--- guile-1.6.4/libguile/gc_os_dep.c.amd64	2003-04-16 22:16:21.000000000 +0200
+++ guile-1.6.4/libguile/gc_os_dep.c	2003-08-28 22:06:33.000000000 +0200
@@ -205,6 +205,10 @@ typedef int GC_bool;
 #    define I386
 #    define mach_type_known
 # endif
+# if defined(LINUX) && defined(__x86_64__)
+#    define X86_64
+#    define mach_type_known
+# endif
 # if defined(LINUX) && (defined(__ia64__) || defined(__ia64))
 #    define IA64
 #    define mach_type_known
@@ -407,6 +411,7 @@ typedef int GC_bool;
 		    /* 		   ARM32      ==> Intel StrongARM	*/
 		    /* 		   IA64	      ==> Intel IA64		*/
 		    /*				  (e.g. Itanium)	*/
+		    /* 		   X86_64     ==> AMD x86-64		*/
 
 
 /*
@@ -1247,6 +1252,44 @@ typedef int GC_bool;
 #   endif
 #endif
 
+# ifdef X86_64
+#   define MACH_TYPE "X86_64"
+#   define ALIGNMENT 8
+#   define CPP_WORDSZ 64
+#   define HBLKSIZE 4096
+#   define CACHE_LINE_SIZE 64
+#   define USE_GENERIC_PUSH_REGS
+#   ifdef LINUX
+#	define OS_TYPE "LINUX"
+#       define LINUX_STACKBOTTOM
+#       if !defined(GC_LINUX_THREADS) || !defined(REDIRECT_MALLOC)
+#	    define MPROTECT_VDB
+#	else
+	    /* We seem to get random errors in incremental mode,	*/
+	    /* possibly because Linux threads is itself a malloc client */
+	    /* and can't deal with the signals.				*/
+#	endif
+#       ifdef __ELF__
+#            define DYNAMIC_LOADING
+#	     ifdef UNDEFINED	/* includes ro data */
+	       extern int _etext[];
+#              define DATASTART ((ptr_t)((((word) (_etext)) + 0xfff) & ~0xfff))
+#	     endif
+#	     include <features.h>
+#	     define LINUX_DATA_START
+	     extern int _end[];
+#	     define DATAEND (_end)
+#	else
+	     extern int etext[];
+#            define DATASTART ((ptr_t)((((word) (etext)) + 0xfff) & ~0xfff))
+#       endif
+#	define PREFETCH(x) \
+	  __asm__ __volatile__ ("	prefetch	%0": : "m"(*(char *)(x)))
+#	define PREFETCH_FOR_WRITE(x) \
+	  __asm__ __volatile__ ("	prefetchw	%0": : "m"(*(char *)(x)))
+#   endif
+# endif
+
 #ifdef LINUX_DATA_START
     /* Some Linux distributions arrange to define __data_start.  Some	*/
     /* define data_start as a weak symbol.  The latter is technically	*/