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Re: PR 70687: Use wide_int in combine.c:change_zero_ext

From: Bernd Schmidt <bschmidt at redhat dot com>
To: gcc-patches at gcc dot gnu dot org, richard dot sandiford at arm dot com
Date: Tue, 3 May 2016 11:43:41 +0200
Subject: Re: PR 70687: Use wide_int in combine.c:change_zero_ext
Authentication-results: sourceware.org; auth=none
References: <874maffquc dot fsf at e105548-lin dot cambridge dot arm dot com>

On 05/03/2016 11:11 AM, Richard Sandiford wrote:

PR 70687 reports a case where combine.c mishandles integer modes
wider than unsigned HOST_WIDE_INT.  I don't have a testcase since
the PR is just pointing out the hole.

Also, I think a ZERO_EXTEND of a vector mode could in principle satisfy
the subreg condition but wouldn't be equivalent to an AND.  E.g.:

   (zero_extend:V4DI (subreg:V4SI (reg:V4DI R) 0))

Tested on x86_64-linux-gnu.  OK to install?

	PR rtl-optimization/70687
	* combine.c (change_zero_ext): Check for scalar modes.  Use wide_int
	instead of unsigned HOST_WIDE_INT.


Ok.


Bernd

References:
- PR 70687: Use wide_int in combine.c:change_zero_ext
  - From: Richard Sandiford

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