Start fixing the stack frame layout

gcc/config/rs6000/rs6000-c.cc

@@ -753,6 +753,8 @@ rs6000_cpu_cpp_builtins (cpp_reader *pfile)
     case ABI_DARWIN:
       builtin_define ("_CALL_DARWIN");
       break;
+    case ABI_XENON:
+      builtin_define ("_CALL_SYSV"); /* Should be okay? */
     default:
       break;
     }

gcc/config/rs6000/rs6000-logue.cc

@@ -767,7 +767,7 @@ rs6000_stack_info (void)
       RS6000_ALIGN (crtl->outgoing_args_size + info->fixed_size,
 		    STACK_BOUNDARY / BITS_PER_UNIT) - info->fixed_size;
   else
-    info->parm_size = RS6000_ALIGN (crtl->outgoing_args_size,
+    info->parm_size  = RS6000_ALIGN (crtl->outgoing_args_size,
 				     TARGET_ALTIVEC ? 16 : 8);
   if (FRAME_GROWS_DOWNWARD)
     info->vars_size
@@ -826,29 +826,51 @@ rs6000_stack_info (void)
       info->lr_save_offset = 2*reg_size;
       break;
 
-    case ABI_V4: /* Just replacing the SV4 ABI with the Xenon one... It's hacky, but I was having trouble defining a special ABI_XENON */
+    case ABI_V4:
-      info->cr_save_p = 0; /* We don't seem to save condition registers on 360 */
+      info->fp_save_offset = -info->fp_size;
+      info->gp_save_offset = info->fp_save_offset - info->gp_size;
+      info->cr_save_offset = info->gp_save_offset - info->cr_size;
+
+      if (TARGET_ALTIVEC_ABI)
+	{
+	  info->vrsave_save_offset = info->cr_save_offset - info->vrsave_size;
+
+	  /* Align stack so vector save area is on a quadword boundary.  */
+	  if (info->altivec_size != 0)
+	    info->altivec_padding_size = 16 - (-info->vrsave_save_offset % 16);
+
+	  info->altivec_save_offset = info->vrsave_save_offset
+				      - info->altivec_padding_size
+				      - info->altivec_size;
+
+	  /* Adjust for AltiVec case.  */
+	  info->ehrd_offset = info->altivec_save_offset;
+	}
+      else
+	info->ehrd_offset = info->cr_save_offset;
+
+      info->ehrd_offset -= ehrd_size;
+      info->lr_save_offset = reg_size;
+      break;
+
+    case ABI_XENON:
       info->gp_save_offset = -0xC - info->gp_size;
       info->fp_save_offset = info->gp_save_offset - info->fp_size;
       info->vrsave_save_offset = info->fp_save_offset - info->vrsave_size;
 
-	  	/* Align stack so vector save area is on a quadword boundary.  */
+	  /* Align stack so vector save area is on a quadword boundary.  */
-	  	if (info->altivec_size != 0)
+	  if (info->altivec_size != 0)
-	    	info->altivec_padding_size = 16 - (-info->vrsave_save_offset % 16);
+	    info->altivec_padding_size = 16 - (-info->vrsave_save_offset % 16);
 
-	  	info->altivec_save_offset = info->vrsave_save_offset
+	  info->altivec_save_offset = info->vrsave_save_offset
 				      - info->altivec_padding_size
 				      - info->altivec_size;
 
-			/* Adjust for AltiVec case.  */
+      info->lr_save_offset = -0x8;
-	  	info->ehrd_offset = info->altivec_save_offset;
+      break;
-
-			info->ehrd_offset -= ehrd_size;
-    	info->lr_save_offset = -0x8;
-    	break;
     }
 
-  save_align = ((TARGET_ALTIVEC_ABI || DEFAULT_ABI == ABI_DARWIN) && DEFAULT_ABI != ABI_V4) ? 16 : 8;
+  save_align = (TARGET_ALTIVEC_ABI || DEFAULT_ABI == ABI_DARWIN) ? 16 : 8;
   info->save_size = RS6000_ALIGN (info->fp_size
 				  + info->gp_size
 				  + info->altivec_size
@@ -865,12 +887,18 @@ rs6000_stack_info (void)
   info->total_size = RS6000_ALIGN (non_fixed_size + info->fixed_size,
 				   ABI_STACK_BOUNDARY / BITS_PER_UNIT);
 
+  if(DEFAULT_ABI == ABI_XENON)
+    /* 0x10 == unknown area (empty?), 0x40 == slots for callee to store r3->r10, */
+    /* 0xC == space before saved regs */
+    info->total_size += RS6000_ALIGN(0x10 + 0x40 + 0xC, ABI_STACK_BOUNDARY / BITS_PER_UNIT);
+
   /* Determine if we need to save the link register.  */
   if (info->calls_p
       || ((DEFAULT_ABI == ABI_AIX || DEFAULT_ABI == ABI_ELFv2)
 	  && crtl->profile
 	  && !TARGET_PROFILE_KERNEL)
       || (DEFAULT_ABI == ABI_V4 && cfun->calls_alloca)
+      || DEFAULT_ABI == ABI_XENON
 #ifdef TARGET_RELOCATABLE
       || (DEFAULT_ABI == ABI_V4
 	  && (TARGET_RELOCATABLE || flag_pic > 1)
@@ -942,7 +970,8 @@ debug_stack_info (rs6000_stack_t *info)
     case ABI_AIX:	 abi_string = "AIX";		break;
     case ABI_ELFv2:	 abi_string = "ELFv2";		break;
     case ABI_DARWIN:	 abi_string = "Darwin";		break;
-    case ABI_V4:	 abi_string = "Xenon";		break;
+    case ABI_V4:	 abi_string = "V.4";		break;
+    case ABI_XENON:   abi_string = "Xenon";     break;
     }
 
   fprintf (stderr, "\tABI                 = %5s\n", abi_string);

gcc/config/rs6000/rs6000-opts.h

@@ -102,7 +102,8 @@ enum rs6000_abi {
   ABI_AIX,			/* IBM's AIX, or Linux ELFv1 */
   ABI_ELFv2,			/* Linux ELFv2 ABI */
   ABI_V4,			/* System V.4/eabi */
-  ABI_DARWIN			/* Apple's Darwin (OS X kernel) */
+  ABI_DARWIN,			/* Apple's Darwin (OS X kernel) */
+  ABI_XENON         /* Xbox 360 OS */
 };
 
 /* Small data support types.  */

gcc/config/rs6000/sysv4.h

@@ -103,6 +103,8 @@ do {									\
     rs6000_current_abi = ABI_V4;					\
   else if (!strcmp (rs6000_abi_name, "openbsd"))			\
     rs6000_current_abi = ABI_V4;					\
+  else if (!strcmp (rs6000_abi_name, "xenon")) \
+    rs6000_current_abi = ABI_XENON; \
   else if (!strcmp (rs6000_abi_name, "i960-old"))			\
     {									\
       rs6000_current_abi = ABI_V4;					\

gcc/config/rs6000/xenon.h

@@ -1,32 +1,11 @@
-/* Redefinitions for FreeChainXenon
+/* Specify Xenon ABI */
-   Copyright (C) 2025 Aiden Isik
+#undef RS6000_ABI_NAME
-
+#define RS6000_ABI_NAME "xenon"
-   This file is part of GCC.
-
-   GCC is free software; you can redistribute it and/or modify it
-   under the terms of the GNU General Public License as published
-   by the Free Software Foundation; either version 3, or (at your
-   option) any later version.
-
-   GCC is distributed in the hope that it will be useful, but WITHOUT
-   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
-   License for more details.
-
-   You should have received a copy of the GNU General Public License
-   along with GCC; see the file COPYING3.  If not see
-   <http://www.gnu.org/licenses/>.  */
-
-#undef TARGET_DEBUG_STACK
-#define TARGET_DEBUG_STACK 1
-
-/* Force the pointer size to 32 bits (even though we run in 64-bit mode) */
-//#undef POINTER_SIZE
-//#define POINTER_SIZE 32
 
 /* Change the fixed area for the 360's stack frame convention */
 #undef RS6000_SAVE_AREA
-#define RS6000_SAVE_AREA 0x10 + (RS6000_ALIGN (crtl->outgoing_args_size.to_constant (), 16) - crtl->outgoing_args_size.to_constant ()) + 0x40
+#define RS6000_SAVE_AREA \
+    (0x10 + (RS6000_ALIGN (crtl->outgoing_args_size, 16) - crtl->outgoing_args_size) + 0x40)
 
 /* Redefine the starting frame offset, since it relies on the size of the fixed area */
 #undef RS6000_STARTING_FRAME_OFFSET