How fasm calculate expressions?

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Roman

Joined: 21 Apr 2012
Posts: 1878

Roman 19 Jul 2019, 01:59

Code:

mov ebx,3+7*2/2-2+2*2+3*(3+2) ;=27

I want find this in fasm source.

And what is do fp_optimize:

Code:

mov     eax,[edi]
        mov     ebp,[edi+4]
        or      ebp,[edi]
        or      ebp,[edi+12]
        jz      fp_zero
      .loop:
        test    byte [edi+7],80h
        jnz     .done
        shld    [edi+4],eax,1
        mov     ebp,[edi+12]
        shld    eax,ebp,1
        mov     [edi],eax
        shl     dword [edi+12],1
        dec     dword [edi+8]
        jmp     .loop
      .done:
        ret
      fp_zero:
        mov     dword [edi+8],8000h
        ret

19 Jul 2019, 01:59

edfed

Joined: 20 Feb 2006
Posts: 4354
Location: Now

edfed 19 Jul 2019, 07:41

this is related to compiler internals.

you should better read the understanding fasm documentation.

19 Jul 2019, 07:41

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8367
Location: Kraków, Poland

Tomasz Grysztar 19 Jul 2019, 09:52

EXPRPARS.INC contains code that converts the original expression (in a preprocessed format, see TOOLS\FAS.TXT for the description of how text tokens are stored) into an RPN bytecode. This is done once per assembly.

EXPRCALC.INC contains code that evaluates the expression in the bytecode form, it is a like running a simple script on a stack-based VM.

19 Jul 2019, 09:52

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