[LLVMdev] Some bugs in x86 disasm (llvm-mc)

[Kay Tiong Khoo]

Hi Jun,

I'm not sure how to fix this yet, but this looks incorrectly defined in
lib/Target/X86/X86InstrInfo.td:

def MOV32o32a : Ii32 <0xA1, RawFrm, (outs), (ins offset32:$src),
                      "mov{l}\t{$src, %eax|eax, $src}", [], IIC_MOV_MEM>,
                     Requires<[In32BitMode]>;

This instruction can be REX-prefixed for a 64-bit move, and that also
doesn't appear to be defined anywhere.

I would file a bugzilla in the x86 component and cc Craig Topper, the x86
disasm/codegen expert.



On Wed, Nov 27, 2013 at 8:56 AM, Jun Koi <junkoi2004 at gmail.com> wrote:

> Hi,
>
> With objdump, i have this (Intel syntax)
>
>          64 a1 00 00 00 00        mov    eax,fs:0x0
>
>
> However, if I pass above string to llvm-mc, I would have:
>
> $ echo "0x64 0xa1 0x00 0x00 0x00 0x00"|./Release+Asserts/bin/llvm-mc
> -disassemble -arch=x86 --output-asm-variant=1
>     .text
>     mov    eax, dword ptr [0]
>
>
> You can see a big difference. This is on the latest code. Any idea how to
> fix this bug?
>
> Thank you,
> Jun
>
>
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