2009-04-07  Robert Dewar  <dewar@adacore.com>

	* checks.adb (Determine_Range): Add Assume_Valid parameter
	
	* checks.ads (Determine_Range): Add Assume_Valid parameter
	
	* errout.adb (Error_Msg_NEL): Use Suppress_Loop_Warnings rather than
	 Is_Null_Loop to suppress warnings in a loop body.
	
	* exp_ch4.adb:
	(Rewrite_Comparison): Major rewrite to accomodate invalid values
	
	* exp_ch5.adb:
	(Expand_N_Loop_Statement): Delete loop known not to execute
	
	* opt.ads:
	(Assume_No_Invalid_Values): Now set to False, and as documented, this
	 fully enables the proper handling of invalid values.
	
	* sem_attr.adb:
	New calling sequence for Is_In_Range
	
	* sem_ch5.adb:
	(Analyze_Iteration_Scheme): Accomodate possible invalid values
	 in determining if a loop range is null.
	
	* sem_eval.adb:
	(Is_In_Range): Add Assume_Valid parameter
	(Is_Out_Of_Range): Add Assume_Valid_Parameter
	(Compile_Time_Compare): Major rewrite to accomodate invalid values and
	 also to do more accurate and complete range analysis, catching more
	 cases.
	
	* sem_eval.ads:
	(Is_In_Range): Add Assume_Valid parameter
	(Is_Out_Of_Range): Add Assume_Valid_Parameter
	
	* sem_util.adb:
	New calling sequence for Is_In_Range
	
	* sinfo.adb:
	(Suppress_Loop_Warnings): New flag
	
	* sinfo.ads:
	(Is_Null_Loop): Update documentation
	(Suppress_Loop_Warnings): New flag
	
	* gnat_ugn.texi: Document -gnatB switch

From-SVN: r145672