aarch64: Mark x18 register as a fixed register for MS ABI

Define the MS ABI for aarch64-w64-mingw32.
Adjust FIXED_REGISTERS, CALL_REALLY_USED_REGISTERS and
STATIC_CHAIN_REGNUM for AArch64 MS ABI.
The X18 register is reserved on Windows for the TEB.

gcc/ChangeLog:

	* config.gcc: Define TARGET_AARCH64_MS_ABI when
	AArch64 MS ABI is used.
	* config/aarch64/aarch64.h (FIXED_X18): Adjust
	FIXED_REGISTERS, CALL_REALLY_USED_REGISTERS and
	STATIC_CHAIN_REGNUM for AArch64 MS ABI.
	(CALL_USED_X18): Likewise.
	(FIXED_REGISTERS): Likewise.
	* config/aarch64/aarch64-abi-ms.h: New file.

3 files changed, 40 insertions, 2 deletions

diff --git a/gcc/config.gcc b/gcc/config.gcc
index 0a737bf3..007a64d 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1271,6 +1271,7 @@ aarch64*-*-gnu*)
         tm_defines="${tm_defines}  TARGET_DEFAULT_ASYNC_UNWIND_TABLES=1"
 	;;
 aarch64-*-mingw*)
+	tm_file="${tm_file} aarch64/aarch64-abi-ms.h"
 	tmake_file="${tmake_file} aarch64/t-aarch64"
 	case ${enable_threads} in
 	  "" | yes | win32)
diff --git a/gcc/config/aarch64/aarch64-abi-ms.h b/gcc/config/aarch64/aarch64-abi-ms.h
new file mode 100644
index 0000000..15dc33d
--- /dev/null
+++ b/gcc/config/aarch64/aarch64-abi-ms.h
@@ -0,0 +1,34 @@
+/* Machine description for AArch64 MS ABI.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+
+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/>.  */
+
+#ifndef GCC_AARCH64_ABI_MS_H
+#define GCC_AARCH64_ABI_MS_H
+
+/* X18 reserved for the TEB on Windows.  */
+
+#undef FIXED_X18
+#define FIXED_X18 1
+
+#undef CALL_USED_X18
+#define CALL_USED_X18 0
+
+#undef  STATIC_CHAIN_REGNUM
+#define STATIC_CHAIN_REGNUM R17_REGNUM
+
+#endif /* GCC_AARCH64_ABI_MS_H.  */
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 4fa1dfc..319fe032 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -537,11 +537,14 @@ constexpr auto AARCH64_FL_DEFAULT_ISA_MODE = AARCH64_FL_SM_OFF;
    register.  GCC internally uses the poly_int variable aarch64_sve_vg
    instead.  */
 
+#define FIXED_X18 0
+#define CALL_USED_X18 1
+
 #define FIXED_REGISTERS					\
   {							\
     0, 0, 0, 0,   0, 0, 0, 0,	/* R0 - R7 */		\
     0, 0, 0, 0,   0, 0, 0, 0,	/* R8 - R15 */		\
-    0, 0, 0, 0,   0, 0, 0, 0,	/* R16 - R23 */		\
+    0, 0, FIXED_X18, 0,   0, 0, 0, 0,	/* R16 - R23.  */	\
     0, 0, 0, 0,   0, 1, 0, 1,	/* R24 - R30, SP */	\
     0, 0, 0, 0,   0, 0, 0, 0,   /* V0 - V7 */           \
     0, 0, 0, 0,   0, 0, 0, 0,   /* V8 - V15 */		\
@@ -565,7 +568,7 @@ constexpr auto AARCH64_FL_DEFAULT_ISA_MODE = AARCH64_FL_SM_OFF;
   {							\
     1, 1, 1, 1,   1, 1, 1, 1,	/* R0 - R7 */		\
     1, 1, 1, 1,   1, 1, 1, 1,	/* R8 - R15 */		\
-    1, 1, 1, 0,   0, 0, 0, 0,	/* R16 - R23 */		\
+    1, 1, CALL_USED_X18, 0, 0,   0, 0, 0, /* R16 - R23.  */   \
     0, 0, 0, 0,   0, 1, 1, 1,	/* R24 - R30, SP */	\
     1, 1, 1, 1,   1, 1, 1, 1,	/* V0 - V7 */		\
     0, 0, 0, 0,   0, 0, 0, 0,	/* V8 - V15 */		\