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 +1390,13 @@ 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
@@ -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 == NORMAL_RETURN && loongarch_can_use_return_insn ())
{
emit_jump_insn (gen_return ());
return;
@@ -1479,7 +1490,9 @@ 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 ();
@@ -1500,11 +1513,12 @@ 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 7a101dd64b7..93b287c7faf 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -118,6 +118,11 @@ (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)
])
@@ -3197,7 +3202,7 @@ (define_expand "epilogue"
[(const_int 2)]
""
{
- loongarch_expand_epilogue (false);
+ loongarch_expand_epilogue (NORMAL_RETURN);
DONE;
})
@@ -3205,7 +3210,7 @@ (define_expand "sibcall_epilogue"
[(const_int 2)]
""
{
- loongarch_expand_epilogue (true);
+ loongarch_expand_epilogue (SIBCALL_RETURN);
DONE;
})
@@ -3262,6 +3267,20 @@ (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 ();
+}
--
2.43.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re:[pushed] [PATCH v5] LoongArch: Fix eh_return epilogue for normal returns.
2023-12-08 10:01 [PATCH v5] LoongArch: Fix eh_return epilogue for normal returns Yang Yujie
@ 2023-12-12 2:03 ` chenglulu
0 siblings, 0 replies; 2+ messages in thread
From: chenglulu @ 2023-12-12 2:03 UTC (permalink / raw)
To: Yang Yujie, gcc-patches; +Cc: xry111, xuchenghua
Pushed to r14-6440.
在 2023/12/8 下午6:01, Yang Yujie 写道:
> 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/loongarch/eh_return-normal-return.c: New test.
> ---
> gcc/config/loongarch/loongarch-protos.h | 2 +-
> gcc/config/loongarch/loongarch.cc | 34 ++++++++++++-----
> gcc/config/loongarch/loongarch.md | 23 ++++++++++-
> .../loongarch/eh_return-normal-return.c | 38 +++++++++++++++++++
> 4 files changed, 84 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 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);
> \f
> 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..1277c0e9f72 100644
> --- a/gcc/config/loongarch/loongarch.cc
> +++ b/gcc/config/loongarch/loongarch.cc
> @@ -1015,7 +1015,8 @@ 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;
>
> @@ -1024,7 +1025,14 @@ 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))
> {
> - if (!cfun->machine->reg_is_wrapped_separately[regno])
> + /* 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 (!(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;
> @@ -1297,7 +1305,7 @@ 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 +1390,13 @@ 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
> @@ -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 == NORMAL_RETURN && loongarch_can_use_return_insn ())
> {
> emit_jump_insn (gen_return ());
> return;
> @@ -1479,7 +1490,9 @@ 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 ();
> @@ -1500,11 +1513,12 @@ 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 7a101dd64b7..93b287c7faf 100644
> --- a/gcc/config/loongarch/loongarch.md
> +++ b/gcc/config/loongarch/loongarch.md
> @@ -118,6 +118,11 @@ (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)
> ])
> @@ -3197,7 +3202,7 @@ (define_expand "epilogue"
> [(const_int 2)]
> ""
> {
> - loongarch_expand_epilogue (false);
> + loongarch_expand_epilogue (NORMAL_RETURN);
> DONE;
> })
>
> @@ -3205,7 +3210,7 @@ (define_expand "sibcall_epilogue"
> [(const_int 2)]
> ""
> {
> - loongarch_expand_epilogue (true);
> + loongarch_expand_epilogue (SIBCALL_RETURN);
> DONE;
> })
>
> @@ -3262,6 +3267,20 @@ (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 ();
> +}
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-12-08 10:01 [PATCH v5] LoongArch: Fix eh_return epilogue for normal returns Yang Yujie
2023-12-12 2:03 ` chenglulu
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