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Re: GCC 2.7.2.3 good, EGCS 1.0.3 bad for x86 subtract then test
- To: Michael Hayes <m dot hayes at elec dot canterbury dot ac dot nz>
- Subject: Re: GCC 2.7.2.3 good, EGCS 1.0.3 bad for x86 subtract then test
- From: Jeffrey A Law <law at hurl dot cygnus dot com>
- Date: Fri, 25 Dec 1998 22:54:54 -0700
- cc: Richard Henderson <rth at cygnus dot com>, Jamie Lokier <egcs at tantalophile dot demon dot co dot uk>, Marc Lehmann <pcg at goof dot com>, egcs at cygnus dot com
- Reply-To: law at cygnus dot com
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.
jeff