Patch from Richard Henderson to fix alpha-linux alloca redefinition problems.

	* alpha/xm-alpha.h (alloca): Define alloca to builtin_alloca for GNUC
	if not already defined, and USE_C_ALLOCA not defined.

From-SVN: r14977

gcc/ChangeLog

+Wed Aug 27 16:35:29 1997  Richard Henderson  <rth@cygnus.com>
+
+	* alpha/xm-alpha.h (alloca): Define alloca to builtin_alloca for GNUC
+	if not already defined, and USE_C_ALLOCA not defined.
+
 Wed Aug 27 16:08:43 1997  Jim Wilson  <wilson@cygnus.com>
 
 	* config.guess: Replace with script that uses ../config.guess.

gcc/config/alpha/xm-alpha.h

@@ -41,12 +41,18 @@ Boston, MA 02111-1307, USA.  */
 #define	SUCCESS_EXIT_CODE	0
 #define	FATAL_EXIT_CODE		33
 
-/* If not compiled with GNU C, use the builtin alloca.  */
-#if !defined(__GNUC__) && !defined(_WIN32)
+/* If compiled with GNU C, use the builtin alloca.  */
+#ifndef alloca
+#if defined(__GNUC__) && !defined(USE_C_ALLOCA)
+#define alloca __builtin_alloca
+#else
+#if !defined(_WIN32) && !defined(USE_C_ALLOCA)
 #include <alloca.h>
 #else
 extern void *alloca ();
 #endif
+#endif
+#endif
 
 /* The host compiler has problems with enum bitfields since it makes
    them signed so we can't fit all our codes in.  */