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Re: Gas is broken for x86-64
- From: "Jan Beulich" <JBeulich at novell dot com>
- To: <amodra at bigpond dot net dot au>
- Cc: <hjl at lucon dot org>,<binutils at sources dot redhat dot com>
- Date: Mon, 08 Nov 2004 09:56:13 +0100
- Subject: Re: Gas is broken for x86-64
>>> Alan Modra <amodra@bigpond.net.au> 08.11.04 09:38:07 >>>
>On Mon, Nov 08, 2004 at 09:20:22AM +0100, Jan Beulich wrote:
>> I would think your patch should have added both suffix-less movsb
and
>> movzb, or neither.
>
>No. movsb is a string move instruction. movzb is an abbreviation of
>movzbl or movzbw depending on data size.
Certainly. But movsb is also a suffix-less variant of movsb[wlq], and
since movz and movs are fully in sync with one another, allowing
abbreviation of one should also allow the same for the other.
One of the points here is that the abbreviation (or suffix) guessing
depends on only the mnemonic, not the operands, thus making things like
movsb (movs[bwlq] vs. movsb[wlq]), movsd (movs[bwdq] vs. movs[sd]), or
cmpsd (cmps[bwdq] vs. cmps[sd]) conflict. But there are more such issues
(like AT&T/Intel syntax insns being visible in the opposite mode). I
think some signficiant amount of cleanup work is necessary here, and
I'll try to get to this hopefully not too far in the future.
Jan