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From: "Chad  R. Meiners" <chad.rmeiners@gmail.com>
Newsgroups: comp.lang.ada
Subject: Tail Recursion (Why it appears that Gnat 3.15p does support it)
Date: 13 Jan 2005 14:04:47 -0800
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Date: 2005-01-13T14:04:47-08:00
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I have noticed that Gnat 3.15p does not optimize the tail recursion in
the following program.

with Ada.Text_IO;
use  Ada.Text_IO;

procedure Tail is

type Int is mod 2**64;

procedure Fib(First, Second : Int) is
Next : constant Int := First + Second;
begin
Put(Int'Image(Next) & ", ");
Fib(Second,Next);
end Fib;

begin
Put("1, 1, ");
Fib(1,1);
end Tail;

Does anyone know why GNAT (or any other compiler) does not always reuse
stack frames for all subroutines that appear right before a return?  Is
there some requirement that prevents such naive optimizations?
Incidently, if anyone knows of a compiler that does optimize the tail
recursion for this program please let me know.
Thank you,
Chad R. Meiners