In Visual Studio, I wrote:
mov eax, [edx][ebx][ecx][edi]
But it assembles just fine.
Why it is not invalid effective address?
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What do you expect `mov eax, [edx][ebx][ecx][edi]` to do? – Nov 08 '15 at 16:39
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nothing, I only wonder why it is correct effective adress. – pawel_bolak Nov 08 '15 at 16:41
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1It doesn't assemble with masm 6.14.8444. What does that instruction disassemble to? – Michael Nov 08 '15 at 16:49
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It appears to be a bug in more recent versions of MASM.
Using the following file as an example:
.586
_TEXT SEGMENT USE32
mov eax, [edx][ebx][ecx][edi]
_TEXT ENDS
END
With MASM 6.11d this generates the following error:
t213a.asm(4) : error A2030: multiple index registers not allowed
With MASM 8.00.50727.42 or more recent there's no error, and the statement assembles to:
00000000: 8B 04 0F mov eax,dword ptr [edi+ecx]
So [edx][ebx][ecx][edi] is not a valid addressing mode. A bug in the version of MASM you're using is accepting it when it should be rejecting it as an error.
Ross Ridge
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Thanks @Ross I found the same thing. You beat me to it. You have my upvote – Michael Petch Nov 08 '15 at 17:02
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@MichaelPetch Thanks, if it wasn't for your comment about 6.14.8444 I would've never have thought to try an older version of MASM to see if this is a regression. – Ross Ridge Nov 08 '15 at 17:14
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