From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Hayes To: law@cygnus.com Cc: Michael Hayes , Richard Henderson , Jamie Lokier , Marc Lehmann , egcs@cygnus.com Subject: Re: GCC 2.7.2.3 good, EGCS 1.0.3 bad for x86 subtract then test Date: Sat, 26 Dec 1998 02:07:00 -0000 Message-id: <13956.46052.667366.129757@ongaonga.elec.canterbury.ac.nz> References: <13956.18174.396993.213410"@ongaonga.elec.canterbury.ac.nz> <16940.914651694@hurl.cygnus.com> X-SW-Source: 1998-12/msg00914.html Jeffrey A Law writes: > > In message < 13956.18174.396993.213410@ongaonga.elec.canterbury.ac.nz >you writ > e: > > Why not use the extra condition to prevent the combination if the > > first input does not match the output operand? > Because that can miss some valueable combination opportunities. It is also > incorrect for a condition on a named pattern to reject any insn based on > anything other than the target flags. I realise you can't do this for named patterns but this is easily overcome using named expanders (with exceptions for movMN and addP patterns required by reload). What valuable combination opportunities are missed if you write the extra condition to only accept the valid operand combinations? [I know this thread popped up a couple of months ago but I feel it was not satisfactorily resolved...] Michael.