On Sun, Mar 21, 2010 at 3:43 AM, Jim Wilson <wil...@codesourcery.com> wrote: > On Sun, 2010-03-21 at 03:40 +0800, fanqifei wrote: >> foor_expand_move is changed and it works now. >> However, I still don't understand why there was no such error if below >> condition was used and foor_expand_move was not changed. >> Both below condition and "(register_operand(operands[0], SImode) || >> register_operand(operands[1],SImode)) ..." does not accept mem&&mem. > > The define_expand is used for generating RTL. The RTL expander calls > the define_expand, which checks for MEM&CONST, and then falls through > generating the mem copy insn. > > The define_insn is used for matching RTL. After it has been generated, > we look at the movsi define_insn, and see that MEM&MEM doesn't match, so > you get an error for unrecognized RTL. > > The define_expand must always match the define_insn(s). They are used > in different phases, and they aren't checked against each other when gcc > is built. If there is a mismatch, then you get a run-time error for > unrecognized rtl. > > Jim > > > Great thanks for your explanation. I will look into the internal reason why they must match although that is beyond my work and what I know.
Thanks again! -- -Qifei Fan http://freshtime.org
