[Bug target/27968] gcc emits (undefined) ffreep opcode which is not understood by Solaris' /usr/ccs/bin/as when tuning for Athlon or Opteron CPUs

["digitale at digitaleric dot net" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from digitale at digitaleric dot net  2006-06-10 18:01 -------
Subject: Re:  gcc emits (undefined) ffreep opcode which
        is not understood by Solaris' /usr/ccs/bin/as when tuning for Athlon or
        Opteron CPUs

> ------- Comment #1 from pinskia at gcc dot gnu dot org  2006-06-09 00:05 -------
> One thing is to use GNU binutil's as instead.  The other thing to do is to file
> a bug with Sun (which is better anyways).

I have filed a bug with Sun.  But I think it would be good to fix gcc too.

Jan Hubicka's comment on the adding the ffreep support to gcc was:

"The instruction is not documented by IA-32 description, but all CPUs in
existence support it and majorty of assemblers seems to know it too.  In case
we will hit assembler that don't I will add configure script code for that."


I also question if it is a mistake for gcc to emit this opcode so readily. 
Quoting the Intel IA-32 manual: "all blanks in the opcode map are reserved and
should not be used.  Do not depend on the operation on these undefined opcodes"
(this is below the opcode map, where the row for ffreep is blank).

-Eric


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27968