Re: How does GNAT (or GCC) compile ADA code?

[dennison@telepath.com]

In article <asmang-1510981424440001@192.168.0.22>,
  asmang@mail.wm.edu (Arun Mangalam) wrote:
> I don't really know how GCC is the backend for GNAT. Does gcc translate
> Ada code into c and then compile c into machine language, or is it from
> Ada code directly to machine language code? I'm just curious, and since I
> don't have gcc installed, I was wondering if someone can either explain
> this or direct me to a place where I can find this out for myself. Thank
> you for any help.

Most compilers don't translate source directly into machine code. Instead they
first translate the source code into a very low-level (yes, even lower-level
than C :-) ) intermediate form that is somewhat machine-independent. Most
optimizations then get performed on that intermediate code. In the final step
the "backend" of the compiler translates the intermediate form into the
appropriate machine code for the target cpu.

All forms of gcc, including gnat, gnu fortran, gnu pascal, etc. do this. One
of the nice things about this approach is that it makes porting easier. Only
the back-end code generator needs to be changed to port the compiler to a new
architecture. It also makes it easier to create new compilers, as multiple
compilers can use the same back-end.

So here's what gnat does. It converts (translates, compiles, whatever term
you prefer) Ada source code into the special intermediate form that the gcc
backend understands. Then it has the gcc backend do optimizations and machine
code generation.

--
T.E.D.

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