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From: Joseph Myers <joseph@codesourcery.com>
To: "Pekka Jääskeläinen" <pekka@parmance.com>
Cc: "Richard Biener" <richard.guenther@gmail.com>,
	"GCC Patches" <gcc-patches@gcc.gnu.org>,
	"Henry Linjamäki" <henry.linjamaki@parmance.com>,
	"Martin Jambor" <mjambor@suse.cz>
Subject: Re: [PATCH] -fftz-math: assume that denorms _must_ be flushed to zero optimizations
Date: Mon, 14 Aug 2017 13:17:00 -0000	[thread overview]
Message-ID: <alpine.DEB.2.20.1708141227130.29224@digraph.polyomino.org.uk> (raw)
In-Reply-To: <CAJk11WDZMdj_fUsBQTsXShZEA4eTb86cGRs4O3zgxq7uWrA1GQ@mail.gmail.com>

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On Mon, 14 Aug 2017, Pekka Jääskeläinen wrote:

> Both the inputs and outputs must be flushed to zero in the HSAIL’s
> ‘ftz’ semantics.

Presumably this means that constant folding needs to know about those 
semantics, both for operations with a subnormal floating-point argument 
(whether or not the output is floating point, or floating point in the 
same format), and those with such a result?

Can assignments copy subnormals without converting them to zero?  Should 
comparisons flush input subnormals to zero before comparing?  Should 
conversions e.g. from float to double convert a float subnormal input to 
zero?

-- 
Joseph S. Myers
joseph@codesourcery.com

  parent reply	other threads:[~2017-08-14 12:31 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-10 17:54 Pekka Jääskeläinen
2017-08-14  9:28 ` Richard Biener
2017-08-14 11:21   ` Pekka Jääskeläinen
2017-08-14 11:25     ` Richard Biener
2017-08-14 13:17     ` Joseph Myers [this message]
2017-08-22 14:10       ` Pekka Jääskeläinen
2017-08-22 14:20         ` Richard Biener

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