Re: Ada95 to ANSI_C converter

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Jon says

<<Emphasis mine.  I read "to catch overflows efficiently" as being
interchangeable with "to avoid inefficiencies in catching overflows".
I think Bob has already agreed with this, but that he meant to also
say he didn't really know for sure if it worked.>>

Well there is efficiency and efficiency, Bob Duff was cerrtainly not
saying that the ICC compiler avoided inefficiencies in catching
overflows, just that they tried to be efficient in handling overflow,
rather different issues.

If Bob DID mean to imply that ICC avoided all efficiency penalties
in handling overflows in C generated code, that's just plain wrong!

So, let's not obscure the semantics here.

Generating C invoves fundamental inefficiencies in a number of areas,
including catching overflows. That's the important point to register
here. Yes, you can try to catch overflow efficiently, but you cannot
avoid fundamental inefficiencies in the result. As I say, we know this
area VERY well, because we are beginning to play more of these efficiency
tricks in catching overflow in GNAT -- that will indeed improve
efficiency, but it will NOT avoid all inefficiencies.

The bottom line here is that there is a significant efficiency penalty
in generating C, and it cannot be eliminated, no matter how clever you are!