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Re: return

From: Chong Yidong
Subject: Re: return
Date: Fri, 03 Dec 2010 22:23:05 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux)

Stefan Monnier <address@hidden> writes:

> The Fwhile function is not used in the byte-compiled version of the
> `while' special form.  Instead, the byte-compiler turns it into a bunch
> of byte-codes like test and jump to label.
> So your "with an internal catch" version should perform 100% identically
> in this test ;-)

Ah, I see.  I guess the key problem is the unacceptably large
performance difference, in byte compiled code, when we wrap `while' in
an additional `catch' (1.75s vs 1.4s without the `catch' in my test).
The `catch' byte operation does this:

    case Bcatch:
        Lisp_Object v1;
        v1 = POP;
        TOP = internal_catch (TOP, Feval, v1);

So presumably it's the Feval that's killing us.  Hmm.

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