From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jerry Quinn" To: law@cygnus.com Cc: binutils@sourceware.cygnus.com Subject: Re: PATCH: add pa2.0 system instructions Date: Fri, 09 Jul 1999 10:17:00 -0000 Message-id: <14214.11878.766249.924457@gargle.gargle.HOWL> References: <14213.64155.863403.101617@gargle.gargle.HOWL> <6127.931537707@upchuck.cygnus.com> X-SW-Source: 1999-q3/msg00110.html >> "jeff" == Jeffrey A Law writes: >> Perhaps I don't understand here, but this doesn't seem ambiguous to >> me. There isn't ambiguity in the 0, 4, or 9. In the old syntax, 5 can >> only be a displacement. jeff> But the code which parses an 'x' operand (or any register operand) will jeff> accept an immediate and treat it like a register number. So, if you jeff> are using existing letters to stand for registers, then you've got no jeff> way to distinguish between those cases. It's a serious issue. jeff> Given the table fragment I posted, there's no way to get load-word with jeff> short displacement without modifying how the 'x' and other register jeff> operands are handled because 'x' will interpret the short displacement jeff> as a register #. OK, I see. Yeah that's a nuisance. But, if we're willing to go to the effort of prefixing to free up codes, we can handle this by adding codes that only accept registers versus the ones that cast immediates to registers. In this case, the stricter syntax restriction comes for free. Jerry