first add files

lib/greenlet/platform/switch_aarch64_gcc.h

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+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 07-Sep-16 Add clang support using x register naming. Fredrik Fornwall
+ * 13-Apr-13 Add support for strange GCC caller-save decisions
+ * 08-Apr-13 File creation. Michael Matz
+ *
+ * NOTES
+ *
+ * Simply save all callee saved registers
+ *
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+#define STACK_MAGIC 0
+#define REGS_TO_SAVE "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26", \
+                     "x27", "x28", "x30" /* aka lr */, \
+                     "v8", "v9", "v10", "v11", \
+                     "v12", "v13", "v14", "v15"
+
+static int
+slp_switch(void)
+{
+	int err;
+	void *fp;
+        register long *stackref, stsizediff;
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+	__asm__ volatile ("str x29, %0" : "=m"(fp) : : );
+        __asm__ ("mov %0, sp" : "=r" (stackref));
+        {
+                SLP_SAVE_STATE(stackref, stsizediff);
+                __asm__ volatile (
+                    "add sp,sp,%0\n"
+                    "add x29,x29,%0\n"
+                    :
+                    : "r" (stsizediff)
+                    );
+		SLP_RESTORE_STATE();
+		/* SLP_SAVE_STATE macro contains some return statements
+		   (of -1 and 1).  It falls through only when
+		   the return value of slp_save_state() is zero, which
+		   is placed in x0.
+		   In that case we (slp_switch) also want to return zero
+		   (also in x0 of course).
+		   Now, some GCC versions (seen with 4.8) think it's a
+		   good idea to save/restore x0 around the call to
+		   slp_restore_state(), instead of simply zeroing it
+		   at the return below.  But slp_restore_state
+		   writes random values to the stack slot used for this
+		   save/restore (from when it once was saved above in
+		   SLP_SAVE_STATE, when it was still uninitialized), so
+		   "restoring" that precious zero actually makes us
+		   return random values.  There are some ways to make
+		   GCC not use that zero value in the normal return path
+		   (e.g. making err volatile, but that costs a little
+		   stack space), and the simplest is to call a function
+		   that returns an unknown value (which happens to be zero),
+		   so the saved/restored value is unused.  */
+           __asm__ volatile ("mov %0, #0" : "=r" (err));
+        }
+        __asm__ volatile ("ldr x29, %0" : : "m" (fp) :);
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+        return err;
+}
+
+#endif