From:	snarfy AT goodnet DOT com
Newsgroups:	comp.os.msdos.djgpp
Subject:	FPU instructions & -lemu
Date:	13 Jan 1997 14:10:24 GMT
Organization:	GoodNet
Lines:	44
Message-ID:	<5bdfog$nme@news.goodnet.com>
NNTP-Posting-Host:	goodnet.com
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Is there a list anywhere of FPU instructions, specifically 387+ 
instructions?  Specifically, I need help with the fwait, fsave, and frstor
instructions.  

Do they work with the emulator?

How large of a buffer do you need for fsave/frstor?

I have some code that uses these instructions but it bombs out if I turn
on any kind of optimizations.  The catch is that the optimizations are 
in a different source file!  I think my struct is getting optimized when
I don't want it to.  Here's a sample:

file lwp.c

typedef struct lwp_struct {
int pid;
int *stack;
...
volatile char fpu[112];
} lwp;

file lwpasm.S

...
fwait
fsave (%esi)  /* pointer to a lwp's fpu[112] member */
fwait
...
fwait
frstor (%esi) /* pointer to a lwp's fpu[112] member */
fwait


This code works without optimizations, but doesn't if I compile lwp.c 
with -O.  It does work with optimizations on if I take out the 
fsave/frstor instructions.  On a side note, does the optimizer touch
.S files? 


Thanks
Josh
snarfy AT goodnet DOT com

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