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Re: i386: Are we settled?



> - How should i386 targets handle the x86 FPU's 80-bit float type?  How
>   can we make sure that hosts capable of handling it properly don't
>   perform lossy conversions?

I think we need some HAVE_* style macro(s) for this.  Given that there
is some #define'd symbol that tells whether long double is supported,
the definition of REGISTER_CONVERT_TO_{RAW,VIRTUAL} should take into
account whether long doubles are supported or not, and DTRT.

I'm guessing that every x86 platform that supports 80-bit FP type
already has such macros (DJGPP defines LD_387 and uses
HAVE_LONG_DOUBLE).  What we need is to unify these into a single set
of x86-specific macros.

One problem that bothers me is that we must define the size of long
double to be 96 to have it supported.  This sounds like some hidden
dependency somewhere in GDB.  No platform should be forced to lie to
GDB about the actual size of its 80-bit float type to get this
support.  What would it take to solve this problem?

> Notably missing from this list are any other questions about tm-i386.h
> as it stands.  Am I correct in thinking that the other x86 port
> maintainers think it's basically sane?

I think it is sane and very useful.  Using it, tm-go32.h went from 211
lines to just 77!

> If so, I encourage folks to start deleting stuff from their more
> specialized tm-*.h files, and using the definitions in tm-i386.h.

Diffs sent to gdb-patches.  I took the opportunity to catch up with
other *-go32.h files in config/i386.

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