Re: GAS illegally encodes FMA4.

[Quentin Neill]

On 18 Sep 08:02, NEGISHI, Kiyoshi <negishi <at> usa.net> wrote:
> Hi,
>
> I believe that encoding old INTEL AVX FMA and AMD FMA4 is different
> specifications.
>
> in gas format:
>      vfmaddpd %xmm4,%xmm6,%xmm2,%xmm7
>
> operand order is
>      vfmaddpd src3, src2, src1, dest
>
> that's right?
>
> gas encoding this is
>      c4 e3 c9 69 fc 20
>
> this means
>      ModRM.reg=%xmm7 VEX.vvvv=%xmm6 ModRM.r/m=%xmm4 imm8[7:4]=%xmm2
>
> This is AVX FMA encoding because src1=imm8[7:4].
>
> The AMD FMA4 encoding is src1=VEX.vvvv, so right:
>      c4 e3 e9 69 fc 60
>
>      ModRM.reg=%xmm7 VEX.vvvv=%xmm2 ModRM.r/m=%xmm4 imm8[7:4]=%xmm6
>
> Negishi.

HI Negishi

Can you post the version, inputs, and options used?

I can't reproduce the problem.

Using trunk from two days ago with this input (see t1 below)
    vfmaddpd %xmm4,%xmm6,%xmm2,%xmm7
encoded as
    c4 e3 ed 69 fc 60

When I feed it this input (t2.s below, note the register arguments)
    vfmaddpd %xmm4,%xmm2,%xmm6,%xmm7
it is encoded as
    c4 e3 c9 69 fc 20

-- 
Quentin


--------------- t1 ---------------
$ /home/qneill/wk/binutils/trunk.git/bld.trunk/gas/as-new --version
GNU assembler (GNU Binutils) 2.20.51.20101101
Copyright 2010 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or later.
This program has absolutely no warranty.
This assembler was configured for a target of `x86_64-unknown-linux-gnu'.
$
$ cat t1.s
        .text
_start:
        vfmaddpd %xmm4,%xmm6,%xmm2,%xmm7

$
$ /home/qneill/wk/binutils/trunk.git/bld.trunk/gas/as-new -msyntax=att
--64 t1.s -o t1-att-64.o
$ /home/qneill/wk/binutils/trunk.git/bld.trunk/binutils/objdump -dw
-Matt,64 t1-att-64.o

t1-att-64.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <_start>:
   0:   c4 e3 e9 69 fc 60       vfmaddpd %xmm4,%xmm6,%xmm2,%xmm7


--------------- t2 ---------------
$ /home/qneill/wk/binutils/trunk.git/bld.trunk/gas/as-new --version
GNU assembler (GNU Binutils) 2.20.51.20101101
Copyright 2010 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or later.
This program has absolutely no warranty.
This assembler was configured for a target of `x86_64-unknown-linux-gnu'.
$
$ cat t2.s
        .text
_start:
        vfmaddpd %xmm4,%xmm2,%xmm6,%xmm7

$
$ /home/qneill/wk/binutils/trunk.git/bld.trunk/gas/as-new -msyntax=att
--64 t2.s -o t2-att-64.o
$ /home/qneill/wk/binutils/trunk.git/bld.trunk/binutils/objdump -dw
-Matt,64 t2-att-64.o

t2-att-64.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <_start>:
   0:   c4 e3 c9 69 fc 20       vfmaddpd %xmm4,%xmm2,%xmm6,%xmm7