Table lookups - this is pretty definitive

[Walter Bright]

On 4/2/2014 12:03 PM, Dmitry Olshansky wrote:
> SwitchCallStatment:
>      goto CallExpression;
>
> Semantics:
> Same as that of a function call expression except:
> a) Can Switch-Call only to a function with the same return type.
> b) Anything below this statement is unreachable, i.e. treat it as return.
> c) Stack frame of the current function is overwritten with that of switched-to
> function. In other words after a switch-call stack looks as if the switched-to
> function was called instead in the first place.
>
> The last point is what modern tail-call optimizations do when one has 2
> functions that tail-recurse to each other. They overwrite stackframes on such
> tail calls.

How is this different from simply recognizing "return foo(arg);" as being a goto?


> However this only happens with certain optimization switch which IMO makes the
> thing totally unreliable. In fact I even observed that I could implement
> threaded-code interpreter by relying on tail-call optimization with LDC, but
> only when compiling with all optimizations enabled. Unoptimized builds simply
> blowup stack. This "semantics are tied to optimization" is a situation that I
> hate about C/C++ and would hope to address in D.

Doesn't seem terribly different than the "force inline" feature discussion.