PUSH IMM problem in USE64

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alorent

Joined: 05 Dec 2005
Posts: 201

alorent

Hello,

use32
push 0F0000000h

It assembles OK with FASM.

use64
push 0F0000000h

[ERROR:] Value out of range.

Is this a bug or I'm doing something wrong?

Thanks.

07 Jan 2006, 12:02

Tomasz Grysztar
Assembly Artist

Joined: 16 Jun 2003
Posts: 7724
Location: Kraków, Poland

Tomasz Grysztar

In long mode 32-bit values are sign-extended into 64 bits when pushed, thus PUSH instruction with 0F0000000h immediate does push the 0FFFFFFFFF0000000h value on the stack. If you do PUSH 0FFFFFFFFF0000000h, fasm will generate the proper opcode, but if you want to push actually the 0F0000000h, it's impossible this way, since it doesn't fit in the signed 32-bit immediate range. Thus you should do it rather this way:

Code:

mov eax,0F0000000h ; this does the zero-extension to RAX
push rax

07 Jan 2006, 13:57

alorent

Joined: 05 Dec 2005
Posts: 201

alorent

Thanks again Tomasz, you are my hero! Very Happy

07 Jan 2006, 19:50

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid

and designer of this 64bit extension isn't my hero

10 Jan 2006, 05:11

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