[Ada] Conversion of arithmetic expression to wider type flagged as redundant

[Arnaud Charlet <charlet at adacore dot com>]

In certain cases, the compiler converts the operands of an arithmetic
expression that is an argument of a conversion to a wider type, to
avoid generation of an overflow check. This can result in the conversion
being wrongly flagged as redundant. By rewriting the operator node, so
that the original node will be retained, the test for redundant conversions
properly recognizes that the conversion in the source was not redundant.

The following test must compile quietly with -gnatwae:

package Nonredundant_Conversion is

   type Unsigned_64 is mod 2 ** 64;

   Nat : Natural;

   Uns : Unsigned_64 := Unsigned_64 (Nat + 1);

end Nonredundant_Conversion;

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

2010-09-09  Gary Dismukes  <dismukes@adacore.com>

	* checks.adb (Apply_Arithmetic_Overflow_Check): When converting the
	operands of an operator to the type of an enclosing conversion, rewrite
	the operator so the conversion can't be flagged as redundant.
	Remove useless assignments to Typ and Rtyp.

Attachment: difs
Description: Text document