alpha haifa regression

[Richard Henderson <rth@cygnus.com>]

With the haifa scheduler, alpha fails 920908-1 with -O2.

What happens is, the insn that loads from the va_list gets moved
before the stores from the register variables.  It does this
because alias decides that a variable struct memory cannot alias
a non-variable non-struct memory.

It seems a bit hoaky to me, but then the C alias rules are a bit
perverse, so I'll assume this is correct.

The solution then, since we don't want to slow down normal code
where we _can_ make these assumptions, is to emit blockage after
dumping the varargs regs to memory.  


r~


Index: alpha.h
===================================================================
RCS file: /cvs/cvsfiles/egcs/gcc/config/alpha/alpha.h,v
retrieving revision 1.3
diff -u -p -d -r1.3 alpha.h
--- alpha.h	1997/09/02 19:37:05	1.3
+++ alpha.h	1997/09/29 05:38:13
@@ -1052,6 +1052,7 @@ enum reg_class { NO_REGS, GENERAL_REGS, 
 		      plus_constant (virtual_incoming_args_rtx,		\
 				     (CUM) * UNITS_PER_WORD)),		\
 	     6 - (CUM), (6 - (CUM)) * UNITS_PER_WORD);			\
+	   emit_insn (gen_blockage ());					\
 	 }								\
       PRETEND_SIZE = 12 * UNITS_PER_WORD;				\
     }									\