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RE: [PATCH 1/2, combine] Try REG_EQUAL for nonzero_bits
- From: "Thomas Preud'homme" <thomas dot preudhomme at arm dot com>
- To: "'Andrew Pinski'" <pinskia at gmail dot com>
- Cc: "Eric Botcazou" <ebotcazou at adacore dot com>, "GCC Patches" <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 10 Feb 2015 10:19:28 +0800
- Subject: RE: [PATCH 1/2, combine] Try REG_EQUAL for nonzero_bits
- Authentication-results: sourceware.org; auth=none
- References: <00f001d044d4$23f37e20$6bda7a60$ at arm dot com> <CA+=Sn1n0FZSdn4RqVHGmuoeA5+gb3MVxZheC0pFELWkRDO-mew at mail dot gmail dot com>
> From: Andrew Pinski [mailto:firstname.lastname@example.org]
> Sent: Tuesday, February 10, 2015 9:57 AM
> > +#ifdef SHORT_IMMEDIATES_SIGN_EXTEND
> > +/* If MODE has a precision lower than PREC and SRC is a non-negative
> > + that would appear negative in MODE, sign-extend SRC for use in
> > + because some machines (maybe most) will actually do the sign-
> extension and
> > + this is the conservative approach.
> > +
> > + ??? For 2.5, try to tighten up the MD files in this regard instead of
> > + kludge. */
> I don't know if this has been mentioned and even though you are just
> copying a comment from below but would it make sense to look fixing
> what the comment says we should look at after GCC 2.5 (which was over
> 20 years ago)? Or maybe just remove the comment if it no longer
Actually this bit seems unnecessary as there is already some logic in
nonzero_bits1 for the CONST_INT case. So I guess the code can be
removed and the comment be moved there at the very least but
I'd prefer people from one of the affected target to test it.
Looking for backend that define SHORT_IMMEDIATES_SIGN_EXTEND, that
would be someone interested in alpha, frv, lm32, m32r, mep, mips, rs6000,
rx, sh, tilegx or tilepro.