From 72ca3f49e3eef9b18946b8d4e77019c1441e1a97 Mon Sep 17 00:00:00 2001
From: Zac Walker <zacwalker@microsoft.com>
Date: Tue, 20 Feb 2024 15:30:33 +0100
Subject: [PATCH v1 03/13] aarch64: Mark x18 register as a fixed register for
 MS ABI

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

gcc/ChangeLog:

	* config.gcc: Define TARGET_ARM64_MS_ABI when Arm64 MS ABI is
	used.
	* config/aarch64/aarch64.h (FIXED_X18): Define if X18
	regsiter is fixed.
	(CALL_USED_X18): Define if X18 register is call used.
	(FIXED_REGISTERS): Adjust FIXED_REGISTERS for different ABIs.
	(STATIC_CHAIN_REGNUM): Define STATIC_CHAIN_REGNUM acording to
	ABI.
---
 gcc/config.gcc               |  1 +
 gcc/config/aarch64/aarch64.h | 19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/gcc/config.gcc b/gcc/config.gcc
index 092a091595d..2a9e4c44f50 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1276,6 +1276,7 @@ aarch64*-*-mingw*)
 	default_use_cxa_atexit=yes
 	need_64bit_isa=yes
 	user_headers_inc_next_post="${user_headers_inc_next_post} float.h"
+	tm_defines="${tm_defines} TARGET_ARM64_MS_ABI=1"
 	;;
 aarch64*-wrs-vxworks*)
         tm_file="${tm_file} elfos.h aarch64/aarch64-elf.h"
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 45e901cda64..36916e7a97d 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -536,11 +536,20 @@ constexpr auto AARCH64_FL_DEFAULT_ISA_MODE = AARCH64_FL_SM_OFF;
    register.  GCC internally uses the poly_int variable aarch64_sve_vg
    instead.  */
 
+/* X18 reserved for the TEB on Windows.  */
+#ifdef TARGET_ARM64_MS_ABI
+# define FIXED_X18 1
+# define CALL_USED_X18 0
+#else
+# define FIXED_X18 0
+# define CALL_USED_X18 1
+#endif
+
 #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 */		\
@@ -564,7 +573,7 @@ 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 */		\
@@ -642,7 +651,11 @@ constexpr auto AARCH64_FL_DEFAULT_ISA_MODE = AARCH64_FL_SM_OFF;
    uses alloca.  */
 #define EXIT_IGNORE_STACK	(cfun->calls_alloca)
 
-#define STATIC_CHAIN_REGNUM		R18_REGNUM
+#ifdef TARGET_ARM64_MS_ABI
+# define STATIC_CHAIN_REGNUM		R17_REGNUM
+#else
+# define STATIC_CHAIN_REGNUM		R18_REGNUM
+#endif
 #define HARD_FRAME_POINTER_REGNUM	R29_REGNUM
 #define FRAME_POINTER_REGNUM		SFP_REGNUM
 #define STACK_POINTER_REGNUM		SP_REGNUM
-- 
2.25.1