Fix IA-64 abort on testcase with switch statement that can be optimized away.

	* cse.c (cse_insn): Don't pass label subtraction to force_const_mem.

From-SVN: r35992

gcc/ChangeLog

 2000-08-25  Jim Wilson  <wilson@cygnus.com>
 
+	* cse.c (cse_insn): Don't pass label subtraction to force_const_mem.
+
 	* function.c (gen_mem_addressof): Clear MEM_ALIAS_SET if no decl.
 
 2000-08-25  Greg McGary  <greg@mcgary.org>

gcc/cse.c

@@ -5328,8 +5328,16 @@ cse_insn (insn, libcall_insn)
 
 	  else if (constant_pool_entries_cost
 		   && CONSTANT_P (trial)
+		   /* Reject cases that will abort in decode_rtx_const.
+		      On the alpha when simplifying a switch, we get
+		      (const (truncate (minus (label_ref) (label_ref)))).  */
 		   && ! (GET_CODE (trial) == CONST
 			 && GET_CODE (XEXP (trial, 0)) == TRUNCATE)
+		   /* Likewise on IA-64, except without the truncate.  */
+		   && ! (GET_CODE (trial) == CONST
+			 && GET_CODE (XEXP (trial, 0)) == MINUS
+			 && GET_CODE (XEXP (XEXP (trial, 0), 0)) == LABEL_REF
+			 && GET_CODE (XEXP (XEXP (trial, 0), 1)) == LABEL_REF)
 		   && (src_folded == 0
 		       || (GET_CODE (src_folded) != MEM
 			   && ! src_folded_force_flag))