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Re: Patch to avoid non-pairable NEG instructions
- To: Jan Hubicka <hubicka at atrey dot karlin dot mff dot cuni dot cz>
- Subject: Re: Patch to avoid non-pairable NEG instructions
- From: Jeffrey A Law <law at upchuck dot cygnus dot com>
- Date: Wed, 14 Apr 1999 00:38:23 -0600
- cc: egcs-patches at egcs dot cygnus dot com
- Reply-To: law at cygnus dot com
In message <19990413151600.35798@atrey.karlin.mff.cuni.cz>you write:
> Hi
> Here is updated version of patch.
> I've tested the xor/not patterns merge as suggested by Jeff, but result
> was worse code. Combiner always changes code to canonical form, where
> xors are converted to nots. So all his proposed changes was refused.
>
> This version also changes the xor patterns to avoid outputing of neg instru
> ction.
>
> BTW the xorhi patterns don't call i386_cc_probably_useless_p before
> emiting non-prefixed opcode. Is this bug or feature?
>
> Honza
> Tue Apr 13 14:22:43 MET DST 1999 Jan Hubicka <hubicka@freesoft.cz>
>
> * i386.md (xorsi3): Do not output NOT instrctions on Pentium.
> (xorqi3): Likewise.
> (xorhi3): Likewise.
> (notsi2): Likewise.
> (notqi2): Likewise.
> (nothi2): Likewise; do not output prefixed opcodes when possible.
Thanks. Installed.
jeff