[Ada] Remove unnecessary range checks

[Arnaud Charlet <charlet at adacore dot com>]

This change removes some unnecessary range checks. The following test
compiled with -gnatdt -gnatc:

     1. procedure RCInteger (X : Integer) is
     2.    type YT is new Integer;
     3.    Y : constant YT := YT(X) * YT(X);
     4. begin
     5.    null;
     6. end;

generates a tree file that has no instances of the Do_Range_Check flag
being set (the multiplication in line 3 needs an overflow check, but
not a subsequent range check).

This test, also compiled with -gnatdt -gnatc:

     1. procedure Assign_Int (X : in out Integer) is
     2.    Tmp : Integer := X + 1;
     3.    Pos : Positive := X + 2;
     4. begin
     5.    X := X + 3;
     6. end Assign_Int;

Generates a tree file with one instance of Do_Range_Check being set.
Line 3 needs a range check, but line 2 does not.

Tested on x86_64-pc-linux-gnu, committed on trunk

2014-08-04  Robert Dewar  <dewar@adacore.com>

	* sem_eval.adb (Test_In_Range): Always in range for
	Is_Known_Valid target type, where input type has smaller or
	equal size and does not have biased rep.

Attachment: difs
Description: Text document