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Re: [2/4] Use tree_to_uhwi when folding (x >> c) << c

From: Jeff Law <law at redhat dot com>
To: gcc-patches at gcc dot gnu dot org, rdsandiford at googlemail dot com
Date: Tue, 19 Nov 2013 11:51:19 -0700
Subject: Re: [2/4] Use tree_to_uhwi when folding (x >> c) << c
Authentication-results: sourceware.org; auth=none
References: <871u2cpq4u dot fsf at talisman dot default> <87pppwob30 dot fsf at talisman dot default>

On 11/19/13 05:00, Richard Sandiford wrote:

The (x >> c) << c folding has:

	  && tree_fits_shwi_p (arg1)
	  && TREE_INT_CST_LOW (arg1) < prec
	  && tree_fits_shwi_p (TREE_OPERAND (arg0, 1))
	  && TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)) < prec)

At first glance the use of tree_fits_shwi_p rather than tree_fits_uhwi_p
made me think this allows negative shift counts, but of course TREE_INT_CST_LOW
is unsigned.  I think it'd be clearer to use tree_fits_uhwi_p instead.

Thanks,
Richard


gcc/
	* fold-const.c (fold_binary_loc): Use unsigned rather than signed
	HOST_WIDE_INTs when folding (x >> c) << c.

OK.
jeff

References:
- [0/4] Make more use of tree_to_[su]hwi
  - From: Richard Sandiford
- [2/4] Use tree_to_uhwi when folding (x >> c) << c
  - From: Richard Sandiford

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