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From: kissell@garth.UUCP (Kevin Kissell)
Newsgroups: comp.arch
Subject: Re: How does compiled code use the floa
Message-ID: <393@garth.UUCP>
Date: Thu, 18-Dec-86 02:39:00 EST
Article-I.D.: garth.393
Posted: Thu Dec 18 02:39:00 1986
Date-Received: Thu, 18-Dec-86 20:48:31 EST
References: <394@houxs.UUCP> <165100001@uiucdcsb> Sender:
Reply-To: kissell@garth.UUCP (Kevin Kissell)
Organization: Fairchild Semiconductor (APD) -- Palo Alto, CA
Lines: 22

In article <165100001@uiucdcsb> robison@uiucdcsb.cs.uiuc.edu writes:
>
>I've heard of another scheme, but never tried it:
>
>Code generation emits a call to a floating point library.
>If the FP hardware is available, the library routine changes 
>(at run time) the call instruction to the equivalent hardware 
>instruction.  This way you pay for the subroutine linkage only 
>on the first call. The disadvantage is that self-modifying code 
>is not allowed on some architectures.

One would not have that problem if one patched the program as it
was brought into memory, rather than on the first library call.
But I doubt that anyone really wants to generate code that *assumes*
that emulation libraries are in use.

Kevin D. Kissell
Fairchild Advanced Processor Division
uucp: {ihnp4, decwrl, ucbvax}!hplabs!harvax!garth!kissell

Disclaimer: All opinions expressed herein are either
            my own or a product of your imagination.