Messages in this thread | | | Date | Thu, 13 Jan 2005 14:46:01 -0800 | From | "H. J. Lu" <> | Subject | Re: Change i386 assembler/disassembler for SIB with INDEX==4 |
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On Thu, Jan 13, 2005 at 12:33:28PM -0800, Allan B. Cruse wrote: > > On Thu, 13 Jan 2005, "H. J. Lu" <hjl@lucon.org> wrote: > > > > > > > > Subject: Change i386 assembler/disassembler for SIB with INDEX==4 > > > > I am proposing to change i386 assembler/disassembler for SIB with > > INDEX==4 > > > > http://sources.redhat.com/bugzilla/show_bug.cgi?id=658 > > > > It will change the assembler output for (%ebx,[1248]). I am not too > > worried about the disassembler output since assembler can't generate > > SIB with INDEX==4 directly today. Any comments? > > > > > > H.J. > > > > > This change would give programmers the freedom to write instruction- > syntax that the processor cannot actually execute, is that right?
No. Assemberl will turn "mov (%ebx,2),%eax" into "8b 04 63", which is valid i386 machine code.
> > Perhaps the downside to this would lie in the hours of debugging and > private research each programmer would then be faced with, trying to > figure out why " movl (%esi,2),%eax " wasn't doing what he/she had > intended, and which the assembler had dutifully accepted. --ABC >
What do you expect "movl (%esi,2),%eax" will do?
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