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Index > Main > [fasmg] movbe (0x0F 0x38 0xF[01]) instruction?

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sylware



Joined: 23 Oct 2020
Posts: 66
Location: Marseille/France
sylware
It seems this instruction is missing, or it is me missing something.
Post 09 Aug 2021, 12:57
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7932
Location: Kraków, Poland
Tomasz Grysztar
MOVBE is one of the single-instruction extensions that have dedicated CPUID bits, in fasmg's headers set it should therefore have its own file (ext/movbe.inc). I've been slowly adding most of the Intel extensions (I did not even begin with AMD-specific stuff), but it's never been complete.
Post 09 Aug 2021, 14:31
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sylware



Joined: 23 Oct 2020
Posts: 66
Location: Marseille/France
sylware
after reading the suggested thread (which the forum search engine did not return to me, sorry)... well it does not make movbe shine.
Now dunno if I should use it.
Post 09 Aug 2021, 15:12
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bitRAKE



Joined: 21 Jul 2003
Posts: 3300
Location: vpcmipstrm
bitRAKE
Code:
; CPUID Fn0000_0001_ECX[MOVBE] = 1
calminstruction movbe? dest*,src*
        asmcmd  =x86.=parse_operand =@dest,dest
        asmcmd  =x86.=parse_operand =@src,src

        local   size

        check   @dest.size <> 0 & @src.size <> 0 & @dest.size <> @src.size
        jyes    operand_sizes_do_not_match

        compute size, @dest.size or @src.size
        check   size > 1
        jno     invalid_operand_size

    main:
        check   @dest.type = 'reg' & @src.type = 'mem'
        jyes    movbe_reg_mem
        check   @dest.type = 'mem' & @src.type = 'reg'
        jyes    movbe_mem_reg

    invalid_combination_of_operands:
        asmcmd  =err 'invalid combination of operands'
        exit

    movbe_reg_mem:
        asmcmd  =x86.=select_operand_prefix =@dest,size
        asmcmd  =x86.=store_instruction <0Fh,38h,0F0h>,=@dest,=@src.=rm
        exit

    movbe_mem_reg:
        asmcmd  =x86.=select_operand_prefix =@src,size
        asmcmd  =x86.=store_instruction <0Fh,38h,0F1h>,=@src,=@dest.=rm
        exit

    invalid_operand_size:
        asmcmd  =err 'invalid operand size'
        compute size, 0
        jump    main

    operand_sizes_do_not_match:
        asmcmd  =err 'operand sizes do not match'
        compute size, 0
        jump    main

end calminstruction    
Just copy-paste (no testing).
This instruction was introduced with Intel Atom and later migrated (movbe'd Very Happy) to higher end processors.

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Post 09 Aug 2021, 15:39
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sylware



Joined: 23 Oct 2020
Posts: 66
Location: Marseille/France
sylware
It does not work. As far I understand, it seems related to modrm/sib bytes computation.
Well, I have to dive into this because I got hit by the missing "pdep" instruction too.
Post 09 Aug 2021, 18:47
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7932
Location: Kraków, Poland
Tomasz Grysztar
sylware wrote:
Well, I have to dive into this because I got hit by the missing "pdep" instruction too.
PDEP is part of the BMI2 extension, you can get it by including "ext/bmi2.inc".
Post 09 Aug 2021, 19:07
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bitRAKE



Joined: 21 Jul 2003
Posts: 3300
Location: vpcmipstrm
bitRAKE
Oh, I got the dest<>src mixed up in the output. Maybe there is something else too?
Code:
    movbe_reg_mem:
        asmcmd  =x86.=select_operand_prefix =@src,size
        asmcmd  =x86.=store_instruction <0Fh,38h,0F0h>,=@src,=@dest.=rm
        exit

    movbe_mem_reg:
        asmcmd  =x86.=select_operand_prefix =@dest,size
        asmcmd  =x86.=store_instruction <0Fh,38h,0F1h>,=@dest,=@src.=rm
        exit    
... fixes it perhaps.

Some more instructions, SSE4a, etc...
https://board.flatassembler.net/topic.php?t=21823

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Post 09 Aug 2021, 19:11
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sylware



Joined: 23 Oct 2020
Posts: 66
Location: Marseille/France
sylware
Tomasz Grysztar wrote:
PDEP is part of the BMI2 extension

ok... my egrep -i was a failure then or I don't know what I did... jez, really unlucky with text search lately.

bitRAKE wrote:
I got the dest<>src mixed up
working now, I get the right modrm byte, thx!
Post 09 Aug 2021, 21:09
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