Date: Sun, 27 Nov 94 19:21:51 -0700
From: "Mathew J. Hostetter" <iclone!mat AT sloth DOT swcp DOT com>
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: More Questions, Doubles

>	Can these registers be using in a meaningful way by a shrewd programmer
>using ASM?  In my program I am using a lot of doubles, and I want to speed up
>my user-friendly but performance-nasty C++ vector library.

The 80387 uses a floating point *stack* (they didn't have enough
instruction bits to use true FP registers like sane architectures),
which makes programming the 80387 tricky.  There are also a host of
clever things you can do on the Pentium to exploit its multiple issue
potential.  None of this is for the faint of heart; you're probably
better off just making sure your C code is written efficiently
(e.g. keep frequently used values in local variables instead of in
memory and study the assembly code gcc generates to look for glaring
problems).

If you are a masochist and you really want to optimize your FP code at
the assembly level, you might want to check out Intel's document
AP-500, "Optimizations for Intel's 32-Bit Processors".  You can call
Intel at (408) 765-8080.  Most of the information in this document is
useful for the Pentium.

-Mat