Index
> Compiler Internals > Opcoding REX.W + C7/0 |
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revolution 05 Apr 2011, 11:27
Looks fine to me:
Code: use64 mov rsi,1 ;48 C7 C6 01 00 00 00 |
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05 Apr 2011, 11:27 |
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MazeGen 05 Apr 2011, 12:52
Only MOV (B8-BF) is "privileged" to use imm64. You can't use AND or any other instruction with immediate value from full 64-bit range.
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05 Apr 2011, 12:52 |
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hopcode 05 Apr 2011, 15:37
MazeGen wrote: Only MOV (B8-BF) is "privileged" to use imm64. You can't use AND or any other instruction with immediate value from full 64-bit range. mmh...,it depends on the point of view. on 64bit platform one should use all of the 64bit cpu capability. also, isnt there a reason, for example, to REX.W 81/4 id ? revolution wrote: Looks fine to me: to me too, but please read the post carefully: Quote: i like a lot this cpu feature, but i opcode it ...when using fasm. if you cannot imagine why, try this Code:
use64
db 0100'1000b
db 0C7h
db 11100000b
dd 80000000h
db 48h
db 0C7h
db 00000000b
dd 80000000h
Cheers,  _________________ ⠓⠕⠏⠉⠕⠙⠑ |
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05 Apr 2011, 15:37 |
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revolution 05 Apr 2011, 15:47
dd 8000000h is the encoding for 0ffffffff80000000h. Same as:
Code: mov rsi,0xffffffff80000000 |
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05 Apr 2011, 15:47 |
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hopcode 05 Apr 2011, 16:01
revolution wrote: dd 8000000h is the encoding for 0ffffffff80000000h. Same as: ...ok... it satisfies the-point-of-view's side, as i said. but apart from the bunch of 0ffffffff to type additionally it doesnt satisfies the following rule: REX.W + C7 /0 MOV r/m64,imm32 Move imm32 sign extended to 64-bits to r/m64. the CPU should "move" imm32 and extend it, not the user  .
in your example the untirable user moves... and the cpu... swings,
Cheers _________________ ⠓⠕⠏⠉⠕⠙⠑ |
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05 Apr 2011, 16:01 |
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revolution 05 Apr 2011, 16:15
If I type mov rsi,0x80000000 then I would expect rsi to be 0x0000000080000000, not 0xffffffff80000000.
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05 Apr 2011, 16:15 |
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hopcode 05 Apr 2011, 16:35
revolution wrote: If I type mov rsi,0x80000000 then I would expect rsi to be 0x0000000080000000, not 0xffffffff80000000. and if you need 0xffffffff80000000 ... what would nt you "type" for that ? that's... funny, revolution !
but why have we imm32 / imm64, two different opcodable data sizes ? for amusement ? sport ? ok! that's my point of view: sport! Cheers, _________________ ⠓⠕⠏⠉⠕⠙⠑ |
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05 Apr 2011, 16:35 |
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revolution 05 Apr 2011, 16:57
Your suggestion to encode 0x80000000 as a dword is wrong because the CPU will place 0xffffffff80000000 into the register. That is what your macro is encoding, the 64 bit sign extended value of imm32 0x80000000.
Either that or I completely misunderstand what you are trying to say. |
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05 Apr 2011, 16:57 |
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hopcode 05 Apr 2011, 17:24
revolution wrote: Your suggestion to encode 0x80000000 as a dword is wrong because the CPU will place 0xffffffff80000000 into the register.... .. the point of view , as i said., do you know the point of view ?; i see a signed DWORD sometimes, sometimes an UNSIGNED one, sometimes something else. i make the policy, because i am the person who codes. what CPU places is correct, when using that encoding ! Quote: Either that or I completely misunderstand what you are trying to say. what you often misunderstand is the meaning of 64bit signing extension for the meaning of "encoding". Most programmers misunderstand that. but as you know, it is basic, the ground when porting to 64bit, not only for that instruction and opcoding above. But, related to fasm, it is always an ecoding problem, not mine (i can use macro) Also,if you misunderstand what i said, well... that's not my problem. that's your encoding.
Cheers... _________________ ⠓⠕⠏⠉⠕⠙⠑ |
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05 Apr 2011, 17:24 |
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revolution 05 Apr 2011, 17:45
Are you saying that you don't care about the upper 32 bits of the 64 bit register? If so then, yes, you can encode as a dword, but otherwise there is no way to encode 0x0000000080000000 in 7 bytes. The CPU will always sign extend it.
hopcode wrote: it should be always |
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05 Apr 2011, 17:45 |
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Tomasz Grysztar 05 Apr 2011, 17:47
You can type "mov rsi,0xffffffff80000000" or "mov rsi,-80000000h", they mean the same. But "mov rsi,80000000h" is a different instruction. fasm focuses on instruction functionality - that is, with assembly mnemonics you specify what instruction exactly should do, and not what kind of encoding it should have (assembler should select the optimal encoding itself). There are some exceptions in fasm 1.x (like when you put size operator just before immediate, you enforce the long encoding of that value), but I plan to separate those things completely with fasm 2.0 (as revolution already knows, BTW).
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05 Apr 2011, 17:47 |
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revolution 05 Apr 2011, 17:54
Tomasz Grysztar wrote: ... I plan to separate those things completely with fasm 2.0 (as revolution already knows, BTW). |
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05 Apr 2011, 17:54 |
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MazeGen 06 Apr 2011, 11:05
hopcode wrote:
REX.W 81/4 id can't use immediate from full 64-bit range, only values from 0 to 7FFFFFFF, and from FFFFFFFF80000000 to FFFFFFFFFFFFFFFF (in contrast to REX.W B8-BF). |
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06 Apr 2011, 11:05 |
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hopcode 06 Apr 2011, 15:38
MazeGen wrote: REX.W 81/4 id can't use immediate from full 64-bit range, only values from 0 to 7FFFFFFF, i didn't say the contrary. id,imm32 are quantities. the problem arises by encoding them, the meaning you give / the assembler gives to that encoding. i said: i use macros. now, please follow the post carefully: revolution wrote:
When you program something for a specified cpu, you open the manual and read what the cpu manual preserves, how data must be "opcoded". but the manual tell you neither how those datas should be symbolized nor what meaning they have for you or fasm. Also we accept sign extension from the manual so exaclty as the fact of the explicit 48C7 z-extension on value below 80_ . your encoding habit maybe fasm encoding habit, but that doesnt mean it is the finest habit or the most flexible and coherent one (the nearest one to the cpu). Genius Tomasz wrote: You can type "mov rsi,0xffffffff80000000" it depends on what flexibility your assembler have, the point of view. When accepting fasm style, we accept obviously this too. Tomasz wrote: But "mov rsi,80000000h" is a different instruction. 
No, why should it be ? it maybe fasm big implicitness that inhibits the flexibility of what the cpu manual preserves as doable or as rule. In fact you could use yet another encoding marker (God save us!) to signify discreptionality, for example "mov rsi,0x80000000L" as DWORD or "mov rsi,0x80000000X" as extendable opcoding just like "0x" marker or the "h" marker or, alike in your habit, the 0xffffffff one. Also then, we weight pros and contras of fasm encoding and this is the result Code:
mov rax,80000000h ; 48B8 0000008000000000 mov rax,0000000080000000
mov rax,7FFFFFFFh ; 48C7 C0 FFFFFF7F mov rax,7FFFFFFF
mov rax,0xffffffff80000000 ; 48C7 C0 00000080 mov rax,FFFFFFFF80000000
mov rax,-80000000h ; 48C7 C0 00000080 mov rax,FFFFFFFF80000000
mov rax,+80000000h ; 48B8 0000008000000000 mov rax,0000000080000000
mov rax,-7FFFFFFFh ; 48C7 C0 01000080 mov rax,FFFFFFFF80000001
mov rax,not 7FFFFFFFh ; 48C7 C0 00000080 mov rax,FFFFFFFF80000000
; mov rax,dword 7FFFFFFFh ; operand sizes do not match !!!
; mov rax,dword -7FFFFFFFh ; operand sizes do not match !!!
Also,laught at your coherence! it's not so bad after all. ipse dixit wrote: but I plan to separate those things completely with fasm 2.0 (as revolution already knows, BTW). But you, Tomasz, again and again with that talking about fasm 2 without having got it publicly accessible... is somewhat "dirty" from you! Make it publicly accessible, then we will see and consider those features you are talking about. If you believe to be cleverer, this doesnt give you permission/right to fool,"punish" i would say, the readers by overbloating them this way. It's fasm-1-encoding's convenience the eventual thema! Then finally: you quoting yourself this way is pure complacency on this dead forum: "pure" because you speak about something that is not under our eyes , and "dead", is the goal in your speaking. because alike most other fine programmers who come anymore or only occasionally here ,-i am here only to review my posts-,or just like the reader, who cannot learn anything from your implicit self cerebral looping... and from the technical level of your superficial discussion, that's all. Horse sense, please , dont take it personally against you ! Bye, _________________ ⠓⠕⠏⠉⠕⠙⠑ |
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06 Apr 2011, 15:38 |
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Tomasz Grysztar 06 Apr 2011, 16:25
hopcode wrote:
hopcode wrote: But you, Tomasz, again and again with that talking about fasm 2 fasm 2 for now exists only in my mind, because I prefer to prepare a good design before I start coding. And as some parts of this design are still subject to change, I do not say too much about the details, though you could hear some elementary information about it on fasmcon 2009. |
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06 Apr 2011, 16:25 |
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Tomasz Grysztar 06 Apr 2011, 16:36
revolution wrote:
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06 Apr 2011, 16:36 |
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