gdb: LoongArch: Handle variadic arguments

According to LoongArch ELF ABI specification [1], variadic arguments
are passed in GARs in the same manner as named arguments. And after
a variadic argument has been passed on the stack, all future arguments
will also be passed on the stack, i.e., the last argument register may
be left unused due to the aligned register pair rule. long double data
tpye is passed in an aligned GAR pair, the first register in the pair
is even-numbered.

[1] https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>

1 files changed, 76 insertions, 29 deletions

diff --git a/gdb/loongarch-tdep.c b/gdb/loongarch-tdep.c
index e63ff01..71a2cfb 100644
--- a/gdb/loongarch-tdep.c
+++ b/gdb/loongarch-tdep.c
@@ -570,6 +570,8 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
       size_t len = TYPE_LENGTH (type);
       int align = type_align (type);
       enum type_code code = type->code ();
+      struct type *func_type = check_typedef (value_type (function));
+      bool varargs = (func_type->has_varargs () && i >= func_type->num_fields ());
 
       switch (code)
 	{
@@ -606,26 +608,63 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 	case TYPE_CODE_FLT:
 	  if (len == 2 * regsize)
 	    {
-	      /* long double type is passed in a pair of GAR,
-		 with the low-order GRLEN bits in the lower-numbered register
-		 and the high-order GRLEN bits in the higher-numbered register.
-		 If exactly one register is available,
-		 the low-order GRLEN bits are passed in the register
-		 and the high-order GRLEN bits are passed on the stack.
-		 If no GAR is available, it's passed on the stack.  */
-	      if (gar >= 2)
+	      if (!varargs)
 		{
-		  pass_in_gar (regcache, gar--, val);
-		  pass_in_gar (regcache, gar--, val + regsize);
-		}
-	      else if (gar == 1)
-		{
-		  pass_in_gar (regcache, gar--, val);
-		  pass_on_stack (regcache, val + regsize, len - regsize, align, &addr);
+		  /* long double type is passed in a pair of GAR,
+		     with the low-order GRLEN bits in the lower-numbered register
+		     and the high-order GRLEN bits in the higher-numbered register.
+		     If exactly one register is available,
+		     the low-order GRLEN bits are passed in the register
+		     and the high-order GRLEN bits are passed on the stack.
+		     If no GAR is available, it's passed on the stack.  */
+		  if (gar >= 2)
+		    {
+		      pass_in_gar (regcache, gar--, val);
+		      pass_in_gar (regcache, gar--, val + regsize);
+		    }
+		  else if (gar == 1)
+		    {
+		      pass_in_gar (regcache, gar--, val);
+		      pass_on_stack (regcache, val + regsize, len - regsize, align, &addr);
+		    }
+		  else
+		    {
+		      pass_on_stack (regcache, val, len, align, &addr);
+		    }
 		}
 	      else
 		{
-		  pass_on_stack (regcache, val, len, align, &addr);
+		  /* Variadic arguments are passed in GARs
+		     in the same manner as named arguments.
+		     And after a variadic argument has been passed on the stack,
+		     all future arguments will also be passed on the stack,
+		     i.e., the last argument register may be left unused
+		     due to the aligned register pair rule.
+		     long double data tpye is passed in an aligned GAR pair,
+		     the first register in the pair is even-numbered.  */
+		  if (gar >= 2)
+		    {
+		      if (gar % 2 == 0)
+			{
+			  pass_in_gar (regcache, gar--, val);
+			  pass_in_gar (regcache, gar--, val + regsize);
+			}
+		      else
+			{
+			  gar--;
+			  pass_in_gar (regcache, gar--, val);
+			  pass_in_gar (regcache, gar--, val + regsize);
+			}
+		    }
+		  else if (gar == 1)
+		    {
+		      gar--;
+		      pass_on_stack (regcache, val, len, align, &addr);
+		    }
+		  else
+		    {
+		      pass_on_stack (regcache, val, len, align, &addr);
+		    }
 		}
 	    }
 	  else
@@ -633,7 +672,7 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 	      /* The other floating-point type is passed in FAR.
 		 If no FAR is available, it's passed in GAR.
 		 If no GAR is available, it's passed on the stack.  */
-	      if (far > 0)
+	      if (!varargs && far > 0)
 		  pass_in_far (regcache, far--, val);
 	      else if (gar > 0)
 		  pass_in_gar (regcache, gar--, val);
@@ -673,7 +712,7 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 		       if no GAR is available, the value is passed on the stack.  */
 		    if (floating_point_members == 1)
 		      {
-			if (far > 0)
+			if (!varargs && far > 0)
 			  pass_in_far (regcache, far--, val);
 			else if (gar > 0)
 			  pass_in_gar (regcache, gar--, val);
@@ -688,7 +727,7 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 		       and passed on the stack if no GAR is available.  */
 		    else if (floating_point_members == 2)
 		      {
-			if (far >= 2)
+			if (!varargs && far >= 2)
 			  {
 			    pass_in_far (regcache, far--, val);
 			    pass_in_far (regcache, far--, val + align);
@@ -724,7 +763,7 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 		       If no GAR is available, it's passed on the stack.  */
 		    else if (floating_point_members == 1 && fixed_point_members == 1)
 		      {
-			if (far > 0 && gar > 0)
+			if (!varargs && far > 0 && gar > 0)
 			  {
 			    if (first_member_is_fixed_point == false)
 			      {
@@ -799,8 +838,16 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 			  }
 			else if (gar == 1)
 			  {
-			    pass_in_gar (regcache, gar--, val);
-			    pass_on_stack (regcache, val + regsize, len - regsize, align, &addr);
+			    if (!varargs)
+			      {
+				pass_in_gar (regcache, gar--, val);
+				pass_on_stack (regcache, val + regsize, len - regsize, align, &addr);
+			      }
+			    else
+			      {
+				gar--;
+				pass_on_stack (regcache, val, len, align, &addr);
+			      }
 			  }
 			else
 			  {
@@ -823,7 +870,7 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 		    else if ((len == 16 && floating_point_members == 2)
 			     || (len == 12 && floating_point_members == 2))
 		      {
-			if (far >= 2)
+			if (!varargs && far >= 2)
 			  {
 			    pass_in_far (regcache, far--, val);
 			    pass_in_far (regcache, far--, val + regsize);
@@ -859,7 +906,7 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 			   the low-order bits are in the GAR
 			   and the high-order bits are on the stack;
 			   And it's passed on the stack if no GAR is available.  */
-			if (far > 0 && gar > 0)
+			if (!varargs && far > 0 && gar > 0)
 			  {
 			    if (first_member_is_fixed_point == false)
 			      {
@@ -872,17 +919,17 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 				pass_in_far (regcache, far--, val + regsize);
 			      }
 			  }
-			else if (far == 0 && gar >= 2)
+			else if ((!varargs && far == 0 && gar >= 2) || (varargs && gar >= 2))
 			  {
 			    pass_in_gar (regcache, gar--, val);
 			    pass_in_gar (regcache, gar--, val + regsize);
 			  }
-			else if (far == 0 && gar == 1)
+			else if ((!varargs && far == 0 && gar == 1) || (varargs && gar == 1))
 			  {
 			    pass_in_gar (regcache, gar--, val);
 			    pass_on_stack (regcache, val + regsize, len - regsize, align, &addr);
 			  }
-			else if (far == 0 && gar == 0)
+			else if ((!varargs && far == 0 && gar == 0) || (varargs && gar == 0))
 			  {
 			    pass_on_stack (regcache, val, len, align, &addr);
 			  }
@@ -990,7 +1037,7 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 		   and the high-order float member bits in the higher-numbered FAR.
 		   If the number of available FAR is less than 2, it's passed in a GAR,
 		   and passed on the stack if no GAR is available.  */
-		if (far >= 2)
+		if (!varargs && far >= 2)
 		  {
 		    pass_in_far (regcache, far--, val);
 		    pass_in_far (regcache, far--, val + align);
@@ -1019,7 +1066,7 @@ loongarch_push_dummy_call (struct gdbarch *gdbarch,
 		   and the high-order bits are on stack,
 		   and passed on the stack if no GAR is available.  */
 		{
-		  if (far >= 2)
+		  if (!varargs && far >= 2)
 		    {
 		      pass_in_far (regcache, far--, val);
 		      pass_in_far (regcache, far--, val + align);