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 <de...@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.
Index: sem_eval.adb
===================================================================
--- sem_eval.adb (revision 213530)
+++ sem_eval.adb (working copy)
@@ -6193,6 +6193,18 @@
then
return In_Range;
+ -- Another special case. For signed integer types, if the target type
+ -- has Is_Known_Valid set, and the source type does not have a larger
+ -- size, then the source value must be in range. We exclude biased
+ -- types, because they bizarrely can generate out of range values.
+
+ elsif Is_Signed_Integer_Type (Etype (N))
+ and then Is_Known_Valid (Typ)
+ and then Esize (Etype (N)) <= Esize (Typ)
+ and then not Has_Biased_Representation (Etype (N))
+ then
+ return In_Range;
+
-- For all other cases, result is unknown
else
