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[Bug gas/10775] x86 64 documentation addenda


From: konrad dot schwarz at siemens dot com
Subject: [Bug gas/10775] x86 64 documentation addenda
Date: 20 Oct 2009 07:44:07 -0000

------- Additional Comments From konrad dot schwarz at siemens dot com  
2009-10-20 07:44 -------
Subject: RE:  x86 64 documentation addenda

> > > movabs is not the only form to load a 64-bit literal into 
> a register.
> > 
> > If there are other forms, where are they documented?
> 
> The normal "mov" insn:
> 
> mov $0x1ffffffff,%rax
> 
> works fine for me.
> 
> > > I don't think we want to go into such details here.
> > 
> > movabs is not an official Intel mnemonic.  Node 
> (as.info)i386-Mnemonics
> documents the detailed differences between Intel and AT&T 
> syntax, so I don't
> understand your reaction at all here.
> 
> movabs is only required only if you want a specific insn encoding
> Otherwise, you can use "mov". Also movabs can also be used in
> 
> movabs 0x1ffffffff,%rax
> 
> which has a different meaning.

What is the point of not writing this in the manual?

> > > > The AT&T/Unixware assembler is documented at
> > > > 
> > > 
> http://docs.sun.com/app/docs/doc/802-1948?l=en&q=assembler+manual and
> > > > http://docs.sun.com/app/docs/doc/817-5477?l=en.
> > 
> > What harm comes of adding this?  The AT&T/Unixware 
> assembler manual is not
> available from SCO's site (makers of Unixware)---only from 
> SUN; they also
> defined the extensions to 64-bit mode.  Again, establishing 
> this probably took
> an hour or two.
> 
> Gas manual isn't a real x86 assembler reference. I always
> point users to Sun's manual if they want to know the details.

So, do you want to continue to do this and have those users who don't think of 
asking you personally luck out, or should this information be put into the GAS 
manual?

[...]
> My Intel64/ia32 SDM doesn't have PUSH EFLAGS nor POP EFLAGS.
> It only has pushf/popf.

I'm sorry, my bad.

> > Does GAS really support cr9--cr15?  These registers are 
> currently not
> documented by the SDM.
> 
> Gas supports r0 to r15. But not all of them are valid, like
> CR1, CR5, CR6, CR7, and CR9-CR15. I will revert it. People
> should read SDM when accessing them.
> 
> > 
> > Documenting how to generate 64-bit code in a section 
> entitled "Writing 16-bit
> Code" seems suboptimal.
> > 
> 
> Please feel free to submit a patch.  Thanks.

Thank you very much.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=10775

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