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Re: [committed, PATCH] Remove Disp16|Disp32 from 64-bit direct branches
- From: Michael Matz <matz at suse dot de>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Jan Beulich <JBeulich at suse dot com>, Binutils <binutils at sourceware dot org>
- Date: Tue, 12 May 2015 16:31:17 +0200 (CEST)
- Subject: Re: [committed, PATCH] Remove Disp16|Disp32 from 64-bit direct branches
- Authentication-results: sourceware.org; auth=none
- References: <20150511212331 dot GA1838 at intel dot com> <5551F4E70200007800079575 at mail dot emea dot novell dot com> <CAMe9rOpDbkeFbmNbQh0a1AKhAQy-cH4HJu20o_ERQaoR6sTxbQ at mail dot gmail dot com> <55520C440200007800079718 at mail dot emea dot novell dot com> <CAMe9rOpFgSyJm-oceuDkrBYnBQGv01ywCc43WySqX21NTJYi4Q at mail dot gmail dot com> <555216370200007800079773 at mail dot emea dot novell dot com> <CAMe9rOpOx=SSUZnCFimn4fBzFqNRDch8QYLn3Os_y7EfQH65Qw at mail dot gmail dot com> <alpine dot LSU dot 2 dot 20 dot 1505121548100 dot 4883 at wotan dot suse dot de> <CAMe9rOqg_H9YXHdoWv-k4zoQm77OoQ19j3djHZ74pgUORiDECw at mail dot gmail dot com>
Hi,
On Tue, 12 May 2015, H.J. Lu wrote:
> > This is with 2.23, so your patch would cause a regression:
>
> 1. This happened before 20140923.
Same with current 2.25-branch.
> 2. Can you speculate what
>
> " jmpw 4"
>
> does?
It should do a jump to $nextip+offset, of course, just like a 32bit
jump. The disassembly is correct, because with a zero offset, that's
indeed '4'.
Ciao,
Michael.
> > x.o: file format elf64-x86-64
> >
> >
> > Disassembly of section .text:
> >
> > 0000000000000000 <bar-0x4>:
> > 0: 66 e9 00 00 jmpw 4 <bar>
> > 2: R_X86_64_PC16 foo-0x2
> >
> > 0000000000000004 <bar>:
> > 4: 89 c2 mov %eax,%edx