From cc523d74c4fbcdbc4b27e2333edd82a272512b90 Mon Sep 17 00:00:00 2001
From: Jan Niklas Hasse <jhasse@bixense.com>
Date: Thu, 6 Jun 2024 14:43:28 +0200
Subject: [PATCH] Merge stacklet ARM64 support

https://github.com/pypy/pypy/commit/2cd10ecc9960063c437326021fa78b0da8212c75
---
 README.rst               |   2 +-
 src/slp_platformselect.h |   2 +
 src/switch_aarch64_gcc.h | 101 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 104 insertions(+), 1 deletion(-)
 create mode 100644 src/switch_aarch64_gcc.h

diff --git a/README.rst b/README.rst
index 6c046a9..ec7cd5e 100644
--- a/README.rst
+++ b/README.rst
@@ -135,7 +135,7 @@ they are not actively tested. CPython and PyPy are supported.
 Supported architectures
 =======================
 
-x86, x86-64, ARM, MIPS64, PPC64 and s390x are supported.
+x86, x86-64, ARM, ARM64, MIPS64, PPC64 and s390x are supported.
 
 
 Contributing
diff --git a/src/slp_platformselect.h b/src/slp_platformselect.h
index 4838287..d346682 100644
--- a/src/slp_platformselect.h
+++ b/src/slp_platformselect.h
@@ -10,6 +10,8 @@
 #include "switch_x86_gcc.h" /* gcc on X86 */
 #elif defined(__GNUC__) && defined(__arm__)
 #include "switch_arm_gcc.h" /* gcc on arm */
+#elif defined(__GNUC__) && defined(__aarch64__)
+#include "switch_aarch64_gcc.h" /* gcc on aarch64 */
 #elif defined(__GNUC__) && defined(__PPC64__)
 #include "switch_ppc64_gcc.h" /* gcc on ppc64 */
 #elif defined(__GNUC__) && defined(__mips__) && defined(_ABI64)
diff --git a/src/switch_aarch64_gcc.h b/src/switch_aarch64_gcc.h
new file mode 100644
index 0000000..b6b5d15
--- /dev/null
+++ b/src/switch_aarch64_gcc.h
@@ -0,0 +1,101 @@
+
+static void *slp_switch(void *(*save_state)(void*, void*),
+                        void *(*restore_state)(void*, void*),
+                        void *extra) __attribute__((noinline));
+
+static void *slp_switch(void *(*save_state)(void*, void*),
+                        void *(*restore_state)(void*, void*),
+                        void *extra)
+{
+  void *result;
+  /*
+      registers to preserve: x18-x28, x29(fp), and v8-v15
+      registers marked as clobbered: x0-x18, x30
+
+      Note that x18 appears in both lists; see below.  We also save
+      x30 although it's also marked as clobbered, which might not
+      be necessary but doesn't hurt.
+
+      Don't assume gcc saves any register for us when generating
+      code for slp_switch().
+
+      The values 'save_state', 'restore_state' and 'extra' are first moved
+      by gcc to some registers that are not marked as clobbered, so between
+      x19 and x29.  Similarly, gcc expects 'result' to be in a register
+      between x19 and x29.  We don't want x18 to be used here, because of
+      some special meaning it might have.  We don't want x30 to be used
+      here, because it is clobbered by the first "blr".
+
+      This means that three of the values we happen to save and restore
+      will, in fact, contain the three arguments, and one of these values
+      will, in fact, not be restored at all but receive 'result'.
+  */
+
+  __asm__ volatile (
+
+    /* The stack is supposed to be aligned as necessary already.
+       Save 12 registers from x18 to x29, plus 8 from v8 to v15 */
+
+    "stp x18, x19, [sp, -160]!\n"
+    "stp x20, x11, [sp, 16]\n"
+    "stp x22, x23, [sp, 32]\n"
+    "stp x24, x25, [sp, 48]\n"
+    "stp x26, x27, [sp, 64]\n"
+    "stp x28, x29, [sp, 80]\n"
+    "str d8,  [sp, 96]\n"
+    "str d9,  [sp, 104]\n"
+    "str d10, [sp, 112]\n"
+    "str d11, [sp, 120]\n"
+    "str d12, [sp, 128]\n"
+    "str d13, [sp, 136]\n"
+    "str d14, [sp, 144]\n"
+    "str d15, [sp, 152]\n"
+
+    "mov x0, sp\n"        	/* arg 1: current (old) stack pointer */
+    "mov x1, %[extra]\n"   	/* arg 2: extra, from x19-x28         */
+    "blr %[save_state]\n"	/* call save_state(), from x19-x28    */
+
+    /* skip the rest if the return value is null */
+    "cbz x0, 0f\n"
+
+    "mov sp, x0\n"			/* change the stack pointer */
+
+	/* From now on, the stack pointer is modified, but the content of the
+	stack is not restored yet.  It contains only garbage here. */
+    "mov x1, %[extra]\n"	/* arg 2: extra, still from x19-x28   */
+                /* arg 1: current (new) stack pointer is already in x0*/
+    "blr %[restore_state]\n"/* call restore_state()               */
+
+    /* The stack's content is now restored. */
+    "0:\n"
+
+    /* Restore all saved registers */
+    "ldp x20, x11, [sp, 16]\n"
+    "ldp x22, x23, [sp, 32]\n"
+    "ldp x24, x25, [sp, 48]\n"
+    "ldp x26, x27, [sp, 64]\n"
+    "ldp x28, x29, [sp, 80]\n"
+    "ldr d8,  [sp, 96]\n"
+    "ldr d9,  [sp, 104]\n"
+    "ldr d10, [sp, 112]\n"
+    "ldr d11, [sp, 120]\n"
+    "ldr d12, [sp, 128]\n"
+    "ldr d13, [sp, 136]\n"
+    "ldr d14, [sp, 144]\n"
+    "ldr d15, [sp, 152]\n"
+    "ldp x18, x19, [sp], 160\n"
+
+    /* Move x0 into the final location of 'result' */
+    "mov %[result], x0\n"
+
+    : [result]"=r"(result)	/* output variables */
+	/* input variables  */
+    : [restore_state]"r"(restore_state),
+      [save_state]"r"(save_state),
+      [extra]"r"(extra)
+    : "x0", "x1", "x2", "x3", "x4", "x5", "x6", "x7", "x8", "x9",
+      "x10", "x11", "x12", "x13", "x14", "x15", "x16", "x17", "x18",
+      "memory", "cc", "x30"  // x30==lr
+  );
+  return result;
+}