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Re: STRIP_NOPS and lower-precision/bit-field types
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Adam Nemet <anemet at caviumnetworks dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Thu, 4 Jun 2009 20:49:31 +0000 (UTC)
- Subject: Re: STRIP_NOPS and lower-precision/bit-field types
- References: <CAEXCH01d3OJXsNQptg00000175@caexch01.caveonetworks.com>
On Thu, 4 Jun 2009, Adam Nemet wrote:
> 1. Change STRIP_NOPS not to remove the cast if it's changing the precision
> (not just when it changes machine modes). And then audit code quality where
> we need to and are allowed to look through these casts.
As I said in <http://gcc.gnu.org/ml/gcc-bugs/2007-03/msg02228.html> and
<http://gcc.gnu.org/ml/gcc/2008-01/msg00215.html>, I think such references
to the mode are as a proxy for precision and machine modes are an
inappropriate level of abstraction for the tree optimizers. So I favour
checking for precision here - but I also favour having a good look at
anything using STRIP_NOPS etc. and considering whether it should use some
better defined function for removing redundant conversions instead.
--
Joseph S. Myers
joseph@codesourcery.com