[PATCH] LoongArch: Fix eh_return epilogue for normal returns.

[PATCH] LoongArch: Fix eh_return epilogue for normal returns.

[Yang Yujie]

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/config/loongarch/loongarch-protos.h |  2 +-
 gcc/config/loongarch/loongarch.cc       | 41 ++++++++++++++++---------
 gcc/config/loongarch/loongarch.md       | 18 +++++++++--
 3 files changed, 44 insertions(+), 17 deletions(-)

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 738911661d7..7f60a4367d3 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -1011,20 +1011,30 @@ 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.  */
@@ -1293,7 +1303,7 @@ 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.  */
@@ -1378,11 +1388,11 @@ 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
@@ -1399,7 +1409,8 @@ 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;
@@ -1475,7 +1486,8 @@ 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 ();
@@ -1500,7 +1512,8 @@ 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 22814a3679c..f388026d50c 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -3156,7 +3156,7 @@ (define_expand "epilogue"
   [(const_int 2)]
   ""
 {
-  loongarch_expand_epilogue (false);
+  loongarch_expand_epilogue (0);
   DONE;
 })
 
@@ -3164,7 +3164,7 @@ (define_expand "sibcall_epilogue"
   [(const_int 2)]
   ""
 {
-  loongarch_expand_epilogue (true);
+  loongarch_expand_epilogue (1);
   DONE;
 })
 
@@ -3221,6 +3221,20 @@ (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;
 })
 
-- 
2.42.1