simplesim-3.0 fix for OSX, tested on Big Sur on M1. Run `make sim-tests` to check that it's working for you.

simplesim-3.0-patch

--- syscall.c
+++ syscall.c
@@ -48,6 +48,39 @@
  * Copyright (C) 1994-2003 by Todd M. Austin, Ph.D. and SimpleScalar, LLC.
  */
 
+#ifdef __APPLE__
+
+#define __unix__
+#define unix
+#include <dirent.h>
+#define __osf__
+
+#ifdef _DARWIN_FEATURE_64_BIT_INODE
+
+/* Darwin doesn't provide a version of getdirentries with support for 64-bit
+ * inodes.  When 64-bit inodes are enabled, the getdirentries symbol is mapped
+ * to _getdirentries_is_not_available_when_64_bit_inodes_are_in_effect so that
+ * we get link errors if we try to use it.  We still need getdirentries, but we
+ * don't need it to support 64-bit inodes.  So, we use the legacy getdirentries
+ * with 32-bit inodes.  We have to be careful to use a corresponding dirent
+ * structure, too.
+ */
+int darwin_legacy_getdirentries(int, char *, int, long *) __asm("_getdirentries");
+#define getdirentries darwin_legacy_getdirentries
+
+struct darwin_legacy_dirent {
+    __uint32_t d_ino;
+    __uint16_t d_reclen;
+    __uint8_t  d_type;
+    __uint8_t  d_namlen;
+    char d_name[__DARWIN_MAXNAMLEN + 1];
+};
+#define dirent darwin_legacy_dirent
+
+#endif // _DARWIN_FEATURE_64_BIT_INODE
+
+#endif // __APPLE__
+
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -184,7 +217,7 @@
 #undef CR0
 #endif
 
-#ifdef __FreeBSD__
+#if defined(__FreeBSD__) || defined(__APPLE__)
 #include <termios.h>
 /*#include <sys/ioctl_compat.h>*/
 #else