"吴曦" <[EMAIL PROTECTED]> writes: > Thanks. But what does it mean by saying: > "Sometimes an insn can match more than one instruction pattern. Then > the pattern that appears first in the machine description is the one > used." > in section 14.10 of gcc internal p259?
(Please don't top post. Thanks.) It means what it says. The effect is that only the first insn in the MD file is used, and the subsequent ones are ignored. This is rarely useful. Ian > 08 Feb 2007 00:09:21 -0800, Ian Lance Taylor <[EMAIL PROTECTED]>: > > "吴曦" <[EMAIL PROTECTED]> writes: > > > > > I observe that there is a ld instruction in 3rd alternative, so I add > > > a new define_insn before it in the hope that it will be matched > > > firstly. > > > > It doesn't work that way. Your new instruction will wind up matching > > all move instructions. Reload will crash because the constraints > > don't work. > > > > Instead just change the existing movqi_internal insn. Don't try to > > write a new one. Change the existing insn to use C code which checks > > which_alternative instead of the @ list it uses now. > > > > Ian > >
