[Bug ada/26797] [4.3 regression] ACATS cxh1001 fails

[kenner at vlsi1 dot ultra dot nyu dot edu]

------- Comment #28 from kenner at vlsi1 dot ultra dot nyu dot edu  2007-03-08 16:52 -------
Subject: Re:  [4.3 regression] ACATS cxh1001 fails

> I don't see what the problem is - you don't have to convert to the base
> type, you can always convert to some standard type of that precision,
> eg int32, before calling the builtin.

Sure, but it's extra tree nodes and more to do.  See below.

> Sure, it's just that overloading V_C_E like this feels somehow wrong to me.

Why?  It's not "overloading".  V_C_E of an expression E of type X to
type Y means "interpret the bits of E as if it were type Y and not type X".
If Y is X'Base, then interpreting E as being Y means that it can now have
all the values of Y.  In other words, we could only change a V_C_E to a
NOP_EXPR if we can prove that the value of E is in range of *both* X
and Y.

Of course, we still have a bit of a mess here in that the real point is
a confusion between what in Ada is called a Bounded Error and C's notion
of "undefined" (Ada's "erroneous").  But I think we can do better in this
area: we just haven't gotten to take a really good look at it.

> However I haven't been able to put my finger on any technical obstacle to
> this use of V_C_E.

Nor can I ...


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26797