Use the MOV instruction to obtain the value in the array

[wanker742126]

I was writing a 64-bit Windows program and noticed something strange:
The following program can be successfully assembled using ML64, but will appear when using UASM64
"Error A2031: invalid addressing mode with current CPU setting"
--------------------------------------------------
array DD 20h DUP (1)
... ...
mov rcx,2
mov eax,array[rcx*4+8]
--------------------------------------------------
Does anyone know what's going on?

[six_L]

Hi,wanker742126
lea    rdx,array    ;mov    rdx,offset array
mov    rcx,2
mov    eax,[rdx+rcx*4]

rdx: the frist address of  your array
rcx: index
4: 1"DD"=4"BYTE"

[wanker742126]

Hello Six_L
I know it can be written like this, but I would like to know why ML64 can be successfully assembled, but UASM64 cannot. Is it necessary to make any settings on the CPU?

[_japheth]

I know it can be written like this, but I would like to know why ML64 can be successfully assembled, but UASM64 cannot. Is it necessary to make any settings on the CPU?

No. It's valid syntax, and if UASM refuses it, it's a bug.

[six_L]

Hi,wanker742126

why ML64 can be successfully assembled, but UASM64 cannot. Is it necessary to make any settings on the CPU?

1,ML64 is written by microsoft; UASM64 is written by John Hankinson and Branislav Habus, _japheth (our forum member). they are different assembler.
2,Assembly language syntax of ML64 is not ml32-compatible, don't support HLL features. But UASM64 does.
3,ML64 only works on MS OS; UASM64 can work on MS OS, Linux and OSX.

[wanker742126]

Thanks for your answer, six_L and _japheth.
Maybe I have to wait until UASM supports this syntax. Or maybe try using macros.

[six_L]

Hi,wanker742126

Maybe I have to wait until UASM supports this syntax.

Maybe You will never be the outcome. because the register addressing is faster than the memory addressing.

[mineiro]

;this is a simple workaround, tested in linux
;I was trying to create a macro but displacement have not been added to array offset
;so I put displacement in a register
mov rcx,2
mov edx,8
mov eax,array[ecx*sizeof dword+edx]

;+8 displacement is not being added
mov eax,array[rcx*sizeof dword+8+rdx]      ;<---
USE32
mov eax,dword ptr [array+8+ecx*4]         ;<---
USE64

[wanker742126]

Today I found that ADD, SUB, MUL, and DIV can all accept array usage, but only MOV cannot.
The following program can be successfully assembled using UASM64

Code Select Expand

OPTION  CASEMAP:NONE
OPTION  WIN64:3

INCLUDELIB      KERNEL32.LIB
INCLUDELIB      USER32.LIB

MessageBoxA     PROTO   :QWORD,:QWORD,:QWORD,:DWORD
ExitProcess     PROTO   :DWORD
;*********************************************************************
.CONST
array           DD      20h DUP (1)
szCaption       DB      "TITLE",0
szText          DB      "64-BIT ASSEMBLY.",0
;*********************************************************************
.CODE
;---------------------------------------------------------------------
main    PROC
        mov     rcx,2
        add     eax,array[rcx*4+8]
        sub     eax,array[rcx*4+8]
        xor     eax,array[rcx*4+8]
        mul     array[rcx*4+8]
        div     array[rcx*4+8]
        invoke  MessageBoxA,0,OFFSET szText,OFFSET szCaption,0
        invoke  ExitProcess,0
main    ENDP
;*********************************************************************
END     main

But the program below will fail to assemble and compile, and the error occurs in the MOV line.

Code Select Expand

OPTION  CASEMAP:NONE
OPTION  WIN64:3

INCLUDELIB      KERNEL32.LIB
INCLUDELIB      USER32.LIB

MessageBoxA     PROTO   :QWORD,:QWORD,:QWORD,:DWORD
ExitProcess     PROTO   :DWORD
;*********************************************************************
.CONST
array           DD      20h DUP (1)
szCaption       DB      "TITLE",0
szText          DB      "64-BIT ASSEMBLY.",0
;*********************************************************************
.CODE
;---------------------------------------------------------------------
main    PROC
        mov     rcx,2
        mov     eax,array[rcx*4+8]
        add     eax,array[rcx*4+8]
        sub     eax,array[rcx*4+8]
        xor     eax,array[rcx*4+8]
        mul     array[rcx*4+8]
        div     array[rcx*4+8]
        invoke  MessageBoxA,0,OFFSET szText,OFFSET szCaption,0
        invoke  ExitProcess,0
main    ENDP
;*********************************************************************
END     main

[six_L]

you are digging the bugs of compiler, not learning the assembler language.
Come on!
the TAIWAN's frog is sitting on well and talking the vastness of sky.