Re: Miscompilation of remainder expressions

[Robert Dewar <dewar at adacore dot com>]

It's interesting that the same issue arose with GNAT, but
we had no option to ignore the special case, since one of
the official Ada validation test programs tested this case,
and indeed as you see below there is a special test:

> function q (a, b : integer) return integer is
> begin
>    return a rem b;
> end;

generates

Source recreated from tree for q (body)
---------------------------------------


function q (a : integer; b : integer) return integer is
begin
   [constraint_error when
     b = 0
     "divide by zero"]
   return integer((if b = -1 then 0 else a rem b));
end q;

And indeed this is a nasty hit in efficiency, though in
practice the wide spread use of integer types with
restricted ranges means that most of the time you
know for example that the divisor cannot be negative.