Re: i386 FP comparsion bug (and sollution)

[Jeffrey A Law <law at cygnus dot com>]

  In message <19981102012555.D7828@cerebro.laendle>you write:
  > I can remember that I explicitly allowed inserting (some) instructions
  > between the setter and the user (in pgcc), and it worked fine with fp-code.
  > Unfortunately I can't remember the details ;) as usual.. The code is buggy,
  > but in practise works perfect (I never reeceived a bug-report that was
  > caused by it).
But the kind of bugs that will occur by putting insns between the setter and
user are going to be very obscure.  I wouldn't be suprised if you hadn't seen
anything fail because of this.  That does not mean what pgcc does is correct.

  > that, of course, is true, changing this isn't possible in the foreseeable
  > future. Lifting this restriction is partly possible, but not a solution for
  > egcs.
  > 
  > OTOH this design decision slowly begins to hurt modern architectures.
Note that modern ports do not use cc0 and thus do not suffer from these
problems.  One could consider rewriting the x86 port to not use cc0, or
revamping passes from final.c backwards to lift this restriction, but it's
a lot of work with unclear benefits.

jeff