This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

Re: Some aliasing questions

From: Richard Henderson <rth at redhat dot com>
To: Alan Modra <amodra at gmail dot com>, Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
Cc: gcc at gcc dot gnu dot org, dje dot gcc at gmail dot com, rguenther at suse dot de
Date: Tue, 12 Apr 2016 08:11:45 -0700
Subject: Re: Some aliasing questions
Authentication-results: sourceware.org; auth=none
References: <1460139016 dot 18355 dot 36 dot camel at oc8801110288 dot ibm dot com> <57081761 dot 8040502 at redhat dot com> <20160412003006 dot GT18129 at bubble dot grove dot modra dot org>

On 04/11/2016 05:30 PM, Alan Modra wrote:

Either way, when we split to
	set (reg tmp) (high (const (minus ((symbol_ref) (reg 2)))))
	.. mem (lo_sum (reg tmp) (const (minus ((symbol_ref) (reg 2)))))
both high and lo_sum reference r2 and the linker could happily replace
rtmp in the lo_sum insn with r2 when the high address is known to be
zero.

It would be interesting to see if the r2 reference in fact gets picked upinside the const. My first reaction is that I could imagine tracking skippingover it completely, since we've been promised that the expression is constant.

Alternately, perhaps alias.c should reuse the existing delegitimize_addresshook, allowing it to look through your current unspecs.

r~

Follow-Ups:
- Re: Some aliasing questions
  - From: Richard Biener

References:
- Some aliasing questions
  - From: Bill Schmidt
- Re: Some aliasing questions
  - From: Richard Henderson
- Re: Some aliasing questions
  - From: Alan Modra

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]