Cleanup some ancient Ultrix / Alpha code in main() that is intended to

modify how unaligned memory accesses are dealt with. Document that this
is really what is going on, and merge the NOFIXADE and NOPRINTADE code
paths.

Author: Neil Conway

src/backend/main/main.c

@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/main/main.c,v 1.89 2004/08/29 05:06:43 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/main/main.c,v 1.90 2004/09/24 06:29:07 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -71,18 +71,23 @@ main(int argc, char *argv[])
 
 #if defined(__alpha)			/* no __alpha__ ? */
 #ifdef NOFIXADE
-	int			buffer[] = {SSIN_UACPROC, UAC_SIGBUS};
-#endif   /* NOFIXADE */
-#ifdef NOPRINTADE
-	int			buffer[] = {SSIN_UACPROC, UAC_NOPRINT};
-#endif   /* NOPRINTADE */
+	int			buffer[] = {SSIN_UACPROC, UAC_SIGBUS | UAC_NOPRINT};
+#endif
 #endif   /* __alpha */
 
 #ifdef WIN32
 	char	   *env_locale;
 #endif
 
-#if defined(NOFIXADE) || defined(NOPRINTADE)
+	/*
+	 * On some platforms, unaligned memory accesses result in a kernel
+	 * trap; the default kernel behavior is to emulate the memory
+	 * access, but this results in a significant performance
+	 * penalty. We ought to fix PG not to make such unaligned memory
+	 * accesses, so this code disables the kernel emulation: unaligned
+	 * accesses will result in SIGBUS instead.
+	 */
+#ifdef NOFIXADE
 
 #if defined(ultrix4)
 	syscall(SYS_sysmips, MIPS_FIXADE, 0, NULL, NULL, NULL);
@@ -94,7 +99,7 @@ main(int argc, char *argv[])
 		write_stderr("%s: setsysinfo failed: %s\n",
 					 argv[0], strerror(errno));
 #endif
-#endif   /* NOFIXADE || NOPRINTADE */
+#endif   /* NOFIXADE */
 
 #if defined(WIN32)
 	{