On Mon, 2006-03-06 at 00:31 +0100, Eric Botcazou wrote:
>
>
> cxa4025 and cxa4033 are very likely yours, originating in a miscompilation of
> the runtime (a-stwifi.adb) at -O2. They succeed if the aforementioned unit
> is compiled at -O2 -fno-tree-vrp. You can pass -a to gnatmake to cause the
> units to be recompiled locally. Same for cxa4028 but with a-strsup.adb.
Here's the relevant bits from the .original dump for
Ada.Strings.Wide_Fixed.Trim:
Ada.Strings.Wide_Fixed.Trim (source, side)
[ ... ]
if (side - 1 <= 1)
{
<<< Unknown tree: loop_stmt
(integer) high >= (integer) low &&
VIEW_CONVERT_EXPR<wide_character[(long int) SAVE_EXPR
<source.P_BOUNDS->LB0>:MAX_EXPR <(long int) SAVE_EXPR
<source.P_BOUNDS->UB0>, (long int) SAVE_EXPR <source.P_BOUNDS->LB0> -
1>]>(*source.P_ARRAY)[(<unnamed type>) (integer) high]{lb: (long int)
SAVE_EXPR <source.P_BOUNDS->LB0> sz: 2} == 32
high = (natural___XDLU_0__2147483647) ((integer) high - 1);
<D5436> >>>
;
}
Of particular interest is the (side - 1 <= 1) conditional which is
implementing this hunk of code from the Trim function:
if Side = Right or else Side = Both then
while High >= Low and then Source (High) = Wide_Space loop
High := High - 1;
end loop;
end if;
side is an enumerated type with the following values
Symbolic name Integer value
left 0
right 1
both 2
The min/max values associated with the type specify that side
should have the values [0, 2].
Note carefully that the expression (side - 1) will produce a value
outside the defined min/max values for side's type [0, 2] when side
has the value "left".
Not surprisingly, we turn the .original code into this gimple code:
D.5765 = side - 1;
if (D.5765 <= 1)
Where D.5765 is of type ada__strings_trim_end, ie, it's got a range
of [0, 2]. So the computation will produce a result outside the
defined range of the type in the case where side == left.
Not surprisingly, the VRP code optimizes this test. If we know that
D.5765's type has the values [0, 2], then the test is equivalent to
D.5765 != 2, and it's all downhill from there when side == left.
I think it's time to hand this one to the Ada guys :-0
Jeff
