Fix ia64-linux miscompilation or tcl/generic/tclCompExpr.c

Fix ia64-linux miscompilation or tcl/generic/tclCompExpr.c
	* loop.c (check_final_value): Check for biv use before checking for
	giv use.  Check for both biv and giv uses.  Always set last_giv_use
	if there is a giv use.

From-SVN: r36104

gcc/ChangeLog

+2000-09-01  Jim Wilson  <wilson@cygnus.com>
+
+	* loop.c (check_final_value): Check for biv use before checking for
+	giv use.  Check for both biv and giv uses.  Always set last_giv_use
+	if there is a giv use.
+
 2000-09-01  Richard Henderson  <rth@cygnus.com>
 
 	* config/ia64/ia64.md (mulsi3): Use grfr_register_operand.

gcc/loop.c

@@ -5677,21 +5677,27 @@ check_final_value (loop, v)
 	  if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
 	      || GET_CODE (p) == CALL_INSN)
 	    {
-	      if (biv_increment_seen)
-		{
+	      /* It is possible for the BIV increment to use the GIV if we
+		 have a cycle.  Thus we must be sure to check each insn for
+		 both BIV and GIV uses, and we must check for BIV uses
+		 first.  */
+
+	      if (! biv_increment_seen
+		  && reg_set_p (v->src_reg, PATTERN (p)))
+		biv_increment_seen = 1;
+		
 	      if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
 		{
+		  if (biv_increment_seen)
+		    {
 		      v->replaceable = 0;
 		      v->not_replaceable = 1;
 		      break;
 		    }
-		}
-	      else if (reg_set_p (v->src_reg, PATTERN (p)))
-		biv_increment_seen = 1;
-	      else if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
 		  last_giv_use = p;
 		}
 	    }
+	}
 
       /* Now that the lifetime of the giv is known, check for branches
 	 from within the lifetime to outside the lifetime if it is still